3种生物柴油氧化降解特性研究

利用Rancimat试验法氧化降解菜籽油生物柴油、大豆油生物柴油、小桐子油生物柴油,采用GC-MS测定不同氧化时间下的生物柴油中主要脂肪酸甲酯含量变化,进而通过半衰期法计算动力学参数(反应级数、速率常数),同时研究生物柴油氧化深度与热值的关系,并对氧化前后生物柴油样品进行FTIR分析。研究表明:除大豆油生物柴油中的硬脂酸甲酯外,3种生物柴油中主要脂肪酸甲酯氧化降解反应级数都为1;氧化降解反应速率从小到大依次为棕榈酸甲酯、硬脂酸甲酯、油酸甲酯、亚油酸甲酯、亚麻酸甲酯;氧化降解时间与热值为一元三次函数关系;另外,FTIR分析表明在1 740 cm~(-1)处的吸光度随着氧化降解时间延长不断增加,说明氧化程度不断加深。

Oxidation degradation characteristics of three kinds of biodiesels

The rapeseed oil biodiesel, soybean oil biodiesel and Jatropha oil biodiesel were oxidized by Rancimat method. The contents of fatty acid methyl esters in biodiesel after oxidation for different time were determined by GC-MS, and the kinetic parameters (reaction order, rate constant) were calculated by half-life method. At the same time, the relationship between oxidation depth and heat value was studied and the biodiesel samples before and after oxidation were analyzed by FTIR. The results showed that except for methyl stearate in soybean oil biodiesel, the reaction order of major fatty acid methyl esters in three kinds of biodiesels was one. The rate of oxidative degradation of methyl linolenate was the fastest, followed by methyl linoleate ester, methyl oleate, methyl stearate and methyl palmitate. The relationship between oxidative degradation time and heat value was cubic function. In addition, FTIR results showed that with the oxidative degradation time prolonging, the absorbance at 1 740 cm-1 increased, revealing an increasing degradation level of the samples.