TABLE OF CONTENTS ABSTRACT 1 INTRODUCTION 3 ... - Biodieselbiodiesel.org/reports/19971201_gen-022.pdf · Table 1 Properties of Biodiesel ... Storage Stability of Biodiesel and Biodiesel

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TABLE OF CONTENTS

ABSTRACT .............................................................................................................1

INTRODUCTION......................................................................................................3

TEST FUELS ...........................................................................................................3

STABILITY TEST PROCEDURE.............................................................................5

TEST PROGRAM ....................................................................................................6

PHASE 1..................................................................................................................7

Phase 1 Results........................................................................................................................................7

PHASE 2..................................................................................................................9

Discussion of Phase 2 Results................................................................................................................12

PHASE 3................................................................................................................15

Results of Phase 3 Tests ........................................................................................................................16

SUMMARY AND CONCLUSIONS.........................................................................22

REFERENCES:......................................................................................................25

APPENDIX .............................................................................................................26

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Tables

Table 1 Properties of Biodiesel Fuel .........................................................................................4

Table 2 Properties of Diesel Fuels Used in Test Program .......................................................5

Table 3 Fuels and Blends for Phase 1 ......................................................................................8

Table 4 Total Sediment in Phase 1 Fuel Blends Aged 12 Weeks at 43° C...............................9

Table 5 Fuel Blends Tested with Each Additive ................................................................... 11

Table 6 Additives for Phase 3................................................................................................ 12

Table 7 Summary of Total Sediment Weights Generated in Fuel/Additive Blends Aged 12 Weeks at 43° C............................................................................... 15

Table 8 Acid Number of Selected Phase 2 Samples After Aging......................................... 16

Table 9 Sample Matrix Tested with Each of the Four Metals--Steel, Copper, Aluminum, Mixture of Lead, Tin, and Zinc.............................................................. 18

Table 10 Summary of Total Sediment in Petrodiesel A Containing No Additive, Aged 12 Weeks at 43°C in the Presence of Metals................................ 22

Table 11 Summary of Total Sediment in Biodiesel Aged12 Weeks at 43°C in the Presence of Metals............................................................................. 22

Table 12 Summary of Total Sediment in Blend of 20% Biodiesel and 80% Petrodiesel A Aged 12 Weeks at 43°C in the Presence of Metals ....................... 23

Table 13 Summary of Acid Numbers for Biodiesel Aged 12 Weeks at 43°C in the Presence of Metals...................................................................................... 24

Table 14 Summary of Acid Numbers for Blend of 20% Biodiesel and 80% Petrodiesel A Aged 12 Weeks at 43°C in the Presence of Metals ........................ 24

Figures

Figure 1 Total Sediment in Blends of Biodiesel and Petrodiesel Aged at 43° C for 12 Weeks .................................................................................................9

Figure 2 Total Sediment in Fuel/Additive Blends Aged at 43° C for 12 Weeks ........................................................................................................... 15

Figure 3 The Influence of Metals on Biodiesel Blends Aged at 43° C for 12 Weeks ........................................................................................................... 23

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Quantification and Improvement of the Long Term Storage Stability of Biodiesel andBiodiesel Blends

NBB Project No. 96207-1

FINAL REPORT

ABSTRACTBiodiesel, produced from renewable vegetable oils and animal fats, is being commercialized as a

substitute or blending stock for diesel fuel. This project investigated the long term storage stability of

biodiesel and various biodiesel blends with straight run petrodiesel, both with and without stability

enhancing additives, and in the presence or absence of common metals. In addition, a 20% blend with

petrodiesel containing cracked stock was also investigated.

Storage stability of the neat (100%) fuels and biodiesel blends was determined by ASTM standard

test method D 4625, an accelerated aging test at 43 C in vented borosilicate glass bottles, followed by

gravimetric determination of filterable and adherant sediment. These conditions replicate approximately one

year in common storage.

The results showed that biodiesel and biodiesel blends produced relatively small amounts of

sediment, although more than either of the petrodiesels used in the testing. The biodiesel blends gave

quantities of sediment intermediate between the two neat fuels: 100% straight run petrodiesel sediment was

0.25 mg/100 mL, 100% biodiesel sediment was 3.95 mg/100 mL. No significant diferences were seen with

the blends between the samples of straight run diesel or that containing cracked stock. Stability was

generally improved with additives, as evidenced by reduction of sediment; however, the effectiveness of

additives varied.

Of the additives investigated, the additive combination providing the most promising results was a

mixture of tert-butylhydroquinone and Ethyl HiTEC 4733 fuel additive. Results of this combination of

additives with pure petrodiesel and with blends containing less than 20% biodiesel, however, produced

increased sediment formation. TBHQ has limited solubility in petrodiesel, which may have caused the

settling out of TBHQ in the high petrodiesel blends. At the time of this report, this phenomenon is being

further investigated.

The effect of metals on storage stability was investigated by repeating ASTM D 4625 and placing

metal specimens in the fuel aging containers with pure biodiesel, pure petrodiesel, and a 20% biodiesel

blend. Steel, copper, and aluminum were tested individually, as well as a mixture of lead, tin, and zinc.

Sediment formation with biodiesel and biodiesel blends was unaffected by the presence of steel and

aluminum. The mixture of lead, tin, and zinc produced severe sediment formation in all samples containing

biodiesel. The presence of copper slightly increased sediment formation in the neat biodiesel, but is within

the repeatability of the testing method. The presence of copper in the biodiesel blend produced similar

sediment to that of the mixture of tin, lead, and zinc.

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The addition of the petroleum based additives with biodiesel and biodiesel blends produced mixed

results in the presence of metals. The addition of TBHQ to these additives had little effect on the samples

containing steel or aluminum, but dramatically reduced the sediment formation in the samples containing

copper or the mixture of lead, tin, and zinc, although these levels were still higher than those of the

petrodiesels used for the study.

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INTRODUCTIONBiodiesel is defined as the mono alkyl esters of long chain fatty acids derived from renewable lipid

feedstocks, such as vegetable oils and animal fats (Ref. 1). It is typically produced from soy bean oil in the

United States, and is currently being commercialized as an alternative, renewable fuel for use in compression

ignition, i.e. diesel, engines. Biodiesel can be used either neat as a complete replacement for petroleum

diesel fuel, or as a blending stock with conventional diesel fuel.

The objectives of this project were to determine the stability of biodiesel and blends of biodiesel with

straight run petrodiesel over an extended storage period, to evaluate the efficacy of stabilizing additives in

extending the storage life of biodiesel and biodiesel/petrodiesel blends, and to determine the effect of typical

metals present in diesel fuel storage systems on the long-term stability of these fuels and fuel blends. In

addition, a 20% blend with petrodiesel containing cracked stock was also investigated.

TEST FUELSThe experimental program called for one biodiesel fuel and two petroleum diesel fuels. One

petroleum diesel fuel was to be a straight-run product that had good storage stability and the second fuel was

to be a diesel containing cracked product, which would likely have lower stability.

The biodiesel fuel was a methyl soyate soydiesel fuel obtained from Ag Environmental Products,

Lenexa, Kansas. The properties of this biodiesel fuel are listed in Table 1, along with the National Biodiesel

Board (NBB) specifications for biodiesel fuel. Values for glycerin content and acid number were provided by

the supplier on a Certificate of Analysis. Cetane number was measured by the Phillips Petroleum Company

Automotive Laboratory and all other properties were determined by the BDM Petroleum Technologies

Analytical Laboratory immediately after the fuel was received. This initial analysis of the biodiesel fuel, as

shown on the Certificate of Analysis and by the properties determined immediately after receipt, indicated

that the fuel met all NBB specification requirements, and some properties, such as carbon residue, ash, sulfur

content, and cetane number, were significantly better than the requirements. However, toward the end of the

project, a sample of this biodiesel fuel analyzed for glycerin by an independent laboratory gave a value for

total glycerin outside the specification requirements. An ASTM task force is planning a round robin on the

gas chromatograph method for free and total glycerin, and this information is being forwarded to them for

consideration.

Table 1.Properties of Biodiesel Fuel

PropertyASTM

Test MethodBiodiesel

Test ResultNBB

Specification

Flash Point, °C D 93 127.5 100.0 (min.)

Water and Sediment, Vol.% D 1796 Est. 0.05 0.050 (max)

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Water, Karl Fischer, Vol. % D 1744 0.041

Carbon Residue, wt. % D 4530 0.007 0.050 (max)

Sulfated Ash, Wt. % D 874 < 0.001 0.020 (max)

Kinematic Viscosity, cSt at 40C D 445 4.319 1.9 to 6.0

Total Sulfur, wt. % D 2622 0.004 0.05 (max)

Cetane Number D 613 48.2 40 (min)

Cloud Point, °C D 2500 – 2 - -

Copper Strip Corrosion D 130 1A 3b (max)

Acid Number, mg KOH/g D 664 0.0661 0.80 (max) “ “ 0.152

Free Glycerin, wt. % GC3 0.0111 0.020 (max) “ “ 0.0144

Total Glycerin, wt. % GC3 0.0111 0.240 (max) “ “ 0.6594

1 Values provided by Ag Environmental Products, on Certificate of Analysis for this fuel.2 Value determined by the BDM-PT Analytical Laboratory3 Christina Plank GC Method (Proposed ASTM Method)4 Values obtained by independent laboratory toward end of project

The two petroleum diesel fuels used in the test program were identified as Petrodiesel A and

Petrodiesel B. Petrodiesel A was a low-sulfur additive-free straight-run diesel fuel, meeting all the

specification requirements for Number 2 automotive diesel fuel. It was fresh fuel obtained directly from the

Phillips Petroleum Company Refinery in Borger, Texas, and was used as received.

