Immobilization of tetramethylguanidine on mesoporous SBA-15 silica: A heterogeneous basic catalyst for transesterification of soybean oil

An active heterogeneous catalyst, namely 1,1,3,3-tetramethylguanidine (TMG) immobilized on mesoporous SBA-15 silica (SBA-15-pr-TMG), was prepared and the catalytic activity was investigated for transesterification of soybean oil with methanol. The heterogeneous catalysts were characterized using Hammett titration method, Fourier transform infrared spectra, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, and X-ray photoelectron spectroscopy techniques. It is shown that the activity of the catalysts for the transesterification reaction is closely related to their basic properties. By using this catalyst, an environmentally benign process for biodiesel production in a heterogeneous manner was developed. When the reaction was carried out at reflux of methanol, with a molar ratio of methanol to soybean oil of 15:1, a reaction time 12 h and a catalyst amount 5 wt%, the oil conversion of 91.7% was achieved. The catalyst could be recovered easily and reused without significant degradation in activity.