The benefit of multipore zeolites: Catalytic behaviour of zeolites with intersecting channels of different sizes for alkylation reactions

The catalytic behaviour of two multipore zeolites containing channels of different sizes, SSZ-33 (10 windows × 12 MR) and ITQ-22 (8 × 10 × 12 MR pores), for alkylation of benzene with ethanol and benzene with isopropanol or propylene, has been studied and compared to that of zeolites with intersecting channels of the same size, ZSM-5 (10 × 10 MR channels) and Beta (12 × 12 MR channels), which are industrially used for the above-mentioned process. For the alkylation of benzene with ethanol in gas phase, ITQ-22 behaves like the 10 MR ZSM-5 with respect to ethylbenzene selectivity, while the behaviour of SSZ-33 is close to that of a 12 MR zeolite such as Beta. For the alkylation of benzene with isopropanol or propylene in gas and liquid phase, Beta and ITQ-22 give similar selectivity values, which are much better than those obtained with ZSM-5. Meanwhile, SSZ-33 gives intermediate selectivity between that of the 10 MR ZSM-5 and the 12 MR Beta zeolite. ITQ-22, therefore, shows a unique behaviour as a multipurpose alkylation catalyst, with characteristics different from those of previously studied zeolites. The catalytic behaviour of ITQ-22 has been rationalized not only in terms of the topology of the channels but also taking into account the location of the protons. A computational study shows preferential Al location at the 10 MR, near the intersection with the 12 MR channels, and at the intersections between 10 and 12 MR channels.