Petrodiesel B was a blend containing 80% of the straight-run fuel (Petrodiesel A) and 20% light

cycle oil. The light cycle oil was a hydrocracked, low-sulfur, highly aromatic stream, which is a typical

blending stock used in commercial diesel fuels. It was also obtained from the Phillips Refinery in Borger,

Texas.

Petrodiesel A had been analyzed for diesel fuel specification properties by the supplier, and

Petrodiesel B was analyzed by the BDM Petroleum Technologies Analytical Laboratory, except cetane

number, which was determined by the Phillips Automotive Laboratory. The properties of the two diesel fuels

are listed in Table 2. The specification requirements listed by the National Biodiesel Board are also included

in Table 2. In order to limit variability in the testing of biodiesel in blends with petrodiesel, the NBB has a

tighter specification for petrodiesel used for its projects than that outlined by ASTM D-975 (Ref. 2).

Table 2.Properties of Petroleum Diesel Fuels

ASTM TEST RESULTS NBB

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Test Petro- Petro- SpecificationProperty Method Diesel A Diesel B for 2-D Diesel

API Gravity D287 34.47 31.4 33.0 to 36.0

Flash Point, °F (°C) D 93 152 (67) 162 (72) 130 °F (min)

Distillation Range, °F D 86 IBP 347.3 353.3 340 - 400 10% pt. 407.8 424.5 400 - 460 50% pt. 495.8 505.5 470 - 540 90% pt. 620.3 586.5 560 - 630 EP 649.3 645.2 610 - 690

Kine. Viscosity, cSt at 40°C D 445 2.46 2.43 2.0 to 3.2

Total Sulfur, wt. % D 2622 0.033 0.015 to 0.05D 3120 0.033

Cetane Number D 613 43.0 38.7 42 to 47

Aromatics, Vol. % D 1319 36 44 28 to 40

The data in Table 2 show that Petrodiesel A was well within the NBB specification requirements.

Although the blend of straight-run fuel and light cycle oil, Petrodiesel B, had several properties that were

slightly outside the requirements, it was used as the second petroleum fuel because it was expected to have

lower stability than straight-run fuel, and a commercial diesel fuel with lower stability could not be obtained.

A preliminary stability test of the two petrodiesel fuels by the severe accelerated stability test ASTM

D 5304 (Ref. 3), in which the fuel samples were aged at 95°C under 100 psi oxygen pressure, showed that

both fuels were relatively stable. However, Petrodiesel B generated slightly more total sediment than

Petrodiesel A (1.60 mg/100 mL for Petrodiesel B versus 1.29 mg/100 mL for Petrodiesel A), suggesting that

Petrodiesel B did have slightly lower stability.

Stability Test ProcedureSeveral test methods are available to monitor and predict the storage stability of middle distillate

fuels. Most of the tests are based on gravimetrtic determination of sediment and gum formed during

accelerated aging of the fuel at elevated temperature. Some also include an oxygen sparge or overpressure

with oxygen to increase degradation reactions even further.

The accelerating aging method that was selected for this program was that described in ASTM D

4625, “Standard Test Method for Distillate Fuel Storage Stability at 43°C (110°F)” (Ref. 4). In this method,

a 400 mL aliquot of the test sample is aged in the dark at 43°C for a specified period of time. After aging,

the sample is cooled to room temperature, and filterable and adherent insolubles are determined

gravimetrically. The mildly elevated aging temperature of 43°C produces an approximate four-fold

acceleration of the degradation rate compared to storage at an ambient temperature of 21°C. Previous

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studies with petroleum diesel fuels have shown that this method generally produces better correlation

between test results and actual field storage than shorter term tests utilizing more severe aging procedures

(Ref. 4, 5, 6).

The sample containers used in this study were 500-mL borosilicate glass bottles with Teflon lined

screw caps. Each bottle was vented by means of a Teflon tube inserted through a hole in the cap. Four

hundred milliliters of fuel sample were placed in each bottle, the bottles were wrapped with aluminum foil to

exclude light, and placed in the aging chamber, which had been previously stabilized at a temperature of

43°C. The aging chamber was a Fisher Scientific Company Model 307 low temperature incubator that

maintained a uniform temperature of 43 ± 0.5°C throughout the entire chamber. An aging time period of

twelve weeks was selected in order to provide a measurable quantity of sediment and still complete the aging

in a reasonable amount of time. Twelve weeks at 43°C is roughly equivalent to one year at ambient

temperature.

At the end of the aging period, the samples were removed from the aging chamber, allowed to cool

to room temperature, and filterable and adherent sediment were determined gravimetrically. The procedure

that was used for determination of sediment was that described in ASTM D 5304, “Standard Test Method for

Assessing Distillate Fuel Storage Stability by Oxygen Overpressure” (Ref. 3 ). This method uses a

membrane-type filter holder with a 47-mm diameter filter for filterable sediment, rather than the 25-mm

diameter Gooch crucible that is used in D 4625, and it uses a disposable aluminum pan for adherent

sediment instead of the glass beaker used in D 4625.

The filters used for filterable sediment determination were 47 mm diameter Whatman Type GF/F

glass fiber filters, which have a nominal pore size of 0.7 micrometers. Two filters were used together. Each

aged fuel sample was filtered through a set of pre-weighed filters. The storage container was rinsed with iso-

octane, and the rinsings passed through the filters. The filters were washed with additional iso-octane to

remove residual fuel, dried in an oven at 95°C, cooled, and weighed. It was observed that washing biodiesel

from the filters required more washing with a larger volume of isooctane than petrodiesel. Consequently,

this more extensive washing procedure was followed for all samples.

Adherent sediment remaining in the storage bottle was dissolved in tri-solvent (an equal volume

mixture of toluene, acetone, and methanol). The tri-solvent solution was poured into a clean pre-weighed

aluminum weighing dish assembly, which consisted of two weighing dishes nested together as described in

D 5304. The weighing dish assembly was placed on a hot plate, and the tri- solvent evaporated. Final

drying of the adherent sediment was accomplished by placing the aluminum dishes in an oven at 95°C.

After drying, the dishes were cooled and weighed.

Test ProgramThe experimental program was divided into three phases. The first phase evaluated the

comparative storage stability of biodiesel, the two petrodiesels, and blends of biodiesel with each of the

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petrodiesels. The second phase investigated the effect of five stabilizing additives on the storage stability of

the biodiesel, two petrodiesels, and their blends. The third phase determined the impact of six common

metals that may be present in fuel storage systems on the storage stability of the biodiesel fuel and a

petrodiesel A/biodiesel blend, both with and without each of the five additives.

PHASE 1Phase 1 evaluated and compared the storage stability of the neat biodiesel, the two petroleum diesel

fuels identified as Petrodiesel A and Petrodiesel B, and a series of blends containing various ratios of the

biodiesel with each of the petrodiesels. No additives were used in Phase 1. Thirteen samples of the neat

fuels and blends were prepared and tested for storage stability in Phase 1. The samples are listed in Table 3.

Table 3.Fuels and Blends for Phase 1

Blend No. Biodiesel%

Petrodiesel A%

Petrodiesel B%

1-1 100 0 -

1-2 0 100 -1-3 2 98 -1-4 10 90 -1-5 20 80 -1-6 40 60 -1-7 60 40 -

1-8 0 - 1001-9 2 - 981-10 10 - 901-11 20 - 801-12 40 - 601-13 60 - 40

Triplicate aliquots of each blend, for a total of 39 individual samples, were aged at 43°C for 12

weeks. At the end of the aging period, the filterable and adherent sediment in each sample were determined

by the procedures previously described.

The color of each aged sample was also measured with a standard ASTM

D 1500 colorimeter and compared to the initial color of the unaged samples.

Phase 1 ResultsThe quantities of total sediment (filterable plus adherent) collected from the aged fuels or fuel

blends are summarized in Table 4 and Figure 1. Each sediment value is the average of triplicate

determinations for that sample. Complete results for Phase 1 are shown in Tables A-1a and A-1b in the

Appendix.

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Table 4.Total Sediment in Blends of Biodiesel and Petrodiesel Aged 12 Weeks at 43°C

Blend Components Total

Blend

No.

