Raney-Ni催化下菜籽油生物柴油催化转移加氢的研究

A study of catalytic transfer hydrogenation of biodiesel from rapeseed oil over Raney-Ni catalyst

在水环境下,以异丙醇为供氢体和Raney-Ni为催化剂,对菜籽油经酯交换得到的生物柴油进行催化转移加氢研究.通过定时取样分析生物柴油的碘值变化和组分含量,研究了生物柴油中亚麻酸甲酯(C18∶3)、亚油酸甲酯(C18∶2)和油酸甲酯(C18∶1)催化转移加氢选择性和反应动力学,以及加氢过程中不饱和脂肪酸甲酯的顺反异构情况.结果表明:在水环境下生物柴油催化转移加氢反应可用拟一级动力学模型来描述;C18∶3和C18∶2的加氢选择性较高,反应速率常数是C18∶1的6倍,但产物主要为反式油酸甲酯(t-C18∶1),而且顺式油酸甲酯(c-C18∶1)进一步加氢变成硬脂酸甲酯(C18∶0)的速率远远高于t-C18∶1.

The catalytic transfer hydrogenation （CTH） of biodiesel from rapeseed oil has been carried out using isopropyl alcohol as the hydrogen donor over Raney-Ni catalyst in aqueous media. The iodine value and the composition of the biodiesel were measured at a given time. The selectivity and the reaction kinetics of methyl linolenate （C18 ： 3）, methyl linoleate （C18 ： 2） and methyl oleate （C18 ： 1）, which are the main components in the biodiesel, were investigated. The cis-trans isomerization of unsaturated fatty acid methyl esters was studied. The results show that the CTH of biodiesel over Raney-Ni in aqueous media could be described by a pseudo-first order kinetic model. The hydrogenation selectivity of C18 ： 3 and C18 ： 2 was much higher than that of C18 ： 1, but the main product was the trans-isomer（t-C18 ： 1）, which had negative effects on the low-temperature fluidity of the biodiesel, and the reaction rate of methyl cis-oleate（c-C18 ： 1）to methyl stearate （C18 ：0）was much higher than that of t-C18 ：1.