Brønsted/Lewis Acid Synergy in H–ZSM-5 and H–MOR Zeolites Studied by 1H and 27Al DQ-MAS Solid-State NMR Spectroscopy

Citations Over TimeTop 13% of 2011 papers

Abstract

The spatial proximities of acid sites in dealuminated H–MOR and H–ZSM-5 zeolites have been comprehensively studied by two-dimensional 1H and 27Al double-quantum magic-angle spinning (DQ-MAS) NMR spectroscopy. 1H DQ-MAS NMR revealed the detailed spatial proximities among Brønsted and Lewis acid sites, while 27Al DQ-MAS NMR probed the detailed spatial proximities among various aluminum species in the dealuminated zeolites. It was found that all of the extra-framework aluminum species (EFAL, Lewis acid sites) are always in close proximity to the framework aluminum (Brønsted acid sites) in both H–MOR and H–ZSM-5 zeolites. The result from 13C CP/MAS NMR of adsorbed acetone demonstrated that the spatial proximities between Brønsted and Lewis acid sites lead to a synergy effect that can remarkably enhance the Brønsted acid strength of the dealuminated zeolites. On the basis of these experimental results, we proposed a model to describe the Brønsted/Lewis acid synergy in the dealuminated zeolites.

Related Papers

• → Promoting a non-heme manganese complex catalyzed oxygen transfer reaction by both lewis acid and Brønsted acid: Similarities and distinctions(2017)15 cited
• → Brönsted and Lewis acid catalysis of XY–ZH cycloadditions(1982)35 cited
• Study on Surface Acidity of Solid-acid Catalysts(2000)
• → On the Role of Bronsted Acid Sites in the Reactions of Ethylene Over ZSM-5 and HZSM-5 Zeolites(1998)
• → Adducts with Brönsted acids(1963)