NATIONAL BUREAU OF STANDARDS REPORT

5436

SEPARATION OF THE WATER-SOLUBLE

DEGRADATION PRODUCTS OF ASPHALT

by

Sidney H. Greenfeld

John P 0 Falzone

Shigeru Ishihara

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT

1004-11-1017 August 14, 1957

NBS REPORT

5436

SEPARATION OF THE WATER-SOLUBLE

DEGRADATION PRODUCTS OF ASPHALT

by

Sidney H. Greenfeld

John P. Falzone

Shigeru Ishihara

Research Associates

Asphalt Roofing Industry Bureau

Floor, Roof and Wall Coverings Section

Building Technology Division

Jointly Sponsored by

Asphalt Roofing Industry Bureau

and

National Bureau of Standards

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U. S. DEPARTMENT OF COMMERCE

SEPARATION OF THE WATER-SOLUBLE

DEGRADATION PRODUCTS OF ASPHALT

by

Sidney H c Greenfeld

John P. Falzone

Shigeru Ishihara

SUMMARY

Several methods for separating the water-soluble

degradation products of asphalt, including paper and

column chromatography, ion exchange, sublimation, derivative formation and liquid-liquid, pH and liquid-solid

extraction, were evaluated. Only the liquid-solid extraction gave reasonably quantitative and reproducible

results. However, during a secondary breakdown by this

procedure some of the materials apparently polymerized

and lost oxygen. It was decided that none of the

techniques investigated was adequate to separate the

water-soluble degradation products quantitatively and

reproducibly without changing some of them.

1. INTRODUCTION

During the course of studying the mechanism of degradation of asphalt, it became apparent that the asphalt itself

was too complex to yield the solution to the problem if

studied only in its entirety. Observation of changes taking

place in certain components of asphalts!/ during exposure

indicated that even the components were too complex for

satisfactory evaluation and that further separations would

be necessary if this approach were to be continued.

The components that were separated were subjected to

ultimate chemical analysis!' and though considerable light

was thrown on the process of degradation, the mechanism of

was still obscure

"" Greenfeld, S. H. , "The Degradation of Two Coating Asphalts"

NBS Report No. 4621, April 16, 1956.

—Greenfeld, S.H„

,

"The Chemical Changes Occurring During the

Degradation of Two Coating Asphalts", NBS Report No 0 4861,

October 1, 1956.
*'
- 3

-

remove any contaminating cations-5/. The solutions became

appreciably lighter during this treatment. The solutions

were then evaporated to dryness under reduced pressure at

about 50-60d C. The solid water-soluble degradation products

were stored for future work. The following quantities of

materials were collected at various periods of exposure in

the accelerated durability machiness

TABLE 1, DEGRADATION PRODUCTS OF ASPHALT C190

Weight of Degradation Products

Period of Exposure Machine #1 Machine #2

Hr • g. g.

0 - 250 — 7.7

250 - 500 — 15.4

0 - 550 Not determined — 500 - 750 11.6

550 - 850 9.4 — 750 - 1000 ___ 11.2

850 - 1350 l6 o 0 -

1000 - 1500 — 14.0

1350 - 1800 Not determined — 1500 - 2000 — 7c 8

The weights of the other samples of degradation products

were not determined.

3. FRACTIONATION OF WATER-SOLUBLE DEGRADATION PRODUCTS

3.1 Liquid-Liquid Extraction

Because the degradation products were always collected

in large volumes of water and eliminating the water was a laborious, time-consuming job, methods were sought that

might fractionate the degradation products while they were

present in their original solution form. Continuous extraction with such water-insoluble solvents as ether, benzene or

i/Preliminary work indicated that the acidic, water-soluble

degradation products reacted with the specimen supports and

materials in the containers in which the specimens were

soaked. A. Schriesheim and S. H. Greenfeld, "Water-Soluble

Degradation Products of Asphalt", A.S.T.M. Bulletin No. 220

February 1957.

- 4 -

pentane yielded only traces of extractable materials. It

was realized that these products were soluble only in

appreciably oxygenated solvents, the best of which (acetone

and ethanol) were also very soluble in water „ Methyl ethyl

ketone extracted portions of the products, but it was

impossible to determine whether the products were dissolved

in the methyl ethyl ketone or in the water that dissolved

in the methyl ethyl ketone. Higher molecular weight ketones,

such as methyl isobutyl ketone, cyclohexanone and acetophenone, all were tried and found to be partially sucessfulo

However, their boiling points are all in the neighborhood

of that of water and involve the same problems of solvent

elimination that water does. Furthermore, a large fraction

of the degradation products was not extracted.

