Potential Analytical Methods for Stability Testing of Biodiesel and Biodiesel Blends

Stavinoha, Leo L.; Howell, Steve

doi:10.4271/1999-01-3520

Cited by 37 publications

(32 citation statements)

References 3 publications

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“…Biodiesel AL-27160, also unstable, produced a B5 blend with a short induction time and low D2274 deposits, but appears to be thermally unstable. These data confirm previous results and indicate that biodiesel and B5 blends are generally thermally stable, 16 and with the implementation of the 3-hour induction period there appears to be no additional information to be gained about blends from the thermal stability values of the B100. Several B5 samples were also treated with antioxidant additives and evaluated on accelerated tests.…”

Section: Accelerated Testssupporting

confidence: 80%

“…These results show acid value and total insolubles in a range similar to that observed in previous investigations that used this test. 5,8,16 The level of B100 total insoluble on this test that is indicative of an unacceptable fuel blending component, and the repeatability of this test for B100, are unknown. The acid number increase may be a more accurate indicator than sediment formation of deleterious changes in B100 under these conditions.…”

Section: Results: Stability Of B100 Accelerated Testing and Charactermentioning

confidence: 99%

“…16 Additionally, we attempted to keep the filtration time as consistent as possible. Iso-octane insolubles of the filtrate were determined by adding 100 ml of the filtered, post-D2274 B100 to 400 ml of prefiltered iso-octane.…”

Section: Accelerated Stability Testsmentioning

confidence: 99%

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Empirical Study of the Stability of Biodiesel and Biodiesel Blends: Milestone Report

McCormick¹,

Westbrook²

2007

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Executive SummaryIn support of the U.S. Department of Energy Fuels Technologies Program Multiyear Program Plan goal of identifying fuels that can displace 5% of petroleum diesel by 2010, the National Renewable Energy Laboratory (NREL), in collaboration with the National Biodiesel Board (NBB) and with subcontractor Southwest Research Institute, performed a study of biodiesel oxidation stability. The objective of this work was to develop a database that supports specific proposals for a stability test and specification for biodiesel and biodiesel blends. B100 samples from 19 biodiesel producers were obtained in December of 2005 and January of 2006 and tested for stability. Eight of these samples were then selected for additional study, including long-term storage tests and blending at 5% and 20% with a number of ultra-low sulfur diesel (ULSD) fuels. These blends were also tested for stability. The study used accelerated tests as well as tests that were intended to simulate three real-world aging scenarios: (1) storage and handling, (2) vehicle fuel tank, and (3) high-temperature engine fuel system. Several tests were also performed with two commercial antioxidant additives to determine whether these additives improve stability. This report documents completion of NREL's Fiscal Year 2007 Annual Operating Plan Milestone 10.1.The B100 samples examined show a broad distribution of stability on accelerated tests, with oil stability index (OSI) or Rancimat induction time results ranging from less than 1 hour to more than 9 hours and ASTM D2274 total insolubles ranging from less than 2 mg/100 ml to nearly 18 mg/100 ml. The accelerated test data indicate that if the B100 stability is above roughly a 3-hour induction time, blends prepared from that B100 appear to be stable on the OSI and D2274 tests.The D4625 long-term storage results for B100 indicate that most biodiesel samples, regardless of initial induction time, will begin to oxidize immediately during storage. If induction time is near or below the 3-hour limit, the B100 will most likely go out of specification for either stability or acid value within 4 months. Even B100 with induction times longer than 7 hours will be out of specification for oxidation stability at only 4 months, although these samples may not have shown a significant increase in acidity or in deposit formation. The 3-hour B100 induction time limit appears to be adequate to prevent oxidative degradation for both B5 and B20 blends in storage for up to 12 months.For tests that simulated fuel tank aging and high temperature stability, we conclude that stable B100 (longer than 3 hours induction time) leads to stable B5 blends. For B20, the results are less definitive, but provide considerable evidence that B100 with induction time of at least 3 hours produces stable B20 blends, but the test cannot differentiate between intermediate and highly stable samples for acid number increase or sediment formation under these worst-case test conditions. Additional work is required to confirm this finding and to...

