生物柴油氧化前后成分分析的研究

Composition analysis of biodiesel before and after oxidation

分别以地沟油、橡胶籽油和小桐子油为原料制备生物柴油,测定了3种生物柴油的氧化稳定性,并采用傅里叶红外光谱及GC-MS分析氧化前后此3种生物柴油的成分。结果表明,地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油的氧化诱导时间分别为1.61、0.81、1.05 h,远不能达到我国生物柴油国家标准的6 h;生物柴油主要成分是脂肪酸甲酯,氧化后脂肪酸甲酯中CC—H基团基本消失;地沟油生物柴油、橡胶籽油生物柴油和小桐子生物柴油主要由棕榈酸甲酯、亚油酸甲酯、油酸甲酯及硬脂酸甲酯组成,氧化前3种生物柴油中此4种脂肪酸甲酯总含量分别为93.07%、95.82%和97.68%,氧化后分别降为77.23%、84.51%和63.66%。氧化后生物柴油成分十分复杂,含有不同的醛、酸、酮、醇及小分子的酯等物质,且亚油酸甲酯的含量大大降低,证实了生物柴油氧化主要是含有不饱和双键或三键的脂肪酸甲酯的氧化。

Biodiesels were prepared from swill-cooked dirty oil, rubber seed oil and Jatropha curcasl L. oil respectively, then their oxidative stabilities were detected,and the compositions of the biodiesels before and after oxidation were analyzed by FTIR and GC-MS. The results showed that the oxidative induction periods of swill-cooked dirty oil biodiesel, rubber seed oil biodiesel and Jatropha curcasl L. oil biodiesel were 1. 61 h, 0. 81 h and 1. 05 h, respectively, which could not reach 6 h of the national standard of biodiesel;the major component of biodiesel was fatty acid methyl ester, and the C—C—H group in fatty acid methyl ester disappeared after oxidation;the main fatty acid methyl esters in the three kinds of biodie-sels were methyl palmitate, methyl linoleate, methyl oleate and methyl stearate, and the total contents of fatty acid methyl esters in the three kinds of biodiesels after oxidation declined from 93. 07%,95. 82%, 97. 68% to 77. 23%,84. 51%,63. 66%;the composition of oxidated biodiesel was very complex containing different aldehydes, acids, ketones, alcohols and small molecular esters, and the content of methyl linole-ate reduced greatly,which demonstrated that the oxidation of biodiesel was mainly the oxidation of unsatu-rated fatty acid methyl esters with double bonds or triple bonds.