NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Teresa L. Alleman, Lisa Fouts, Jon 

Luecke, and Matt Thornton 

National Renewable Energy Laboratory

Casey McAlpin 

NREL and Colorado School of Mines

5 May 2009

100th AOCS Meeting, Orlando, FL

NREL/PR-540-45813

Biodiesel Utilization: Update on 

Analytical Techniques
Key Points of Biodiesel Utilization

• 2007: Energy Independence and Security Act mandates 

biodiesel production in the United States starting with 

500M gallons in 2009, increasing to 1B gallons in 20121

• Diesel sales are 63B gallons in 20072

• 2008: 700M gallons of biodiesel produced in United 

States3

• October 2008: ASTM adopted Bxx blend specifications

• March 2009: EU added tariff on imported biodiesel4

• Therefore, biodiesel is being used in the United States

1. http://www.renewableenergyworld.com/rea/partner/stoel-rives-6442/news/article/2008/01/eisa-of-2007-callsfor-additional-production-of-biofuels-51063

2. http://tonto.eia.doe.gov/dnav/pet/pet_cons_821dst_dcu_nus_a.htm

3. http://www.biodiesel.org/resources/faqs/

4. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:067:0022:0049:EN:PDF

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Topics for Discussion

• Biodiesel in lubrication oil

• Cold soak filtration

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Biodiesel in Lubrication Oil

• Biodiesel is less volatile than diesel fuel

• Possible accumulation in lubrication oil

• Traditional GC methods for fuel dilution don’t 

account for biodiesel (ASTM D3524)

• FTIR/ATR method (D7371) for biodiesel in diesel 

fuel may be modified to detect biodiesel in lube oil

• Strong C=O stretch between 1750 cm-1 to 1650 cm-1

• How does lube oil base stock impact results?

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Benefits of FTIR/ATR

• Horizontal ZnSe 45° multi-bounce ATR cell

• Short path length (10-20 μm) allows measurement of 

used lubrication oil (soot readily absorbs IR)

• Cell maintains fixed path length over useful life

• Rapid analysis time (~60 seconds) for 32 scans and 

4 cm-1 resolution

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Engine Durability Tests

• Run diesel engine over durability cycle with 

advanced emission control systems − NAC and SCR

• Late cylinder injection and/or fuel injection into exhaust 

for emission control

• Oil was changed at recommended intervals

• Collect aliquot for fuel dilution analysis

• Validate FTIR/ATR technique to quantify biodiesel 

dilution in lube oil

• PLS model built with fresh oil from project and typical soyderived biodiesel

• Base stock character can impact quantitation results

NAC = NOx adsorber catalyst

SCR = selective catalytic reduction 

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Engine and Fuel

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Engine Power 113 kW at 4,000 rpm

Peak Torque 360 Nm at 2,000 rpm

Max. Engine Speed 4,700 rpm

Max. BMEP 21 bar

Cylinder/Firing Order I-4, 1-3-4-2

Bore to Stroke Ratio 1.0034

Displacement 2.15 L

Compression Ratio 18:1

Fuel Injection System 2nd Generation Common Rail

Fuel Soybean-derived B20

Source: SAE 2009-01-1790
Emission Control System Parameters

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Vol. 

(L)

Cell Density 

(cpsi)

PGM Loading

(g/ft3)

NAC system DOC 0.8 400 150

DPF 3.3 300 60

NAC 4.1 400 120

SCR system DOC 1.23 400 150

DPF 4.1 300 60

SCR FeZSM-5 4.43 300 NA

Source: SAE 2009-01-1790
Differences in Base Oil

• Note the differences between 1800 cm-1 and 1700 cm-1

(carbonyl stretch ~1750 cm-1)

• These differences can lead to over/underreporting of 

biodiesel dilution

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“Good” vs. “Bad” Calibration Model

• Same sample quantified with parent and 

unrelated base oil

• Dissimilar base oil leads to underestimation of 

biodiesel dilution (blue/purple curves)

• Red curve is correct  6.5 vol% biodiesel

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Another Example

• Valid result (red) is 7.0 vol% dilution; invalid result 

(blue/purple) is ~50% low 

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Results

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Sample

#

Oil Age 

(hrs)

System 

Age (hrs)

Biodiesel 

(vol%)

1 48 48 4.7

2 92 140 6.6

3 65 205 5.2

4 90 295 5.7

5 67 362 5.3

6 65 427 6.8

7 65 492 5.9

8 100 592 8.3

9 158 750 10.1

NAC SCR

Sample

#

Oil Age 

(hrs)

System 

Age (hrs)

Biodiesel 

(vol%)

1 65 65 8.0

2 76 141 7.6

3 54 195 6.5

4 65 260 7.0

5 59 319 4.1

6 63 382 4.7

7 58 440 4.1

8 64 504 3.7

9 64 568 3.6

10 45 613 3.7

Diesel dilution tracks biodiesel dilution, but is typically 50%-67% lower.
Additional Lubricant Results

