Diethyl Ether Conversion to Ethene and Ethanol Catalyzed by Heteropoly Acids

The conversion of diethyl ether (DEE) to ethene and ethanol was studied at a gas-solid interface over bulk and supported Bronsted solid acid catalysts based on tungsten Keggin heteropoly acids (HPAs) at 130-250 degrees C and ambient pressure. The yield of ethene increased with increasing reaction temperature and reached 98% at 220-250 degrees C (WHSV = 2.2 h(-1)). The most active HPA catalysts were silica-supported H3PW12O40 and H4SiW12O40 and the bulk heteropoly salt Cs2.5H0.5PW12O40. The HPA catalysts outperformed zeolites HZSM-5 and USY reported elsewhere. A correlation between catalyst activity and catalyst acid strength was established, which indicates that Bronsted acid sites play an important role in DEE elimination over HPA catalysts. The results point to the reaction occurring through the consecutive reaction pathway: DEE -> C2H4 + EtOH followed by EtOH -> C2H4 + H2O, where ethene is both a primary product of DEE elimination and a secondary product via dehydration of the primary product EtOH. Evidence is provided that DEE elimination over bulk HPA and high-loaded HPA/SiO2 catalysts proceeds via the surface-type mechanism.