NBSIR 84-2821

Friction and Wear Characteristics

of Molecular Compound Classes

From Lubricating Base Oils

Part 1 Separation and Chemical Characterization

ECUT

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Measurement Laboratory

Center for Materials Science

Inorganic Materials Division

Washington, DC 20234

December 1 983

Issued February 1984

Prepared for

-QC

100

,156

34-2821

1334

U.S. Department of Energy

Dak Ridge National Laboratory

Dak Ridge, TN 37830

NBSIR 84-2821

FRICTION AND WEAR CHARACTERISTICS

OF MOLECULAR COMPOUND CLASSES

FROM LUBRICATING BASE OILS

Part 1 Separation and Chemical Characterization

>'rS»5S°

library

ac

I oo

( U &

AA

S. M. Hsu, P. Pei, and R. S. Gates

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Measurement Laboratory

Center for Materials Science

Inorganic Materials Division

Washington, DC 20234

December 1983

Issued February 1984

Prepared for U.S. Department of Energy

Oak Ridge National Laboratory

Oak Ridge, TN 37830

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
FRICTION AND WEAR CHARACTERISTICS OF MOLECULAR

COMPOUND CLASSES FROM LUBRICATING BASE OILS

S. M. Hsu, P. Pei, and R. S. Gates

National Bureau of Standards

Washington, DC 20234
TABLE OF CONTENTS

Paae

1. Introduction 1 1.1 Technical Approach 2 1.2 Test Development and Standardization 3

1.3 Technology Transfer 9

2. Separation Method Development 12

2.1 Large Scale Activated Alumina Column 12

2.2 Clay/Silica Gel Chromatography 16

2.3 Preparative HPLC Method 16

2.3.1 Polar Fraction Separation 17

2.3.2 Separation of the Saturate/Aromatic Fraction — 17

2.3.3 Separation Optimization 19

2.3.4 Purity of the Separated Fractions 19

2.3.5 Summary of the HPLC Separation 28

2.4 Ion-Exchange Column Chromatography for Polar

Separation 28

- 2.5 Neutral Alumina Column Chromatography for Polar

Separation 28

3. Analytical Characterization of Fractions 33

3.1 150N Mid-East Base Oil 33

3.1.1 150N Saturate Fraction Characterization- 33

3.1.2 150N Aromatic Fraction Characterization 38

3.1.3 150N Polar Fraction Characterization 42

3.1.4 Comparison of the 150N Fractions-- 42

3.1.5 150N P-2 Polar Subfraction 42

3.1.6 150 P-3 Polar Subfraction-- 46

3.1.7 150N P-5 Subfraction 46

3.1.8 150N P-6 Subfraction —- 46

3.1.9 Summary of 150N Polar Subfractions-- 47

3.2 300N Mid-East Base Oil- 47

3.2.1 300N Saturate Fraction Characterization 47

3.2.2 300N Aromatic Fraction Characteri zation 49

3.2.3 300N Polar Fraction Characterization 49

3.2.4 Comparison of the 300N Fractions 49

3.2.5 300N P-2 Subfraction 51

3.2.6 300N P-3 Polar Subfraction 51

3.2.7 300N P-5 Polar Subfraction 51

3.2.8 300N P-6 Subtractions 54

3.2.9 Comparison of the 300N Polar Subtractions 54

3.3 600N Mid-East Base Oil 55

3.3.1 600N Saturate Fraction Characterization-- 55

3.3.2 600N Aromatic Fraction Characterization 55

3.3.3 600N Polar Fraction Characterization 55

l
Pa^e

3.3.4 Comparison of the 600N Fractions 58

3.3.5 600N P-2 Polar Subtraction 58

3.3.6 600N P-3 Polar Subtraction 58

3.3.7 300N P-5 Polar Subtraction 61

3.3.8 600N P-6 Polar Subtraction 61

3.3.9 Comparison of 600N Polar Subtractions 61

3.4 Comparison of Fractions and Subtractions 62

Appendix A Characterization of Fractions from Large Scale

Alumina Column Chromatography 76

Appendix B Characterization of Separated Fraction from

ASTM D-2007 Method 82

Appendix C Characterization of Fractions from Ion-Exchange

Column Chromatography 84

Appendix D Characterization of Polar Fraction and Subtractions

from Neutral Alumina Column Chromatography by

High Resolution Mass Spectrometry 93
Part 1

Separation and Chemical Characterization

1. INTRODUCTION

Tribology is the science and technology concerned with the control of

friction and wear of interacting surfaces in relative motion. It is

a generic technology which supports the manufacturing industries, power

industries, and transporation industries. As such, tribology plays a key role in energy conversion and utilization technology concepts.

One of the most widely used means to control friction and wear is the

use of lubricants. Most lubricants today are derived from petroleum

which is relatively low cost and abundant. As the energy conversion

and utilization technologies continue to advance, lubrication

environments and demands become more difficult, and new generations of

lubricants are needed to meet the high temperature and sometimes

corrosive environments. In addition, as new classes of materials are being developed for advanced heat engines (high temperature, high

thermal efficiency engines), lubricant-material compatibility and

interactions need to be understood. Lack of basic knowledge of how

lubricants function and the mechanisms of friction control often

impedes the technology advance. Molecular design basis for lubricants

is not available at present.

Lubricants consist of base oils and additives. While the additives

control the initial friction and wear characteristics of the lubricant,

the base oils control the breakdown and failure mechanisms, as well as the additive response. Industry has reported that different base oils

with the same additive treatment could perform significantly different

in engine performance tests [1], Yet, no basic understanding of the

phenomenon is available. Oftentimes, the search for new base oils

and additives for new lubricants becomes a process of trial and error

using expensive full-scale engine tests.

A clear understanding of the lubrication mechanism in existing

technologies and a systematic data base linking molecular structures to

lubricating properties related to various materials are clearly needed

to build new advanced lubricants for high efficiency energy conversion

concepts in the future. Such understanding and data base could yield

significant savings in existing technologies as well.

1
1.1 TECHNICAL APPROACH

In lubricated contacts, friction and wear are governed by

load, speed, lubricant film thickness, surface topography, metallurgy,

and contact geometry. Under low and moderate loads, the lubricating

oil film is relatively thick and continuous, and the surface asperityasperity contacts are often elastic in nature. Frictional forces are governed mostly by the viscous drag of the fluid and the frequency

and magnitude of elastic collisions of the surface asperities. The

coefficient of friction is generally between 0.01 and 0.06.

Predictive models have been developed [2-4]. For most engineering

surfaces on gears and bearings, the load is sufficiently high

that the lubricating oil film is very thin. In this region, the

surfaces are in constant contact, and the asperity-asperity interactions result in plastic, as well as elastic deformations. Friction

and wear are influenced by adhesion, abrasion, displacement,

intermolecular forces, and the chemical compositions of the lubricating

film. Surface temperature and surface chemistry [5] are important in

controlling the amount of plastic collisions and the properties of the

surface film. Coefficient of friction in this region ranges from

0.08 to 0.15.

It is in this region of highly loaded lubricated contact that most

advances can be made through systematic research, because the lubricantsurface interactions are complex and the least understood. Lubrication

in this region is controlled by surface topography and lubricant

chemistry. Bowden and Tabor [6] in 1964 summarized a series of experiments demonstrating the effects of chain length of fatty acids on friction and wear. Greenhill [7] and Sanders [8] studied the effects

of esters, alcohols, and long chain polar compounds on friction and

wear in various simple sliding experiments. Goldblatt [9,10] studied

the antiwear behavior of polynuclear aromatics in basestocks and

their influence on antiwear additives. Groszek [11,12] measured heats

of adsorption of various molecular structures of surfactants and some phosphorous and sulfur additives on solid surfaces and was able to

explain some observed lubrication phenomena.

In developing the basic data linking molecular structures to friction

and wear characteristics, one of the most difficult questions is what

molecular structures are significant in friction and wear control.

Model compounds seldom provide the practical link to actual lubricants.

Obviously lubricating base oils and additives are important, yet it is

not clear which structures in the lubricants control the tri bochemical

reactions.

2
Our work on recycled base oils provided some interesting results.

In an effort to isolate and identify contaminants in re-refined

lubricating base oils, we developed a separation scheme to isolate

the polar fractions using liquid chromatography. Characteristics

of the fractions are shown in Table 1. The polar fraction (1 to 2%

by wt. ) contains most of the sulfur, nitrogen and acidic species and

at the same time possesses almost all of the antioxidant capacity

of the oil (Table 2). Figures 1 and 2 demonstrate the effect of

this fraction on friction and wear. As shown in Figure 1, at low

concentrations in pure saturates, the polar fraction lowers the wear.

With some antiwear additive added, the’ polar fraction increases the

wear by reducing the effectiveness of the additive. Figure 2 shows that

addition of polar fraction to pure saturates can influence friction.

These data suggest that the polar structures in base oils exert a large influence on friction and wear characteristics.

If the antiwear additives in oils provide antiwear performance, i.e,

wear and friction control, as long as the additives remain in the

system, then the natural polar structures in the base oil control the

friction and wear failure. Identification of these polar fraction

structures could provide a basis for model compounds selection.

Therefore, the approach that we have chosen is to separate three

lubricating base oils, as illustrated in Figure 3, to provide basic

structural information on the constituents in base oil that control

friction and wear. After careful characterization of these compound

classes, model compounds of various molecular structures will be used

to measure their effects on friction and wear under different load/

speed combinations.

1.2 TEST DEVELOPMENT AND STANDARDIZATION

Within the general framework of the technical approach, many

significant technical challenges exist in spite of recent advances.

Compound separation, isolation, and identification of a particular specie

from a complex mixture such as base oils remain formidable. Conventional

liquid chromatographic methods are time consuming and yield only

milligram quantities of separated materials. Large scale and rapid

separation techniques need to be developed. Mi cro-characteri zati on of

limited quantities of materials in terms of compound identification is

difficult. Various analytical instrumentations run in tandem such as GC-FTIR, GC-MS, HPLC-FTIR may be required for positive compound

identification.

3
Table 1

Physical

and

Chemical

Properties

of

Separated

Fractions

C\J »—» c 00 o o LC O i- -r- LO O LO 03 CNJ t—

H

LO

fO -t-> • • • • a • • • • • i— CJ o o o t-H r-H o LO CNJ CNJ o r^. CNJ O rt3 LO CNJ CNJ r-H *3- Q- i~ LO V

Lil><. CU e lo 03 e o CO o fO •<- o CO r—H

co LO CO (T> 00

+-> +-> • • • • • • • • • • • e u CO O'1

t-H o o t-H o 00 CNJ LO LO C-. <U eo 1

03 i—*CO CNJ LO C\J Q_ iLi— CNJ

co LO 9 e 03 03 o LO co

CU -r- 00 «3" CO o 03 CNJ CO co LO CNJ S_ +J • • • • • • • • • • 3 O lo 00 CO i—< o o o o CO LO 00 co CO

Q- <T3 LO o o LO J". LO CNJ S- t-H LO

Lt— o o

i— LO 00

•r— CO r-«. 00 o <3- co t—H

>=3- LO LO o • • • • • 1 1 • • • a; co 03 1 t o o O o 1 1 r- CO LO

00 r-^ o LO LO CNJ

<T3 t—

H

r»

CO t—

H

-M +-> 39

oo co a a #» 0)

«\ 3

r— o c_> E O • i

o o Q. • r— r—* o Q. E cu o o X .e CO E

a> o ai •» o 1 1 39 3-5

(/) t-H -a to E CU

a

fO e E <u t— <a i — «

CO -t-> +j >—4c_> 03 r— e o C_> <a 03 \ a: o E c o +1 -a at 03 o s- CL o >i o o C_) CU =0 >> > -M CL •r— r-~ JO •r— •r— E +-> +-> •f— A •r— +-> o e E CJ

•p— • r—

r

>1 03 Z •t <a o cu • r— <U •rLf— m m a +-> E S- i

CNJ Q. 4- -E J-> aj o o fO •1— u 3 o >, 4- -t-> ca s- o u s_ m A •r— 4- a 1— <TJ o: E i </) in 4— e z m f— s- h— s- CL O

O) •r- r— »—JCU <u

C ro 3 ai oo o n3 fT3 L_

cc. > > > QC

a l

CO in CL. c nr Q. Z <C 4
Table 2

Antioxidant Capacity of Various Base Oil Fractions

ANTIOXIDANT CONCENTRATION, 10~

3 MOLAR

OILS ORIGINAL "PURE" PENTANE

POLAR

ACETONE

A 12 2 1 420

B 7 1 1 210

C

- 1 1 270

D

- 1 1 260

E 8 2 1 230

5
Wear

Scar

Diameter,

mm

Apparatus: NBS Modified 4-Ball Wear Tester

Speed: 600 RPM

Load: 40 kg

Temperature: 75 °C

Duration: 60 minutes

Atmosphere: 0.25 2,/min dry Air

Lubricant: Purified Fraction Blended with Polars

Pure Percent Polars

FIGURE 1. EFFECTS OF ZDDP - POLAR FRACTION

INTERACTIONS ON WEAR

6
COEFFICIENT

OF

FRICTION

(XIO" 3

Apparatus:

Speed:

Load:

Temperature:

Duration:

Atmosphere:

Lubri cant:

NBS Modified 4-Ball Wear Tester

600 RPM

40 kg

75 °C

60 minutes

0.25 £/nin air atmosphere

10 ml Purified Fraction Blended with Polars

FIGURE 2. COEFFICIENT OF FRICTION AS A FUNCTION

OF POLAR CONCENTRATION

7
Figure 3

Molecular Structure Separation/Characterization Scheme

8
Performance characterization techniques for lubricants are usually

conducted using laboratory simulation tests. These are usually

oxidation and wear tests. However, the significance of these test

results is often questioned. A methodology needs to be established

to link laboratory test results to actual field experience.

These tests, once developed, have to be standardized to provide

comparable data base by different workers. In an interdisciplinary

subject such as tribology, the necessity of standardization for

technological advancement is crucial.

This report describes in part, the technical activities associated

with the ECUT project from March 15, 1982 to June 30, 1983. The

emphasis is restricted to separation science and test method

development.

The scope of the overall long-term project goals can be described as follows

1. Increase the understanding of the basic lubrication and

friction mechanisms and develop predictive models.

2. Specifically, understand how the molecular structure of

lubricants interact with surfaces to control friction.

3. Develop an understanding of the chemistry taking place at

lubricated surfaces and its effect on lubricity.

4. Understand the effects of lubricant molecular structure on adsorption, and the dependence of friction on different

surface materials.

5. Develop measurement techniques and standardized test methods

on friction.

6. Technology transfer through cooperative study with industries.

A schematic of the technical objectives is shown in Figure 4.