Biodiesel

%

Petrodiesel A

%

Petrodiesel B

%

Sediment,

mg/100 mL

1-2 0 100 - 0.251-3 2 98 - 0.361-4 10 90 - 0.581-5 20 80 - 0.951-6 40 60 - 1.411-7 60 40 - 2.391-1 100 0 - 3.95

1-8 0 - 100 0.321-9 2 - 98 0.331-10 10 - 90 0.501-11 20 - 80 0.901-12 40 - 60 1.301-13 60 - 40 2.13

Figure 1. Total Sediment in Blends of Biodiesel and Petrodiesel

Aged at 43° C for 12 Weeks

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 2 10 20 40 60 100

Percent Biodiesel in Blend

BLEND WITH PETRODIESEL A

BLEND WITH PETRODIESEL B

100% BIODIESEL

The straight-run petroleum diesel fuel, Sample 1-2, aged 12 weeks at 43°C, produced only a small

quantity of total sediment, with a average value of 0.25 mg/100 mL. The petroleum fuel containing 20%

hydrocracked light cycle oil, Sample 1-8, generated only slightly more sediment, indicating that both

petroleum fuels had good storage stability according to this stability test method. As the proportion of

biodiesel in the fuel blends increased, the amount of sediment also increased, with the pure biodiesel

producing an average total sediment of 3.95 mg/100 mL. Test results of biodeisel blends with petroleum

diesel containing the cracked stock were similar, although the quantity of sediment was slightly less than in

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those blends containing the straight run petrodiesel. This indicates that the presence of the cracked stock did

not impact the stability of the biodiesel blends.

The repeatability given for the D 4625 storage stability test method, determined with petroleum

diesel fuel, is 0.62 √X, where X equals the average value of duplicate results. Therefore, at an average

value of 0.25 mg/100 mL the repeatability is 0.31 and the true value could vary between 0 and 0.56, while at

an average value of 3.95 mg/100 mL the repeatabilility is 1.23 and the true value could range from 2.72 to

5.18. All values obtained were within the repeatability range of the test method, although more variability

between the repeats using pure biodiesel and the 60% biodiesel blend with straight run petrodiesel were

observed.

It was found experimentally that even with the increased washing procedure previously discussed,

the filters retained more biodiesel fuel than they did petrodiesel. A filter pair used to filter unaged and

previously filtered biodiesel had a weight increase of about 0.2 mg/100 mL, compared to about 0.1 mg/100

mL or less for petrodiesel. However this weight increase due to retained fuel is relatively insignificant

compared to the total sediment weight in aged biodiesel and the repeatability of the method.

The ASTM specification for diesel fuels, ASTM D 975 (Ref. 2), does not include the D 4625

accelerated stability test. However, in previous stability studies at this laboratory with typical straight-run

additive-free petroleum diesel fuels aged 13 weeks at 43°C, the quantity of total sediment produced by the

fuels ranged from 0.12 mg/100 mL to 0.28 mg/100 mL (Ref. 6). Those sediment values are in the same

range as the quantities of total sediment produced by the neat petroleum fuels in the present study.

Therefore, the petrodiesel used in this project appears to have storage stability comparable to typical straight-

run petroleum diesel fuels. The neat biodiesel fuel formed more sediment in this accelerated storage

stability test than the neat straight-run petroleum diesel fuel, although the actual quantity was still relative

small.

The D 1500 colors of both the unaged and aged samples are included in Table A-1. The colors of

the aged samples were only slightly darker than the initial colors of the unaged blends, and were not

meaningful for stability comparisons.

The acid number of the aged biodiesel, Sample No. 1-1, was 0.48. This represents a modest

increase over the acid number of the fresh biodiesel, which was 0.15. Acid numbers of the blends and neat

petrodiesel samples were not determined.

PHASE 2Phase 2 evaluated the efficacy of several stability additives in inhibiting sediment formation during

long-term storage in neat biodiesel fuel, neat petrodiesel A, and blends of biodiesel with the two

petrodiesels. The stability test procedure was the same as that used in Phase 1. The fuels and fuel blends

that were tested with each additive are listed in Table 5.

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Table 5.Fuel Blends Tested with Each Additive

Fuel Blend Components

Blend No. Biodiesel%

Petrodiesel A%

Petrodiesel B%

1 100 - - - -

2 - - 100 - -

3 2 98 - -

4 10 90 - -

5 20 80 - -

6 40 60 - -

7 60 40 - -

8 20 - - 80

The five additives investigated in Phase 2 were selected in cooperation with the National Biodiesel

Board and based on previous work completed by Williams Pipeline Company. The selected additives, and

the concentrations that were added to the fuels, are listed in Table 6.

Four different additive materials were used alone or in various combinations to produce the five

additives that were studied. Additional information about each of the additive materials is given below.

Table 6.Additives for Phase 2

No. Additive Concentration in Blend1 Octel FOA-35 70 mg/L (25 lbs/1000 bbl)

2 NALCO/EXXON 303-MC 100 PPM by volume

3 NALCO/EXXON 303-MC + Tert-Butylhydroquinone (TBHQ)

100 PPM0.25 % (2.5 g/L) *

4 NALCO/EXXON 303-MC + Tert-Butylhydroquinone (TBHQ) + Water

100 PPM0.25 % *Saturated

5 Ethyl HiTEC 4733 + Tert-Butylhydroquinone (TBHQ) + Water

22.8 mg/L (8 lbs/1000 bbl)0.25% *Saturated

* The concentration in the neat petrodiesel samples was only 0.07 to 0.08%.

Octel FOA-35 is a fuel oil additive produced by Octel America, Inc., Newark, Delaware. It is

claimed to be a multifunctional additive providing rust inhibition, dispersancy, antioxidant properties, color

stability and copper deactivation; especially appropriate for long-term storage of diesel fuels. The

ingredients are organic amines and trade secret materials in an aromatic hydrocarbon solvent. A fresh

sample of the additive was obtained directly from Octel America for use in this project.

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NALCO/EXXON 303 MC is a fuel oil treatment produced by NALCO/EXXON Energy Chemicals,

Sugar Land, Texas. It consists of an amine substituted resin and an imidazoline in an aromatic hydrocarbon

solvent. The material used in this project was provided by NALCO/EXXON Energy Chemicals.

Ethyl HiTEC 4733 is an antioxidant produced by Ethyl Corporation, Richmond, Virginia, for use in

a wide variety of petroleum products. HiTEC 4733 is a liquid mixture of single-ring phenol antioxidants. A

sample was obtained from Ethyl Corporation for this project.

Tert-butylhydroquinone (TBHQ) is a pure chemical compound, which is sometimes used as an

antioxidant in vegetable oils and other materials. The material used in this project was manufactured by

Acros Organics and purchased from Fisher Scientific Company, Pittsburgh, Pennsylvania.

The concentrations shown in Table 6 for the commercial additives were chosen to be approximately

the midpoint of the concentration range suggested by the manufacturers for use in diesel fuel. The

concentration of TBHQ was the same as that used by Williams Pipeline Company in previous work.

The Octel FOA-35, NALCO/EXXON 303MC and Ethyl HiTEC 4733 were liquids and were

completely miscible with both petrodiesel and biodiesel. A quantity of the liquid additive sufficient to

provide the desired concentration in the fuel was measured with a positive-displacement microliter pipet and

injected into a previously measured fuel sample. Each sample was mixed thoroughly with a magnetic stirrer,

filtered through a GF/F glass fiber filter, and poured into the storage bottles, with 400 mL in each bottle. The

bottles were wrapped with aluminum foil and placed in the 43°C aging chamber.

Since tert-butylhydroquinone is a solid powder, the required quantity to provide a concentration of

0.25% by weight in the fuel sample was measured by weight and dissolved in the proper volume of fuel.

TBHQ is readily soluble in biodiesel, but has only limited solubility in petrodiesel. Therefore, for those

samples consisting only of biodiesel, the TBHQ was simply weighed out and added to a measured volume of

biodiesel. For those samples that were blends of biodiesel and petrodiesel, the TBHQ was first dissolved in

the biodiesel, then the biodiesel plus TBHQ was added to the petrodiesel. The quantity of TBHQ dissolved

in the biodiesel was such that the concentration of TBHQ in each final biodiesel/petrodiesel blend was the

desired 0.25%. The TBHQ remained in solution, even in the blends containing only 2% biodiesel, at least

during the initial mixing and until the samples were placed in the aging chamber. In the case of the neat

petrodiesel samples, a weighed quantity of TBHQ was added to the fuel, it was mixed for a period of time

with a magnetic stirrer, then filtered through a weighed GF/F filter to collect the undissolved TBHQ. The

filter and undissolved TBHQ were washed with a small quantity of iso-octane (which also has low solubility

for TBHQ) to remove the fuel, then the filter was dried and weighed. The difference between the final filter

weight and initial filter weight represented the weight of undissolved TBHQ, which was then subtracted

from the weight of TBHQ added to the fuel to obtain the weight of TBHQ that dissolved. The calculated

concentration of TBHQ in the neat petrodiesel samples, based on the weight that dissolved, was 0.07 to 0.08

wt. %.

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There were eight fuel blends and five additives, for a total of forty samples in Phase 2. Triplicate

aliquots of each sample were aged, making a total of 120 stability determinations. The samples were aged at

43°C for 12 weeks. At the end of the aging period, the samples were removed from the aging chamber,

allowed to cool to room temperature, and filterable sediment, adherent sediment and color were determined

for each aliquot, following the same procedure as used for the Phase 1 samples. The total sediment weights

resulting from the Phase 2 tests are summarized in Table 7 and Figure 2, and the complete Phase 2 test data

are included in the Appendix in Tables A-2a through A-2e.

Discussion of Phase 2 ResultsThe samples containing additive Octel FOA 35 appeared to produce slightly smaller quantities of

sediment than the same fuel blends without additives. However, the differences in sediment quantity between

the additive-free samples and the samples containing FOA 35 were within the stated repeatability of the

method, so no definite conclusion can be made about the effectiveness of FOA 35 in reducing sediment

formation in these fuels and fuel blends.