3.2 pH Extraction

When simple solvent extraction proved unsuccessful,

modifications of the method were attempted. The acids in

the degradation products were completely neutralized and

an attempt made to extract any non-acidic material with

benzene and ether. Again only slight traces of material

were extracted after prolonged contact between the two

phases in a continuous extractor.

The pH was lowered two units at a time (with HC1) and

further extraction was attempted with both of these solvents

and methyl ethyl ketone and cyclohexanone. Very little

material was extracted evan at a pH of 2. The ketones

affected the pH of the aqueous phase considerably as it

became saturated with them and made the pH readings almost

meaningless. For example the cyclohexanone dropped the

pH reading of the neutralized aqueous solution from 10.5

to 5*8 during the course of the first extraction.

3 o3 Column Chromatography

There are several ways of utilizing columns of adsorbents for separating mixtures of acids in solution. These

range from partition chromatography, in which the solid

adsorbent functions primarily as a support for an immobile

liquid phase, to adsorption chromatography, in which the

solids actually adsorb the acids and the separation is

accomplished by the use of several desorbing solvents.

Many practical separations are accomplished through combinations of the several phenomena involved. A large number of

- 5 -

combinations of supports, solvent systems and conditions were

evaluated. Such materials as silicic acid, celite, silica,

carborundum, crushed glass and cellulose were used as supports,

These were used "as received", washed, acid washed, buffered

(glycine plus NaOH or HC1), and activated to various degrees.

They were used as adsorbents and with varying ratios of immobile phases. Many different solvent systems, including

numerous combinations of the following solvents; water,

acetone, ethanol, methyl ethyl ketone, butanol, iso-butanol,

ter- butanol, amylol, iso-amylol, ter-amylol, chloroform,

benzene, ether, cyclohexanol , cyclohexanone, methyl cyclohexanone, dimethyl f ormamide , 2-e thyl-l-hexanol and 4-methyl2-pentanol, were used.

The degradation products were always more or less

separated into from 3 to 10 or 12 fractions, but the

separations were not very reproducible and the recoveries

were rarely quantitative. Very frequently, even though

recoveries of over 100% were measured, the columns of

adsorbent were still colored, indicating the presence of

degradation products. Functional group analyses of some

of the separated materials were often negative and inconclusive . 3.4 Paper Chromatography

Both ascending and circular paper chromatography were

used to try to separate the water-soluble degradation

products. The former was the more successful, resulting in

one instance in five spots. However, despite the fact that

ionization was suppressed with formic acid, "tailing" was

usually prevalent and reproducibility was not good. No

quantitative evaluation was attempted.

3 . 5 Ion Exchange

Ion-exchange resins have been used successfully to

separate both cations and ions. The Project has used a Dowex-50X8 resin to remove all cations from the degradation

products. In doing so, certain organic cationic materials,

which comprised a small percentage of the degradation products

were also removed. These materials were regenerated with a 5% sodium hydroxide solution and were found to contain

amines or amino acids.

- 6 -

In order to remove the anions from solution, a different

type of resin, an anion-exchange resin, was used. This

polyamine -type resin, marketed under such names as Amberlite

IRAm- 00 or ^B, De Acidite, Permutite S-2 or Dowex 3, removed

all of the acids from solution until it approached saturation.

However, only about 60% of the anions could be recovered

even with regenerants strong enough to attack the resins.

This phenomenon has been observed by other investigators

with some high molecular weight acids.

3.6 Sublimation

The volatility of the water-soluble degradation products

is very low and the use of distillation as a method of

separation was beyond consideration. However, preliminary

work indicated that a component of these materials might

possibly be separated from the bulk of them by sublimation

at low pressure. A white, powdery material sublimed from

a sample of degradation products that was obtained from a roof. When an attempt was made to check these results on

degradation products collected in the laboratory, however,

only a slight, oily product was obtained at a relatively

high temperature. There was evidence that decomposition

had occurred. The original sublimation product had probably

been some impurity.

