Dimethyl ether conversion to olefins in a slurry reactor: the effect of MFI zeolite catalyst acidity and selectivity control

The textural, acidic and catalytic properties of nanosized samples of commercial MFI zeolites with SiO2/Al2O3 molar ratios of 30, 50 and 80 supplied by Zeolyst Co. and some synthesized nanocrystallites of MFI zeolites with a SiO2/Al2O3 molar ratio of 55 and 80 were compared. It was shown that the SiO2/Al2O3 ratio had no impact on catalyst deactivation in the slurry reactor as in the conventional fixed-bed reactor. Irreversible deactivation was observed only for the samples with an extremely high external surface Bronsted acidity indicating that near-surface secondary processes are responsible in catalyst deactivation. It was shown that the reaction temperature influenced the product selectivity due to change in the contribution of both hydrogen transfer reaction and arene/alkene circles and can be considered to be an efficient tool of selectivity control for DME conversion in the slurry reactor.