1.3 TECHNOLOGY TRANSFER

In addition to the normal publications and society presentations,

many cooperative research programs have been initiated with universities

and industries. Details are shown in Figure 5. An industrial working

group comprised of nine major oil companies and five additive companies

has been formed to conduct base oil research. Industry supplied over

100 base oil samples with extensive analytical data, and NBS conducted

simulation tests to assess the effects of base oil compositions on oxidation stability [13].

9
FIGURE 4. NBS/ECUT TECHNICAL PROGRAM OBJECTIVE

10
Universities Industries

Pa. State (Grad. Coop.)

Northwestern (IPA)

Minnesota (IPA)

Martin Marietta

Cummins Engine

Hughes Aircraft

Geo Centers

Lubrizol

Bendix

Mack Truck

Caterpillar

(Adsorption)

(Ceramics)

(Bearings)

(Organic Synthesis)

(Additive Research)

(Ceramics)

(Diesel)

(Diesel)

1 NBS/ECUT

'TRIBOLOGY PROGRAM

IL_

Agencies Industrial Working Group

DOE Exxon Paramins

U.S. ARMY Mob i l Oronnite

U.S. AIRFORCE Texaco Amoco Chemicals

U.S. NAVY Amoco Lubrizol

Chevron Ciba Geigy

Imperial

SAE Shell

ASLE Arco

ASTM Union

ASME

FIGURE 5. NBS/ INDUSTRY/ UNIVERSITY INTERACTIONS
2. SEPARATION METHOD DEVELOPMENT

A variety of lubricating base oils were used to develop the separation

method. These oils represent the current technologies and are the

most widely available commercial ly . Detailed characterization results

are shown in Table 3.

Several separation techniques were examined. These included:

activated alumina column chromatography, clay-silica gel combination

column chromatography, ion exchange column chromatography, and

preparative High Performance Liquid Chromatography (HPLC) methods.

The final separation scheme uses the HPLC apparatus and is a three

stage process: (1) a clay column to separate the oi 1 into polar

and saturate/aromatic fractions, (2) silica-gel/activated alumina

combination column to separate the saturate/aromatic fraction into

its respective fractions, and (3) a neutral alumina column to

separate the polar fractions into four major subfractions (P-2, P-3,

P-5, and P-6). The following sections discuss the advantages and

disadvantages of each separation technique examined.

2.1 LARGE SCALE ACTIVATED ALUMINA COLUMN

To isolate alarge quantity of the polar fraction (1 to 2% by wt.)

in a base oil, a large scale activated alumina column of 182 cm length

and 5 cm internal diameter was used. About 2000 gram of a 80/200 mesh

alumina adsorbent, whi ch was activated at 200 °Cfor6 hours, was employed

for each separation. About 3.5 kg of oil was charged under one atmosphere of nitrogen pressure. The conditions and the apparatus

are shown in Table 4 and Figure 6. The procedure produced purified

saturate fraction, and a polar fraction. The purified oil fraction

was collected until the infrared aromatic absorbance at 1605 cm- 1 reached 6.3 x 10”2 absorbance units. This gave a good balance of yield

and purity in the first fraction. The remaining nonabsorbed material

in the column was removed by eluting with pentane. The end point for

the pentane fraction elution was determined using a Refractive Index

(RI) detector. When the RI value of the column eluent matched the RI value of n-pentane, only the polar materials remained on the column.

Acetone was used to remove the absorbed material from the column, and was collected as the polar fraction.

Pentane and acetone were removed from the respective fractions by

evaporation at 60 °C under vacuum in a rotary evaporator, followed by

stripping with nitrogen. Completion of solvent removal was checked

by the constant weight method, followed by analysis of the fractions

by gas chromatography.

12
CHEMICAL

AND

PHYSICAL

PROPERTIES

OF

BASE

OIL

SAMPLES

N

ppm 00

r-H r** rH 24 <T> f-H rH

r-H 42 58 00

r-H - -O , T-

•r- S-C

f) OJ ^ r'

C CM CO

00 cn 00 CM o o r-H 1 ^ z£ i-H CD r-H O o o o 1,3 =3 O • • • • • o o r-H o o o o o oi

E

00 cn cn r-H in o CO r-H r-H f“H CM o CD CO CO o # , • • • • • • uo o o o o o o o o

to CO E x cr> CD CO cn CM CTi CO

r— Q. cn • O rH • rH • o O CL H x O'! o

CM o

CM o

>1

4-> '—

X

in 0) O “O o c 00 CM o CO CM o

to »

1 •r— or-H ot“H or-H or-H cn or-H or-H or-H >

>>

+j

•r- <_) I/ICO -U o CD CM cn CM

m CO CO o o co CO CM <3- m CD CM r-H to o • CO • o rH o x o CO cn

•I- +->

x CD o CO in > «X3 rH

O)>

•rO 4_) <X> CM LT> o cn =3- 00 o x C}" CD x o r-H rH CT> 00 CO 00 x cn CO CO

S_ T3 H- •=3" <=3- «d- •d- «d- M— C

CU

—

• r-H • r-H • r-H i-H

H r-H r-H r-H cc

>> +JCO

•1— CM LD cn CO CM

V) E o OO r-H CO CM CM LO c a 00 cn r-H CO x cn 1—1 cn

CL) \ x 00 CD CO CD

X CD

Q

m 00 00 00 CO CO 00 00 00 • • • • • • • o o o o o o o o z z z z z z o o o o o o rH o in o LO Z 00 z CM CD r-H CO CM o CM o

CO rH

X

XXX

X

oo co

CM OO 00 oo oo OO

>>

rt3

4-> rO >»

<a +J +J -M -M r— c cn cn in c. -a a E f— a o <a <T3 <o o

(U 3 •!— o UJ LU LU

V c: -o 3 +-» -a 1 •r- •r U in •r— -o -a -o a “O

<+- o u c •r- •r— •1— •r* •r* <u

s- <c > a <c •r—

CT1 Ss:

T s 21 s:

A

a: «=c CO o

•r- > Q LU U.

O 3: i 13

Re-refined

base

oil

"C"

received

minimum

re-refining

treatment

and

was

used

asa

reference

oil

for

method

development

only.
Table 4

Experimental Conditions for the Activated

Alumina Column

Column Dimension

Wt. of Alumina Used

Wt. of Base Oil Charged

Pressure

Pentane Used to Elute

Acetone Used to Elute

Wt. Recovered

182 cm long 5 cm ID with 2 liter capacity

reservoi

1847 g to 2000 g

3530 g

Q. 1 MPa (1 Atm)

4 liters

4 liters

^99 %

14
Ni trogen

Solvent Resistant Rubber

Alumina

5 cm I.D. Borosilicate

Glass Tubing

Glass Wool Plug

Teflon Stopcock

FIGURE 6. LARGE SCALE ACTIVATED ALUMINA LIQUID CHROMATOGRAPHY

COLUMN FOR BASE OIL SEPARATION

15
This procedure takes 3 to 4 weeks per oil sample. The physical and

chemical characteristics and the infrared spectra of the three base

oils and their fractions separated on activated alumina are listed in

appendix A.

Chemical analyses and IR spectra show the acetone eluted polar

fraction contains large amounts of oxygen and sulfur compounds. This

is indicated by a high weight percent of elemental sulfur, and high

total acid number, as well as the presence of strong hydroxy (3450 cm- 1

) and carbonyl peaks (1700 cm- 1

) in the infrared absorbance spectrum.

The pure fraction contains a small amount of aromatic compounds as shown by the aromatic band at 1600 cm- 1 in the IR spectrum. The

pentane eluted oil fraction is free of any carbonyl compounds as no carbonyl band is observed at 1700 cm1

. The main difficulty with this preparative method is the long period

of time required to separate one oil into its compound fractions.

During the 3 to 4 weeks time, undesirable oxidation of the base oil

constituents may also occur.

2.2 CLAY/SILICA GEL CHROMATOGRAPHY

A clay-gel adsorption chromatographic method based on ASTM D-2007

was examined. The method uses a dual column (silica gel and clay

adsorbents) to separate oils into three fractions: (1) saturated

compounds, which are not adsorbed on either the silica gel or clay

columns, (2) aromatic compounds which are adsorbed on the silica gel

column, and (3) polar compounds which are adsorbed on a clay column of

specific activity.

This method offers a rapid means to separate base oils into major

hydrocarbon types such as polar compounds, aromatics and saturates.

A base oil was evaluated by this method and found the method useful

as an analytical tool. The fractions obtained by this method are characterized by infrared spectroscopy. The fractions are found to

be relatively pure. The IR spectra of the fractions of the sample

are shown in appendix B. The polar fraction contains most of the

sulfur and acidic compounds. The advantages of this method are its

simplicity and the excellent recovery of all three hydrocarbon fractions.

However, the quantity recovered from the separation is very small

because the starting oil feed to the column is limited to 10 gm.

A scaled up version of this method requires 4 to 6 weeks to complete

testing one oil. Therefore, a fast preparative scale liquid chromatographic method is sought.

2.3 PREPARATIVE HPLC METHOD

With the advent of High Performance Liquid Chromatography (HPLC),

the time consuming aspect of the open column chromatography has been

reduced. A modification of Hirsh's method was reported by Sawatzky

16
et. al [14] , which consists of using high pressure to give

enhanced separation in a much shorter period of time. At present, HPLC

methods, either analytical or preparative, generally have limited sample

loading capacities in the range of one gram or less [15-20], This means

the amount of polar fraction separated from a run will be in the milligram

range, not sufficient for performance testing. Therefore, an effort was initiated to develop a rapid multi gram chromatographic method for the isolation

of active species in base oils. In this respect, good mass balance becomes

an important factor, since loss of a significant amount of the active species

in an oil will render the separation unacceptable.

A commercial preparative HPLC unit with dual 5 cm I.D. radially compressed

column was used. The first column was packed with 450 grams of attapulgus

clay as specified by ASTM D-2007 clay specifications. The second column was packed with 300 gm of silica gel (60/200 mesh) and 300 gm of activiated

alumina successively.

The separation scheme developed is shown in Figure 7. The process is

divided into two steps: (1) the polar fraction is separated from the base

oil on an attapulgus clay column, generating a polar fraction and a saturate/

aromatic hydrocarbon fraction, and (2) the saturate/aromatic hydrocarbon

fraction is then separated into pure saturate and aromatic hydrocarbon fractions

on a dual packed alumina/silica gel column.

2.3.1 POLAR FRACTION SEPARATION

The packed clay column was placed in a stainless steel chromatographic chamber,

and the chamber was pressurized to 3.0 MPa (440 psi). After flushing the column

with 1 liter of n-pentane, the sample solution (50:50 oil and pentane) was pumped onto the column at the rate of 50 mL/min. After the sample has been

pumped onto the column, four liters of n-pentane were used to sweep the

clay column at the same flow rate. The fraction eluted by the n-pentane was designated the saturate/aromatic fraction. One liter of acetone/toluene

(1 to 1 by volume) was then pumped through the column to elute the polar

fraction. Both fractions were evaporated to dryness using a rotary evaporator.

When the fractions approached dryness, evaporation was completed under a nitrogen atmosphere. The fractions were then dried to a constant weight and

their weights recorded. To determine mass balance, the sample at the

detector outlet of the instrument was also collected and weighed.

2.3.2 SEPARATION OF THE SATURATE/AROMATIC FRACTION

After flushing the preparative unit with one liter of n-pentane, a freshly

packed column containing alumina and silica gel was oriented in the chamber

so the eluent first passed through the alumina, then through the silica gel.

Approximately 75 g of the saturate/aromatic fraction obtained from the first

separation were weighed out and dissolved in 500 mL of n-pentane. This solution

was pumped onto the column as described in the previous section. An

17
BASE

OIL >>W /“K lu t. Z Z GC o <

Q. C/3 Ic

LU

>!

LU CD 2 r- R 6)

CM

O o >

CM > X

Xo <

C/D

18

FIGURE

7.

PREPARATIVE

HPLC

SEPARATION

SCHEME
additional 1000 mL of n-pentane was then pumped through the column to

elute the fractions. The first 500 mL of eluent collected was designated

the saturate fraction. After the elution with n-pentane, one liter of

methylene chloride in toluene (50%), followed by one liter of 10% ethanol

in tetrahydrofuran, was pumped through the column. The fractions were

again evaporated to dryness on a Rotavap under nitrogen atmosphere. The

final two elution volumes were combined for the aromatic fraction as shown in Figure 7.

2.3.3 SEPARATION OPTIMIZATION

The three factors involved in the optimization of a preparative liquid

chromatographic separation are: (1) speed of the separation, (2) sample

load capacity, and (3) resolution of the peaks. If improved resolution

of peaks is required, some sacrifice in speed and load size is necessary,

such as decreasing the sample size placed on the column and/or slowing the

elution rate of the mobile phase. In the chromatographic separation of

polar compounds from the saturate/aromatic fraction, the resolution factor

is large and so a larger load size and faster elution rate can be used.

However, in separating the combined saturate/aromatic fractions into pure

saturate and aromatic fractions, the resolution factor becomes comparatively

small, necessitating a decrease in load size in order to obtain complete

separation. Hence, the two stage-method was necessary due to the difference

in resolution factors and the small amount of polar fraction present in

the base oil relative to the saturate and aromatic fractions. By utilizing

this two-step process 5 gm of the polar fraction, 15 g of the aromatic

faction, and 60 g of the saturate fraction can be obtained in a single

run requiring less than 8 hours for completion.

2.3.4 PURITY OF THE SEPARATED FRACTIONS

A total of eight lubricating base oils were studied: three re-refined base oils

and five virgin base oils with viscosity range from 30-110 Cst (150-600N).

Table 5 shows that the mass balance and precision achieved with the preparative

HPLC method is excellent. The recovery is better than 99% by wt. in duplicate

runs for the clay column and 98% for the dual alumina/silica gel column.

Table 6 shows that the values obtained from the preparative HPLC method

agree well with those obtained with the ASTM D2007 method.

The agreement of the data suggests that the new method, while preparative

in nature, yields results which are quantitatively comparable with an analytical method.

Several tests were performed to determine if the fractions designated

saturate, aromatic and polar were free of other types of hydrocarbons.

These tests included refractive index determinations, infrared spectroscopy, C 13 NMR, mass spectroscopy (both high and low resolution) and

gel permeation chromatography. All tests suggested good separation by

the preparative HPLC method.

19
Table 5

Mass Balance and Precision of the Preparative HPLC Method

Sample Clay

(G

Column Separation

ram)

Alumina/Silica Gel

Separation

(Gram)

Column

Injected Recovered Wt. % Rec. Injected Recovered Wt. % Recovery

'A' 251.88 250.72 99.5 70.2 68.9 98

251.83 251.29 99.8 70.4 68.8 98

' B

250.6 249.8 99.7 70.3 69.0 98

251.0 250.5 99.8 70.5 69.3 98

C' 250.0 248.7 99.5 70.5 69.1 98

249.8 248.3 99.4 70.1 68.7 98

' D

251.2 250.9 99.9 70.1 68.3 97.4

251.5 250.5 99.6 70.1 69.2 98.7

20
TABLE 6

COMPARISON OF PREP HPLC WITH ASTM METHOD D2007

Saturate Aromatic Polar

wt . %, wt .%> wt .%

Sample Prep HPLC D2007 Prep HPLC D2007 Prep HPLC D2007

A 76 .

