Preparation of dandelion-type silica spheres and their application as catalyst supports

摘要

Dandelion-type silica spheres with a dendri-mer-like porous structure were prepared by adding pore modifiers into aqueous synthetic mixtures of tetraethylor-thosilicate (TEOS), hexadecyltrimethylammonium bromide (CTAB), ammonium hydroxide, and acetone. The formation of silica spheres and their porous characteristics were investigated using various techniques, including electron microscopy, nitrogen adsorption, and thermo-gravimetric analysis. Benzyl acetate (BENA) was very effective in the formation of a dendrimer-like porous structure. However, the composition of TEOS, CTAB, acetone, and BENA strongly influenced the size and shape of the silica spheres and their porous structure. The synthetic mixture of 1 TEOS: 0.22 CTAB: 1.9 BENA: 0.32 NH_4OH: 36 acetone: 236 H_2O produced dandelion-type silica spheres with diameters of ～ 300 nm. The phosp-hazenium hydroxide (PzOH) catalyst supported on the dandelion-type silica spheres prepared by adding BENA showed high catalytic performance in the transesterifica-tion of soybean oil with methanol due to its high feasibility for rapid access of large triglyceride molecules into the basic PzOH moieties incorporated in the pores.