Preparation, Surface Acidity and Catalytic Esterification Activity of Solid Acid S2O2-8/TiO2-La2O3

Solid acid S2O 8/TiO2-La2O3 (STL) was prepared by calcination at high temperature using complex oxide of TiO2 doped La2O3 as the supporter, and anion S2O 8 as the accelerant. The catalytic synthesis of n-butyl propanoate over STL was selected as the probe reaction to examine its catalytic esterification activity. The preparing conditions of STL were optimized via Taguchi method. The acidic structure, species and strength of STL were characterized by FTIR directly, FTIR spectrum of pyridine adsorbed on its surface and Hammett indicator, respectively. The esterification product was characterized by HNMR and FTIR. The experimental results showed that the optimum preparation conditions were as follows: molar ratio of Ti to La at 5:1, (NH4)2S2O8 solution concentration of 2.0 mol∙L and calcination temperature of 500 C. STL belonged to the solid superacid (Ho=−13.75) with Brönsted acid sites. The esterification rate of above probe reaction could reach 99.3% at the reaction time of 90 min.