The samples containing the additive NALCO/EXXON 303 MC generated quantities of sediment

similar, i.e. within the repeatability of the method, to the same fuel blends without additives. Based on these

results, it appears that NALCO/EXXON 303 MC did not have any significant effect on the storage stability,

as measured by sediment formation, of the fuels and fuel blends.

The combination of NALCO/EXXON 303 MC and tert-butylhydroquinone (additives 3 and 4) had

mixed results on sediment formation in the fuel samples. Sediment formation was reduced, compared to the

additive-free samples, in the neat biodiesel and the blends containing more than 20% biodiesel. However,

the blends containing less than 20% biodiesel produced more sediment with this additive combination than

with no additive. The blend consisting of 2% biodiesel and 98% petrodiesel generated the most sediment,

much more than the same blend without additives. The 100% petrodiesel sample containing TBHQ and

303MC (additive 3 or 4) produced less sediment than the 2% biodiesel/98% petrodiesel blend with the same

additive, but the 100% petrodiesel also contained a lower concentration of TBHQ. It was initially suspected

that the sediment from these low biodiesel blends was TBHQ that had precipitated from solution during

aging because of the limited solubility of TBHQ in petrodiesel. However, analysis by gas chromatography-

mass spectrometry of the sediment from the 2% biodiesel blend showed that it contained less than one

percent free TBHQ. Further investigation is necessary to determine the exact cause of the increased

sediment formation in the low biodiesel blends, but is outside the scope of this report.

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Table 7.Summary of Total Sediment in Fuel/Additive Blends Aged 12 Weeks at 43°C

BLEND COMPONENTSTOTAL SEDIMENT, mg/100 mL, After 12 Weeks at 43°C

BIO-DIESEL

%

PETRO-DIESEL A

%

NoAdditive

(fromPHASE 1)

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ

Add. #4303 MC +TBHQ +

Water

Add. #54733 +

TBHQ +Water

0 100 0.25 0.26 0.47 2.99 2.21 1.07

2 98 0.36 0.24 0.51 7.15 6.95 3.50

10 90 0.58 0.30 0.56 1.94 1.98 1.10

20 80 0.95 0.46 0.68 0.89 0.88 0.56

40 60 1.41 1.07 1.27 1.15 1.14 0.57

60 40 2.39 1.64 1.94 1.48 1.47 0.68

100 0 3.95 2.74 3.75 2.28 2.17 1.53

BIO-DIESEL

%

PETRO-DIESEL B

%20 80 0.90 0.52 1.35 0.82 0.81 0.48

FIGURE 2. Total Sediment in Fuel/Additive Blends Aged at 43° C for 12 Weeks

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

0 2 10 20 40 60 100

Percent Biodiesel in Blend

NO ADDITIVE

ADDITIVE 1: OCTEL FOA 35

ADDITIVE 2: NALCO/EXXON 303 MC

ADDITIVE 3: NALCO/EXXON 303 MC and TBHQ

ADDITIVE 4: NALCO/EXXON 303 MC AND TBHQ, PLUS WATER

ADDITIVE 5: ETHYL HiTEC 4733 AND TBHQ, PLUS WATER

The quantity of total sediment in the samples containing NALCO/EXXON 303 MC and TBHQ was

a minimum in the fuel blends consisting of 20% biodiesel and 80% petrodiesel, with no significant

difference between Petrodiesel A and Petrodiesel B. The quantity of sediment increased in blends containing

14

more than 20% biodiesel, although in these blends the amount of sediment was still less than in the same

fuel blends without additives.

Adding a small quantity of water to the blends with additive 4 (303 MC and TBHQ) did not have

any significant effect on sediment formation. The water simply settled to the bottom of the container as

discrete droplets.

The samples with additive 5 (Ethyl HiTEC 4733, TBHQ, and water) exhibited a pattern of sediment

formation similar to that with additives 3 and 4, but the quantities of sediment with additive 5 were less than

in the blends containing additives 3 or 4. Additive 5 was the most effective of any of the additives tested for

reducing sediment formation in the fuel blends containing 20% or more biodiesel. The water included with

this additive had no apparent effect.

Acid numbers of selected aged samples were determined by ASTM D 664 (Ref. 7) and are shown in

Table 8. Where no value is shown, the acid number was not determined since it was expected to be very low.

Table 8.Acid Number of Selected Phase 2 Samples After Aging

BLEND COMPONENTSACID NUMBER, After 12 Weeks at 43°C

BIO-DIESEL

%

PETRO-DIESEL A

%

NoAdditive

(fromPHASE 1)

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ

Add. #4303 MC +

TBHQ + Water

Add. #54733 +

TBHQ +Water

0 100 -- 0.01 0.01 0.02 0.02 0.02

2 98 -- -- -- -- -- --

10 90 -- 0.02 0.02 -- -- --

20 80 -- 0.05 0.05 0.08 0.08 0.09

40 60 -- 0.11 0.13 0.11 0.11 0.13

60 40 -- 0.23 0.27 0.14 0.14 0.17

100 0 0.48 0.79 0.52 0.25 0.24 0.26

The acid numbers of the fuel blends made up primarily of petrodiesel were very low, as expected for

petroleum fuels. As the amount of biodiesel in the blends increased, the acid number also increased,

although it remained relatively low. The aged 100% biodiesel sample containing Octel FOA 35 had a higher

acid number than the same fuel aged without additives, and the aged biodiesel sample containing

NALCO/EXXON 303 MC had an acid number nearly the same as the fuel without additives. In contrast, all

three aged biodiesel samples containing TBHQ and either 303 MC or HiTEC 4733 had lower acid numbers

than the biodiesel without additives, suggesting that the TBHQ was responsible for the reduction in acid

number. Acid number was not determined on the aged blend of 20% biodiesel/80% petrodiesel B.

The color of all samples darkened slightly as a result of aging, but did not appear to be a useful

measure of degradation.

15

PHASE 3In Phase 3, the effect of various metals on storage stability of biodiesel and biodiesel/petrodiesel

blends, both with and without additives, was investigated. Steel was the metal of most concern, since most

fuel storage systems are constructed primarily of steel. Other metals that might be present in fuel system

components include brass (alloy of copper and zinc), bronze (alloy of copper and tin), aluminum, and lead

solder. Copper is known to have a deleterious effect on petroleum products, such as jet fuels.

Bessee and Fey (Ref. 8) recently reported that aging biodiesel and biodiesel/petroleum fuel blends in

the presence of metals, including steel, aluminum, copper, brass, and bronze, produced significant acid

number increase in the fuels. In adddition, the biodiesel/petroleum fuel blends aged in the presence of

copper or copper containing alloys formed large amounts of gum.

On the basis of the above considerations, the six metals selected for study in Phase 3 were: steel

(SAE No. 1018, mild carbon steel), copper, aluminum, lead, tin and zinc.

The steel, copper, and aluminum were tested individually, while the lead, tin, and zinc were tested

together. The steel, copper, aluminum, and lead were in the form of rectangular coupons 1/2 inch by 1 inch

by 1/16 inch. The tin was cylindrical pellets, 1/8 inch diameter and 1/4 inch long, and the zinc was in

circular pieces with diameters ranging from about 3/16 to about 5/16 inch and thickness of about 1/16 inch.

For the three metals that were tested individually, two coupons, or 1 square inch, of one of the metals were

added to each container of fuel. For the other three metals that were tested together as a mixture, one

coupon of lead, three pellets of tin, and three or four pieces of zinc (depending on size of the pieces) were

added to each container of fuel.

One square inch of metal surface in 400 mL of fuel is equal to 9.5 square inches of metal surface

area to one gallon of fuel. In the case of steel, this is approximately equivalent to the ratio of steel surface

area to fuel volume in a 300 barrel steel storage tank. Smaller containers would have a larger ratio of steel

surface area to fuel volume, while larger containers would have a smaller ratio of surface area to fuel

volume. For example, a 55 gallon drum would have a surface area to fuel volume ratio of approximately 56

square inches per gallon of fuel (about 6 times the metal area to fuel volume ratio in the sample containers),

and a 10,000 barrel tank would have about 3 square inches of surface area per gallon of fuel (about 1/3 the

ratio in the sample containers). In the case of the other five metals, which would likely be present only in

fuel system components such as valves, connecting tubing, or soldered joints, the metal surface area exposed

to fuel in the sample containers is much larger than it would be in a typical fuel storage system.

The test fuels were petrodiesel A, biodiesel, and a blend of 20% biodiesel/ 80% petrodiesel A. All

three of these fuels, without additives, were tested with each of the metals or the metal mixture. The

biodiesel and 20% biodiesel/80% petrodiesel A blend were tested with each of the five additives used in

Phase 2 and each of the metals or the metal mixture listed above, as shown in Table 9.

16

Table 9.Sample Matrix Tested with Each of the Four Metals--Steel, Copper, Aluminum, Mixture ofLead, Tin, and Zinc

Sample Petrodiesel A Biodiesel20% Biodiesel/

80%Petrodiesel AFuel, No additive X X X

Fuel + Additive #1 X X





This matrix included 13 samples for testing with each of the three metals and one metal mixture,

making a total of 52 different fuel-additive-metal combinations. The samples containing steel were tested in

triplicate, and all others in duplicate, making a total of 117 stability determinations for Phase 3.

