Thermal/Oxidation Storage Stability of Bio-Diesel Fuels Fuels Industry... · The use of renewable fuels, such as biodiesel, in motor vehicle fuels is expected to grow rapidly in North

Thermal/Oxidation Storage Stability of Bio-Diesel Fuels ___________________________________________________ Funded by Imperial Oil, Canadian Petroleum Products Institute and Natural Resources Canada under National Renewable Diesel Demonstration Initiative (NRDDI)

Research conducted by Imperial Oil, Products and Chemicals Division Research Department Sarnia, Ontario, Canada R399-2009 December, 2009

TABLE OF CONTENTS Page SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (i) 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. TEST PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 Oxidation Stability of the Bio-diesel Fuels by the Rancimat Test Method . . . . . . . . 2 2.2 Long Term Storage Stability of the Bio-Diesel Fuels . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Filter Blocking Tendency (FBT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. EXPERIMENTAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1 Properties of the Petroleum Base Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2 Properties of the Fatty Acid Methyl Esters (FAME) . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.3 Preparation of the Bio-Diesel Fuel Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1 Effect of the Storage Stability of Bio-Diesel Fuels on the Rancimat Induction Time . . . 4 4.1.1 Rancimat Oxidation Stability of the B5 Canola Methyl Esters (CME) . . . . . . . . . . . . . . . 4 4.1.2 Rancimat Oxidation Stability of the B5 Soybean Methyl Esters (SME) . . . . . . . . . . . . . . 5 4.1.3 Rancimat Oxidation Stability of the B5 Tallow Methyl Esters (TME) . . . . . . . . . . . . . . . 5 4.1.4 Rancimat Oxidation Stability of the B20 CME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1.5 Rancimat Oxidation Stability of the B20 SME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1.6 Rancimat Oxidation Stability of the B20 TME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2 Effect of the Storage Stability of Bio-Diesel Fuels on the Total Insolubles and FBT . . . . 8 4.2.1 Total Insolubles and FBT of the B5 CME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2.2 Total Insolubles and FBT of the B5 SME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2.3 Total Insolubles and FBT of the B5 TME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2.4 Total Insolubles and FBT of the B20 CME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.2.5 Total Insolubles and FBT of the B20 SME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2.6 Total Insolubles and FBT of the B20 TME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7 TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8. APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Disclaimer

This report is produced with financial support from Natural Resources Canada. Its content does not necessarily reflect the opinions of the Government of Canada.

(i)

Thermal Storage Stability of Bio-diesel Fuels

SUMMARY The use of renewable fuels, such as biodiesel, in motor vehicle fuels is expected to grow rapidly in North America as a result of government mandates, both federal and state/provincial. Bio-diesel is a fuel component made from plant or animal feed stocks through an esterification process. Because of its chemical structure, bio-diesel namely fatty acid methyl esters (FAME) can be very sensitive to oxidation and thermal degradation. Depending on the feedstock, some bio-diesels may contain naturally occurring antioxidants. The oxidation stability properties of bio-diesel can also be improved through the use of commercially available antioxidant or stability additives. Oxidation of bio-diesel can lead to the formation of corrosive acids and deposits that could increase wear in engine fuel pumps and fuel injectors. To gain a better understanding on the oxidation stability of bio-diesel fuel blends, the 12-weeks storage stability of fifty four bio-diesel fuels comprising essentially B5 and B20 made with canola methyl ester (CME), soybean methyl ester (SME) and tallow methyl ester (TME) was examined with and without an antioxidant. Two commercially available antioxidants chemistries (tert-butylhydroquinone and hindered phenols/amine mixture) were used in this study. The laboratory program was designed to address the formation of insoluble oxidation products produced in the bio-diesel fuel blends during long-term storage. The oxidation stability was assessed by performing the Rancimat oxidation stability test (prEN 15751-08) before and after the long-term storage as well as the total insolubles (ASTM D4625-04) and filter blocking tendency test (ASTM D2068-08) on the samples after the long-term storage. The study showed that the use of antioxidant additives improved the long term storage stability of B5 and B20 CME, SME and TME bio-diesel fuel blends as measured by Total Insolubles (ASTM D4625), Rancimat Oxidation Stability (prEN 15751) and Filter Blocking Tendency (ASTM D2068) test methods. Both of the antioxidant chemistries (tert-butylhydroquinone and amine/hindered phenol mixture) tested were able to provide adequate long term storage stability performance. No attempt was made to optimize the treat rate of the antioxidant additive. The 50 vppm treat rate worked very well for the B5 fuels. The B20 fuels may require a treat rate >50 vppm. The results of this study confirm that antioxidant use will assure the long term storage stability of bio-diesel fuels. This is a very important consideration when formulating renewable diesel fuels to prevent thermal degradation and sediment formation during long term storage. To maximize the benefit of the antioxidant, the additive should be added to the B100 during the manufacturing process after the trans-esterification and purification steps per industry best practice. The information generated by this study will be used to direct future renewable diesel blending formulations and by standard-setting bodies to set specifications on oxidation stability of bio-diesel fuel blends that will ensure "fit for service" fuel products.

