Host–Guest Interactions and Their Catalytic Consequences in Methanol to Olefins Conversion on Zeolites Studied by 13C–27Al Double-Resonance Solid-State NMR Spectroscopy

Abstract

Methanol conversion over zeolites with different topologies (H-ZSM-5, H-SSZ-13, and H-MOR) was studied using solid-state NMR spectroscopy and gas chromatrography mass spectroscopy (GC-MS). Host–guest interactions between active hydrocarbon pool (HP) species and zeolite framework (Bronsted acid/base site) were observed, and the supramolecular reaction centers (SMCs) generated by the interactions were unambiguously identified by 13C–27Al double-resonance NMR. The internuclear spatial interaction/proximity between the 13C nuclei (associated with HP species) and the 27Al nuclei (associated with Bronsted acid/base site) was analyzed and compared over the three zeolites. The product shape selectivity of zeolites greatly influences the catalytic performance that can be linked to the nature of HP species and the host–guest interactions. Closer spatial proximity and stronger interaction between methylbenzenes (MBs) and Bronsted acid/base sites were observed over H-SSZ-13 and H-MOR zeolites, which facilitate aromat...