Production of middle distillate through hydrocracking of paraffin wax over Pd_(0.15)Cs_xH_(2.7-x)PW_(12)O_(40) catalysts: Effect of cesium content and surface acidity

摘要

Palladium-exchanged heteropolyacid Pd_(0.15)Cs_xH_(2.7-x)PW_(12)O_(40) catalysts were prepared by an ion-exchange method with a variation of cesium content (x=2.0,2.2,2.5, and 2.7) for use in the production of middle distillate through hydrocracking of paraffin wax. Surface acidity of Pd_(0.15)Cs_xH_(2.7-x)PW_(12)O_(40) catalysts determined by NH_3-TPD experiments showed a volcano-shaped trend with respect to cesium content. Surface acidity of the catalysts played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing surface acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to surface acidity of the catalyst. Among the catalysts tested, Pd_(0.15)Cs_xH_(2.7-x)PW_(12)O_(40) catalyst with moderate surface acidity showed the best catalytic performance.