The Effect of Zeolite Structure on the Activity and Selectivity in p-Xylene Alkylation with Isopropyl Alcohol

The effect of zeolite architecture and channel dimensionality on p-xylene conversion and selectivity to 1-isopropyl-2,5-dimethyl-benzene was investigated in p-xylene alkylation with isopropyl alcohol over novel zeolites SSZ-33 and SSZ-35. Catalytic behavior of these zeolites was compared with those of zeolites Beta, mordenite, ZSM-11 and ZSM-5. It was found that p-xylene conversion increases with increasing pore size and connectivity of the channel system of individual zeolites with the exception of SSZ-35, which possesses a system of one-dimensional 10-ring channels that periodically open into wide, shallow cavities circumscribed by 18-rings. SSZ-35 exhibited the highest conversion among all zeolites at the reaction temperature of 150 degrees C and also the highest selectivity to 1-isopropyl-2,5-dimethyl-benzene. Molecular modeling confirmed the dimensions of the 18-ring cages are optimal for the formation of this alkylation product.