Results of Phase 3 TestsThe results of the sediment determinations in the Phase 3 stability tests are summarized in Tables

10 to 12, and Figure 3, and the complete test results are shown in Tables A-3a through A-3f in the

Appendix.

As the data in Table 10 show, 100% petrodiesel A, without additives, aged in the presence of steel,

aluminum, or the mixture of three metals produced only a small increase in the amount of sediment

compared to the quantity of sediment in the same fuel aged without metals in Phase 1, which was 0.25

mg/100 mL. Copper caused an approximate doubling of sediment formation compared to the Phase 1 test,

but the quantity of sediment was still small. There was very little change in the appearance of the metal

pieces, all remained bright and shiny.

The test data for the 100% biodiesel fuel aged in the presence of metals is shown in Table 11. The

biodiesel fuel, both without and with additives, aged in the presence of steel or aluminum produced

quantities of sediment similar to, or even less than, biodiesel fuel aged without metals in Phases 1 and 2.

However, aging in the presence of copper caused a moderate increase in sediment formation, and the copper

pieces darkened considerably in color. The additives had little effect in reducing sediment formation in the

presence of copper; in fact, the sample containing NALCO/EXXON 303 MC generated the largest amount of

sediment of any of the biodiesel samples aged in the presence of copper.

All samples of the biodiesel fuel, with or without additives, aged in the presence of the three metals

lead, tin, and zinc generated very large quantities of sediment, greater than 100 mg/100 mL. None of the

additives tested were effective in reducing sediment with pure biodiesel in the presence of lead, tin, and zinc.

Again, the sample containing NALCO/EXXON 303 MC additive generated the most sediment. In all cases,

the lead and zinc pieces became very discolored and corroded, with the surface covered with white corrosion

17

products. The tin showed only a slight discoloration and was probably not a significant contributor to the

fuel degradation.

Addition of a small amount of water to the biodiesel fuel, in additives 4 and 5, had no noticeable

effect on sediment formation. In those samples with steel coupons, where the water droplets were in contact

with the steel there was slight corrosion of the steel, but it did not increase sediment formation. The

biodiesel sample containing 303 MC, TBHQ, and water, in contact with steel coupons, produced less

sediment than the biodiesel sample containing 303 MC and TBHQ without water. Thus, the presence of

water did not adversely effect sediment, but more data is necessary before saying the presence of water

actually reduces sediment as observed in these tests.

The stability test results for the 20% biodiesel/80% petrodiesel A blend, with and without additives,

are shown in Table 12. The results show that aging this fuel blend in the presence of steel or aluminum

generally had little effect on sediment formation, with the quantity of sediment being similar to the quantity

of sediment formed in the same blend with the same additives and aged without metals present.

However, the sediment forming behavior of the blend of 20% biodiesel/80% petrodiesel aged in the

presence of copper or metal mixture was much different than that of either 100% petrodiesel or 100%

biodiesel. The additive-free fuel blend aged in the presence of copper generated a very large amount

of sediment, but addition of the additives greatly reduced sediment formation. TBHQ was especially

effective in reducing sediment formation in fuels aged in the presence of copper, with the mixture of TBHQ

and HiTEC 4733 exhibiting the largest reduction—this additive mixture reduced the amount of sediment by

a factor of 50 compared to the quantity of sediment in the additive-free blend.

Aging the additive-free fuel blend in the presence of lead, tin, and zinc also generated a very large

quantity of sediment, which included both solid sediment and a gum that clogged the filters, making

filtration very difficult. The first two additives, Octel FOA-35 and NALCO/EXXON 303 MC, actually

increased sediment formation in the 20% biodiesel/80% petrodiesel blend, to over 340 mg/100 mL in the

case of the 303 MC. Adding TBHQ greatly reduced sediment formation, although these samples still

produced a significant amount of sediment. The best results were obtained with the mixture of TBHQ and

HiTEC 4733, in agreement with the results obtained in the fuel blend aged in the presence of copper.

Addition of water to the blend of 20% biodiesel and 80% petrodiesel, in additives 4 and 5, appeared

to increase sediment formation in blends stored with steel coupons because of corrosion of the steel. There

was also significant variation in weight of sediment between the triplicate determinations. In the fuel blend

aged with steel and additive 4, one sediment value was much higher than the other two values (see Table A-

3e in Appendix); the high value was not included in the average value shown in Table 12. The steel coupons

in all the samples of 20% biodiesel/80% petrodiesel that included water had more corrosion that those stored

in 100% biodiesel samples that included water. Although the steel coupons in the presence of water were

not tested in 100% petrodiesel, the results with the 20% biodiesel/80% petrodiesel blend with water were

similar to that expected with 100% petrodiesel and water.

18

Addition of water to the 20% biodiesel/80% petrodiesel blend aged in the presence of other metals

had no significant effect on sediment formation.

The acid numbers of the aged blends were determined by ASTM D 664 (Ref. 7), as another measure

of fuel degradation. Acid numbers for the Phase 3 tests are summarized in Tables 13 to 14. Where no value

is shown, the acid number was not determined. The difference in acid numbers between blends aged with

various combinations of additives and metals was not nearly as dramatic as the differences observed with

sediment formation. Acid numbers of the biodiesel fuel aged in the presence of steel, copper, or aluminum

were very similar to the acid numbers of the same fuel- additive combinations aged without metals (Table 8).

The mixture of the three metals, lead, tin, and zinc, produced higher acid numbers in the aged samples, but

the differences were not as large as might have been expected from the sediment quantities. In the blend of

20% biodiesel/80% petrodiesel, aging in the presence of steel or aluminum did not cause any significant

increase in acid number, while copper and the mixture of three metals produced only a moderate increase in

acid number.

The addition of TBHQ to the 303 MC or HiTEC 4733 additives reduced the acid number of the

20% biodiesel blend aged in the presence of copper or the lead, tin, and zinc mixture, compared to the same

blends without TBHQ.

19

Table 10. Summary of Total Sediment in Petrodiesel A Containing No Additive, Aged 12 Weeksat 43°C in the Presence of Metals

ADDED METAL TOTAL SEDIMENT, mg/100 mL

None (from Table 7) 0.25

1018 STEEL 0.35

COPPER 0.54

ALUMINUM 0.33

MIXTURE 0.35(LEAD, TIN, ZINC)

Table 11. Summary of Total Sediment in Biodiesel Aged 12 Weeks at 43°C in the Presence ofMetals

TOTAL SEDIMENT, mg/100 mLADDEDMETAL

Add. #0None

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ


Water

Add. #54733 +

TBHQ +Water

None (from Table 7) 3.95 2.74 3.75 2.28 2.17 1.53

1018 STEEL 2.68 2.52 2.50 4.25 1.39 1.24

COPPER 5.11 4.65 9.17 4.25 4.37 5.28

ALUMINUM 3.06 1.76 2.52 1.75 2.76 0.76

MIXTURE 107.91 134.88 174.53 122.03 114.45 117.21(LEAD, TIN, ZINC)

20

Table 12. Summary of Total Sediment in Blend of 20% Biodiesel and 80% Petrodiesel A Aged12 Weeks at 43°C in the Presence of Metals

TOTAL SEDIMENT, mg/100 mLADDEDMETAL

Add. #0None

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ


Water

Add. #54733 +

TBHQ +Water

None (from Table 7) 0.95 0.46 0.68 0.89 0.88 0.56

1018 STEEL 0.87 0.40 1.12 0.92 3.22* 1.52

COPPER 119.65 10.28 57.34 3.49 3.81 2.30

ALUMINUM 0.96 0.35 1.04 1.14 1.25 0.67


* One high value was excluded from this average. See Table A-3e in Appendix.

FIGURE 3. THE INFLUENCE OF METALS ON BIODIESEL BLENDS AGED AT 43° C

FOR 12 WEEKS

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

Pb,

Sn,

Zn

100%

BIO

DIE

SE

L

Pb,

Sn,

Zn

20%

BIO

DIE

SE

L

ST

EE

L

100%

BIO

DIE

SE

L

ST

EE

L

20%

BIO

DIE

SE

L

ALU

MIN

UM

100%

BIO

DIE

SE

L

ALU

MIN

UM

20%

BIO

DIE

SE

L

CO

PP

ER

100%

BIO

DIE

SE

L

CO

PP

ER

20%

BIO

DIE

SE

L

TO

TA

L S

ED

IME

NT

, MG

/100

ML

ADDITIVE 0: NO ADDITIVE

ADDITIVE 1: OCTEL FOA 35

ADDITIVE 2: NALCO/EXXON 303 MC

ADDITIVE 3: NALCO/EXXON 303 MC + TBHQ

ADDITIVE 4: NALCO/EXXON 303 MC + TBHQ + WATER

ADDITIVE 5: ETHYL HiTEC 4733 + TBHQ + WATER

Table 13. Summary of Acid Numbers for Biodiesel Aged 12 Weeks at 43°C in the Presence ofMetals