75.3 21.5 22.5 2.0 2.2

B 76.0 77.6 22.7 20 .

1.3 1.7

C 72.5 72.5 24 .

8

24.1 2.9 3-4

D 82.9 83 • 4 16.7 16.2 0.3 0.4

E 64.5 62.9 34.5 35.4 0.8 1.7

F 65.8 67.4 32.6 32.1 0.32 0.5

G 74 .

8

78.0 24 .

5

21 .0.4 0.6

H 78.8 80.7 19.6 19 .

0

0.05 0.3

21
The IR spectra of the fractions of oil samples 'A' and ' D

' are shown in Fi quires 8 and 9. The aromatic carbon-carbon stretch band

at 1600 cm- 5

- is absent from the IR spectra of the saturate fractions

(Figures 8a and 9a) but is strongly present in the IR spectra of

the aromatic fraction (Figures 8b and 9b), indicating that the

saturate fraction contains very little aromatic hydrocarbon. The

strong absorption band observed at the C = 0 stretch frequency (1700

cm- 1

) in the IR spectra of the polar fraction shows that most of

the oxygenated compounds such as esters, acids, ketones and other

active components of the base oil are concentrated in the polar

fraction (Figures 8c and 9c).

C 13 NMR of the fractions of one re-refined oil 'A' are shown in

Figure 10. The absence of aromatic C 13 (120-170 ppm) in the NMR

spectra of the saturated fraction is again consistant with the purity of

the fraction. The integral ratio of linear carbon to the total carbon

is 0.23 in the saturate fraction. The ratio of aromatic carbon to

aliphatic carbon is 0.27 in the aromatic fraction. The ratio of aromatic

carbon to aliphatic carbon in the polar fraction is 0.18. The extra peak

at 89.3 ppm in the aromatic and polar fractions is due to the contamination by a residual additive, polyisobutylene, which is not completely

removed during the re-refining process.

Low resolution mass spectroscopy was performed on the saturate fraction

to determine the percentage of aromatic rings. The values found in

each saturate fraction are listed in Table 7. Approximately 2 %,

monoaromatics are found in the saturate fraction, which is considered

acceptable for such separation. High resolution mass spectroscopy

was performed on the polar fraction of three base oils to determine

the major constituents of the polar compounds. Results suggest that

the polar fractions remain too complex a mixture for accurate identification. By this technique with a probe temperature at 100 °C, considerable

residual remained. Further separation of the polar fraction is required.

Figure 11 shows the molecular weight profile, determined by gel

permeation chromatography, of the fractions collected from oil 'D

1 . The molecular weight standards used in the calibration of the

gel permeation chromatography are polysytrenes of known molecular

weight. The profile of the aromatic fraction shows the presence of

smaller molecular weight compounds while the profile of the polar

fraction is broad, since it contains both the highest and lowest

molecular weight portion of the base oil.

22
TRANSMISSION

(%)

TRANSMISSION

(%)

TRANSMISSION

(%)

a. Saturates

r

WAVENUMBER (cm -1)

FIGURE 8. INFRARED SPECTROGRAMS OF OIL A FRACTIONS

23
TRANSMISSION

(%)

TRANSMISSION

(%)

TRANSMISSION

(%)

WAVENUMBER (cm- 1 )

FIGURE 9. INFRARED SPECTROGRAMS OF OIL D FRACTIONS

24
a. Saturates 30.1

195 163 131 99 67 35 3

ppm

FIGURE 10. C 13 NMR SPECTROGRAMS OF OIL A FRACTIOUS

25
TABLE

Sh

oaQU

dcS3CO<w

s:

dc

CO E < Ws 2 o O DC H E E O O w < CC

DC CO

Ph CO

CO

w <

Em s <

CC 2 2 OH < E

co 22 w O

sc CO E w

DC fco o >M 2 EM

DC2

Ohw

scE co mo

•H

4-3

Cti EO<

CM CO LH -=X • • • • OJ i—I CM i—I

(U rHaE

n5 co < CQ

O

Q

26
SATURATES

27

10 J

500

300

200

100

MOLECULAR

WT.

FIGURE

11.

MOLECULAR

WEIGHT

DISTRIBUTION

OF

FRACTIONS

FROM

OIL

D
2.3.5 SUMMARY OF THE HPLC SEPARATION

A preparative multi gran HPLC method has been developed

for the separation of lubricating base oils according to hydrocarbon

types. This preparative method can produce multigram quantities of

various hydrocarbon/compound types. The fractions produced are saturates, aromatics and polar compounds. In comparison to open

column methods, the step-wise scheme described here is rapid and

efficient. The method is especially effective for the isolation of

large quantities of minor components in complex hydrocarbon mixtures.

The multigram quantities of minor fractions of lubricating oil prepared

by this method are sufficient not only for chemical characterization,

but also for performance studies such as oxidation, friction, and wear. Such a fraction scheme greatly simplifies subsequent

separation and characterization by analytical HPLC, GC, and GC/MS

and will serve as a first step toward a scheme for isolating

molecular compound classes in a base oil.

2.4 ION-EXCHANGE COLUMN CHROMATOGRAPHY FOR POLAR SEPARATION

Jewell et al. [21] reported an ion-exchange, coordination and

adsorption chromatographic method for separation of heavy-end petroleum

distillates into acids and bases, neutral -ni trogen , saturates, and

aromatic fractions. Both cationic and anionic exchange resins were

used to isolate the acids and bases while the neutral -ni trogen fraction

was separated by coordination complex formation with ferric chloride

supported on attapulgus clay. Silica gel was used to separate the

remaining hydrocarbon and nonpolar compounds into saturates and

aromatics.

A modified version of the separation was examined to further separate

the polar fraction. The separation scheme illustrated in Figure 12 was attempted on the polar fraction of a 350N re-refined base oil.

The last acid fraction (POLA-5), and base fractions POLB-4 were not

characterized chemically due to negligible recovery. Detailed

characterization data and discussion are shown in appendix C.

Preliminary data on this separation method were encouraging. However,

Holmes [22] reported some artifacts and molecular rearrangement of

materials separated by this method. Controlled experiments in our laboratory confirmed Holmes' finding. Therefore, this method was not

pursued fuiher.

2.5 NEUTRAL ALUMINA COLUMN CHROMATOGRAPHY FOR POLAR SEPARATION

A new separation scheme using a neutral alumina column was developed.

28
Neutral

Basicity ^

FIGURE 12. SEPARATION SCHEME OF THE ION-EXCHANGE COLUMN

CHROMATOGRAPHIC METHOD

29
A glass column, 45 cm long by 1 cm I.D. having a 100 mL reservoir was used

for the separation of the polar fraction. The column has a tapered-end tip.

The other end of the column is fitted with a 100 mL reservoir, on top of which

is a ground-glass socket so that 4 psig of back pressure can be applied to the

column. A glass wool plug is placed at the bottom of the column. Another

glass wool plug is placed on the top of the packed adsorbent to protect it from

flow disturbances when eluting solvents are added. Twenty-five grams of

neutral alumina adsorbent are added to the column in small increments, and

the column is packed uniformly with the aid of a vibrator.

Approximately 1 gram of the polar fraction was dissolved in 50 mL n-hexane.

The solution was then charged onto the alumina in the glass column. The

following step-gradient elution scheme was used to elute the polar subtractions according to their polarities: 125 mL n-hexane, 100 mL toluene,

200 ml chloroform with 0.75 percent ethanol, 200 mL of 10 percent ethanol

in t.etrahydrofuran, and 200 ml methanol. Five subtractions were obtained.

However, the first subtractions contain only a negligible amount of saturates,

and the last two subtractions were combined due to small quantities eluted.

As a result, three subtractions were isolated and studied.

The three polar subtractions were carefully characterized using infrared,

high resolution mass spectroscopy, and elemental analysis. The first

subtraction was found to consist of mainly polynuclear aromatics with

esters, phthalates, and amides. The second subtraction consisted of amines

and amides, and the third subfracation was found to be mainly oxygenated

molecules with phenolic structures (oxygen content 25.4% by weight). There were some nitrogen compound classes overlapping among the subtractions, but

no molecular rearrangement occurred on the column. The major limitation of

this method appears to be the small size of the isolated sample. Thus,

effort in developing a HPLC version of this procedure was underway.

2.6 PREPARATIVE HPLC NEUTRAL ALUMINA COLUMN SEPARATION PROCEDURE

FOR POLAR SEPARATION

A preparative HPLC method based on the neutral alumina column method

was developed. The separation scheme is shown schematically in Figure 13.

The procedure is described below.

About 770 grams of neutral alumina is used to pack a column 33 cm long

by 5 cm I.D. The packed column is placed in the chromatographic

chamber of the preparative HPLC unit. After the chamber has been radially

compressed to 3.0 MPa (30 atm.), 100 mL of n-hexane was pumped onto the column.

Then a sample of 5 g of polar fraction dissolved in 100 m of n-hexane

was pumped onto the column at the rate of 50 mL/min. After the sample

has been pumped onto the column, 40 mL of n-hexane was pumped through

at the same rate. One liter of toluene followed.

30
*P-1 contains only a small amount of saturates, therefore, it is not

characterized P3 and P4 are comDined into one P3 fraction due to

similar characteristics.

FIGURE 13. SEPARATION SCHEME OF THE NEUTRAL ALUMINA COLUMN

CHROMATOGRAPHIC METHOD
After the toluene, the following solvent systems were sequentially

pumped onto the column at the 50 mL/min rate. They are : one liter of 0.75% ethanol in methylene chloride; 2% ethanol

in methylene chloride; 10% ethanol in tetrahydrofuran; and finally

two liters of methanol. All together six subfractions were collected.

The first subfraction collected was the 600 mL n-hexane and it is

designated as PI subfraction. This subfraction was found to contain only an insignificant quantity of saturate compounds and therefore was not

studied. The second subfraction designated as P2 is the one liter of

toluene eluent. The third and fourth subfractions are the two liters

of methylene chloride with 0.75% and 2% ethanol. These two subfractions

were combined to produce the P3 subfraction. One liter of 10% ethanol

in tetrahydrofuran was collected as P5 subfraction. The remaining

1.5 liters of methanol is collected as P6 subfraction. All five subfractions were separately evaporated to dryness using a Rotavap. When

the fraction approached dryness, evaporation was completed under a nitrogen atmosphere. The fractions were dried to a constant weight

and their weights recorded. To determine mass balance, the sample

from the detector was also collected, evaporated, and weighed.

Three base oils of 150N, 300N, and 600N from mid-eastern crude were separated using the HPLC method described in section 2.3 to generate

the polar fractions. The polar fractions were then separated using

the method described above. Detailed characterization of the polar

subfractions is described in the next section and will not be

duplicated here. It is suffice to say that the separation is found

to be satisfactory in isolating molecules of varying polarity for

subsequent testing.

32
3. ANALYTICAL CHARACTERIZATION OF FRACTIONS

Three lubricating base oils were selected for detailed characterization

and evaluation. These base oils represent the typical cornmercially

available base oils of 150N, 300N, and 600N viscosity grades from

mid-eastern crudes. Detailed physical and chemical properties of

these oils are shown in Table 8.

The schematic separation scheme for these three base oils is shown in

Figure 14. Each oil is first separated into a saturate/aromatic hydrocarbon fraction and a polar fraction on a clay column. The saturate/

aromatic hydrocarbon fraction is further separated into a saturates

fraction and an aromatics fraction on a dual packed, alumina/silica

gel column. The detailed separation procedures have been described

in section 2.3 The polar fraction is further separated on a neutral

alumina absorbant to obtain four subfractions containing mainly

four different compound classes such as polynuclear aromatic

compounds, nitrogen-containing compounds, ester, and phenol type of

compounds, and carboxylic acidic type of compounds. The detailed

separation procedures are described in section 2.6. These three

steps provide the flexibility necessary to optimize the separation of

the base oils and the isolation of the major polar molecular compounds.

The weight percent data of each fraction of the original base oil are shown in Table 9. It can be seen that the polar molecules are generally less than one percent of the base oils, yet they exert

significant influence on oxidation stability and friction performance

of the base oils.

Each major fraction and compound class was characterized chemically

by analytical methods such as IR, mass spectroscopy, gel permeation

chromatography. In addition to analytical characterization,

performance evaluation tests were performed on these fraction and

compound classes. The performance tests include antioxidant capacity

titration method and micro sample step loading wear tests which

determine oil's resistance to wear under boundary lubricating

conditions. This section will describe the detailed analytical

characterizations of the fractions and their subfractions. High

resolution mass spectroscopy data for all the fractions and subtractions are shown in appendix D for reference.

3.1 150N MID-EAST BASE OIL

3.1.1 15ON SATURATE FRACTION CHARACTERIZATION

The physical properties of the saturate fraction are shown in

Table 10. The Viscosity Index (VI) of the saturate fraction increases

33
CO©

re3

re CO

COo

reEo<

COu

reE

CO T> o C CO <

w. 3O

Q.

Oc

CD

©

(D E -c o a. 3o o CO c o CO >>

CO

© 2 o re CO o

CL CD UJ <

CM CO in CO 1 1 i I Q_L

CLt

Q.

_L

Q. J

© 3 O Z< U

~rCO—

_reo

a.