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1. INTRODUCTION The use of renewable fuels, such as biodiesel, in motor vehicle fuels is expected to grow rapidly in North America as a result of government mandates, both federal and state/provincial. Bio-diesel or B100 obtained from trans-esterification of fat and vegetable oils with methanol are composed of fatty acid methyl esters (FAME). FAME is more prone to oxidation than typical petroleum diesel unless it is treated with antioxidants. Resistance to oxidative degradation during storage is an important issue for the successful development of alternative fuels.

The oxidation mechanism of FAME is generally well understood (1). Fatty acid alkyl chains have varying numbers of double bonds. Generally, the rate of oxidation of fatty acid alkyl esters depends on the number of double bonds and their position on the chain (2,3). When multiple double bonds are present they are in allylic position, which means they are separated by a single methylene group. Common FAME such as rapeseed methyl ester (RME), canola methyl ester (CME), soybean methyl ester (SME) and tallow methyl ester (TME) contain primarily C16 to C18 carbon chains with zero to three double bonds. The eighteen-carbon chain oleic acid contains one double bond, two for linoleic acid and three for the linoleic acid. The relative oxidation rates for these C18 esters are linolenic > linoleic >> oleic (4).

Several studies related to the stability of bio-diesel have been reported in the literature. Westbrook (5) has examined the storage stability of the B100 by the ASTM D4625 for a 12-weeks period. The author reported wide variations of insolubles formation, acid number and viscosity increase. The least stable samples exhibited unacceptable levels of insolubles and acidity 4 to 8 weeks into the test. McCormick et al. (6) examined the stability characteristics of bio-diesel samples that were commercially available at blenders and distributors during 2004 and showed that the stability range results primarily from differences in fatty acid makeup and natural antioxidant content. Bondoli et al. (7) and Thompson et al. (8) studied the deterioration of RME under different storage conditions, including changes in acidity, peroxide value, and viscosity, and found that acid value, peroxide value, and viscosity increased with time.

Several studies have showed that antioxidants improve bio-diesel oxidation stability. Plant-

derived bio-diesel contains naturally occurring tocopherols, which slightly stabilize the bio-diesel (9). Distillation of bio-diesel removes the natural antioxidant and reduces the Rancimat oxidation stability. Westbrook (5) and Schneller (9) have shown that addition of antioxidants can improve bio-diesel oxidation stability. The presence of high levels of oxidation products in the bio-diesel can lead to formation of insolubles gums and sediment deposits in the fuel systems that can influence vehicle operability. This is one of the main concerns for engine and fuel injector manufacturers. Terry et al. (10) showed that at very high levels of oxidation, bio-diesel blends can separate into two phases to cause fuel pump and injector operational problems or lacquer deposits on fuel system components. To gain a better understanding of the long-term storage stability of bio-diesel fuel blends, the oxidation stability, the total insolubles and the filter blocking tendency (FBT) of fifty four bio-diesel fuels comprising essentially B5 and B20 made with canola methyl ester, soybean methyl ester and tallow methyl ester was examined. The laboratory program was designed to address the effect of antioxidants on the Rancimat oxidation stability, the total insolubles formation and the filter blocking tendency after storage for a 12-week period. Although it is recognized that other

