Probing the Catalytic Function of External Acid Sites Located on the MFI Nanosheet for Conversion of Methanol to Hydrocarbons

Abstract

The surfactant-directed MFI zeolite nanosheet of 2.5-nm thickness has been re-investigated to clarify whether the catalytic function in the methanol-to-hydrocarbon (MTH) reaction originates from acid sites located solely in the internal micropores or also on the external surfaces. Two catalytic reactions were measured after all acid sites on the external surfaces were poisoned with triphenylphospine oxide. One reaction was the catalytic cracking of triisopropylbenzene, which can occur only on external surfaces. This reaction was completely killed by poisoning. The second reaction was MTH conversion. Unlike the catalytic cracking of triisopropylbenzene, the MTH reaction proceeded at the same rate, even when the external acid sites were poisoned. The result indicated that the MTH reaction occurred inside the internal pores, not at the external surfaces. This information will be useful for understanding MTH catalysis of other hierarchical zeolites.