Mesoporous SBA-15 Silica-supported Diisopropylguanidine: an Efficient Solid Catalyst for Interesterification of Soybean Oil with Methyl Octanoate or Methyl Decanoate

The organosilane agent, namely 3-(N,N'-diisopropylguanidine)-propyltriethoxysilane, was firstly prepared by the reaction of diisopropylcarbodimide with (3-aminopropyl)triethoxysilane, and then employed for grafting guanidine base onto the surface of the mesoporous SBA-15 silica to afford an organic-inorganic hybrid catalyst. The prepared solid catalyst was fully characterized by various techniques such as small-angle X-ray power diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption and elemental analysis techniques. The obtained results showed that the guanidine base was successfully tethered onto the SBA-15 silica and the ordered mesoporous structure of the SBA-15 material remained almost unchangeable after the orgnofunctionalization. The solid catalyst was found to have appreciable catalytic activities to the interesterification of soybean oil with methyl octanoate or methyl decanoate under solvent-free conditions. Influence of various reaction parameters, such as the substrate molar ratio, reaction temperature, catalyst loading and reaction time, on the catalytic interesterification was investigated to optimize the interesterification condition for the production of structured lipids containing medium-chain fatty acids. The hybrid solid catalyst was easily separated and reused for four runs without significant loss of catalytic activity.