O

h-o

LUCO<

CD0O

Hi

LUIO

CO<

DC<

CLLUCO

LU

DCDa

L_

34

FRACTIONS

and

COMPOUND

CLASSES
Table 8

Chemical and Physical Properties of the Base Oils

1 50N 300N 600N

Mid-East Mid-East Mid East

Kinematic Viscosity 40 °C 30.25 53.16 107.65

Kinematic Viscosity 100 °C 5.23 7.48 11.53

Refractive Index 1.4819 1 .4814 1 .4904

Density (gm/cm 3

) 0.86990 0.87151 0.88749

Pour Point (°C) -15 -7 -10

Flash Point (°C) 235 241 244

Sulfur (wt. %) 0.49 0.36 0.67

Tan (mg KOH/g) 0 0 0.022

TBN (mg KOH/g) - 0.343

Moisture ppm 95 139 65

Chlorine (ppm) 0.16 2.9 2.9

Bromine (ppm) 0 < 0.02 0.02

Sul fated Ash (wt %) 0 0 0

Carbon Residue 0.03 0.03 0.16

Total Nitrogen (ppm) 42 58 114

Boiling Point, °C IBP 286 343 313

5% off 349 410 405

10% off 375 426 434

50% off 451 477 498

90% off 498 532 552

Hydrocarbon Types

Saturates , wt% 67.0 78.0 63.0

Aromatics, wt% 32.5 21.4 35.3

Polars, wt% 0.5 0.6 1.7

35
Table

ro CM

CD

OO o

Q- • • • O o o toc to o c

•r— o

4-> •r- CD cn «d- u M LO o o 03 (_) O. • • • s_ ro o o o 4— S- -O 4— 3 -Q

IS) 3 CO LO

IS) ro i— o s_ Q_ • • • 03 S- o o o r—

03

O r—

D_ o

Q. -o >3- 00 r^» C CM o o 1

03 o_ • • • o o o tocop—

4-> to U S- C\J o o 03 03 ro 00

s- i— • • • Ll. O O o o Cl. 4-Oco to

•F— o

+-> • r— CO LO LO 3 -M • • • jQ 03 OJ >50- >d- r— E ro CM ro

SO

+-> s_ to =c

•f— o

CL) CD to

03 CD +J +-> CO 00 LO C 03 • • • cd S- lo «=3" u 3 to r-~ to

i~ +-> <D 03 Q_ 00

-*-> x:

O') •r— CD CD i

3 CLE 3 20 2: 03 O o o OO LO o o r— ro to r—

•f— o

36
Table 10

Physical Properties of the Base Oils

and the Base Oil Fractions

Viscosity, cSt

40 °C 100 °C

Viscosity

Index

Avg.

Molecular Weight

Refractive

Index

150N

Base Oil 30.3 5.2 103 402 1.4830

Saturate 25.1 4.8 116 404 1.4693

Aromatic 60.0 7.0 58 396 1.5134

300N

Base Oil 53.2 7.5 102 459 1.4816

Saturate 46.1 7.0 109 457 1.4749

Aromatic 162.4 11.7 34 436 1.5214

600N

Base Oil 107.7 11.5 93 520 1.4907

Saturate 73.4 9.7 109 520 1.4769

Aromati

c

95.5 11.0 99 524 1.5039

37
from 103 to 116 when compared to the original base oil. The

refractive index (Ri) of the fraction decreases from 1.4819 to 1.4693.

Both data indicate that the saturate fraction has predominately

paraffinic molecules. The average molecular weight derived from

the viscosity data suggests that the saturate fraction is similar

to base oil (402 vs. 404).

However, the measured molecular weight distribution profile by

gel permeation chromatography (Figure 15) of the saturate fraction

shows that the saturate fraction has more of the higher molecular

weight distribution within the base oil molecular weight profile.

The molecular weight scale of the gel permeation chromatography is

calibrated with polystyrene and hydrocarbon standards of known

molecular weight.

The saturate fraction as separated is found to be relatively free

of aromatic and heteroatom compounds . The infrared (IR) spectrum of

the saturate fraction (shown in Figure 16b) is free of aromatic band

at 1600 cm" 1 and also the carboxyl and hydroxyl bands at 1700 and

3400 cm

-1

. The presence of CH2 band at 720 cm

-1 is strong. The

purity of the saturate fraction is again confirmed by the elemental

analysis results as shown in Table 11. The carbon and hydrogen

content of the fraction has accounted for about 99.9% of the material,

and so there are relatively no heteroatom compounds detected in the

saturate fraction.

3.1.2 150N AROMATIC FRACTION CHARACTERIZATION

The physical properties of the aromatic fraction are shown in Table 10.

The VI of the fraction has decreased from 103 (base oil) to 58

(aromatic) indicating the decrease of the paraffinic content, and the

RI has increased from 1.4830 (base oil) to 1.5134 (aromatic)

suggesting predominately the presence of aromatic compounds. The

average molecular weight derived from the viscosity data of the fraction

is similar to that of the base oil, but the measured molecular weight

profile of the fraction as shown in Figure 15 indicates that the

aromatic fraction contains more lower molecular weight compounds than the

saturate fraction. Elemental analysis results (Table 11) indicate

a large concentration of sulfur compounds associated with the aromatic

structures. The sulfur content of the fraction is 1.5%. These

sulfur compounds appear to be thiophenes. The IR spectrum of the

aromatic fraction is shown in Figure 16c. The aromatic band at 1600 cm

-1

is very pronounced. It does not have carbonyl and hydroxyl bands at

1700 cm

-1 and 3400 cm

-1

.

38
REFRACTIVE

INDEX

RESPONSE,

ARBITRARY

UNITS

FIGURE 15. MOLECULAR WEIGHT DISTRUBITON OF 150N

BASE OIL AND BASE OIL FRACTIONS

39
Transmission

(%)

Wavenumber (cm"’ )

FIGURE 16. INFRARED SPECTRA OF HYDROCARBON

FRACTIONS OF THE 150N BASE OIL:

a) BASE OIL; b) SATURATE FRACTION;

c) AROMATIC FRACTION; d) POLAR FRACTION

40
Table ll

Elemental Analyses of the Base Oils

and the Base Oil Fractions

150N

C H Base Oil 86.2 13.2

Saturate 85.9 14.0

Aroma ti

c

86.7 11.8

Polar 82.6 11.3

300N

Base Oil 86.2 13.2

Saturate 86.3 13.8

Aromatic 86.3 11.8

Polar 83.2 11.5

600N

Base Oil 86.1 13.2

Saturate 86.4 13.5

Aromatic 85.9 13.0

Polar 84.3 11.5

Weight %

N S 0

< 0.01 0.42 < 0.3

< 0.01 0.01 < 0.3

< 0.01 1.54 < 0.3

1.8 2.83 1.6

< 0.01 0.33 0.34

< 0.01 0.01 < 0.3

< 0.01 2.26 < 0.3

1.4 1.68 1.5

0.02 0.69 < 0.3

0.01 0.09 < 0.3

0.01 1.24 < 0.3

1.2 2.19 0.8

41
3.1.3 150N POLAR FRACTION CHARACTERIZATION

The polar fraction is dark, viscous, and available in very small

quantities. Therefore, kinematic viscosities and refractive index

measurements are not made. The molecular weight profile of the

polar fraction is approximately in the same range as the base oil.

For chemical characterization of the polar fraction, elemental

analysis, High Resolution Mass Spectrometry (h'RMS), and Infrared

Spectrophotometry (IR) were used. The polar fraction appears to

contain large amount of sulfur-, nitrogen-, and oxygen-containing

molecules relative to other fractions, as evidenced by the elemental

analysis results in Table 11. The infrared spectrum shown in Figure 16

indicates the following bonds are distinctly present: NH/OH at

3400 cm" 1

, C=0 at 1700 cm" 1

, and aromatic structure at 1600 cm

-1

.

The existence of these molecular bonding is further supported by HRMS

results (Appendix D). Substituted thiophene, pyridine, indoles, quinoline,

carbazoles, phthalates, phenols, and carboxylic acids functional

groups have been identified. At this stage, the polar fraction is

still very complex and further separation is needed to identify

molecular compound classes.

3.1.4 COMPARISON OF THE 150N FRACTIONS

The separation of the 150N base oil into saturates, aromatics, and

polars is relatively clean as evidenced by the IR and elemental

analyses. Most of the heteroatom compounds appear to be concentrated in

the polar fraction. Sulfur compounds appear in two groups: the non- polar sulfur compounds such as thiophenes collected in the aromatic fraction

and the polar sulfur compounds are collected in the polar fraction.

Molecular weight profiles of the fractions as shown in Figure 15 show

that the saturates have slightly higher molecular weight than the

aromatic and the polar fracti ons, whi ch have nearly the same molecular

weight range as the base oil.

3.1.5 150N P-2 POLAR SUBFRACTION

The polar fraction of the 150N is separated on a neutral alumina HPLC

column as described in section 2.5.1. The four subfractions collected

are designated as P-2, P-3, P-5, and P-6. P-2 is the subfraction eluted

with toluene and therefore should contain predominately aromatic

structures. Elemental analysis results shown in Table 12 suggest that

P-2 contains the least amount of oxygen. The molecular weight distribution

as shown in Figure 17 indicates that P-2 contains more low molecular

wei-ght compounds compared with other polar subfractions from the same base oil. The infrared spectrum in Figure 18a suggests little or no oxyqenhydrogen bonds at 3400 cm

-1 or carbon-oxygen carbonyl bonds at 1700 cm" 1 wavenumbers. The aromatic structure at 1600 cm

-1 wavenumber is very

42
Table 12

Elemental Analyses of the Polar and the Polar Subtractions

Weight %

C H N S 0

150N

Polar 82.6 11.3 1.8 2.83 1.6

P-2 84.1 11.2 1.6 2.71 0.7

P-3 82.4 11.4 1.6 2.66 2.1

P-5 81.0 11.3 1.2 3.52 3.2

P-6 75.3 10.0 1.0 3.11 7.3

300N

Polar 83.2 11.5 1.4 1.68 1.5

P-2 85.0 11.4 < 0.01 1.60 0.4

P-3 83.9 10.9 1.9 2.28 1.2

P-5 83.7 11.5 1.3 1.65 1.8

P-6 82.5 12.7 0.2 0.47 4.3

600N

Polar 84.3 11.5 1.2 2.19 0.8

P-2 84.5 11.6 1.1 2.53 0.6

P-3 84.0 11.7 1.3 1.78 1.1

P-5 82.1 11.4 0.8 2.53 2.9

P-6 67.9 9.8 0.8 1.21 17.0

43
REFRACTIVE

INDEX

RESPONSE

POLAR SUBFRACTIONS OF THE 150N 3ASE OIL

44
Transmission

(%)

Wavenumber (cm -1

) FIGURE 18. INFRARED SPECTRA OF POLAR SUBFRACTIONS

OF THE 150N BASE OILS:

a) P-2 SUBFRACTION; b) P-3 SUBFRACTION

c) P-5 SUBFRACTION; d) P-6 SUBFRACTION

45
strong, thus confirming the predominately aromatic nature of the

P-2 subfraction. High resolution mass spectroscopy results suggest

the presence of thiophenes and benzothiophenes

3.1.6 150N P-3 POLAR SUBFRACTION

Subtraction P-3 is eluted from the neutral alumina column with

methylene chloride solution containing low concentrations of ethanol

(0.75% - 2% by weight) and should contain moderately polar

compounds. Elemental analysis results in Table 12 suggest that

the oxygen content has increased significantly from 0.7% to 2.1% relative

to P-2. The molecular weight distribution (Fig. 17) indicates that P-3

contains mostly the same molecular weight compounds from the same base oil

but with a tailing distribution of high molecular weight materials to about

1500. The infrared spectrum in Figure 18b suggests possible nitrogenhydrogen amine bond at 3300 cm

-1 and strong carbonyl bonds in the'

1690 cm

-1 region indicating possible amides, Possibly sulfoxides are present in P-3> as indicated by the strong 1030 cm

-1 bond. High

resolution mass spectroscopy results suggests the presence of

quinolines, and carbazoles as nitrogen compounds.

3.1.7 150N P-5 Subfraction

Subfraction P-5 is eluted from the neutral alumina column with a stronger polar solvent of 10% ethanol in tetrahydrofuran. This subtraction should contain more polar compounds which have higher oxygen

and sulfur content as indicated by the elemental analysis results

shown in Table 12. The molecular weight distribution as shown in

Figure 17 indicates that P-5 contains more higher molecular weight

compounds than P-2 and P-3 subfractions from the same base oil.

The infrared spectrum of the P-5 subfraction in Figure 18c is similar

to the IR spectrum of the P-3 subfraction, suggesting the presence

of ni trogen-hydrogen, amine bond at 3300 cm

-1

; carbon-oxygen bond

at 1700 cm

-1

; aromatic carbon at 1600 cm" 1

; and sulfur-oxygen bond

at 1030 cm

-1

. High resolution mass spectroscopy of the P-5

subfraction suggest the presence of quinolines and carbazoles for

nitrogen compounds and thiophenes for sulfur compounds.

3.1.8 150N P-6 SUBFRACTION

The P-6 subfraction is eluted from the neutral alumina column with

methanol. This subfraction contains the most polar compounds of the polar

fraction and consists predominately of oxygenated compounds. Elemental

analyses shown in Table 12 confirm that P-6 contains the highest

proportion of oxygen (7.3%) among the polar subfractions. The molecular

weight distribution of the P-6 subfraction as shown in Figure 17

indicates that P-6 contains the most high molecular weight comoounds

(about 3000) compared to the other polar subfractions from the same base oil. The infrared spectrum shown in Figure 18d shows a strong IR

absorption at 3350 cm"1

, suggesting that a phenolic-OH group for the high

46
oxygen content of this subtraction. This is confirmed by the high

resolution mass spectroscopy results (Appendix D) indicating the presence

of phenolic alcohol in the P-6 subtraction. The absorption peak at

1735 cm" 1 suggests the presence of esters and sulfoxide peak (1030 cm" 1

) is also present. High resolution mass spectroscopy results suggest

the presence of quinolines, thiophenes, and phenols.

3.1.9 SUMMARY OF 150N POLAR SUBFRACTIONS

The chromatographic separation of the 150N polar fraction was achieved

on a neutral alumina column and various molecular compounds were eluted

off the column with solvents of different polarity. P-2 subtraction

contains the least polar compounds and P-6 subtraction contains the most

polar compounds. Elemental analysis results shown in Table 12 suggest

the P-2 subtraction has the least amount of oxygen while the P-6 subtraction has the most, while sulfur and nitrogen molecules are distributed

evenly among the four subtractions. Infrared spectra shown in Figure 18

suggest that P-2 subtraction contains predominantly aromatic compounds;

P-3 and P-5 subtractions contain amides, sulfoxides, and esters; P-6

sufraction contains phenols, and esters. High resolution mass spectroscopy

data (Appendix D) suggests the presence of the following probable compounds

in each subtraction:

1. P-2, aromatic compounds;

2. P-3, thiophenes, amides, and sulfoxides;

3. P-5 carbazoles, quinolines, amides, and sulfoxides; and

4. P-6, phenols, esters, acids, and sulfoxides.

3.2 300N MID-EAST BASE OIL

3.2.1 300N SATURATE FRACTION CHARACTERIZATION

The 300N is a heavier cut than the 150N, i.e., the boiling points and

molecular weights are higher. The saturate fraction of the 300N is obtained

by the HPLC separation scheme (section 2.3). It has higher viscosities

and average molecular weight than the 150N saturates. The physical

property data are presented in Table 10.

Again, the saturate fraction of the 300N oil is pure when compared to the

base oil. The paraffinic content is high as evidenced by the increase

of viscosity index from 102 to 109 and the decrease of refractive index

from 1.4816 to 1.4749. The molecular weight distribution of the saturate

fraction is similar to those of the base oil as shown in Figure 19.

