Esterification of glycerol using acidic mesoporous silica catalyst

Abstract

The large pore cubic la-3d mesoporous silica have been synthesized in acidic condition by microwave and hydrothermal direct synthesis using tetraethoxysilane (TEOS) and 3-mercaptopropyltrimetoxysilane (MPTMS) as the silica in the presence of triblock copolymers Pluronic P123 (EO20PO70EO20) as a structure directing agent. The gel composition of synthetic porous material was 1.0 TEOS : 0.089 MPTMS : 0.018 P123 : 2.0 HCL : 148 H20. In the synthesis procedure, the amount of MPTMS in range of 4.1- 16.4% of silicon sources exhibited the phase transition from 2d-hexagonal structure SBA-15 to the cubic la-3d structure. Moreover, MPTMS addition prior to TEOS hydrolysis in the surfactant solution can cause cubic la-3d structure. On the other hand, if TEOS was added Before, the 2d-hexagonal structure would be formed. The crystallinity of catalyst depended on aging temperature and crystallization time. The microwave synthesis could reduce crystallization time with a good crystallinity, in a total processing time for 3 hr. The synthesized materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy. transmission electron microscopy and acid-base titration the sulfonated catalyst was used in synthesis of triacetin from esterification of glycerol and acetic acid, caproic acid, lauric acid and oleic acid, which was analyzed by Gas Chromatography. The multi-dimensional cubic la-3d mesostructure was more efficient than 2d-hexagonal structure SBA-15 and commercial Amberlyst-15 catalyst.