Temperature-dependent synthesis of dimethyl ether (DME) from methanol over beta zeolite: a novel approach to a sustainable fuel.

Abstract

Crystalline beta zeolite molecular sieve with SiO2/Al2O3 molar ratio of 28.5 was synthesized by the hydrothermal crystallization method and examined for methanol dehydration reaction. The micro-mesoporous beta zeolite was active between 280 and 450°C. Dimethyl ether (DME) was observed as the predominant product at all reaction temperatures, with a maximum selectivity of 47.9% at 300°C and a methanol turnover frequency (TOFMeOH) of 741.9 h-1. At increased reaction temperatures, beta zeolite showed enhanced strong acid site fraction, promoting higher hydrocarbon formation following the olefin-based cycle. It was revealed that the crystallinity, porosity and acidity of beta zeolite change in the reaction environment. Amorphous carbon deposition occurred on beta zeolite, which involved a loss in crystallinity to some extent. The temperature increase showed a pore-broadening phenomenon at elevated temperature regions. Regeneration cycle testing demonstrated beta zeolite activity maintained stable throughout a 280 h time-on-stream period.