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首页> 外文会议>ASME Internal Combustion Engine Division fall technical conference 2011 >OXIDATIVE STABILITY OF ALGAE DERIVED METHYL ESTERS CONTAINING VARYING LEVELS OF METHYL EICOSAPENTAENOATE AND METHYL DOCOSAHEXAENOATE
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OXIDATIVE STABILITY OF ALGAE DERIVED METHYL ESTERS CONTAINING VARYING LEVELS OF METHYL EICOSAPENTAENOATE AND METHYL DOCOSAHEXAENOATE

机译：藻类衍生的甲基异辛酸戊二酸酯和十二烷基己二酸甲酯变化水平的甲基酯的氧化稳定性

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Microalgae is currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gallons/acre/year) in comparison to current terrestrial feedstocks. Microalgae lipids can be converted into a variety of biofuels including fatty acid methyl esters (e.g. biodiesel), renewable diesel, renewable gasoline or synthetic paraffinic aviation kerosene. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. For example, it is well known that oxidative stability decreases with increasing levels of LC-PUFA. However, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 hours and 6 hours, respectively. Tests were conducted at a temperature of 110℃ and airflow of 10 L/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0 to 100 percent LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45 to 65 percent of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability.
机译：由于与目前的陆上原料相比，其理论上的高产量（加仑/英亩/年），微藻作为一种潜在的生物燃料原料正在得到广泛考虑，以帮助实现《 2007年能源独立与安全法》规定的先进生物燃料。微藻类脂质可以转化为多种生物燃料，包括脂肪酸甲酯（例如生物柴油），可再生柴油，可再生汽油或合成石蜡航空煤油。对于藻类甲酯生物柴油，燃料性质将直接与给定微藻菌株产生的脂质的脂肪酸组成有关。与陆生原料相比，正在考虑进行大规模培养的几种微藻物种（例如Nannochloropsis）会产生具有脂肪酸成分的脂质，其中脂肪酸成分的含量明显高于长链多不饱和脂肪酸（LC-PUFA）。预期增加LC-PUFA的含量将对满足当前所有生物柴油的ASTM规范造成问题。例如，众所周知，氧化稳定性随LC-PUFA含量的增加而降低。然而，已知这些相同的LC-PUFA脂肪酸，例如二十碳五烯酸（EPA：C20：5）和二十二碳六烯酸（DHA：C22：6）具有高营养价值，从而使这些化合物的分离在经济上具有吸引力。考虑到这些LC-PUFA化合物未来价值的不确定性以及分离过程的经济可行性，本研究的目的是研究EPA和DHA含量不同的藻类甲酯的氧化稳定性。使用Metrohm 743 Rancimat进行测试，并根据ASTM D6751和EN 14214标准自动确定诱导期，这分别要求诱导期至少为3小时和6小时。测试是在110℃的温度和10 L / h的空气流量下进行的，使用了由各种来源合成的模型藻类甲酯化合物，以匹配几种藻类的脂肪酸组成，这些藻类的去除率在大约0％到100％之间变化，LC-PUFA 。此外，还对由多种来源生产的真实藻类甲酯进行了测试。计算每个燃料样品的双烯丙基位置当量（BAPE），以量化不饱和度。然后将诱导期绘制为BAPE的函数，表明氧化稳定性随LC-PUFA的量呈指数变化。结果表明，从基于Nannochloropsis的藻甲基酯中除去45％至65％的LC-PUFA足以满足现有的ASTM氧化稳定性要求。

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