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
(TOFMeOH) 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.