Effects of Bio-Fuels on Vehicle Performance: Degradation Mechanism Analysis of Bio-Fuels

Miyata, Itsuki; Takei, Yasunori; Tsurutani, Kazushi; Okada, Masanori

doi:10.4271/2004-01-3031

Cited by 26 publications

(16 citation statements)

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“…Figure 11 shows that at 4 weeks the only samples that had gone out of specification for acid value had initial induction times of 3.1 hours or lower. Our experience agrees with that of other researchers, 5,7,8,9,14,15,17 that B100 samples with longer induction times are more stable in real-world settings. Thus, we take these results to mean that most biodiesel samples, regardless of initial induction time, will begin to oxidize immediately during storage.…”

Section: Storage Stabilitysupporting

confidence: 82%

“…Results of these scoping tests are shown in Table 1, which shows that ullage purge had no significant effect on the results, and thus was not used in subsequent tests. 17 to correlate well with Rancimat induction time.…”

Section: Accelerated Stability Testsmentioning

confidence: 55%

“…Based on an earlier report, we anticipated that these tests would correlate to some extent. 17 The circled data points indicate that no oxidation was observed after 780 minutes, and the results are simply plotted as 780 minutes. Figure 3 indicates a poor correlation between these methods (r 2 of 0.4).…”

Section: High-temperature Fuel System Environmentmentioning

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: Storage Stabilitysupporting

confidence: 82%

Section: Accelerated Stability Testsmentioning

confidence: 55%

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

McCormick¹,

Westbrook²

2007

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“…Induction Period Stability The IP stability, sometimes called the Rancimat or Oil Stability Index (OSI), is an indicator of the oxidative stability of fuels. The IP for neat diesel fuel is well over 24 hours [8,9]. Previous work has shown the IP of biodiesel and biodiesel blends to be significantly less than that of diesel fuel unless treated with a synthetic antioxidant [10].…”

Section: Standard Testsmentioning

confidence: 73%

Analysis of Biodiesel Blends Samples Collected in the United States in 2008 (Revised)

Alleman¹,

Fouts²,

McCormick³

2010

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In the summer of 2008, NREL conducted a nationwide survey of the quality of B20, a blended fuel consisting of about 20 volume percent (vol%) biodiesel and 80 vol% petroleum diesel. Thirty-three samples were collected prior to the announcement of a new ASTM specification, D7467, for B6−B20. The B20 samples were tested against multiple properties-those included in the eventual D7467 specification and other properties of interest. Because this study preceded the announcement of the specification, the samples could not be termed "on" or "off" specification.Previous NREL surveys have shown that biodiesel blending has been problematic, because the samples have been almost evenly distributed above and below B20. In this survey, only 60% of the samples were nominally B20 (i.e., B18−B22), and the majority of the rest of the samples contained less biodiesel, typically B2, B5, and B10. Two samples contained over 20 vol% biodiesel, likely the result of poor blending.The induction period (IP) stability and acid value (AV) are key parameters in the quality of a Bxx blend. Although the D7467 specification was not applicable at the time of sample collection, 25% of the samples were below the 6-hour proposed limit. It is noteworthy that the average IP, 8.4 hours, was well above the 6-hour limit. Every sample but one met the proposed AV specification of 0.3 mgKOH/g, a low failure rate similar to that of previous NREL surveys.The minimum flash point of Bxx blends is allowed to vary depending on the type of diesel fuel used and the cloud point of the blend. The average cloud point was -12.6°C, and the samples all readily met the flash point minimum of 38°C. The B20 samples all met the sulfur limit of 15 ppm, except for one sample that was likely contaminated. The range of cetane number for the blends was 46 to 52.The current specification contains a combined water and sediment value, although there is interest in separating these parameters into Karl Fisher water and particulate contamination. As expected by its polar nature, biodiesel will have a higher water saturation point than that of diesel fuel. The average Karl Fisher water content of the B20 samples was 130 ppm, about 30% higher than that of conventional diesel fuel. Almost all the samples showed very low particulate contamination except one, which was likely contaminated during collection. The metal content of the blends was also low, although the amount of sodium in one sample would not have allowed the B100 to meet the D6751 specification.

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“…First, ROOH levels can increase, achieve a plateau, and then hold that level in a steady state 4,50,87,95,100,101,106 . Alternatively, ROOH levels can increase, achieve a peak level, and then decrease 4,50,70,96,106,117 . The reasons why two such behaviors exist are not clearly resolved in prior work.…”

Section: Figure 3 Reaction Schemementioning

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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Effects of Bio-Fuels on Vehicle Performance: Degradation Mechanism Analysis of Bio-Fuels

Cited by 26 publications

References 1 publication

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

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

Analysis of Biodiesel Blends Samples Collected in the United States in 2008 (Revised)

Characterization of Biodiesel Oxidation and Oxidation Products

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