3.7 Derivative Formation

In many instances when satisfactory separations of

organic materials cannot be accomplished by conventional

techniques, derivatives can be made that are more readily

separable. Two such attempts were made on the water-soluble

degradation products.

Hydrogen bonding of many organic acids results in their

having volatilities considerably lower than other closely

related derivatives and makes separation of the acids by

distillation unfeasible. Conversion to the methyl esters

often reduces the boiling points of acids as much as 100°C,

bringing them into a range where they can be distilled without decomposition.
*
- 7

-

Two samples of water-soluble degradation products were

esterified with methyl alcohol (sulfuric acid as catalyst)

and attempts made to distill out the ester after the catalyst had been neutralized and removed,, The principal ingredient that distilled over was water. Apparently the

esters were not volatile. No further work was done because

insufficient material was available.

In several instances it has been reported that derivatives or organic acids were separated by paper chromatography

more readily than the acids themselves, because the derivatives

did not exhibit as much hydrogen bonding or ionization.

Attempts to make the anilides of the water-soluble degradation

products were unsuccessful because of very poor conversions

and the formation of insoluble compounds.

3.8 Decarboxylation

Another procedure for increasing the volatility of

organic acids is to remove their carboxyl groups. Since

the degradation products averaged 2.4 carboxyl groups per

molecule, in addition to reducing hydrogen bonding, removal

of the carboxyl groups would lower the average molecular

weight by 110.

An attempt was made to decarboxylate about 3-1/2 grams

of degradation products in quinoline, with copper sulfate

as the catalyst. Collection of the carbon dioxide liberated

indicated that the reaction had gone to completion, but

recovery of the liquid and solid products was not quantitative. The copper sulfate had decomposed, introducing sulfur

into other molecules. This type of reaction should be repeated, using copper oxide as a catalyst. In order to yield

materials which might be separated by distillation, or fed

into the mass spectrometer for analysis.

3.9 Extraction from Solid Phase

Among the more promising techniques evaluated was extraction of components of the water-soluble degradation

products by various solvents while the products were present

in a finely divided solid state. Considerable effort was

expended in exploring various techniques involving this

principle
. .

,
- 8 -

Extraction from the solid state proved very slow when

first tried, because the material tended to cake in the extraction apparatus* Both Soxhlet and batch extraction were

interminable and not reproducible. In order to overcome

these problems of caking and incomplete extraction, the

material was dispersed on numerous, more or less inert,

finely divided carriers. The same difficulties were encountered in the extraction operation as were in the column

chromatography work. No satisfactory quantitative and reproducible system was found. Usually recoveries were too

high.

In the course of the extractions it was found that the

process was considerably accelerated if the carrier material

was kept in suspension by stirring with a magnetic stirrer.

Pursuit of this approach indicated that the extraction of

the finely divided degradation products themselves could

be greatly improved by this technique. The carrier was then

eliminated. Primary extractions were made with ether, methyl

ethyl ketone, acetone and water. The materials from each

exposure interval were separated into two parts in order to

check the precision of the method. The average results are

reported in Table 2.

TABLE 2. EXTRACTION OF WATER-SOLUBLE DEGRADATION PRODUCTS

Exposure Period 0-250 500-750* 750-1000 1000-1500

Hr. % % % %

Ether Soluble 24.7 25.5 30.9 25.3

MEK Soluble 58.7 60.2 57.7 68.5

Acetone Soluble 3.8 6.

2.5 7.9

Water Soluble ** 2.4 5.4 0.0

Water + Acetone Soluble 12.2 5.7 0.4 0.0

Recovery 99.5 100.0 96.9 101.7

*Single Determination.

**Not Determined.

Just as in the infrared analyses, these extractions indicate that there are differences in the materials collected

during the several exposure periods, but the degrees and

types of differences are not clear. Since most of the degradation products were soluble in methyl ethyl ketone, it was

decided to fractionate that portion further first.

- 9

-

When the MEK fraction was extracted with water, the recovery was very poor and the material had apparently undergone some change So The work was repeated, with the same

results, as shown in Table 3°

TABLE 3*

Secondary Extraction

Sample

% of

Fraction

Mole

Wt

Neutral

Equiv. COOH/Molo

%

Oxygen

MEK 100 760 184 4.12 33.5

Water Sol. of MEK 55.9 560 162 3A6 36.9

Water Insol. of MEK 31.1 2000 297 6.73 29.9

Recovery 87.0

These data indicate that polymerization has taken place

either during the extraction or during the vacuum drying operation following it. The molecular weight has increased and the

oxygen content decreased. It is apparent that much more highly

refined techniques will have to be developed if these degradation products are to be separated without being changed.