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Section: Accelerated Testssupporting

confidence: 80%

Section: Results: Stability Of B100 Accelerated Testing and Charactermentioning

confidence: 99%

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Empirical Study of the Stability of Biodiesel and Biodiesel Blends: Milestone Report

McCormick¹,

Westbrook²

2007

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“…Sometimes the rapid increase in PV is used as the endpoint determination. A similar method developed in the petroleum fuels industry, ASTM D2274, uses a filtration and gravimetric determination to measure the insolubles produced during a heated oxidation period in which O 2 is bubbled through the sample (typically 16 hours at 95°C) 90 . A less oxidatively severe test is ASTM D4625.…”

Section: Stability Test Methodsmentioning

confidence: 99%

“…When air-oxidized at 95°C, soy ethyl esters gave lower TAN values (less secondary oxidation products) than soy methyl esters 90 . Also, the ethyl esters had longer oxidation induction periods than then the methyl esters when measured by ASTM D525, a pressurized bomb test procedure commonly used for gasoline oxidation stability evaluation.…”

Section: Other Factors Affecting Fatty Oil Oxidationmentioning

confidence: 99%

Characterization of Biodiesel Oxidation and Oxidation Products

2005

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This report must be reproduced in full,unless SwRI approves a summary or abridgement. iii EXECUTIVE SUMMARY Stability Chemistry FundamentalsChemical reactivity of fatty oils and esters can be divided into oxidative and thermal instability. Both of these types of instability are determined by the amount and configuration of the olefinic unsaturation on the fatty acid chains. Many of the plant-derived fatty oils, including soy and rapeseed, contain polyunsaturated fatty acid chains that are methylene-interrupted rather than conjugated. This structural fact is key to understanding both oxidative and thermal instability.In oxidative instability, the methylene carbons between the olefinic carbons are the sites of first attack. After hydrogen is removed from such carbons oxygen rapidly attacks and a hydroperoxide is ultimately formed where the polyunsaturation has been isomerized to include a conjugated diene. This reaction is a chain mechanism that can proceed rapidly once an initial induction period has occurred. The greater the level of unsaturation in a fatty oil or ester, the more susceptible it will be to oxidation. Once the hydroperoxides have formed, they decompose and inter-react to form numerous secondary oxidation products including aldehydes, alcohols, shorter chain carboxylic acids, and higher molecular weight oligomers often called polymers. Another polymerization mechanism, vinyl polymerization, has been proposed as being part of the degradation process of fatty oils and esters. However, conventional understanding of oxidation chemistry would imply that such processes would not be significant when oxygen was abundant, so its precise level of importance has not been determined.Metals, free fatty acids, acidic fuel additives, the size of the alcohol group (for mono-esters), and the presence of natural antioxidants can all impact the oxidative stability of fatty oils and/or esters. Oxidation can also be catalyzed by light, but such photo-oxidation should not be a significant factor for the manufacture and transportation of biodiesel fuel.Thermal polymerization of fatty oils and esters does not become important until temperatures of 250-300°C are reached. This is because the methylene-interrupted polyunsaturated structure cannot participate in such reactions until it isomerizes into a conjugated configuration, and such isomerization will not occur until that temperature range is reached. Thermal polymerization occurs by the Diels Alder reaction, and two fatty acid chains are linked by a cyclohexene ring. Higher order oligomers are also possible, although the exact mechanism is still not established. Certain thermal polymerization products in used cooking oils may carry over to non-distilled biodiesel. The verification of such compounds and their impact on fuel quality has not been determined. Thermal polymerization may be of limited importance in biodiesel fuel that is repeatedly heated by the engine and recycled to the fuel tank before actual combustion. However, thermal polymerization will not impact stor...

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Evaluation of biodiesel storage stability using reference methods

Bondioli¹,

Gasparoli²,

Bella³

et al. 2002

Euro J Lipid Sci & Tech

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Evaluation of biodiesel storage stability using reference methodsThe recorded changes in 8 different samples of biodiesel (from 4 different feedstocks, both undistilled and distilled) during accelerated ageing are shown in this paper. ASTM D 4625 method for quick ageing of common diesel fuels, carried out at 43 °C, allows to simulate the changes taking place in fuel during a long-term storage. All quality parameters of biodiesel are changing during time, according to the storage stability of different samples. The changes in other parameters not included in CEN tentative specification such as polymer content and peroxide value were recorded and plotted against storage time. Samples were also evaluated in terms of insoluble formation (filterable + adherent) but in any case significant insoluble formation was observed. The conclusion was that polymers formed during storage of biodiesel in controlled conditions are soluble in oxidised biodiesel, thanks to its high polarity and become insoluble only when oxidised biodiesel is mixed with diesel fuel.

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Potential Analytical Methods for Stability Testing of Biodiesel and Biodiesel Blends

Cited by 37 publications

References 3 publications

Empirical Study of the Stability of Biodiesel and Biodiesel Blends: Milestone Report

Empirical Study of the Stability of Biodiesel and Biodiesel Blends: Milestone Report

Characterization of Biodiesel Oxidation and Oxidation Products

Evaluation of biodiesel storage stability using reference methods

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