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factors such as light, metals and water may have significant impact on the oxidation stability of biodiesel fuels, they were not examined in this study. It is expected that the results will lead to a better understanding of the influence of antioxidant during long term storage and will provide information to direct future renewable diesel blending formulations. 2. TEST PROCEDURES 2.1 Oxidation Stability of the Bio-diesel Fuels by the Rancimat Test Method

The oxidation stability of bio-diesel (B100) and bio-diesel blends (B2 to B99) is determined using prEN 15751 test method (11). This test is based on EN 14112 (12) and utilizes the Rancimat instrument that measures the induction time or oxidation stability index. The Rancimat instrument is shown below.

As bio-diesel and bio-diesel blends are exposed to air, acids begin to form, which are

transferred to a conductivity cell containing de-ionized water. Once the acid concentration in the water is high enough, the conductivity undergoes a rapid increase that is called the induction period. This test is used to assess the storage stability of bio-diesel and bio-diesel blends. The repeatability of the test method is given by the following equation:

r = 0.22027 + 0.04344X where X represents the mean of two results

The ASTM D6751 Standard for FAME (13) requires having a minimum of three hours

induction period whereas the European EN 14214 (14) requires a minimum of six hours. It is interesting to note that the ASTM 7467 Standard (15) for B6-B20 fuels also requires a minimum of six hours induction time. 2.2 Long Term Storage Stability of Bio-Diesel Fuels ASTM D4625 (16) is the most widely accepted test method for assessing the storage stability of middle distillate fuels. This test method was used in this study to assess the storage stability of the bio-diesel fuel blends. The fuel is stored at 43°C for selected periods up to 24 weeks. In this study, we have selected 12 weeks. One week storage at this test temperature is generally accepted as equivalent to one month storage at 17°C. At the end of the test period, the sample is filtered to determine the total insolubles. We have followed ASTM D4625-04 which uses 0.8µm nylon, 47 mm diameter filter. Bio-diesel is known to be relatively inert to nylon.

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2.3 Filter Blocking Tendency Test The ASTM D2068 test method is used to determine the filter blocking tendency (FBT) and filterability of middle distillate fuel oils and liquid fuels such as bio-diesel and bio-diesel blends. It is applicable to fuels within viscosity range of 1.3 to 6.0 mm2/s at 40°C. In this study we have followed the Procedure A that uses a 1.6µm glass fiber, 13 mm diameter filter. The filtration step was performed at ambient temperature. 3. EXPERIMENTAL 3.1 Properties of the Petroleum Base Fuels Three Canadian commercial low sulphur diesel fuels having low cloud points (ULSD- Cloud Point, °C) which represent typical winter fuels were selected for this study: a ULSD-25, a ULSD-29, and a ULSD-46. The low sulphur diesel fuels ULSD-29 and ULSD-46 were acquired from Imperial Oil refineries whereas the ULSD-25 was obtained from another Canadian refiner. These petroleum diesel fuels were used as blend stock for the preparation of laboratory bio-diesel fuel blends. The diesel fuels did not contain any flow improver but some contained cetane improver and Stadis 450 conductivity improver. The aromatic content of these fuels ranges from 0 to 42.7%. The properties of the diesel fuels are presented in Table 1. All the fuels met the CAN/CGSB-3.517 Standard. 3.2 Properties of the Fatty Acid Methyl Esters (FAME) Three typical FAME or B100 bio-diesels consisting of CME, SME and TME were selected for this study. FAME samples were acquired from three suppliers designated A, B and C, respectively. The CME and SME used in this study did not contain antioxidant. With regard to the TME, about 150 wppm butyl hydroxy toluene (BHT) was added to the fat prior to the trans-esterification process. The properties of the FAME taken from the C's of A (Appendices 1 to 3) are presented in Table 2. The density for the SME and TME was determined by Imperial Oil. The gas chromatographic compositional analysis of the CME, SME and TME is illustrated below.