Based on a discussion of these data, it has been decided

to divert the efforts of the project to approaches to the

problem of degradation that may be expected to yield more

immediate results,.

4. REFERENCES

The following list of references will prove helpful to

those interested in general treatments of the various techniques employed. No effort has been made to include all of

the references consulted because in many instances only minor

contributions were obtained from them.

4.1 Liquid-Liquid Extraction

(1) "Techniques of Organic Chemistry", Arnold Weissberger,

Editor, Vol VI, pp. 93-105, Interscience Publishers, Inc.,

New York, 195^

( 2 ) Ibid., Vol. Ill, pp. 152-393, 1956.
*
10

(3) Van Nes, K. and Van Westen, H. A 0 , "Aspects of the

Constitution of Mineral Oils", Elsevier Pub 0 Co.,

New York, pp. 137-141, 426-430, 1951*

(4) Montgomery, R. S., (pH Extraction), Chem. & Eng 0 News,

3955, October 4, 1954.

4.2 Column Chromatography

(1) Martin, A.J.P. and Synge, R.L.M C , "A New Form of Chromatogram Employing Two Liquid Phases", Biochem 0 J.

,

1358- 1368 , 19V1 .

(2) "Partition Chromatography", Biochemical Society Symposium No. 3, R» T 0 Williams, Editor, Cambridge University Press, 1950.

(3) "Progress in Chromatography", L. Zechmeister, Chapman

and Hall, Ltd., London, 195(4

(4) "An Introduction to Chromatography", T 0 I. Williams,

Chem. Pub. Co. , Brooklyn, 1947.

(5) Kay, L. M. and Trueblood, K. N„ , "Immobile Phase in

Chromatography on Silicic Acid-Celite " , Anal. Chem.

26, 1566-1572, 1954.

( 6 ) Corcoran, G. B. , "Chromatographic Separation of Monoand Dibasic Acids", Anal. Chem. 28, Feb c 1956.

4.3 Paper Chromatography

(1) "A Manual of Paper Chromatography and Paper Electrophoresis", R. J. Black, E. J. Durrum and G. W. Zweig,

Academic Press, New York, 1955.

(2) Stark, J. B. , Goodban, A. E. and Owens, H. S., "Paper

Chromatography of Organic Acids", Anal. Chem. 23., 413-

415, 1951.

(3) Rappaport, Calvert, Loeffler and Gast, "Chromatographic

Separation and Determination of Porphyrin Methyl Esters",

Anal. Chem. 2^, 820, 1955.
<-9g

.

*

.

.
11

4.4 Ion Exchange

(1) "Synthetic Ion Exchanger s" , G. H. Osborn, The Macmillan

Co. , New York, 1956.

(2) Fisher, S. and Kunin, R. , "Routine Exchange Capacity

Determinations of Ion Exchange Resins", Analo Chem. 27 , 1191-1194, 1955.

4.5 Sublimation

(1) Chemical Engineers Handbook, McGraw-Hill Company,

New York.

(2) "Technique of Organic Chemistry", A. Weissberger, Ed.,

IV, 603-645, Inters-cience Pub. Co. , New York.

4.6

Derivative Formation

(1) Green, J. W. , "Chromatographic Separation of Saccharinlc

Acids as the Anilides", presented before A.S.C. in

Minneapolis, 1955.

(2) "Organic Syntheses", H. Gilman, Editor, Second Edition,

J. Wiley & Sons, Inc., New York.

(3) "Reactions of Pure Hydrocarbons", G. Egloff, Reinhold

Pub. Co.

,

New York, 1937°

4.7

Decarboxylations

(1) Montgomery, R. S. & Holly, E. D. , "Decarboxylation

Studies of Structures of the Acids Obtained by Oxidation

of Bituminous Coal", Fuel 36 , 63-75, 1957; 35, 60-65,

1956.

(2) Hughes, D. M. and Reid, J. C., J. Org. Chem. 14, 516,

1949. ~~
'
U. S. DEPARTMKNT OK COMMERCE

Siucluir Weeks, Secretary

NATIONAL BUREAU Ol STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

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