Development of heterogeneous catalyst for biodiesel production

Abstract

Biodiesel has been considered as an important alternative energy for diesel engines. Most of biodiesel is produced via transesterification of vegetable oils and alcohols using a homogeneous basic catalyst to accelerate reaction. KOH seems to be the promising catalyst which is used in a commercial industry; however, its properties, such as regeneration and deduction, have been unsolved problems in the present process. To overcome these drawbacks, heterogeneous catalysts have been proposed by some researchers to substitute homogeneous catalysts. In this work, the practically commercial materials which were often selected to use as a support (Al₂O₃, NaY and mordenite zeolite, and bentonite clay) that was loaded by KOH with vary loading by impregnation method finding an optimum condition which gave the highest biodiesel yield or fatty acid methyl ester content (FAME) in a batch and packed-bed reactors. A catalyst with 15 wt% KOH/NaY, 20 wt% KOH/mordenite and 20 wt% KOH/bentonite clay was found to be the optimum catalyst, which gave the highest basic properties and the best catalytic activity. The reusability of these spent catalysts was observed under consecutive runs. The minimum leaching of K on support was suggested to have high ability to reuse in the process. The result found that the amount of leached potassium of the KOH/Al₂O₃ was higher compared to that of the KOH loaded on NaY and mordenite zeolite. The packed-bed reactor exhibited higher possibility to regenerate catalyst than the batch reactor. However, the deactivation of this catalyst still occurred due to causing from glycerol molecules which blocked the basic site on the catalyst surface.