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3.3 Preparation of Bio-Diesel Fuel Blends Eighteen (3litre) bio-diesel fuel blends comprising in B5 and B20 were prepared and used for the 12-weeks storage stability study. Two (1litre) samples of each blend were additized with 50 vppm antioxidant D and E respectively and one (1litre) sample was not additized. Additive D contains tert-butylhydroquinone chemistry whereas additive E is a mixture of amines and hindered phenols. Additive D contains 31.5 wt% active ingredients whereas Additive E contains 70 wt% active ingredients. Two 400 ml of each blend were stored in the stability oven at 43°C for 12-weeks. One 400 mL bottle was used for the determination of the total insolubles by ASTM D4625-04 and the other 400 mL of same blend was used for the Rancimat oxidation stability and the filter blocking tendency according to ASTM D2068-08. A description of the bio-diesel fuel blends is presented in Tables 3 and 4. 4. RESULTS AND DISCUSSION 4.1 Effect of the Storage Stability of Bio-Diesel Fuels on the Rancimat Induction Time

About 100 mL of the "fresh" and aged bio-diesel fuel blends (total 54 samples) were sent to the Alberta Research Council (ARC) for the Rancimat oxidation stability measurement by prEN 15751. A single determination was performed on each sample. The test results are presented in Appendices 4 to 17 and summarized in Table 3 and 4. The effect of FAME type and antioxidant (Additive D and E) on the Rancimat oxidation stability is discussed in the following sections. Note that a significant difference is defined as two results which differ by > 2 x r (see Section 2.1).

4.1.1 Rancimat Oxidation Stability of the B5 Canola Methyl Esters (CME) The effect of antioxidant and aging on the Rancimat oxidation stability of the B5 CME bio-diesel fuels is illustrated in Figure 1.

Figure 1. Rancimat Oxidation Stability - B5 CME

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The unadditized "fresh" and "aged" B5 CME bio-diesel fuels met the ASTM D7467

oxidation stability limit of 6 hours minimum. The presence of 50 vppm antioxidant, Additives D

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and E, significantly improved the Rancimat oxidation stability of the "fresh" bio-diesel fuel blends. Figure 1 shows that Additive E is consistently more effective than Additive D for improving the Rancimat oxidation stability even for the "aged" fuel samples. The Rancimat oxidation stability of the B5 CME bio-diesel fuel blends did not degrade significantly after 12-weeks at 43°C. Comparison of the ULSD-25 (0% aromatics) fuel with the ULSD-29 (42.7% aromatics) fuel indicates that the fuel composition does not have a significant impact on the Rancimat oxidation stability.

4.1.2 Rancimat Oxidation Stability of the B5 Soybean Methyl Esters (SME)

The effect of antioxidant and aging on the Rancimat oxidation stability of the B5 SME bio-

diesel fuels is illustrated in Figure 2.

Figure 2. Rancimat Oxidation Stability - B5 SME

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Similarly to the B5 CME fuels, the unadditized "fresh" and "aged" B5 SME met the ASTM

ASTM D7467 oxidation stability limit of 6 hours minimum. Both additives significantly improve the Rancimat oxidation stability. Additive E provided consistently better Rancimat oxidation stability than Additive D in the B5 SME bio-diesel fuels. The Rancimat oxidation stability of the B5 SME did not degrade significantly after aging 12-weeks at 43°C with the exception of additized ULSD-46.

4.1.3 Rancimat Oxidation Stability of the B5 Tallow Methyl Esters (TME)

The effect of antioxidant and aging on the Rancimat oxidation stability of the B5 TME bio-


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Figure 3. Rancimat Oxidation Stability - B5 TME

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The Rancimat oxidation stability of the B5 TME bio-diesel fuels is similar to the B5 CME

and B5 SME bio-diesel fuels. It is interesting to note that the Rancimat oxidation stability can be improved significantly with Additive E although TME contains a significant amount of saturated methyl esters (41wt%, Section 3.2) that are more resistant toward oxidation than the unsaturated esters (1). The Rancimat oxidation stability remained about the same after aging 12-weeks at 43°C with the exception of ULSD-25 and ULSD-46 fuels containing Additive E. However, the induction time for the bio-diesel fuels containing Additive E remained higher than those containing Additive D after aging 12-weeks at 43°C.

