Basic Ionic Liquid Supported on Mesoporous SBA-15 Silica as an Efficient Heterogeneous Catalyst for Biodiesel Production

Abstract

In the present study, SBA-15 silica-supported basic ionic liquid was prepared through grafting of 4-butyl-1,2,4-triazolium hydroxide onto SBA-15 silica using 3-chloropropyltriethoxysilane as a coupling reagent. The structural properties of the prepared catalysts were investigated by a series of techniques, such as Hammett titration method, elemental analysis, small angle XRD, FT-IR, SEM, TEM, and N 2 adsorption–desorption. The characterization results demonstrated that the ionic liquid was successfully tethered on the SBA-15 support, and the hexagonally ordered mesoporous structure of SBA-15 silica was well retained even after the chemical grafting reaction. The so-obtained solid catalyst showed excellent catalytic activities toward the transesterification of soybean oil with methanol to produce biodiesel in a heterogeneous manner. The influences of various transesterification parameters such as the subtract ratio, reaction time, catalyst amount, and catalyst reusability on the oil conversion to methyl esters were investigated systematically. Using this solid catalyst for the transesterification reaction, the high conversion of 95.4% was achieved at reflux of methanol for 8 h when the methanol/oil molar ratio of 20:1 and catalyst loading of 7 wt % were employed. Moreover, the solid catalyst could be recycled for four cycles without significant degradation of catalytic activity.