21

ACID NUMBERADDEDMETAL

Add. #0None

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ


Water

Add. #54733 +

TBHQ +Water

None (from Table 8) 0.48 0.79 0.52 0.25 0.24 0.26

1018 STEEL 0.56 0.65 0.45 0.26 0.25 0.24

COPPER 0.43 0.29 0.39 0.49 0.33 0.46

ALUMINUM 0.62 0.69 0.52 0.25 0.25 0.25


Table 14. Summary of Acid Numbers for Blend of 20% Biodiesel and 80% Petrodiesel A Aged12 Weeks at 43°C in the Presence of Metals

ACID NUMBERADDEDMETAL

Add. #0None

Add. #1FAO 35

Add. #2303 MC

Add. #3303 MC +

TBHQ


Water

Add. #54733 +

TBHQ +Water

None (from Table 8) -- 0.05 0.05 0.08 0.08 0.09

1018 STEEL 0.08 0.05 0.06 -- -- --

COPPER 0.40 0.30 0.36 0.09 0.09 0.08

ALUMINUM 0.10 0.05 0.05 -- -- --


22

SUMMARY AND CONCLUSIONSLong term storage stability of biodiesel and blends of biodiesel with petrodiesel were evaluated, both

with and without stability enhancing additives and in the presence or absence of common metals. The fuels

included one biodiesel and two petrodiesels; one petrodiesel was a straight-run fuel and the other was a blend

of straight-run fuel with 20% hydrocracked light cycle oil. Storage stabilities were estimated from the

quantity of sediment formed by aging the fuels and fuel blends at 43°C for 12 weeks using ASTM test

method D 4625, followed by gravimetric determination of sediment using the procedure described in ASTM

D 5304. The efficacy of additives in reducing sediment formation was investigated, and the effect of several

common metals on stability, as well as the impact of free water on stability, were determined.

Aging the neat fuels and fuel blends without additives provided an evaluation of the intrinsic

stabilities of the fuels. Both neat petrodiesels generated only very small quantities of sediment, indicating

that both had good storage stability, although the second fuel, containing cracked stock, had been expected to

be less stable than the straight run fuel. The neat biodiesel generated more sediment than the petrodiesels

although the total amount of sediment was still small, and the biodiesel/petrodiesel blends generated

intermediate amounts of sediment. The quantity of sediment increased as the proportion of biodiesel

increased. There was no significant difference between blends containing the two types of petrodiesel.

Additives, such as antioxidants and stabilizers, are frequently added to diesel fuels to inhibit fuel

degradation and prolong storage life. In this project, several typical diesel fuel additives and the antioxidant,

tert-butylhydroquinone (TBHQ), in combination with a fuel additive, were investigated for their effectiveness

in inhibiting sediment formation during aging in the biodiesel, one petrodiesel, and biodiesel/petrodiesel

blends. The results showed a large difference in effectiveness between the additives, and also a large

difference in additive response between petrodiesel and biodiesel.

The common fuel oil additive Octel FOA 35 had no noticeable effect on sediment formation in the

neat petrodiesel; however, this fuel produced very little sediment even without additives. FOA 35 showed

more effect in the biodiesel/petrodiesel blends and the neat biodiesel, decreasing the amount of sediment

generated during aging in all of these samples compared to the fuel without additives, although the amount

of sediment still increased with increasing proportion of biodiesel.

The diesel additive NALCO/EXXON 303 MC increased sediment formation in the petrodiesel and

blends consisting primarily of petrodiesel, but decreased sediment formation in blends containing a higher

concentration of biodiesel, although the effect was less than that of FOA 35. The biodiesel/petrodiesel blend

prepared with petrodiesel containing cracked stock generated about twice as much sediment as the same

blend prepared with straight-run petrodiesel, indicating that the action of this additive may be dependent on

the types of chemical compounds making up the petroleum fuel.

The addition of tert-butylhydroquinone with the Nalco 303MC additive as well as with another

additive, HiTEC 4733, at the suggested treat rates provided the best improvement in stability for blends of

23

biodiesel containing more than 20% biodiesel. At lower biodiesel inclusion rates (higher petrodiesel rates)

the addition of TBHQ increased sediment formation. Further information regarding the proper treat rate of

TBHQ in biodiesel blends is warranted.

The final phase of the project investigated the effect of common metals on storage stability of

biodiesel and a 20% biodiesel/80% petrodiesel blend, both with and without additives. The presence of steel

or aluminum had no effect on the stability of the biodiesel, the blend, or the pure petrodiesel, and results

were analogous to those of the fuels which did not contain metals.

Copper is known to have a deleterious effect on petroleum fuels. The presence of copper increased

the amount of sediment in the unadditized pure petrodiesel and unadditized pure biodiesel, but the

differences are within the repeatability of the test method. The addition of the stability additives to pure

biodiesel containing copper appeared to have little, if any, effect in reducing the amount of sediment

formation. The 20% blend of biodiesel with petrodiesel produced significantly more sediment than either

neat fuel, resulting in over 100 mg/100ml of sediment after 12 weeks at 43C, and the copper coupon became

discolored and corroded. FOA 35 and Nalco 303 MC reduced the amount of sediment substantially. The

addition of TBHQ to Nalco 303 MC and the use of TBHQ with HiTEC 4733 provided further substantial

reductions in sediment formation in the presence of copper, although the levels were still higher than those

containing either steel or aluminum.

A mixture of three metals, lead, tin, and zinc, produced even more sediment than copper. In the

neat biodiesel fuel aged in the presence of these three metals, none of the additives were effective in reducing

sediment formation. The two diesel fuel additives Octel FAO 35 and NALCO/EXXON 303 MC actually

increased sediment formation, although the levels of sediment are high enough that the test method may not

be valid. The biodiesel/petrodiesel blend aged with the three metals generated more sediment than neat

biodiesel did, and again the two diesel fuel additives increased sediment formation. However, in the

biodiesel/petrodiesel blend, additive mixtures containing TBHQ significantly reduced sediment formation,

whereas they had not in neat biodiesel. The lead and zinc, in both neat biodiesel and the

biodiesel/petrodiesel blends, became very corroded, while the tin remained relatively clean.

Overall conclusions from this study were that the biodiesel, without additives, had lower storage

stability and produced more sediment during aging than the petrodiesel, and blends of the two fuels

generated intermediate amounts of sediment. Based on this study, it is recommended that pure biodiesel

without stability enhancing additives should not be stored longer than one year. Additives improved the

stability of biodiesel and biodiesel/petrodiesel blends; however, additives had different effectiveness in

biodiesel compared to petrodiesel. Of the additives studied, the most effective for reducing sediment

formation in biodiesel and biodiesel/petrodiesel blends containing 20 percent or more biodiesel was a

mixture of TBHQ and HiTEC 4733. Some metals were also found to affect storage stability of biodiesel and

a biodiesel/petrodiesel blend. Steel had little effect, and aluminum had only a small effect, but copper, lead,

and zinc caused severe deterioration of the fuel during aging, with greatly increased sediment formation.

24

Therefore, copper, lead, zinc, and their alloys, such as brass, bronze, and solder, should be excluded from

fuel storage systems for biodiesel or biodiesel/petrodiesel blends.

25

REFERENCES:1. Howell, Steve. 1997. Biodiesel Fuel Standard Making Progress. ASTM Standardization News, No.

4 (April), pp. 16-19.

2. ASTM D 975. Standard Specification for Diesel Fuel Oil. Annual Book of ASTM Standards, Vol.

05.01, West Conshohocken, PA.

3. ASTM D 5304. Standard Test Method for Assessing Distillate Fuel Storage Stability by Oxygen

Overpressure. Annual Book of ASTM Standards, Vol. 05.03, ASTM, West Conshohocken, PA.

4. ASTM D 4625. Standard Test Method for Distillate Fuel Storage Stability at 43°C (110°F). Annual

Book of ASTM Standards, Vol. 05.02, West Conshohocken, PA.

5. Stavinoha, L.L., and S. R. Westbrook. 1980. Accelerated Stability Test Techniques for Diesel

Fuels. DOE/BC/10043-12, Southwest Research Institute, San Antonio, TX, 137 pp.

6. Proprietary research, BDM Petroleum Technologies and IITRI/NIPER.

7. ASTM D 664. Standard Test Method for Acid Number of Petroleum Products by Potentiometric

Titration. Annual Book of ASTM Standards, Vol. 05.01, ASTM, West Conshohocken, PA.

8. Bessee, Gary B., and Joseph P. Fey. 1997. Compatibility of Elastomers and Metals in Biodiesel

Fuel Blends. SAE Paper 971690, Society of Automotive Engineers, Warrendale, PA.

26

APPENDIX

27

Table A-1a. Phase 1 Stability Test Results forBiodiesel/Petrodiesel A Blends

AFTER AGING 12 WEEKS AT 43°CBLEND COMPONENTS SEDIMENT, mg/100 mL

BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

INITIALCOLOR

FILTERABLE ADHERENT TOTAL MEAN FINALCOLOR

ACIDNO.