4.1.4 Rancimat Oxidation Stability of the B20 CME The effect of antioxidant and aging on the Rancimat oxidation stability of the B20 CME bio-diesel fuels is illustrated in Figure 4.

Figure 4. Rancimat Oxidation Stability - B20 CME

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Figure 4 shows that Rancimat oxidation stability of the unadditized bio-diesel fuels is quite reasonable (~ 12 hours) but degraded significantly after 12-weeks at 43°C due to the lack of antioxidant (B20 Vs B5). Additive D and E directionally improved the Rancimat oxidation stability maintaining a 6 hours induction time after aging 12-weeks at 43°C. At 50 vppm treat rate, Additive

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D provided better performance in the B20 CME bio-diesel fuels than Additive E in maintaining the Rancimat oxidation stability during aging. The Rancimat oxidation stability of B20 CME could likely be improved by the addition of more antioxidant. 4.1.5 Rancimat Oxidation Stability of the B20 SME

The effect of antioxidant and aging on the Rancimat oxidation stability of the B20 SME bio-


Figure 5. Rancimat Oxidation Stability- B20 SME

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The Rancimat oxidation stability decreases with increasing amount of SME in the blend (B5

Vs B20). This is illustrated by comparing Figure 5 with Figure 2. This comment also applies to the CME bio-diesel fuel blends (Figure 4 and Figure 1). Additive D gave similar performance to Additive E in the B20 SME. The Rancimat oxidation stability of the B20 SME bio-diesel fuel blends degraded significantly after aging 12-weeks at 43°C. This observation was also noticed for the B5 SME.

4.1.6 Rancimat Oxidation Stability of the B20 TME

The effect of antioxidant and aging on the Rancimat oxidation stability of the B20 TME bio-diesel fuels is illustrated in Figure 6.

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Figure 6. Rancimat Oxidation Stability - B20 TME

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Figure 6 shows that Additive E provided significantly better Rancimat oxidation stability than Additive D for the B20 TME bio-diesel fuel blends. This performance may be explained by the presence of significantly less unsaturated esters (Section 3.2) in the TME and more active ingredients in Additive E (70wt%) than in Additive D (31.5wt%). Both additives show similar performance in terms of retention of the Rancimat oxidation stability during aging for 12-weeks at 43°C. Similar behavior was observed for the B5 TME bio-diesel fuel blends (Figure 3). The B20 TME bio-diesel fuel blends would require less Additive E to achieve similar Rancimat oxidation stability to B20 CME (Figure 4) and B20 SME (Figure 5) bio-diesel fuel blends.

4.2 Effect of the Storage Stability of Bio-Diesel Fuels on the Total Insolubles and FBT The total insolubles comprising of the filterable insolubles and adherent insolubles were determined on 400 mL of each of the fifty four bio-diesel fuel blends according to ASTM D4625-04 (16) test procedure. The filter blocking tendency (FBT) was also determined on another 400 mL sample for each of the fifty four bio-diesel fuel blends according to ASTM D2068-08 (17). Both of these tests were performed at Imperial Oil Limited. The test results for the total insolubles and the FBT are presented in Table 3 (B5 blends) and Table 4 (B20 blends). 4.2.1 Total Insolubles and FBT of the B5 CME

The effect of antioxidant and aging on the total insolubles and FBT of the B5 CME bio-


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Figure 7. Total Insolubles (TI) and FBT - B5 CME

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Figure 7 shows that the total insolubles of all the B5 CME are significantly lower than the

generally accepted 1.6mg/100 mL limit for diesel fuels. The antioxidants (Additives D and E) have no impact on the total insolubles for the B5 CME. The base fuel composition (e.g. ULSD-25 with 0 wt% aromatics and ULSD-29 with 42.7wt% aromatics) also has no impact on the total insolubles after aging 12-weeks at 43°C. The FBT's are similar to a base fuel (18).

