Investigation of Propene Oligomerization Catalyzed by Phosphotungstic Acid Catalysts

In this paper, the propene oligomerization reaction catalyzed by phosphotungstic acid supported on two kinds of silica gel was studied, it had been found out that the conversion of propene catalyzed by the type A silica gel-phosphotungstic acid catalyst was 3.38 m%, while the conversion of propene catalyzed by the type B silica gel-phosphotungstic acid catalyst was 90.1 m% with a nonene selectivity of 42.33 m%, and a dodecene selectivity of 31.79 m%. The influence of reaction temperature, pressure and liquid hourly space velocity (LHSV) on the reaction catalyzed by the type B silica gel-phosphotungstic acid catalyst was investigated. It had been verified that when the reaction temperature increased from 170 degrees C to 190 degrees C, the conversion of propene increased while the selectivity of nonene and dodecene decreased; when the reaction pressure increased from 3.5 MPa to 4.5 MPa, the conversion of propene increased also, and the selectivity of nonene and dodecene changed very little. The conversion of propene at a space velocity of between 0.5 h(-1) and 1.0 h(-1) was higher than that achieved at 2.0 h(-1), but the selectivity of nonene and dodecene did not show regular fluctuations. An optimum conversion of propene (91.05 m%) and an optimum selectivity of nonene and dodecene (89.51 m%) could be achieved at a reaction temperature of 170 degrees C, a reaction pressure of 4.5MPa, and a LHSV of 1.0 h(-1). The experiments on catalyst life showed that the activity of the type B silica gel-phosphotungstic acid catalyst could be only maintained in 25 hours, and the reason was explained also.