Effect of temperature in methanol conversion to dimethyl ether (DME) and light hydrocarbons with beta zeolite

Crystalline beta zeolite molecular sieve with SiO₂/Al2O₃ molar ratio of 28.5 was synthesized by the hydrothermal crystallization method and examined for the methanol dehydration reaction. The micro-mesoporous beta zeolite was active between 250 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 (TOF_MeOH) of 741.9 h-1. At increased reaction temperatures, the 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 the beta zeolite change in the reaction environment. Amorphous carbon deposition occurred on beta zeolite, which involved the loss in crystallinity to some extent. The temperature increase showed a pore-broadening phenomenon at elevated temperature regions. The regeneration cycle test showed stable activity of regenerated beta zeolite for 280 h time-on-stream.