47
ARBITRARY

UNITS

(REFRACTIVE

INDEX

RESPONSE)

FIGURE 19. MOLECULAR WEIGHT PROFILE OF THE 300N BASE OIL AND ITS FRACTIONS

48
Transmission

(%)

Wavenumber (cm' 1 ) FIGURE 18. INFRARED SPECTRA OF POLAR SUBFRACTIONS

OF THE 150N BASE OILS:

a) P-2 SUBFRACTION; b) P-3 SUBFRACTION

c) P-5 SUBFRACTION; d) P-6 SUBFRACTION

45
strong, thus confirming the predominately aromatic nature of the

P-2 subfraction. High resolution mass spectroscopy results suggest

the presence of thiophenes and benzothiophenes.

3.1.6 150N P-3 POLAR SUBFRACTION

Subfraction P-3 is eluted from the neutral alumina column with

methylene chloride solution containing low concentrations of ethanol

(0.75% - 2% by weight) and should contain moderately polar

compounds. Elemental analysis results in Table 12 suggest that

the oxygen content has increased significantly from 0.7% to 2.1% relative

to P-2. The molecular weight distribution (Fig. 17) indicates that P-3

contains mostly the same molecular weight compounds from the same base oil

but with a tailing distribution of high molecular weight materials to about

1500. The infrared spectrum in Figure 18b suggests possible nitrogenhydrogen amine bond at 3300 cm

-1 and strong carbonyi bonds in the'

1590 cm

-1 region indicating possible amides, Possibly sulfoxides are present in P-3> as indicated by the strong 1030 cm

-1 bond. High

resolution mass spectroscopy results suggests the presence of

quinolines, and carbazoles as nitrogen compounds.

3.1.7 150N P-5 Subfraction

Subfraction P-5 is eluted from the neutral alumina column with a stronger polar solvent of 10% ethanol in tetrahydrofuran. This subtraction should contain more polar compounds which have higher oxygen

and sulfur content as indicated by the elemental analysis results

shown in Table 12. The molecular weight distribution as shown in

Figure 17 indicates that P-5 contains more higher molecular weight

compounds than P-2 and P-3 subtractions from the same base oil.

The infrared spectrum of the P-5 subtraction in Figure 18c is similar

to the IR spectrum of the P-3 subtraction, suggesting the presence

of ni trogen-hydrogen, amine bond at 3300 cm

-1

; carbon-oxygen bond

at 1700 cm

-1

; aromatic carbon at 1600 cm

-1

; and sulfur-oxygen bond

at 1030 cm" 1

. High resolution mass spectroscopy of the P-5

subtraction suggest the presence of quinolines and carbazoles for

nitrogen compounds and thiophenes for sulfur compounds.

3.1.8 150N P-6 SUBFRACTION

The P-6 subtraction is eluted from the neutral alumina column with

methanol. This subtraction contains the most polar compounds of the polar

fraction and consists predomi nately of oxygenated compounds. Elemental

analyses shown in Table 12 confirm that P-6 contains the highest

proportion of oxygen (7.3%) among the polar subtractions. The molecular

weight distribution of the P-6 subtraction as shown in Figure 17

indicates that P-6 contains the most high molecular weight compounds

(about 3000) compared to the other polar subtractions from the same base oil. The infrared spectrum shown in Figure 18d shows a strong IR

absorption at 3350 cm

-1

, suggesting that a phenolic-OH group for the high

V

46
oxygen content of this subtraction. This is confirmed by the high

resolution mass spectroscopy results (Appendix D) indicating the presence

of phenolic alcohol in the P-6 subtraction. The absorption peak at

1735 cm

-1 suggests the presence of esters and sulfoxide peak (1030 cm" 1

) is also present. High resolution mass spectroscopy results suggest

the presence of quinolines, thiophenes, and phenols.

3.1.9 SUMMARY OF 150N POLAR SUBFRACTIONS

The chromatographic separation of the 150N polar fraction was achieved

on a neutral alumina column and various molecular compounds were eluted

off the column with solvents of different polarity. P-2 subtraction

contains the least polar compounds and P-6 subtraction contains the most

polar compounds. Elemental analysis results shown in Table 12 suggest

the P-2 subtraction has the least amount of oxygen while the P-6 subtraction has the most, while sulfur and nitrogen molecules are distributed

evenly among the four subtractions. Infrared spectra shown in Figure 18

suggest that P-2 subtraction contains predomi nantly aromatic compounds;

P-3 and P-5 subfractions contain amides, sulfoxides, and esters; P-6

sufraction contains phenols, and esters. High resolution mass spectroscopy

data (Appendix 0) suggests the presence of the following probable compounds

in each subtraction:

1. P-2, aromatic compounds;

2. P-3, thiophenes, amides, and sulfoxides;

3. P-5 carbazoles, quinolines, amides, and sulfoxides; and

4. P-6, phenols, esters, acids, and sulfoxides.

3.2 300N MID-EAST BASE OIL

3.2.1 300N SATURATE FRACTION CHARACTERIZATION

The 300N is a heavier cut than the 150N, i.e., the boiling points and

molecular weights are higher. The saturate fraction of the 300N is obtained

by the HPLC separation scheme (section 2.3). It has higher viscosities

and average molecular weight than the 150N saturates. The physical

property data are presented in Table 10.

Again, the saturate fraction of the 300N oil is pure when compared to the

base oil. The paraffinic content is high as evidenced by the increase

of viscosity index from 102 to 109 and the decrease of refractive index

from 1.4816 to 1.4749. The molecular weight distribution of the saturate

fraction is similar to those of the base oil as shown in Figure 19.

47
ARBITRARY

UNITS

(RFFRACTIVF

INDEX

RFSPONSF)

FIGURE 19. MOLECULAR WEIGHT PROFILE OF THE 300N BASE OIL AND ITS FRACTIONS

48
Elemental analysis results indicate little or no heteroatoms present

,

the amount of oxygen, sulfur, and nitrogen is well below 0.01%

(Table 11). The IR spectrum of the fraction shown in Figure 20b

indicates the absence of the hydroxyl, aromatic, and carbonyl bonds

at 3400, 1600, and 1700 cm

-1

, respectively.

3.2.2 300N AROMATIC FRACTION CHARACTERIZATION

The kinematic viscosity of this fraction at 40 °C is the highest of

the three base oils but the viscosity index is the lowest of all the

fractions, which suggests that the aromatic compounds in this fraction

have much stronger intermolecular attraction forces. This may be due to

the presence of more polar functional groups. The refractive index

value again is higher than that of the base oil (1.5214 vs. 1.4816),

indicating high aromatic content. The molecular weight profile as shown in Figure 19 indicates smaller molecules than other fractions.

Elemental analysis data in Table 11 show that the aromatic fraction

has the highest sulfur content among the major fractions of the 300N.

It is essentially free of nitrogen and oxygen-containing molecules.

The infrared spectrum in Figure 20c shows strong aromatic absorption

at 1600 cm

-1 and the absence of bands attributable to hydroxyl and

carbonyl bonds. These data tend to suggest the aromatic fraction contains

monoaromatics and thiophenes of lower molecular weight, hence lower

polarity than the aromatic compounds in the polar fraction.

3.2.3 300N POLAR FRACTION CHARACTERIZATION

The molecular weight distribution of the polar fraction presented

in Figure 19 shows the presence of high molecular weight compounds in

this fraction. The range of molecular weight is from 500 to 2000.

Elemental analysis data in Table 11 show most of the nitrogen- and

oxygen-containing compounds are concentrated in the polar fraction.

The infrared spectrum of the polar fraction (Figure 20d) shows the

presence of very strong hydroxyl, carbonyl , aromatic, sulfur-oxygen,

and amide bonds. This is confirmed by high resolution mass spectroscopy

results indicating the presence of nitrogen compounds such as homologs of quinoline; sulfur compounds such as homologs of thiophenes and oxygenated compounds such as esters, phenols, and acids.

3.2.4 COMPARISON OF THE 300N FRACTIONS

The separation of the base oil into the three major fractions is relatively

clean and most of the polar functional compounds are concentrated in the

49
Transmission

(%)

4000 3500 3000 2500 18001600 1400 800 200

Wavenumber (cm -1

) FIGURE 20. INFRARED SPECTRA OF HYDROCARBON

FRACTIONS OF THE 300N BASE OIL:

a) BASE OIL; b) SATURATE FRACTION;

c) AROMATIC FRACTION; d) POLAR FRACTION

50
polar fraction. The aromatic fraction of the 300N has the highest sulfur

content in contrast with the 150N base oil. The nitrogen, and

oxygen distributions are similar to the 150N. Molecular Weight (MW)

profiles show that the polar fraction contains a large amount of high

MW (2500) materials.

3.2.5 300N P-2 SUBFRACTION

This subfraction is eluted from the column with toluene. Similar to

the 150N P-2 subfraction, it has the lowest oxygen content of 0.4%,

and negligible nitrogen content (Table 12). The molecular weight

distribution curve shown in Figure 21 suggests a higher proportion of

high molecular weight materials than the 150N P-2. The infrared

spectrum in Figure 22 indicate the presence of strong aromatic peaks

at 1600 cm

-1

, 1500 cm" 1, and 1400 cm" 1

, suggesting mixtures of mono

and fused aromatic ring structures. The carbon-oxygen peak at about

1800 cm" 1 is very distinct and isol ated while P-3, P-5, and P-6 subtractions show much broader peaks, indicating the presence of some carbonates and anhydrides. High resolution mass spectroscopy results

suggest the presence of phthalates, indoles, and quinolines (Appendix D).

3.2.6 300N P-3 POLAR SUBFRACTION

The P-3 subtraction is eluted with methylene chloride with a small amount

of ethanol. Elemental analysis results in Table 12 suggest that P-3

contains the highest sulfur and nitrogen content among the 30QN polar

subtractions (2.28% sulfur, 1.9% nitrogen). The oxygen content has also

increased from 0.4% (P-2) to 1.2% (P-3). The molecular weight distributions

in Figure 21 indicate that P-2 is similar to P-3 except that P-3 has a high molecular tail distribution to 3000 MW. Infrared spectrum shown

in Figure 22 suggests nitrogen-hydrogen bonds at 3300 cm

-1

, carbon-oxygen

bonds at 1690 cm" 1 and 1710 cm"1

, and sulfur-oxygen bonds at 1030 cm- 1 wavenumbers. These peaks suggest the presence of carboxylic acids, amides,

and aromatic structures. High resolution mass spectroscopy results suggest

P-3 contains quinolines, carbazoles, phthalates. However, no significant

amount of sulfur compounds were identified. This may be due to the fact

that the sulfur containing compounds are not volatile enough to be

ionized* hence are not detected in the mass spectrophotometer.

3.2.7 300N P-5 POLAR SUBFRACTION

P-5 Polar Subfraction is eluted from the neutral alumina column with a polar solvent, 10% ethanol in tetrahydrofuran . The elemental analysis

results shown in Table 12 indicate that this subfraction has a lower

amount of nitrogen and sulfur than P-3 but has higher oxygen content

than P-3. The molecular weight distribution shown in Fiaure 21 has

the highest proportion of high molecular weight comoounds when compared

to polar subfractions. Infrared spectrum of the P-5

51
REFRACTIVE

INDEX

RESPONSE

Molecular Weight

FIGURE 21. MOLECULAR WEIGHT PROFILE OF THE POLAR SUBFRACTIONS

OF THE 300N BASE OIL

52
Transmission

(%)

3000 1600

Wavenumber (cm

" 1 ) FIGURE 22. INFRARED SPECTRA OF POLAR SUBFRACTIONS

OF THE 300N BASE OIL:

a) P-2 SUBFRACTION; b) P-3 SUBFRACTION

c) P-5 SUBFRACTION; d) P-6 SUBFRACTION

53
subfraction shown in Figure 22 is similar to that of the P-3 subfraction

suggesting the presence of similar compounds; nitrogen-hydrogen, amine

bond at_3300 cm

1

; carbon oxygen bond at 1700 cm” 1, aromatic carbon at

1600 cm” 1 and sulfur-oxygen bond at 1030 cm” 1

. High resolution mass spectroscopy results (Appendix D) suggests the presence of quinolines,

carbazoles, indoles, phthalates, and phenols. The increased oxygen

content and the high molecular weight are the two main characteristics

of P-5 compared with P-3, suggesting higher polarity of the same functional

groups.

3.2.8 300N P-6 SUBFRACTIONS

Subfraction P-6 is eluted from the neutral alumina column with methanol

and this subfraction should contain the most polar compounds. Elemental

analysis results listed in Table 12 suggest that the oxygen content of

this subfraction is the highest among the 300N subfractions. The

molecular weight distribution shown in Figure 21 suggests that the

molecular weight of P-6 subfraction is about the same as that of P-2

and P-3 but higher than the base oil itself. The infrared spectrum shown

in Figure 22 strongly indicates hydrogen-oxygen bond at 3400 cm" 1 and

carbon-oxygen bond at 1735 cm" 1

. Very little or no aromatic structure

at 1600 cm

-1 is apparent. High resolution mass spectroscopy results

(Appendix D) of the P-6 subfraction suggest the presence of phenols and

carboxylic acids.

3.2.9 COMPARISON OF THE 300N POLAR SUBFRACTIONS

The polarity of compounds in the polar subfractions are in the increasing

order of the P-2, P-3, P-5, and P-6. Elemental analysis results shown

in Table 12 suggest that the P-2 subfraction has the lowest amount of

oxygen compounds while P-6 has the highest oxygen content. Sulfur and

nitrogen compounds are present in P-3 and P-5 subfractions. Molecular

weight distributions shown in Figure 21 suggest P-2, P-3, and P-6

subfractions have relatively low molecular weight compounds while P-5

has the highest molecular weight compounds. Infrared spectra shown

in Figure 22 suggest the variation of the wavenumber of the carbonyl

peaks in each subfraction. Possibly the carbon-oxygen bond in P-2

is due to esters; in P-3 and P-5 it is due to aromatic carboxylic acids

and amides; in P-6 it is due to esters, and acids. High resolution mass spectroscopy data (Appendix D) suggest the presence of the following

possible compounds:

1. P-2, aromatic hydrocarbons, phthalates, quinolines,

carbazoles;

2. P-3, phthalates, quinolines, carbazoles;

3. P-5, phthalates, phenol, quinolines, carbazoles, indoles; and

4. P-6, phenols and carboxylic acids.

54
3.3 SOON MID-EAST BASE OIL

3.3.1 600N SATURATE FRACTION CHARACTERIZATION

The 600N is a heavier distillate than the 150N or the 300N. This is

reflected in the higher viscosities of the base oil as shown in

Table 10. The saturate fraction viscosities also reflect this trend

when compared to the 150N saturates and the 300N saturates. The

viscosity index changes from 93 (600N base oil) to 109 (600N saturate)

and the refractive index changes from 1.4907 to 1.4769. Both data again

indicate the paraffinic saturate content has been successfully isolated

by the separation method. The molecular weight distribution shown in

Figure 23 suggests that the saturate has the same distribution profile

as the base oil. Elemental analysis data in Table 11 again suggest

that this fraction contains little or no hetroatoms of nitrogen and oxygen.

