Structure–reactivity correlation in zeolites for simultaneous catalytic dehydration of methanol and ethanol

The simultaneous conversion of light alcohols, specifically methanol and ethanol, over acidic zeolites was investigated to assess the role of the zeolite channel system on alcohol activity and product distribution. To this end, EUO, FER, MFI, and BEA zeolites were synthesized and characterized in terms of their acidic and textural properties. These materials were then tested in a packed bed reactor for the simultaneous conversion of methanol and ethanol within the temperature range of 160–220°C. The results indicate that the zeolite channel system plays a crucial role during alcohol conversion, significantly impacting the relative conversion rate of the alcohols, which exhibits different behavior depending on whether they are fed individually or as a mixture to the reactor. The product distribution also changes considerably with the channel system. While methyl-ethyl ether (MEE) is the main product at low temperatures, dimethyl ether (DME) formation is preferentially inhibited on 3D structures, i.e., MFI and BEA. This suggests that the methanol-ethanol reaction to MEE is favoured in zeolites with large voids or channel intersections. The ratio of DME produced to the total amount of products formed, including MEE, diethyl ether (DEE), and ethylene (resulting from ethanol), was calculated. At low temperatures, this ratio strongly depends on the zeolite structure, with the highest value observed for the 1D EUO zeolite. It progressively decreased from 1D to 2D zeolites, reaching its lowest value for 3D zeolites. In conclusion, the zeolite structure significantly influences the reaction mechanism, affecting both alcohol conversion and product distribution. Furthermore, higher Brønsted acidity promotes ethylene formation at higher temperatures, while no significant effect of Lewis acidity on product distribution was observed.