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.

Two multipore zeolites, ITQ-22 and SSZ-33, have been studied as catalysts for the alkylation of benzene to ethylbenzene and cumene. Whereas SSZ-33, which could be seen as a zeolite with 12 MR “cavities” connected by 10 and 12 MR, presents an intermediate behaviour as compared to ZSM-5 and Beta, zeolite ITQ-22 shows a unique behaviour as a multipurpose alkylation catalyst, close to that of the medium pore ZSM-5 in the case of alkylation with ethanol, and close to the large pore Beta for alkylation with isopropanol or propylene. These results are discussed on the basis of its particular topology and on the location of the acidic protons as determined by means of a computational study.Figure optionsDownload high-quality image (185 K)Download as PowerPoint slide