1-2-A 0 100 L1.0 0.16 0.08 0.24 .025 L1.51-2-B 0.16 0.09 0.24 L1.51-2-C 0.18 0.10 0.27 L1.5

1-3-A 2 98 1.0 0.26 0.10 0.36 0.36 1.51-3-B 0.28 0.09 0.37 1.51-3-C 0.27 0.09 0.36 1.5

1-4-A 10 90 L1.5 0.34 0.33 0.67 0.58 L2.01-4-B 0.33 0.20 0.53 L2.01-4-C 0.37 0.17 0.55 L2.0

1-5-A 20 80 1.5 0.73 0.24 0.97 0.95 L2.01-5-B 0.55 0.33 0.88 L2.01-5-C 0.80 0.20 1.01 L2.0

1-6-A 40 60 L2.0 0.94 0.50 1.44 1.41 L2.01-6-B 0.47 0.99 1.46 L2.01-6-C 0.53 0.81 1.34 L2.0

1-7-A 60 40 L2.0 1.16 0.75 1.91 2.39 2.01-7-B 1.34 1.28 2.62 2.01-7-C 0.78 1.85 2.63 2.0

1-1-A 100 0 L2.0 3.66 1.47 5.13 3.95 1.5 0.481-1-B 1.13 1.98 3.11 1.51-1-C 2.46 1.16 3.61 1.5

28

Table A-1b Phase 1 Stability Test Results forBiodiesel/Petrodiesel B Blends


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

INITIALCOLOR


ACIDNO.

1-8-A 0 100 1.0 0.19 0.16 0.35 0.32 L2.01-8-B 0.17 0.13 0.30 L2.01-8-C 0.16 0.15 0.31 L2.0

1-9-A 2 98 1.0 0.26 0.08 0.33 L2.01-9-B 0.24 0.08 0.32 0.33 L2.01-9-C 0.26 0.07 0.33 L2.0

1-10-A 10 90 L1.5 0.33 0.18 0.52 0.50 L2.51-10-B 0.33 0.17 0.51 L2.51-10-C 0.33 0.15 0.47 L2.5

1-11-A 20 80 1.5 0.69 0.23 0.93 0.90 2.01-11-B 0.66 0.16 0.82 2.01-11-C 0.77 0.17 0.94 2.0

1-12-A 40 60 L2.0 0.48 0.78 1.26 1.30 L2.01-12-B 0.49 0.81 1.30 L2.01-12-C 0.60 0.73 1.33 L2.0

1-13-A 60 40 L2.0 1.79 0.36 2.15 2.13 L2.51-13-B 1.82 0.34 2.15 2.01-13-C 1.75 0.32 2.07 L2.5

29

Table A-2a. Phase 2 Stability Test ResultsAdditive #1: OCTEL FOA 35

Additive Concentration: 70 mg/L


BLENDNO. *

BIO-DIESEL

%

PETRO-DIESEL A

%

PETRO-DIESEL B

INITIALCOLOR


ACIDNO.

2-1-2-A 0 100 L1.0 0.18 0.05 0.22 0.26 L1.5 0.012-1-2-B 0.24 0.04 0.282-1-2-C 0.23 0.04 0.27

2-1-3-A 2 98 1.0 0.19 0.05 0.24 0.24 L1.52-1-3-B 0.18 0.04 0.222-1-3-C 0.18 0.07 0.25

2-1-4-A 10 90 L1.5 0.24 0.12 0.35 0.30 1.5 0.022-1-4-B 0.26 0.04 0.302-1-4-C 0.24 0.02 0.26

2-1-5-A 20 80 1.5 0.39 0.07 0.46 0.46 L2.0 0.052-1-5-B 0.35 0.08 0.432-1-5-C 0.42 0.06 0.48

2-1-6-A 40 60 L2.0 0.90 0.09 0.99 1.07 L2.0 0.112-1-6-B 0.93 0.17 1.102-1-6-C 0.92 0.19 1.11

2-1-7-A 60 40 L2.0 1.45 0.12 1.56 1.64 L2.0 0.232-1-7-B 1.54 0.13 1.672-1-7-C 1.53 0.15 1.68

2-1-1-A 100 0 L2.0 2.35 0.49 2.84 2.74 1.5 0.792-1-1-B 2.43 0.27 2.702-1-1-C 2.41 0.26 2.67

0.46 0.11 0.56 0.52 2.02-1-11-A 20 80 1.5 0.44 0.07 0.512-1-11-B 0.45 0.04 0.492-1-11-C

*Blend Number Code: Phase-Additive-Fuel Blend-Bottle

30

Table A-2b. Phase 2 Stability Test ResultsAdditive #2: NALCO/EXXON 303 MCAdditive Concentration: 100 ppm v/v


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

PETRO-DIESEL B

INITIALCOLOR


ACIDNO.

2-2-2-A 0 100 L1.0 0.35 0.16 0.51 0.47 L1.5 0.012-2-2-B 0.34 0.10 0.442-2-2-C 0.37 0.10 0.47

2-2-3-A 2 98 1.0 0.30 0.23 0.53 0.51 L1.52-2-3-B 0.28 0.23 0.512-2-3-C 0.30 0.20 0.50

2-2-4-A 10 90 L1.5 0.27 0.36 0.63 0.56 1.5 0.022-2-4-B 0.27 0.25 0.532-2-4-C 0.28 0.24 0.52

2-2-5-A 20 80 1.5 0.29 0.37 0.66 0.68 1.5 0.052-2-5-B 0.28 0.40 0.692-2-5-C 0.27 0.41 0.68

2-2-6-A 40 60 L2.0 0.36 0.99 1.35 1.27 L2.0 0.132-2-6-B 0.36 1.00 1.362-2-6-C 0.36 0.73 1.09

2-2-7-A 60 40 L2.0 0.44 1.40 1.84 1.94 L2.0 0.272-2-7-B 0.54 1.49 2.032-2-7-C 0.47 1.47 1.94

2-2-1-A 100 0 L2.0 2.33 1.09 3.42 3.75 1.5 0.522-2-1-B 2.47 1.52 3.992-2-1-C 2.26 1.58 3.83

0.29 2.26 2.55 1.35 L2.02-2-11-A 20 80 1.5 0.28 0.42 0.702-2-11-B 0.33 0.48 0.812-2-11-C

31

Table A-2c. Phase 2 Stability Test ResultsAdditive #3: NALCO/EXXON 303 MC + Tert-BUTYLHYDROQUINONE (TBHQ)

Additive Concentration: NALCO/EXXON 303 MC: 100 ppm v/vTBHQ: 0.25%


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

PETRO-DIESEL B

INITIALCOLOR


ACIDNO.

2-3-2-A 0 100 L1.0 1.90 1.16 3.06 2.99 L2.5 0.022-3-2-B 1.49 1.40 2.892-3-2-C 1.41 1.63 3.03

2-3-3-A 2 98 1.0 0.21 7.49 7.70 7.15 L3.52-3-3-B 0.27 6.99 7.262-3-3-C 0.18 6.32 6.49

2-3-4-A 10 90 L1.5 0.24 1.77 2.01 1.94 L3.02-3-4-B 0.23 1.68 1.912-3-4-C 0.22 1.69 1.91

2-3-5-A 20 80 1.5 0.27 0.57 0.84 0.89 L2.5 0.082-3-5-B 0.27 0.63 0.892-3-5-C 0.27 0.69 0.95

2-3-6-A 40 60 L2.0 0.28 0.85 1.13 1.15 2.0 0.112-3-6-B 0.28 0.89 1.172-3-6-C 0.32 0.82 1.14

2-3-7-A 60 40 L2.0 0.36 1.15 1.52 1.48 L2.5 0.142-3-7-B 0.34 1.11 1.442-3-7-C 0.32 1.15 1.47

2-3-1-A 100 0 L2.0 0.54 1.70 2.24 2.28 2.0 0.252-3-1-B 0.54 1.83 2.362-3-1-C 0.55 1.70 2.26

2-3-11-A 20 80 1.5 0.34 0.49 0.83 0.82 L3.02-3-11-B 0.28 0.52 0.802-3-11-C 0.32 0.51 0.83

32

Table A-2d. Phase 2 Stability Test ResultsAdditive #4: NALCO/EXXON 303 MC + TBHQ + WATER

Additive Concentration: NALCO/EXXON 303 MC: 100 ppm v/vTBHQ: 0.25%

Water: Saturated


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

PETRO-DIESEL B

INITIALCOLOR


ACIDNO.

2-4-2-A 0 100 L1.0 1.95 0.57 2.52 2.21 L2.5 0.022-4-2-B 1.38 0.27 1.652-4-2-C 1.92 0.53 2.45

2-4-3-A 2 98 1.0 0.43 6.28 6.71 6.95 3.02-4-3-B 0.45 6.61 7.062-4-3-C 0.41 6.66 7.07

2-4-4-A 10 90 L1.5 0.20 1.81 2.01 1.98 2.52-4-4-B 0.23 1.79 2.022-4-4-C 0.19 1.73 1.92

2-4-5-A 20 80 1.5 0.27 0.65 0.93 0.88 L2.5 0.082-4-5-B 0.29 0.57 0.862-4-5-C 0.33 0.52 0.85

2-4-6-A 40 60 L2.0 0.34 0.78 1.12 1.14 L2.5 0.112-4-6-B 0.32 0.83 1.142-4-6-C 0.31 0.84 1.15

2-4-7-A 60 40 L2.0 0.44 1.11 1.55 1.47 2.0 0.142-4-7-B 0.38 1.11 1.492-4-7-C 0.35 1.04 1.38

2-4-1-A 100 0 L2.0 0.99 1.09 2.08 2.17 2.0 0.242-4-1-B 1.06 0.96 2.022-4-1-C 0.56 1.86 2.42

2-4-11-A 20 80 1.5 0.43 0.36 0.79 0.81 L3.02-4-11-B 0.35 0.41 0.752-4-11-C 0.38 0.51 0.89

33

Table A-2e. Phase 2 Stability Test ResultsAdditive #5: ETHYL HiTEC 4733 + TBHQ + WATERAdditive Concentration: ETHYL HiTEC 4733: 22.8 mg/L

TBHQ: 0.25%Water: Saturated


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

PETRO-DIESEL B

INITIALCOLOR


ACIDNO.

