Synthesis of PW/MCM-41 catalyst and its performance in synthesis of tri-n-butyl-citrate

PW/MCM-41 catalysts consisting of H_3PW_(12)O_(40) heteropoly acid (PW) supported on MCM-41,a mesoporous molecular sieve, was prepared and the pore structure characterized by XRD and BET. PW crystal phase was not observed in XRD patterns at PW loading of as high as 40%. The effects of PW loadings on the reaction was investigated. The influences of calcination temperature, citric acid /butanol molar ratio and reaction temperature on the esterification reaction were investigated, too. The optimum reaction condition was obtained as follows: PW loading = 40%, calcination temperature =130 ℃, citric acid /butanol molar ratio = 1∶4, reaction temperature =140 ℃, and reaction time = 6～7 h.The experimental results showed that PW(40)/MCM-41 is an ideal substitute for sulfuric acid as the catalyst for synthesis of tri-n-butyl-citrate with high and stable activity.