The sulfur level is small (0. 09%) compared to the other 600N fractions,

but is much higher than the 150N and 300N saturate fractions. The infrared

spectrum in Figure 24 confirms the purity of the saturate fraction.

3.3.2 600N AROMATIC FRACTION CHARACTERIZATION

As the viscosities of the base oil increase from 150N to 600N, the

average molecular weight as well as the molecular weight distribution

will shift to the higher values. The average molecular weight

data in Table 10 reflect this change. As the molecular weight increases,

aliphatic side chains attached to the aromatic or other ring structures

will also increase. The viscosity index of the aromatic fraction is 99,

in fact higher than the base oil itself (93). The refractive index,

however, shows an increase from 1.4907 to 1.5039 suggesting more

aromatic content. The infrared spectrum in Figure 24 confirms this

observation. The aromatic peak at 1600 cm

- ' 1 is very distinct, but

the rest of the spectrum looks like the saturate fraction. This indicates

there are many mixed molecular structures where the aromatic ring

structures are often hidden in the aliphatic chains. This 600N aromatic

fraction is relatively free of nitrogen and oxygen compounds. Sulfur

in the form of thiophenes is present as evidenced from the elemental

analysis data in Table 11. The molecular weight distribution profiles

in Figure 23 suggest that the aromatic fraction has more low molecular

weight molecules than the 600N base oil and other fractions.

3.3.3 600N POLAR FRACTION CHARACTERIZATION

The 600N polar fraction appears to concentrate most of the heteratoms

present in the base oil, having the highest proportion of nitrogen (1.2%),

sulfur (2.19%), and oxygen (0.8%) compared to the 600N saturate and aromatic

fractions. When compared with the 150N and 300N polar fractions, the 600N polar

fraction has the lowest nitrogen and oxygen content and intermediate sulfur

55
REFRACTIVE

INDEX

RESPONSE

v o'5Cj'ar Weignt

F!3'JRE 23. MOLECULAR „EI3H7 =RCFILE OF THE 52CN 3ASE OIL

AND . . S r . . wNS

56
Transmission

(%)

Wavenumber (cm -1

) FIGURE 24. INFRARED SPECTRA OF HYDROCARBONS

FRACTIONS OF 600N BASE OIL:

a) BASE OIL; b) SATURATE FRACTION;

c) AROMATIC FRACTION; d) POLAR FRACTION

57
content. The molecular weight distribution profile of the 600N polar

fraction indicates much higher (up to 3700 ) molecular weight than

the other 600N fractions, as shown in Figure 23. Infrared spectrum in

Figure 24 suggests presence of hydrogen-oxygen, aromatic, sulfur-oxygen,

and carbon-nitrogen bondings. When compared with the 150N and 300N polar

fractions, the peak at 1775 cm

-1 is unique to this 600N polar fraction.

This may be due to the presence of cyclic anhydrides. High resolution

mass spectroscopy results (Appendix D) suggest the probable presence

of carbazoles, quinolines , thiophenes, esters, and organic acids. This

seems to support the infrared data.

3.3.4 COMPARISON OF THE 600N FRACTIONS

The separation of the 600N base oil appears to be clean. The distinction

between the saturate fraction and the aromatic fraction is not as pronounced as the 150N and 300N. The molecular weight of the polar

fraction is much higher than that of the other fractions. There is a progressive increase of molecular weights from 150N to 300N and 600N.

3.3.5 600N P-2 POLAR SUBFRACTION

The 600N polar fraction was separated on a neutral alumina HPLC column

as discussed in section 2.6. The four subfractions collected are designated as P-2, P-3, P-5, and P-6. P-2 subfraction is the fraction

eluted from the neutral alumina column with toluene. Elemental analysis

results in Table 12 show that this subfraction has relatively low oxygen,

high sulfur, and high nitrogen content among the 600N polar subfractions. The

molecular weight distribution of P-2 subfraction as shown in Figure 25

indicates that P-2 contains some high molecular weight compounds up

to 4000 MW. Infrared spectrum of P-2 shown in Figure 26 suggests that

there is little or no hydrogen-oxygen bond at 3400 cm

-1 but carbonoxygen bond and aromatic carbon are strongly indicated at 1700 cm" 1 1600 cm' 1

, and 1570 cm

-1 respectively. High resolution mass spectroscopy results (Appendix D) suggest the presence of phthalates, quinolines,

carbazoles , and thiophenes.

3.3.6 600N P-3 POLAR SUBFRACTION

P-3 subfraction is eluted from the neutral alumina column with methylene

chloride with 0.75% to 2% ethanol. Elemental analysis results in Table 12

shows that sulfur has dropped and oxygen and nitrogen has increased

over P-2. The molecular weight distribution shown in Figure 25

suggests that P-3 subfraction has the highest amount of high molecular

compounds among the 600N polar subfractions. Infrared spectrum of P-3

subfraction in Figure 26b suggests possibly nitrogen-hydrogen bond

at 3300 cm' 1

, carbon-oxygen bond at 1770 and 1690 cm" 1 and sulfur58
REFRACTIVE

INDEX

RESPONSE

FIGURE 25. MOLECULAR WEIGHT PROFILE OF THE POLAR

SUBFRACTIONS OF THE SOON BASE OIL

59
Transmission

(%)

4000 3500 30002500 1800 1600 1400 800 200

Wavenumber (cm

1 )

FIGURE 26. INFRARED SPECTRA OF POLAR SUBFRACTIONS OF 600N BASE OIL:

a) P-2 SUBFRACTION; b) P-3 SUBFRACTION

c) P-5 SUBFRACTION; d) P-6 SUBFRACTION

60
oxygen bond at 1030 cm

-1

. High resolution mass spectroscopy data (Appendix D)

suggest that phthalates, indole quinolines, carbazoles, and thiophenes

are present.

3.3.7 300N P-5 POLAR SUBFRACTION

Subtraction P-5 is eluted from the column with a polar solvent, 10%

ethanol in tetrahydrofuran. Elemental analysis results in Table 12

indicate the presence of high sulfur and high oxygen but low nitrogen

among the 600N polar subtractions. The molecular weight distribution

of P-5 subtraction is similar to P-2 and P-3 subtractions containing

high molecular weight compounds. The infrared soectrum shown in Figure 26

suggests hydrogen-oxygen bond at 3300 cm" 1

, carbon-oxygen bond at

1690 cm

-1

, aromatic structures at 1600 cm" 1 and sulfur oxygen bond at

1030 cm

-1

. The peaks between 1600 to 1800 cm

-1 and the peaks between

1000 to 1400 cm

-1 have decreased significantly. This suggests that the

functional groups have shifted from aromatic to more alkylated carboxylic

structures. High resolution mass spectroscopy data suggest the presence

of phenols, esters, indoles, and carbazoles.

3.3.8 60 ON P-6 POLAR SUBFRACTION

Subfraction P-6 is eluted from the column with methanol, and therefore,

this subfraction contains the most polar compounds. Elemental analysis

results listed in Table 12 indicate the highest oxygen content among all

polar subfractions of the three base oils. The carbon hydrogen ratio

has decreased from 8:1 to 7:1. The molecular weight distribution of

P-6 subfraction as shown in Figure 25 suggests that the P-6 subfraction

contains the lowest amount of high molecular weight compounds among the

600N polar subfractions, but still contains molecules of up to 2000 MW. It

should be noted that materials of high polarity, like P-6, could have

interacted with the polystyrene packing material in the gel

permeation column resulting in artifically low molecular weight

distribution profile. Infrared spectrum in Figure 26 suggest the

presence of oxygen-hydrogen bond at 3400 cm

-1

, carbon oxygen bond at

1775 cm" 1 as 2-lactone or chloride structures, and esters at 1735 cm" 1

, aromatic carbons at 1600 cm" 1

, and sulfur-oxygen bond at 1030 cm" 1

. High resolution mass spectroscopic data suggest the presence of phenols,

carboxylic acids, thiophenes, and esters.

3.3.9 COMPARISON OF 600N POLAR SUBFRACTIONS

Elemental analysis data of the four polar subfractions (Table 12)

suggest that more sulfur compounds are in P-2 and P-5 subfractions

but nitrogen compounds are evenly distributed among the subfractions.

However, oxygen compounds are concentrated in the P-6 subfraction as high as 17%. Molecular weight distribution of the subfractions shown in

61
Figure 25 suggest that the P-6 subtraction has the lowest amount

of high molecular weight molecules among the subtractions. Infrared

spectra (Figure 26) suggest that the carbon-oxygen bond at 1775 cm" 1 in P-3 and P-6 may be due to the presence of cyclic structures (such as ^-lactones) anhydrides or chlorides. The oxygen-hydrogen band at

3300 cm

-1 is observed in P-3, P-5, and P-6, but is absent in P-2.

The carbonyl bond attributable to ester linkage at 1735 cm

-1 is

observed in all subtractions. Sulfur-oxygen bond at 1030 cm"1 is

observed in P-3, P-5, and P-6. High resolution mass spectroscopy results

(Appendix D) suggest the presence of possibly the following structures.

1. P-2, aromatic hydrocarbons , phthalates, quinolines,

carbazoles, and thiophenes.

2. P-3, phthalates, quinolines, carbazoles, indoles, and

thiophenes.

3. P-5, phthalates, phenols, carboxylic acids, indoles,

quinolines, and carbazoles.

4. P-6, phenols, carboxylic acids, phthalates, and thiophenes.

3.4 COMPARISON OF FRACTIONS AND SUBFRACTIONS

In the previous sections, detailed analytical characterization of

an individual fraction and subfraction has been described and

compared within each base oil. The effectiveness and the extent of

the separation of the base oils into narrow compound classes have

been demonstrated. The data are summarized in Table 13 for easy

comparison of the separated compound classes from the three base

oils. The 150N and the 600N are refined from the same crude source.

The 300N is refined from another crude source in Middle East. Overall,

there are similarities among the separated fractions from these three

oils indicating the effectiveness of the separation method. There

are also differences among the fractions suggesting different initial

compositions, hence different compounds.

Table 13 lists the most probable molecular structures present in each

fraction and subfractions. There are the best estimates from infrared,

elemental analysis, high resolution mass spectroscopy. Molecular

information in C 20 plus compounds is usually diffused and complex.

Definitive structural determination will require further separations.

Overall, the separation of the base oils into saturates, aromatics, and

polars is very clean. The separation of the polars into molecular

compounds classes of varying polarity necessitates overlapping molecular

structures (but different polarity). One of the key pieces of information

is the molecular weight distribution since ofentimes the alkyl chain length,

or the molecular weight affects the oolarity of a macromolecule. Figures

27 to 33 compares molecular weight distributions of each fraction from the

62
Table

13

Comparison

of

Rase

Oil

fractions

in

Terms

of

Elemental

Analysis

and

Molecular

Structures

cmc

ro

to to u (U —

c 4-J to CJ to

ra

u ra

u

CL p^p

O 4-4

O 4-J to L. ra ra

OJ; ra E ra s- o 4-J o 3 i- i_ to sp^> to ro ra CD — ra a O OJ >* 3 to >j 3 •p— r— OJ *C

*P— 4-J

u o ,3 o 4-J to ra c. u CL

1/1

a c O ra -a O >> — -t—

—

s-

—

S_ F^— to o to

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M to

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to 3- C- CL ' C- G- CL 3 re s re ro o ra ra ro o o o — — E ra i— o ra u u 2: Z* 2Z s- s- - o O o

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u_ tu. cu- I 1 p— S- L. s_ CL ra ra

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tT3 ra re o o =0 <D CD <u o ^z «sz 3 c -3

i- S- L» 3 G .x -U> +4 4-J •f— 4-5 4-4 •p— 4-5 fD fC ra c c p— CD CD aj JZ f"" 3 3 — CL c. = sE ro -C -G .c 4-J Cl CL C“ C- C- m ro ro ro ro ro to in CO to CM ^4 O O o O* o o’ o o' o o CM V V V V V V

ai VO ro CO CT> o ro to CO CO

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of2

c

o

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0) JO

ra

to

<uc

<u JO

Q.o

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to CU to (D TO

<u •r-> s_ O s_ 3 a to o 4-> c CU r— u F— c JO 3 CU u

s_ 41 j:

4-> to to CL s_ tD cu f— o o

c o •*“ s_ •r- c JO CU

ra CU to 4-> c

r— o JO TO o

3 c CL «T— — 4-> u •F— u to u

<u 3 41 ra CU ra O- to TO I— o a o

s: — T— •r— X

CO o r— o to to <u -a ra >> 4- TO CU r— X r— T— TO

J3 u u o 3 a •f—

(TJ ra r— JO to ra X

4- JO F— i- o O </l o o >k ra 4k cj 4-

0) S- •r- X u to •4* F—

(/I S- Q_ r— o F— 3

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S- 3 4-> X s- to JO X

<U U to o ra <D o o - t— 3 O JO O r— u JO to

S- 22 i- O r— s- TO C 4J 1X3 — TO ra ra ‘r“ f- c/i o to C u CJ

CU •r— — ra to S- 4k 4-> u — C (O to ra • •r- to — O 1— r— f— to to

•F- 3 o tX3 s_ O o &. -M CJ c JO CU e c CU U CU a; 4-> 4-J CU CU 4-> fO r— JO JO to -c JO to

S- O CL CL CU CL CL CU u_ 2: r— -O

•*- C O ra

O) vo to

(T3 to CO >1

CSJ ao cr> CO CO o 4- "(0 o • • 4 4 4 4 O C CO CSJ ra* r««. <c F—

t

c

o

to ra f- 4-> s- c

1X3 CU CL E C\J ID CO r4 r«- F—

t

E <u ID VO ID H ra

- CNJ o i— <D • • • 4 4 '4F O UJ CO F*^J CSJ CO o F—t

c\j co co

f—t H O

owe 4 4 4 «-H O O

ID

I o_

oo o

o •—i co tD VO o o o LD O O «—t CO to

64
three base oils. Generally, the molecular weight increases from

150N fractions to 600N fractions, but there are a few exceptions

in the polar subfractions.

In the polar subfraction separation, the data in Table 13 suggest

that P-2 and P-6 are the most different. P-2 fractions are generally

mostly polynuclear aromatics but contain little or no oxygenated

compounds. P-6 fractions are mostly oxygenated compounds with few

aromatics. The P-3 and P-5 fractions have overlapping structures

between these two extremes.

