Study On The Catalysts And Process For Alkylation Of Toluene With Isopropanol

Isopropenyl Toluene（IPT） is extensively used as an important chemical raw material. In this paper, the catalytic performance of β zeolite and supported heteropolyacid PWH/Si O₂ which were used to catalyze the alkylation of toluene with isopropanol was studied. In addition, β zeolite was modified by acid. The effect of different loadings and calcination temperature in the progress of preparing supported heteropolyacid catalysts on catalytic performance was researched. The catalysts were characterized by means of XRD、FT-IR、BET etc., and these results were related to their catalytic performances.When zeolite was used as the catalysts of alkylation of toluene with isopropanol, the optimal reaction conditions were: reaction temperature was 220℃, molar ratio of toluene to isopropanol was 4:1, space velocity was 2h-1. Under this reaction conditions, the effect of β zeolite content and citric acid and phosphate modification on catalytic performance was researched. Based on these studies, such conclusions were obtained: when the content of β zeolite was 70%, the catalytic activity was the best, while the conversion of isopropanol was 90.12%, and the selection of alkylation was 61.96%. The appropriate concentration of citric acid modification was 0.5mol·L-1 Under this reaction conditions, the conversion of isopropanol reached up to 91.56%, and the selection of alkylation was 83.94%. The appropriate concentration of phosphate modification was 0.1mol·L-1. Under this reaction conditions, the conversion of isopropanol reached up to 90.22%, and the selection of alkylation was 85.19%. The catalytic performance of modified zeolite was superior to unmodified zeolite.Supported heteropolyacid PWH/SiO₂ catalysts were prepared by impregnation method. The optimized preparation parameters for supported heteropolyacid catalyst which were determined by investigation of the alkylation of toluene with isopropanol were heteropolyacid load of 40%, and calcination temperature of 200℃. The most favorable alkylation reaction parameters determined according to experimental results were as follows: reaction temperature was 200℃, toluene/isopropanol ratio was 4:1, and space velocity was 2h-1. Under these optimized conditions, the conversion of isopropanol reached up to 92.94%, and the selection of alkylation was 83.89%. The effect of different carrier on alkylation reaction was researched under the same conditions. With PWH/MCM-41 as the catalyst, the conversion of isopropanol was unchanged, but the selection of alkylation dropped to 39.46%.From all above, the catalytic performance of supported heteropolyacid PWH/SiO₂ catalyst was better than zeolite. At last, the stability of zeolite and supported heteropolyacid PWH/SiO₂ catalyst were investigated, the result of continuous reaction of 24 h indicated that both catalysts can keep active.