4.2.2 Total Insolubles and FBT of the B5 SME

The effect of antioxidant and aging on the total insolubles and FBT of the B5 SME bio-diesel fuels is illustrated in Figure 8.

Figure 8. Total Insolubles (TI) and FBT - B5 SME

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Very low ( < 1.6 mg/100 mL) total insolubles was also measured for the B5 SME bio-diesel fuel blends. No significant performance difference was observed for the B5 SME bio-diesel fuel blends containing Additives D and E. A FBT of 1.0 was measured for all fuels with the exception of the unadditized B5 SME in ULSD-29 which was 1.2. However, the FBT is still typical of that for a conventional diesel fuel.

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4.2.3 Total Insolubles and FBT of the B5 TME The effect of antioxidant and aging on the total insolubles and FBT of the B5 TME bio-diesel fuels is illustrated in Figure 9.

Figure 9. Total Insolubles (TI) and FBT - B5 TME

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Low (< 1.6 mg/100 mL) total insolubles were measured for the B5 TME bio-diesel fuel blends. Although the total insolubles are low, the presence of Additive D and E directionally reduced the level of total insolubles. In view of the B20 TME in ULSD-46 (Figure 12), the 1.4 mg/100mL total insolubles appear to be too high. All FBT are 1.0 with the exception of the unadditized B5 TME in ULSD-29 which was 1.2. 4.2.4 Total Insolubles and FBT of the B20 CME The effect of antioxidant and aging on the total insolubles and FBT of the B20 CME bio-diesel fuels is illustrated in Figure 10.

Figure 10. Total Insolubles (TI) and FBT - B20 CME

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The total insolubles for all B20 CME bio-diesel fuel blends are less than 1.6 mg/100 mL with the exception for the unadditized ULSD-25. The higher total insolubles as compared with the B5 CME (Figure 7) is explained by the presence of more CME in the blend. The B20 CME in the ULSD-46 fuel produced lower total insolubles. The presence of Additive D and E reduced the total insolubles of the B20 CME bio-diesel fuel blends. In view of other results with Additive D (also see Figures 11 and 12), we believe the total insolubles of 2.3 mg/100 mL for the B20 CME in ULSD-46 is an outlier. The FBT for all the B20 CME bio-diesel fuel blends were low at 1.0. 4.2.5 Total Insolubles and FBT of the B20 SME The effect of antioxidant and aging on the total insolubles and FBT of the B20 SME bio-diesel fuels is illustrated in Figure 11.

Figure 11. Total Insolubles (TI) and FBT - B20 SME

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0 m

L


The total insolubles for all B20 SME bio-diesel fuel blends are significantly less than the 1.6 mg/100 mL target limit. The presence of antioxidant (Additive D and E) directionally reduces the total insolubles. High FBT (> 1.4) were observed for the B20 SME with and without Additive E with base fuels ULSD-25 and ULSD-46. Additive D was effective in maintaining the FBT of 1.0 in all bio-diesel fuel blends. Since low FBT( <1.4) were measured for all B5 SME fuels (Figure 8), the high FBT for the B20 SME is attributed to the presence of more oxidatively unstable compounds (Section 3.2) in the blends as well as the lower effectiveness of Additive E. 4.2.6 Total Insolubles and FBT of the B20 TME The effect of antioxidant and aging on the total insolubles and FBT of the B20 TME bio-diesel fuels is illustrated in Figure 12.

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Figure 12. Total Insolubles (TI) and FBT - B20 TME

0.00.20.40.60.81.01.21.41.61.82.02.22.42.6

ULSD-25TI

ULSD-25FBT

ULSD-29TI

ULSD-29FBT

ULSD-46TI

ULSD-46FBT

FBT

or m

g/10

0 m

LNoneAdditive DAdditive E

Total insolubles of less than 1.6 mg/100 mL were measured in all B20 TME bio-diesel fuel blends. Additves D and E directionally reduced the levels of total insolubles. The FBT were low (< 1.4) for all B20 TME bio-diesel fuel blends.