65
REFRACTIVE

INDEX

RESPONSE

FIGURE 27. COMPARISON OF THE MOLECULAR WEIGHT PROFILES

OF THE SATURATE FRACTIONS FROM BASE OILS

66
REFRACTIVE

INDEX

RESPONSE

37K. 3K 395 255

MOLECULAR WEIGHT

FIGURE 28. COMPARISON OF THE MOLECULAR WEIGHT PROFILES OF

AROMATIC FRACTIONS OF BASE OILS

67
REFRACTIVE

INDEX

RESPONSE

i

FIGURE 29. COMPARISON OF THE MOLECULAR WEIGHT PROFILES OF THE

POLAR FRACTIONS FROM THE THREE BASE OILS

68
REFRACTIVE

INDEX

RESPONSE

FIGURE 30. COMPARISON OF THE MOLECULAR WEIGHT PROFILES OF

P-2 SUBFRACTIONS FROM THE THREE BASE OILS

69
REFRACTIVE

INDEX

FIGURE 31. COMPARISON OF THE MOLECULAR WEIGHT PROFILES

OF P-3 SUBFRACTIONS OF BASE OILS

70
REFRACTIVE:

INDEX

RESPONSE

1

FIGURE 32. COMPARISON OF THE MOLECULAR WEIGHT PROFILES OF

P-5 SUBFRACTIONS P-5 OF BASE OILS

7 1
refractive

index

response

FIGURE 33. COMPARISON OF THE MOLECULAR WEIGHT PROFILES OF

P-6 SUBFRACTIONS OF BASE OILS

72
References

1. Sands, T.P., "Comments on Additive Response to Different Base

Oils," NBS SP 488, 1977.

2. Patir, N. and Cheng, H.S., "Effect of Surface Roughness Orientation

on the Central Film Thickness in EHD Contacts," Proc. 5th LeedsLyon Symp. on Tribology, Mech. Eng. Publ . Ltd., England, 1979.

3. Hamrock, B.J. and Dowson, D., "Minimum Film Thickness in Elliptical

Contacts for Different Regimes of Fluid Film Lubrication,"

Proc. 5th Leeds-Lyon Sump, on Tribology, Mech. Eng. Publ. Ltd.,

England, 1979.

4. Cheng, H.S. and Dyson, A., "Elastohydrodynamic Lubrication of

Circumferential ly Ground Rough Discs," ASLE Preprint No. 76-LC-1A-2,

1976.

5. Hsu, S.M. and Klaus, E.E., "Estimation of Molecular Junction

Temperatures in Four-Ball Contacts by Chemical Reaction Rate Studies,"

ASLE Trans., 21, 201-10, 1978.

6. Bowden, F. P. and Tabor, D., "The Friction and Lubrication of Solids,"

2nd Ed., Clarendon Press, London, England, 1954.

7. Greenhill, E.B., "The Adsorption of Long Chain Polar Compounds

from Solution on Metal Surfaces," Trans., Far. Soc., 45, 625-31,

1949.

8. Sanders, J.V. and Tabor, D., "Structure of Thin Films of Aliphatic

Esters and Alcohols on Metals," Proc. Roy. Soc., 204, 525-33, 1951.

9. Goldblatt, I.L., "Model for Lubrication Behavior of Polynuclear

Aromatics," I & EC Product Research and Develop., 10, 3, 270, 1971.

10. Goldblatt, I.L. and Appledoorn, J.K., "The Anti-Wear Behavior of

TCP in Different Atmosphere and Different Basestocks," ASLE Trans.,

13, 1970.

11. Groszek, A.J., "Heats of Preferential Adsorption of Surfactants

on Poruous Solids and its Relations to Wear of Sliding Steel

Surfaces," ASLE Trans., 5, 1962.

12. Groszek, A.J., "Heats of Preferential Adsorption of Boundary

Additives at Iron Oxide/Liquid Hydrocarbon Interfaces,"

ASLE Trans. , 13, 1970.

73
13. Hsu, S.M., Ku, C.S., and Lin, R.S., "Relationship between

Lubricating Basestock Composition and the Effects of Additives

on Oxidation Stability," SAE Reprint #821237, December 1982.

14. Sawatzky, H., George, A.E., Smiley, G.T., and Montgomery, D.S.,

"Hydrocarbon Type Separation of Heavy Petroleum Fractions,"

Fuel, 55, 16, 1976.

15. Vogh, J.W. and Thompson, J.S., "Preparative Liquid Chromatography

for Fractionation of Petroleum and Synthetic Crude Oils,"

Anal. Chem., 53, 1345, 1981.

16. Suatoni , J.C., Garber, H.R., and Davis, 3.E., "Hydrocarbon Group

Types in Gasoline-Range Materials by High Performance Liquid

Chromatography," J. Chromatography Science, 13, 367, 1975.

17. Suatoni, J. C., and Swab, R.E., J., "Rapid Hydrocarbon GroupType Analysis by High Performance Liquid Chromatography,"

J. Chromatography Science, 13, 361, 1976.

18. Suatoni, J.C., and Swab, R.E., "Preparative Hydrocarbon Compound

Type Analysis by High Performance Liquid Chromatography,"

J. Chromatography Science, 14, 535, 1976.

19. McKay, J.F. and Latham, D.R., "High Performance Liquid

Chromatographic Separation of Olefins, Saturate, and Aromatic

Hydrocarbons in High Boiling Distillates and Residues of Shale

Oil," Anal. Chem., 52, 1618, 1980.

20. Radke, M., Willsch, H., and Welte, D., "Preparative Hydrocarbon

Group Type Determination by Automated Medium Pressure Liquid

Chromatography," Anal. Chem., 52, 406, 1980.

21. Jewell, D.M., Wober, J.H., Bunger, J.W., Plaucher, H., and Latham, D.R.,

"Ion-Exchange, Coordination and Adsorption Chromatographic Separation

of Heavy-End Petroleum Distillate," Anal. Chem., 44, 1391, (1972).

22. Holmes, S.A., "Artifacts from Ion-Exchange and Coordination-Complex

Chromatography: Effect upon Characterization of Nitrogen Compounds

in Shale Oil", Paper #172, 1982 Pittsburgh Conference, Atlantic

City, NJ, March 1982.

74
APPENDIX A

CHARACTERIZATION OF FRACTIONS FROM

LARGE SCALE ALUMINA COLUMN CHROMATOGRAPHY

75
Table A1

Activated Alumina

Wt. % Distribution of Base Oils

Pure Fraction

Pentane Eluted

Oil Fraction

Acetone Eluted

Fraction

Mid-East ( 150N

)

49 48 2

Mid-East (600N) 35 61 3

Re-refined (350N) 58 39 3

76
Table

A2

Physical

and

Chemical

Properties

ofa

350N

Re-refined

Base

Oil coo -M

CU <T3 CM r—1 m c s- CO r^. a> O U- CO o +-*

LO o

cu "O . • • * • • a cu T~H H o o o 00 CO C 4-> CO CM CO A 3 in V /\

LO

1'-- CM

a)to

<T3 CO

-a

cu£

<U

s-I a) oc

CU

O r-. £ UD cd

«3 T3 CO

4-> CU CO o £ +-> • . • • CU 3 f-H o CO O'! Q_ i—

LU i—i

<d oo o

CM

CMo o

in

CO CO

CU CD CD

S- r— r-* in 3 -r- *3" CO CO o

Q_

O . • • • r-H o in CO CO CO r-l to o CD _J

rH o o CU in CO

to i

CO r-> CO •!— xcf 00 in

CQ

O • •

•• • • r-H o CO CD CM to

r-»

O o _i

cu

r-H in

JO3

+J

S- CD CU £ +-> T3 cu O 00 -M E o CM o

JSZ r-H fO •(— in in r". o o

+-> CM S- to *3- CM in in

cu

r—1

-Q £ CM CM r-H o

•r- CU > Q o Q o Q

O ooVoCMO

CM

inmo

i-oo

CO

4-> £

COEo 4-> +j ’oE

C_) CO S 4-> l— -r- 11

cS-S 3 cn cn tn £ | +j CD o o CD < 3 1 3 u o X o

CU o X CO -a o o cu 4-> £ f-H -a • ra >, —i £ 4-> O +> c& CHi i—i 3

S_ CU • CU > >> 50 >> • a

Cl •p* +-> +> 4-> i— to O +-> >> •»

•r— *iO -r- S- o +-> to to to s >

D. (T3 •r- o o O

s_ to

a o a • E o

4- £ to to to CD

O r—

CU CU •r— > sO

a; o > > > <c 4- c_>

s_3

CO

77

Total

Acid #

MgKOH/gOi 1D

664

0.18

0.03

0.10

0.74
Table

A3

Physical

and

Chemical

Properties

ofa

150N

Virgin

Base

Oil i i "O u

0) <o c s- O U.

qj -a U QJ «t 4-> 3

CDOCDID

OID

CM

ID

00 oV ,— O CD 1 •r— fli fO T“H 1 o c s- CO co 1 r>- CO CO LD l 'S' 0) 4-> • i • • 1 * 1 • </) r-H r-H ID CM O 1 O 10 5 <u CO O _J 1 CD a.

+-> 1 3 1 C . 1 •f* LxJ 1 CD 1 S- 1 • r— C 1 > o LO 1 (U ' r~ CO ID 1 00 z 2. LD rH o o o 3 <-> • • • 1 • LD (£ <T3 r-H oo LD CD o o 1-H s_ C\J O 1 Li- r-H 1

CO LD 11 ft) o CO 1

(/) i-. CO LD LD CO 1 ID

-r- cr 00 o CM LD 1 CO CQ O t—H o o' ID •S’ «=)- o’ 1 o CO o o 1

<u s_ JO QJ -ao 00 3 +-> 1— QJ

r— o CM

-1Z fH

C ID ID r^.

O +J CVJ OVr- 'S’ CM ID

QJ

C CO <r 'S’ CM CM

s: o

•r—

C

-M <D

ra

O o a

O o

s- JD

OoIDa

$-o 5 oo to

id c < =3

CM

ID

IDO

X

uo o

a)

O

X

a o o ft) 4-> c r-4 a • <o >1 c M O 4-> C2> o -H 2 s_ ft) • QJ > >> >* >* • u

Q. 4-> 4-> *— to O 4-> >> -v— T— O -r- i- U 4-» to to to z >

Q. <o

O o o u

u LO o u

u • E o L*- c 1/1 1/1 l/l CD O

ai ft) •»— f— > t- o

a: o > > > < «4- o

s_3

l/i

78

Total

Acid #

MgKOH/gOil D

664
Table

AA

Physical

and

Chemical

Properties

ofa

600N

Virgin

Base

Oil o

in

rai -o

u

0) <TJ c s_ o u_

+J

a) -a U CL) < -M3

oo

onin

LO ocn

CMCM

COCM

COCM

<d

in

ra CO

CD

s-

<_> <D ra C i- <a u_ 4-> c -a

CD CD a. -m3

<Ti Ocn

"O' LO

CO

COo

CM

'O' cn

O')

r*. o ooCO o

CD •<— i- -4-> 3 U

a. ras_

CO

CMCO

*0" CO

LO

LO00

*d-

'O- o

LOo

a>

LO r—

ra •«- CO O oCP)

•O'

*0-

r^. CO

CO

O')

r^. o

CM

LO

cn

O') CM

LO

LOCM

LO

CO

CD i- J2 0) 3 -M 11 -o J— <D o 00 £ o CM o CM

.c OV-r- in LO o O 1 LO M CM C L0 'O' CM LO in 1 LO

CD •rC CM CM r*H s; Q

4-> 0)

ra

QS_ JO

aQQQa || o

•r— > $- i oo

L0

O 1 -M m r— CO 1 •r— E O S -M 1 c u 4-* •M E H* **— • =5 in LO in c | 4-> O) o O a> =0 1 3 o oo 1 X o | CD o X <a •o o o CD *-» | c ^r rH TJ • <a > C M Q I •M 
 <s« 1—H 3 1 <u • | a> > >> >> >» • u

Cl 4J •MM r— LO | O 4-> >> *r“ •T— o

su 4-> LO LO LO z > s_ o. <a o O O s- 1 3

s_ LO

u

u

U • E o 4-

H- c LO LO LO cn o

CD <D •v* •r* > 4- o , 3

a:O > > > C <4- <_> 1 in

79

Total

Acid #

MgKOH/gOI 1D

664
Q£

etI OCL.

C_) c o o LiJ LlJ o h- 1

hH ID ZD 1— 1 1 o UJ LU <q; UJ LU

Ll_ Zo LU h- 1—

cd LU

ZD UJ

O

Q_ Cl cl A A A «—I | C\J I OO I

LlJ UJ

O

LU

1/1 «C

CO Q.

O

CCo

C_J

C/1

«=£ o;<t

Q.

LlJ C/1 Q

q:o

c;ZD

C3

80

ACTIVATED

PREPARATIVE

ALUMINA

COLUMN
FIGURE A2- IR SPECTRA OF FRACTIONS FROM ACTIVATED ALUMINA COLUMN

(a) Original Oil

(b) Pure Fraction

(c) Pentane Eluted Fraction

(d) Acetone Eluted Fraction

8 1
Appendix B

CHARACTERIZATION OF SEPARATED FRACTION

FROM ASTM D-2007 METHOD

82
80

60

40

20

80

60

3400 3000 2200 1800 1400 1000 600

Wave Number (cm" )

FIGURE Bl. INFRARED SPECTRA OF FRACTIONS OF

OIL D BY ASTM D2007 METHOD

83
Appendix C

CHARACTERIZATION OF FRACTIONS FROM

ION-EXCHANGE COLUMN CHROMATOGRAPHY

IR spectra of these isolated fractions are illustrated in Figures Cl

and C2. Molecular weight profiles of the polar subfractions are shown

in Figures C3, C4, and C5 obtained by Gel Permeation Chromatograms (GPC).

IR spectra of the polar subfractions from the ion-exchange column do show

similar IR bands except the neutral fraction (POLB-1) which does not have

the NH/OH" band. This is expected as POLB-1 should not contain any phenols,

acids, and amines.

The molecular weight profile for the POLB-1, neutral fraction is similar

to the polar fraction. Both GPC curves of basic fractions POLB-2 and

B-3 are very uniform with even Gaussian distribution with peaks at

300 and 500 molecular weight. However, for the acidic fractions, the apparent

molecular weight profile is very broad covering a range of high molecular

weight from 100 to 100,000 mw.

