Mesostructured Sr AND Ti mixed oxide catalysts for synthesis of fatty acid methyl esters

Abstract

The objectives of this research were synthesis of mesostructured Sr and Ti mixed oxides (MSTs) via a self-assembly sol-gel combustion method using Pluronic P123 as a structure-directing agent, in order to use them as heterogeneous catalyst in transesterification of palm kernel oil (PKO) and methanol. Firstly, the effects of synthesis parameters on physicochemical properties of MSTs were studied. The results showed that the MST synthesized with molar ratio of citric acid: total metals at 1: 1, amount of Pluronic P123 at 0.17 mmol and calcination temperature at 600 °C exhibited good structural and textural properties. After that, the catalytic activity and stability of MST synthesized without citric acid (MST-0C-0.17P(600)) and MST synthesized with adding citric acid at molar ratio of citric acid: total metals 1: 1 (MST-1C-0.17P(600)) were comparatively studied in transesterification. Although the reaction over MST-1C-0.17P(600)) required the temperature higher than that over MST-0C-0.17P(600)), to achieve the fatty acid methyl esters (FAME) yield of 99.8 wt%, the MST-1C-0.17P(600)) showed superior chemical stability compared to the MST-0C-0.17P(600)) in the transesterification. Finally, the results from in situ FTIR showed that MST-1C-0.17P(600)) had Lewis acid sites and 4 types with different strength of basic sites. Furthermore, in situ FTIR results provided the information about the nature of adsorbed methanol and ethyl propionate species on the active sites of MST-1C-0.17P(600). Moreover, the reaction mechanism for the transesterification using the MST-1C-0.17P(600) as catalyst was proposed.