5. CONCLUSIONS

1. The use of antioxidant additives improved the long term storage stability of B5 and B20 CME, SME and TME bio-diesel fuel blends as measured by Total Insolubles (ASTM D4625), Rancimat Oxidation Stability (prEN 15751) and Filter Blocking Tendency (ASTM D2068) test methods.

2. Both of the antioxidant chemistries (tert-butylhydroquinone and amine/hindered phenol mixture) tested were able to provide adequate long term storage stability performance.

3. No attempt was made to optimize the treat rate of the antioxidant additive. The 50 vppm treat rate worked very well for the B5 fuels. The B20 fuels may require a treat rate >50 vppm.

The results of this study confirm that antioxidant use will assure the long term storage stability of bio-diesel fuels. This is a very important consideration when formulating renewable diesel fuels to prevent thermal degradation and sediment formation during long term storage. To maximize the benefit of the antioxidant, the additive should be added to the B100 during the manufacturing process after the trans-esterification and purification steps per industry best practice. The information generated by this study will be used to direct future renewable diesel blending formulations and by standard-setting bodies to set specifications that will ensure "fit for service" fuel products. 6. REFERENCES 1. Waynick, J.A., "Characterization of Biodiesel Oxidation and Oxidation Products", CRC

Project No. AVFL-2b. National Renewable Energy laboratory, NREL/TP-540-39096, 2005. 2. Frankl E.N., "Lipid Oxidation". Scotland: The Oily Press, 19, 1998

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3. Bouaid Abderrahim, Martinez Mercedes and Aracil José, "Long Storage Stability of

Biodiesel from Vegetable and Used Frying Oils", Fuel, 86, 2596-2602, 2007. 4. Cosgrove, J.P., Church, D.F. and Pryor, W.A., "The Kinetics of the Autooxidation of

Polyunsaturated Fatty Acids", Lipids, 22, 299-304, 1987. 5. Westbrook, S.R., "An Evaluation and Comparison of Test Methods to Measure the

Oxidation Stability of Neat Biodiesel".Subcontract report. National Renewable Energy Laboratory, NREL/SR-540-38983, 2005.

6. McCormick, R.L., Ratcliff, M., Moens, L., and Lawrence, R.," Several Factors Affecting the

Stability of Biodiesel in Standard Accelerated Tests", Fuel Processing Technology, 88, 651-657, 2007.

7. Bondoli, P., Gasparoli, A., Lanzani, A., Fedeli, E.Veronese, S. and Sala, M., Amer. Soc.

Agric. Eng. (ASAE) 72, 699-702, 1995. 8. Thompson, J.C., Peterson, D.L., Reece, D.L. and Beck, S.M., Trans ASAE, 41, 931-939,

1998. 9. Schneller Emily and Gatto Vincent, "Improving the Quality of Biodiesel Through the Use of

Antioxidants and Metal Chelators", Biodisel Magazine, February 2008. 10. Terry, B., McCormick, R.L. and Natarajan, M.,"Impact of Biodiesel Blends on Fuel System

Component Durability", SAE Paper No. 2006-01-3279, 2006. 11. prEN 15751-08, Automotive Fuels – Fatty Acid Methyl Ester (FAME) Fuel and Blends with

Diesel Fuel – Determination of Oxidation Stability by Accelerated Oxidation Method. 12. EN 14112-03, Fat and Oil Derivatives - Fatty Acid Methyl Esters (FAME) - Determination of Oxidation Stability (Accelerated Oxidation Test). 13. ASTM D6751-08, Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle

Distillate Fuels. 14. EN 14214-08, Automotive Fuels - Fatty Acid Methyl Esters (FAME) for Diesel Engines -

Requirements and Test Methods. 15. ASTM D7467-08, Standard Specification for Diesel Fuel Oil, Biodiesel Blend (B6 to B20). 16. ASTM D4625-04, Standard Test Method for Middle Distillate Fuel Storage Stability at 43°C (110°F). 17. ASTM D2068-08, Standard Test Method for Determining Filter Blocking Tendency.