• Each oil change 

represents ~10,000 mi

• TBN decrease is due to 

normal lubricant aging

• TBN and TAN never cross

• Lubricant is within normal 

service interval

TBN = total base number

TAN = total acid number

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Oil Age, hr

0 50 100 150 200

TBN or TAN, mgKOH/g

0

1

2

3

4

5

6

7

TBN for NAC

TBN for SCR

TAN for NAC

TAN for SCR
Wrap-up

• FTIR/ATR is a robust analytical technique to 

quantify biodiesel dilution in lubrication oil

• It is critical to use the same base oil for calibration 

that is used in testing

• Poorly designed model can lead to over/underestimation

• Future research should examine a single technique 

to quantify biodiesel and diesel in lubrication oil, 

especially if base stock is unknown

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Cold Soak Filtration Analysis

• Some biodiesel samples exhibit precipitates above the 

cloud point

• Cold soak filtration test (CSFT) was adopted as performance 

specification in ASTM D6751 in October 2008

• CSFT results are bimodal, either passing (<360 second 

filtration time) or failing (>720 second filtration time)

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CSFT Method

• B100 is chilled to 4.5°C for 16 hours, then warmed 

and vacuum filtered through 0.7 μm filter; filtration 

time is reported

• Intent was to make Annex method “official”

• Annex method was used as a starting point to 

develop ASTM D7501

• D7501 was published May 2009

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Comparison of CSFT Annex to D7501

CSFT Annex

• Sample can be 

cooled in lunchroom 

fridge

• Warm sample on 

bench top

• Time to warm may 

vary greatly

• Filter selection is 

overly broad

D7501 CSFT

• Tighter control of 

chilling apparatus

• Warm sample in 

25°C circulating 

liquid bath

• Warm time is 

specified

• Specific filter 

brand/type

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Impact of Filter Type on CSFT

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Annex Method,

Filtration Time, sec

0 50 100 150 200 250

D7501 Method,

Filtration Time, sec

0

50

100

150

200

250

FIlter A

Filter B

Filter C

Filter D

Annex Method,

Filtration Time, sec

60 80 100 120 140 160 180 200

D7501 Method,

Filtration Time, sec

60

80

100

120

140

160

180

200
Filter Differences

• Data was validated in a single lab, all data is 

average of duplicate runs

• For most fuels, differences between filters 

are nominal

• Some fuels show significant variability

• Annex method was developed on Filter A

• Wide variety of filters available led to poor repeatability

• In round robin testing, specification of filter in D7501 

method led to better repeatability

• Annex method has reduced cold weather problems 

• Still no fundamental understanding of the root cause

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Experimental Design to Determine Root 

Cause of Filter Plugging

• Cause of precipitates and failing filtration times are not well 

understood

• Potential compounds have similar character as FAME

• Separation becomes limiting step to analysis

• Goal was to develop high-throughput technique to analyze 

precipitates inside the biodiesel matrix

• Previous work in lipid-based chemotaxonomic studies of bacteria 

shows that matrix-assisted laser desorption ionization time-of -

flight mass spectrometry (MALDI-TOF MS), with an optimized 

matrix system, is effective in analyzing diacylphosphatidylethanolamines and diacyl-phosphatidylglycerols1

• Can biodiesel precipitates be fingerprinted in the same fashion?

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(1) Y. Isahida, A.J. Madonna, J.C. Rees, M.A. Meetani and K.J. Voorhees 

Discrimination of Enterobacteriaceae based on Spectral Patterns of 

Phospholipids using MALDI-TOF/MS Combined with On-Probe 

Sample Pretreatment, Rapid Commun. in Mass Spectrom., 2002 16, 

1877.
MALDI

ionization

TOF

Mass analyzer Detector

MALDI-TOF Background
MALDI

ionization

TOF

Mass analyzer Detector

MALDI-TOF Background
MALDI

ionization

TOF

Mass analyzer Detector

MALDI-TOF Background
Mass Analysis TOF

• Ions are analyzed by the amount of time taken to 

reach detector1

24

• Potential energy assumed to 

be converted to kinetic:

Ep = Ek

Ep = zVo

Ek = 1/2mv2

zVo = 1/2mv2

• Ions of lower mass have 

higher velocity 

• Potential can be positive or 

negative

(1) Gross, Jurgen H. Mass Spectrometry a Textbook. 1

st

ed., Springer 2004, 411-435
Methodology

• Take a stepwise approach

• Identify individual trace compounds thought to be 

present in biodiesel

• Use traditional matrix systems to evaluate pure 

components

• Test combinations of matrix systems to determine 

system over the range of components

• Utilize MS2 for positive peak identification

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Single Component Results
Results (mixture): Complex Mixture Results
Comparison of Different Biodiesels

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Results: MS2

Source: Poster to be presented at ASMS

Meeting, June 1-3, 2009
Closing Thoughts

• While biodiesel is mostly FAME, industry is concerned 

that trace components can impact operability 

significantly

• To fully understand the utilization of biodiesel, careful 

attention needs to be paid to the analytical 

methodology

• Methods need to be shared and compared to ensure 

that accurate data is gathered for this increasingly 

complex fuel

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