Mesoporous solid acid catalysts of sulfated zirconia/SBA-15 derived from a vapor–induced hydrolysis route

Abstract

Mesoporous solid acid catalyst, sulfated zirconia loaded mesoporous silica, was reported here by a facile vapor–induced hydrolysis method. The zirconia precursor of Zr(SO4)2 was introduced into the mesopore of SBA-15 by impregnation, and then hydrolyzed under a NH3/H2O vapor ambience to form a thin zirconia layer coated on the pore surface of SBA-15, which was followed by the sulfation of SO42− ions with calcinations. The catalyst was characterized by powder X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy and infrared spectroscopy, and the results indicated that the catalyst retained the ordered mesoporous structure, high BET surface area, connected pore channel without pore blocking and a 0.7nm thin layer of sulfated zirconia coated on the pore surface. This super acid catalyst showed much higher activity compared with those of unloaded sulfated zirconia and sulfated zirconia loaded SBA-15 hydrolyzed by ammonia aqueous solution, for catalyzing the esterification reaction of oleic acid and methanol. The experimental parameters including the molar ratio of reactants and reaction time were optimized, and approximately 70% of acid sites were remained after three cycles.