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18. Low Temperature Storage Test Phase 2- Identification of Problem Species, Study Funded by Imperial Oil, Canadian Petroleum Products Institute and Natural Resources Canada under NRDDI Program. Final Report R230-2009, May 25, 2009.

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7. TABLES

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Table 1. Properties of the Petroleum Diesel Fuels

Sample ID 48909 47424 47497 CGSB-3.517 Product ULSD-25 ULSD-29 ULSD-46 CGSB Type Type B Type B Type B Type A Type B ULSD No. 2 2 2 Limits Limits Properties Min Max Min Max Appearance C&B C&B C&B Density at 15°C, kg/m3 843 844 845 Flash Point,°C 81 64 51 40.0 40.0 Viscosity @ 40°C, mm2/s 3.16 2.05 2.04 1.30 3.60 1.701 4.10 Aromatics, wt% 0 42.7 39.3 Sulphur, mg/kg < 1.2 5 3.1 15 15 Cetane Index 49.1 44.3 42.5 40.0 40.0 Cloud Point, °C -24.7 -28.7 -46.0 Conductivity @ 20°C, pS/m 292 750 1750 25 25 Distillation D86

IBP 201.5 173.3 156.7 5% 211.1 197.2

10% 216.3 208.4 183.6 20% 223.0 221.2 30% 231.5 232.5 214.1 40% 243.5 243.0 50% 261.1 251.1 245.8 60% 288.8 258.9 70% 317.4 267.1 80% 335.8 275.6 90% 351.4 286.5 306.8 290.0 360.0 95% 363.0 295.5 321.1 FBP 364.6 304.9 331.0

1) For a fuel designed for an operability temperature colder than -20°C, the minimum viscosity shall be 1.30 mm2/sec.

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Table 2. Properties of the FAME

Sample ID BIO- BIO- BIO- 50345 50341 51740 Supplier A B C ASTM D6751 EN 14214 Properties CME SME TME Min Max Min Max Density @ 15°C, kg/m3 883.5 885.7 876.2 - - 860 900 KV @ 40°C, mm2/s 4.45 4.10 4.28 1.9 6.0 3.5 5.0 Total sulphur, mg/kg 7.5 0.7 7.6 15 10

Water & Sediment, vol% 0.000 0.001 <

0.005 0.050 - - Water, mg/kg - 230 - - - 500 Cloud Point, °C 0.5 1 11 - - - - Flash Point, °C 182 156 174 93 120 Acid Number, mg KOH/g 0.09 0.34 0.21 0.50 0.50 Carbon Residue, wt% 0.001 < 0.050 0.011 0.050 - - Carbon Residue, 10% Distillation residu, wt% - - - - - 0.30 Copper Corrosion 1a 1 1a1 3 Cetane Number 54.6 51 58.21 47 51 Oxidation Stability, hours > 6.0 6.7 9.2 3 6.0 Sulfated Ash, wt% 0.001 0.005 0.0011 0.020 0.02

Free Glycerin, wt% < 0.001 0.003 0.001

9 0.020 0.02

Total Glycerin, wt% 0.026 0.140 0.056

1 0.240 0.25 Monoglycerides, wt% 0.039 0.475 - - - 0.80 Diglycerides, wt% 0.081 0.060 - - - 0.20 Triglycerides, wt% 0.031 0.055 - - - 0.20 Cold Soak Filtration, sec1 110 65 82 2002 - - 1) Typical. 2) For operability below -12°C.

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8. APPENDICES

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Appendix1

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Appendix 2

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Appendix 3

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Appendix 4

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Appendix 5

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Appendix 6

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Appendix 7

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Appendix 8

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Appendix 9

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Appendix 10

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Appendix 11

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Appendix 12

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Appendix 13

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Appendix 14

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Appendix 15

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Appendix 16

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Appendix 17

Documents

Thermal/Oxidation Storage Stability of Bio-Diesel Fuels Fuels Industry... · The use of renewable fuels, such as biodiesel, in motor vehicle fuels is expected to grow rapidly in North