Two performance evaluation tests have been applied on these neutral acid

and base fractions. The tests are the antioxidant titration method

developed by Mahoney [cl] and the micro-sample step loading seizure test

developed by Gates and Hsu[C2]. The antioxidant test is intended to

determine the oxidation stability of the base oils and the microsample step loading seizure test is designed to measure an oil's antiwear

behavior under boundary lubricating conditions. The result of both

tests are listed in Tables Cl and C2. The antioxidant value of a 350N

base oil is 0.009 X 10" 3 mole/g but the polar fraction has a value

of 0.305 x 10-3 mole/g. This value indicates that the neutral and acidic

polar subfractions have very high antioxidant capacities. Phenols in

P0LA-2 and P0LA-3 and the amides in the neutral, POLB-1 are suspected

of being responsible for the high antioxidant values. In the case of the

micro-sample step loading seizure test, the test results indicate that the

neutral fraction (POLB-1) can effectively increase the seizure load

from 180 kg to 300 kg with the addition of 1.9% of POLB-1. However,

the wear scar diameter measurements do not show any difference among

the polar subfractions by ion-exchange resins.

84
Appendix C - References

Cl. Mahoney, L.R., Korcek, S., Hoffman, S., and Willermet, P.A.,

"Determination of the Antioxidant Capacity of New and Used

Lubricants; Method and Applications," Ind. Eng. Chem. Prod.

Res. Dev., Vol . 17, No. 3, pp. 250-255, 1978.

C2. Gates, R.S., and Hsu, S.M. "Development of an Oxidation-Wear

Coupled Test for the Evaluation of Lubricants," ASLE Preprint

No. 82-LL-1D-2

85
Table Cl

The Anti -Oxidant Values from the Polar Subfraction

by Ion-Exchange Resin Columns

Anti -Oxidant Value

Re- refi ned Base Oil 0.009 X 10" 3

Polar faction 0.305 X 10' 3

POLB-1 Neutral 1.3 X 10" 3

POLB-2 —

0.59 X 10" 3

POLB-3 Basic 0.085 X 10' 3

POLB-4 JNot determined

POLA-2 1.06 X 10" 3

POLA-3 > Acidic 1.70 X 10‘ 3

POLA-4 Not determined

86
Table C2

Micro Sample Loading Seizure Test Results on the Polar Subtractions by Ion-Exchange Column

Seizure Load Wear Scar Diameter

kc| mm

RB0033 > 300 0.69

RB0033 Sat. 180 0.61

RB0033 Sat. + 1.9% Neutral

(P0LB-1)

> 300 0.69

RB0033 Sat. + 1.9% Acid

(POLA-2)

> 270 0.655

RB0033 Sat. + l.(% Basic B2)

225 0.69

RB0033 Sat.

B3

165 0.61

Conditions

Apparatus: NBS Modified Four-Ball Wear Tester

Speed: 400 rpm

Load: 15 mg increments

Duration: 30 second intervals

Atmosphere: 0.25 2,/mi n dry Air

Lubricant: 6 yil samples

87
FIGURE Cl. IR SPECTRA OF POLAR ACIDIC SUBFRACTIONS

ROM ION-EXCHANGE COLUMNS

(a) Polar Fraction

(b) Polar A-2 Sub-Fraction

(c) Polar A-3 Sub-Fraction

(d) Polar A-4 Sub-Fraction

88
%

T

RA

N

SM

IS

S

I0

N

i i i i t i i i 4000 2500 2000 1800 1600 1400 1200 1000 800 600

FIGURE C2. IR SPECTRA OF POLAR BASIC SUBFRACTIONS FROM

ION-EXCHANGE COLUMNS

(a) Neutral Subfraction POLB-1

(b) Basic Subfraction POLB-2

(c) Basic Subfraction P0L3-3

89
oinomooinoooooooo

90

FIGURE

C3.

MOLECULAR

WEIGHT

PROFILE

OF

POLAR

FRACTIONS

AND

ITS

NEUTRAL

SUBFRACTION

BY

ION-EXCHANGE

COLUMNS
91

FIGURE

C4.

MOLECULAR

WEIGHT

PROFILE

OF

THE

ACIDIC

SUBFRACTION

BY

ION-EXCHANGE

COLUMN

IN

COMPARISON

TO

POLAR

FRACTION
92

FIGURE

C5

.

MOLECULAR

WEIGHT

PROFILE

OF

BASIC

SUBFRACTIONS

(POLB-2

AND

POLB-3)

OF

THE

POLAR

FRACTION

SEPARATED

BY

ION-EXCHANGE

COLUMN
APPENDIX D

CHARACTERIZATION OF POLAR FRACTION AND SUBFRACTIONS

FROM NEUTRAL ALUMINA COLUMN CHROMATOGRAPHY BY

HIGH RESOLUTION MASS SPECTROMETRY

ANALYTICAL PROCEDURES:

Mass spectra were recorded at a resolution of approximately 10,000 using

direct probe introduction and electron impact ionization. A relatively

stable ion current could be maintained for several minutes at a probe

temperature of 100 °C, thereby allowing several spectra of each sample

to be recorded. The spectra were then averaged by the computer. In

order for an ion to appear in the final report, it must have appeared

in at least two of the scans.

RESULTS:

The summary report format gives the summed intensities of all the ions

of a particular heteroatom content, distributed by the degree of

unsaturation.

93
TABLE D1

ELEMENTAL DISTRIBUTION OF THE 150N POLAR FRACTION BY

HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 52

-2 213 63

-4 242 83 34

-6 255 40 10 23

-8 228 16 89 14

-10 83 16 488 11

-12 141 28 894

-14 123 17 1035

-16 14 1059

-18 101 15 876

-20 41 494

-22 34 216

TOTAL 1527 32 246 5161 82

TOTAL INTENSITY OF UNASSIGNED IONS: 90

94
TABLE D2

ELEMENTAL DISTRIBUTION OF THE 150N P-2 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 136 4 78

-2 343 30 4

-4 276 60 5 -6 175 40 10 12

-8 132 6 48 150

-10 79 24 164 3

-12 73 46 272 4

-14 82 303

-16 28 267

-18 40 9 264 4

-20 18

• 174

-22 89

-24 3 38

-26 4 36

-28 4 36

-30 4

TOTAL 1393 6 261 1885 32

TOTAL INTENSITY Of UNASSIGNED IONS: 405

95
TABLE D3

ELEMENTAL DISTRIBUTION OF THE 150N P-3 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 48 6 6

-2 211 102 18

-4 228 62

-6 158 24 11

-8 176 15 133 4

-10 53 5 10 303 5

-12 92 615

-14 90 638

-16 31 590

-18 39 4 519

-20 26 236

-22 8 71

-24 6

-26 6 8

-46 6

TOTAL 1178 9 219 3174 33

TOTAL INTENSITY OF UNASSIGNED IONS: 289

96
TABLE D4

ELEMENTAL DISTRIBUTION OF THE 150N P-5 POLAR FRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 61 8

-2 239 18 25

-4 326 32 24

-6 329 10 23

-8 349 30 31 22 15

-10 98 27 148

-12 169 12 304

-14 124 304

-16 58 325

-18 113 13 157

-20 18 43

-22 9

-24 9

-26 12

TOTAL 1905 70 12 89 1322 87

TOTAL INTENSITY OF UNASSIGNED IONS: 117

97
TABLE D5

ELEMENTAL DISTRIBUTION OF THE 150N P-6 POLAR FRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 49 7

-2 250 100 19 15 21

-4 310 14 13 22 24

-6 284 40 20

-8 342 97

-10 129 57 78

-12 226 40 19 279

-14 163 342

-16 95 50 298

-18 219 169 148

-20 106 86 53

-22 36 13

1 CsJ *3" 12

-26 5

-42 13

-44 7

TOTAL 2226 613 32 123 1211 65

TOTAL INTENSITY OF UNASSIGNED IONS: 155

98
TABLE D6

ELEMENTAL DISTRIBUTION OF THE 300N POLAR FRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 84 5 20

-2 269 11 35 26

-4 252 18 42

-6 214 43 33 18

-8 219 35 62 16 15

-10 61 83 77

-12 138 9 37 240

-14 74 9 6 216

-16 19 11 183

-18 19 13 204

-20 16 13 101

-22 21 13 37 15

-24 11 15

-26 7

-28 13

-30 12

-32 6 23

-34 5 50

-36 9 26 21

-38 10 34

-40 41 34

TOTAL 1423 144 103 325 1147 207

TOTAL INTENSITY OF UNASSIGNED IONS; 387

99
TABLE D7

ELEMENTAL DISTRIBUTION OF THE 300N P-2 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1

0 160 17

-2 461 29

-4 465 155

-6 296 194

-8 258 205 32

*H o

1 82 129 181

-12 109 112 524

-14 80 66 910

-16 18 1068

-18 26 43 1038

-20 685

-22 429

-24 112

TOTAL 1937 43 925 4979

TOTAL INTENSITY OF UNASSIGNED IONS: 138

100
TABLE D8

ELEMENTAL DISTRIBUTION OF THE 300N P-3 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1

0 32

-2 177 82

-4 146 247

-6 82 130

-8 145 27 202 23

-10 18 181 114

-12 43 110 994

-14 27 1300

-16 34 50 1589

-18 1633

-20 1172

-22 801

-24 190

-26 73

-30 23 32

TOTAL 700 27 1061 7889

TOTAL INTENSITY OF UNASSIGNED IONS: 289

101
TABLE D9

ELEMENTAL DISTRIBUTION OF THE 300N POLAR P-5 SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 62

-2 253 8 56 38

-4 275 81

-6 212 115 8

-8 162 51 13 48 40

-10 51 3 25 205

-12 58 18 418

-14 67 7 3 342

-16 31 420

-18 17 326

-20 6 155

-22 64

-24 11

TOTAL 1163 100 13 346 1989 38

TOTAL INTENSITY OF UNASSIGNED IONS: 167

102
TABLE DIO

ELEMENTAL DISTRIBUTION OF THE 300N P-6 POLAR SUBFRACTION

’ BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02

0 5 -2 21 18 4

-4 10 3 3

-6 5 -8 4 1

-22 1

CH03 CHN1 CHS1

1

TOTAL 46 22 1

TOTAL INTENSITY OF UNASSIGNED IONS: 136

103
TABLE Dll

ELEMENTAL DISTRIBUTION OF THE 600N POLAR FRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 51 6

-2 215 8

-4 205 19 38

-6 89 25 21

-8 146 10 18 14

-10 49 37 24

-12 53 11 88 4

-14 15 5 153 7

-16 29 180

-18 12 149

-20 4 7 84

-22 59

-24 5

-26 6 12

-28 4

TOTAL 878 10 13Q 768 76

TOTAL INTENSITY OF UNASSIGNED IONS: 259

1Q4
TABLE D12

ELEMENTAL DISTRIBUTION OF THE 600N P-2 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 330 16 15

-2 473 47 8 30 6 16

-4 322 42

-6 173 8 5

-8 249 15

-10 150 6 12

-12 87 37 71 8

-14 80 6

-16 23 10 34

-18 22 20 63

-20 15 31

-22 21 4

-24 9 11

-30 8

TOTAL 1917 118 55 182 155 56

TOTAL INTENSITY OF UNASSIGNED IONS: 267

105
TABLE D13

ELEMENTAL DISTRIBUTION OF THE 600N P-3 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 62 36

-2 283 9 58 21

-4 306 283 23

-6 348 245 11 25

-8 311 15 112 93 36

-10 84 17 288 358 50

-12 136 11 199 525 39

-14 111 15 15 133 590

-16 69 13 11 56 798

-18 175 9 65 564

-20 21 32 545

-22 107 13 282

-24 26 147

-26 95 24 91

-28 9 39

-30 52

-32 15

TOTAL 2210 108 76 1475 4043 194

TOTAL INTENSITY OF UNASSIGNED IONS: 266

106
TABLE D14

ELEMENTAL DISTRIBUTION OF THE 600N P-5 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 89 10

-2 283 45 45 34 25

-4 350 31 16 38 27

-6 363 14 37 12

-8 323 58 25 23

-10 143 20 11 116 12

-12 146 11 199

-14 120 155

-16 69 19 143 8

-18 83 14 131

-20 18 18 49

-22 16

-24 16 7

-26 22

-28 18

-30 12

-36 10

-42 11

-44 11 10

-46 24

TOTAL 2021 232 106 203 823 105

TOTAL INTENSITY OF UNASSIGNED IONS: 436

107
TABLE D15

ELEMENTAL DISTRIBUTION OF THE 600N P-6 POLAR SUBFRACTION

BY HIGH RESOLUTION MASS SPECTROMETRY

(ION-INTENSITY UNITS)

UNSAT. CH CHOI CH02 CH03 CHN1 CHS1

0 7 1 1 -2 21 105 19 3 1 -4 19 16 14 4

-6 12 1 1 1 -8 11 1 -10 4 2

-12 2 4 1 -14 1 1 -16 1 -18 1 1

-20 1

-22 1

-24 1

-26 2

-28 1 1 -30 1 1

-36 .1 -42 1 -44 1 -46 11 7 1 1

TOTAL 81 138 49 12 3 5

TOTAL INTENSITY OF UNASSIGNED IONS: 45

108
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 84-2821 (DOE)

2. Performing Organ. Report No. 3. Publication Date

February 1984

4. TITLE AND SUBTITLE „ , , „ , , . Friction and Wear Characteristics of Molecular Compound Classes from Lubricating

Base Oils/ Part 1. Separation and Chemical Characterization

5. AUTHOR(S)

S. M. Hsu, P. Pei, and R. S. Gates

6 . PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7 . Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State. ZIP)

National Bureau of Standards

Room A215/Building 220

Washington, DC 20234

10.

SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

A high performance liquid chromatography separation scheme which subdivides three

lubricating base oils into molecular compound classes has been developed. These

compound classes were characterized analytically and also with regard to oxidation,

friction, and wear characteristics. In part 1 of this report, the separation scheme and

chemical characterization of the fractions are described.

The separation scheme is subdivided into two stages. During the first stage, the

lubricating base oil is separated into three major fractions-- saturates, aromatics, and

polars using clay-silica gel liquid chromatography. The saturate fraction consists

mainly of paraffinic and cyclic paraffinic compounds. The aromatic fraction is composed

of mono-, di - , and tri -aromatic compounds. Both polynuclear aromatic compounds and

hetroatoms such as nitrogen, sulfur, halogen, and oxygen are present in the polar

fraction. The polar fraction is found to have the most influence on performance. The

polar fraction is further separated into narrow molecular compounds classes having

different polarities and functional structures via neutral alumina column chromatography

Analytical methods such as elemental analyses, infrared and high resolution mass spectrometry were used to elucidate the functional structures of the compounds in each

fracti on.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) HPLC; hydrocarbon separation; liquid-solid chromatography; lubricating base oilsj

molecular structural influence; polar molecules; structural characterization; tribology

13.

AVAILABILITY

Uni imited

| | For Official Distribution. Do Not Release to NTIS

[~n Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

[j£] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

114

15. Price

$13.00

USCOMM-DC 6043-P80

* U.S. GOVERNMENT PRINTING OFFICE: 1984 0 - 420-997 (76)