2-5-2-A 0 100 L1.0 0.16 1.06 1.21 1.07 L2.0 0.022-5-2-B 0.25 0.76 1.012-5-2-C 0.25 0.74 0.99

2-5-3-A 2 98 1.0 0.42 3.15 3.58 3.50 2.52-5-3-B 0.33 3.51 3.842-5-3-C 0.32 2.77 3.09

2-5-4-A 10 90 L1.5 0.24 0.81 1.04 1.10 2.52-5-4-B 0.29 0.89 1.192-5-4-C 0.30 0.77 1.08

2-5-5-A 20 80 1.5 0.40 0.14 0.53 0.56 2.5 0.092-5-5-B 0.44 0.11 0.552-5-5-C 0.53 0.09 0.61

2-5-6-A 40 60 L2.0 0.35 0.21 0.57 0.57 L2.5 0.132-5-6-B 0.35 0.19 0.552-5-6-C 0.38 0.22 0.60

2-5-7-A 60 40 L2.0 0.37 0.34 0.71 0.68 L2.5 0.172-5-7-B 0.31 0.34 0.652-5-7-C 0.32 0.35 0.67

2-5-1-A 100 0 L2.0 0.60 0.77 1.37 1.53 L2.0 0.262-5-1-B 0.60 1.24 1.842-5-1-C 0.46 0.93 1.39

2-5-11-A 20 80 1.5 0.36 0.09 0.45 0.48 3.02-5-11-B 0.41 0.08 0.492-5-11-C 0.43 0.70 0.50

34

Table A-3a. Phase 3 Stability Test ResultsAdditive #0: None

AFTER AGING 12 WEEKS AT 43°CBLEND SEDIMENT, mg/100 mL

BLENDNO. *

BIO-DIESEL

%

PETRO-DIESEL A

%

METAL INITIALCOLOR


ACIDNO.

3-0-P-S--A 0 100 STEEL L1.0 0.18 0.20 0.38 0.35 L1.5 0.013-0-P-S--B 0.18 0.16 0.34 L1.53-0-P-S--C 0.20 0.13 0.33 L1.5

3-0-P-C--A 0 100 COPPER L1.0 0.40 0.30 0.70 0.54 L2.0 0.013-0-P-C--B 0.21 0.17 0.38 L1.5

3-0-P-A--A 0 100 ALUMINUM L1.0 0.19 0.15 0.34 0.33 L1.5 0.013-0-P-A--B 0.19 0.13 0.32 L1.5

3-0-P-M--A 0 100 Pb, Sn, Zn L1.0 0.12 0.20 0.32 0.35 L1.0 0.013-0-P-M--B 0.16 0.22 0.38 L1.0

3-0-B-S--A 100 0 STEEL L2.0 2.06 0.61 2.67 2.68 L1.5 0.563-0-B-S--B 1.54 0.55 2.09 1.03-0-B-S--C 2.59 0.70 3.29 L1.5

3-0-B-C--A 100 0 COPPER L2.0 3.96 1.35 5.31 5.11 L1.0 0.433-0-B-C--B 4.38 0.53 4.91 L1.0

3-0-B-A--A 100 0 ALUMINUM L2.0 1.65 0.62 2.27 3.06 L1.0 .0623-0-B-A--B 3.29 0.57 3.86 L1.0

3-0-B-M--A 100 0 Pb, Sn, Zn L2.0 40.27 33.46 73.73 107.91 L0.5 1.13-0-B-M--B 106.74 35.36 142.10 L0.5

3-0-PB-S--A 20 80 STEEL 1.5 0.67 0.23 0.90 0.87 L2.0 0.083-0-PB-S--B 0.62 0.24 0.86 L2.03-0-PB-S--C 0.61 0.23 0.84 L2.0

3-0-PB-C--A 20 80 COPPER 1.5 2.38 82.54 84.92 119.65 L1.5 0.403-0-PB-C--B 22.76 131.62 154.38 L1.5

3-0-PB-A--A 20 80 ALUMINUM 1.5 0.50 0.56 1.06 0.96 L1.5 0.103-0-PB-A--B 0.49 0.36 0.85 L1.5

3-0-PB-M--A 20 80 Pb, Sn, Zn 1.5 137.12 64.22 201.34 184.18 L1.5 0.443-0-PB-M--B 113.81 53.20 167.01 L1.5

* Blend Number Code: Phase-Additive-Fuel-Metal-Bottle“Fuel” Code: P = Petrodiesel A; B = Biodiesel; PB = 80% Petrodiesel A/20% Biodiesel“Metal” Code: S = Steel; C = Copper; A = Aluminum; M = Mixture (Lead, Tin, Zinc)

35

Table A-3b. Phase 3 Stability Test ResultsAdditive #1: OCTEL FOA 35

Conc.: 70 mg/L (25 lb/1000 bbl)


BLENDNO.

BIO-DIESEL

%

PETRO-DIESEL A

%

METAL INITIALCOLOR


ACIDNO.

3-1-B-S--A 100 0 STEEL L2.0 3.10 0.09 3.19 2.52 L1.5 0.653-1-B-S--B 2.22 0.10 2.31 L1.53-1-B-S--C 1.95 0.10 2.05 L1.5


3-1-B-A--A 100 0 ALUMINUM L2.0 1.53 0.08 1.61 1.76 L1.5 0.693-1-B-A--B 1.75 0.16 1.91 L1.5






36

Table A-3c. Phase 3 Stability Test ResultsAdditive #2: NALCO/EXXON 303 MC

Conc.: 100 ppm v/v


BLENDNO.

BIO-DIESEL

PETRO-DIESEL A

METAL INITIALCOLOR


ACIDNO.

% %3-2-B-S--A 100 0 STEEL L2.0 1.80 0.47 2.27 2.50 L1.5 0.453-2-B-S--B 1.64 0.62 2.26 L1.53-2-B-S--C 2.61 0.38 2.99 L1.5








37

Table A-3d. Phase 3 Stability Test ResultsAdditive #3: NALCO/EXXON 303 MC + Tert-butylhydroquinone (TBHQ)

Conc.: NALCO/EXXON 303 MC: 100 ppm v/vTBHQ: 0.25 % (2500 ppm)


BLENDNO.

BIO-DIESEL

PETRO-DIESEL A

METAL INITIALCOLOR


ACIDNO.





3-3-PB-S--A 20 80 STEEL 1.5 0.42 0.60 1.01 0.92 L2.0 --3-3-PB-S--B 0.29 0.48 0.77 L2.03-3-PB-S--C 0.41 0.58 0.99 L2.0


3-3-PB-A--A 20 80 ALUMINUM 1.5 0.63 0.50 1.13 1.14 L2.5 --3-3-PB-A--B 0.66 0.48 1.14 L2.5


38

Table A-3e. Phase 3 Stability Test ResultsAdditive #4: NALCO/EXXON 303 MC + TBHQ + WATER

Conc.: NALCO/EXXON 303 MC: 100 ppm v/vTBHQ: 0.25 %

WATER: Saturated


BLENDNO.

BIO-DIESEL

PETRO-DIESEL A

METAL INITIALCOLOR


ACIDNO.





3-4-PB-S--A 20 80 STEEL 1.5 1.79 0.34 2.13 3.22 L2.5 --3-4-PB-S--B 1.96 18.50 20.46* L2.53-4-PB-S--C 3.60 0.70 4.30 L2.5


3-4-PB-A--A 20 80 ALUMINUM 1.5 1.01 0.28 1.29 1.25 L2.5 --3-4-PB-A--B 0.89 0.31 1.20 L2.5


* Not included in average.

39

Table A-3f. Phase 3 Stability Test ResultsAdditive #5: ETHYL HiTEC 4733 + TBHQ + WATERConc.: ETHYL HiTEC 4733: 22.8 mg/L (8 lbs/1000 bbl)

TBHQ: 0.25 %WATER: Saturated


BLENDNO.

BIO-DIESEL

PETRO-DIESEL A

METAL INITIALCOLOR


ACIDNO.





3-5-PB-S--A 20 80 STEEL 1.5 1.82 0.69 2.51 1.52 L2.5 --3-5-PB-S--B 0.96 0.49 1.45 L2.53-5-PB-S--C 0.49 0.12 0.61 L2.5


3-5-PB-A--A 20 80 ALUMINUM 1.5 0.51 0.09 0.60 0.67 2.5 --3-5-PB-A--B 0.61 0.14 0.75 2.5


40

41

Documents

TABLE OF CONTENTS ABSTRACT 1 INTRODUCTION 3 ... - Biodieselbiodiesel.org/reports/19971201_gen-022.pdf · Table 1 Properties of Biodiesel ... Storage Stability of Biodiesel and Biodiesel