Pd Modification and Supporting Effects on Catalytic Dehydration of Ethanol to Ethylene and Diethyl Ether over W/TiO2 Catalysts

In the present work, the palladium (Pd) modification and supporting effect of W/TiO2 catalysts on catalytic ethanol dehydration to ethylene and diethyl ether were investigated. The Pd modification with different sequence of Pd and W impregnation on the catalysts was prepared by the incipient wetness impregnation technique. The catalyst characterization and activity testing revealed that the different sequence during impregnation influenced the physicochemical properties and ethanol conversion of catalyst. The differences in structure and surface properties were investigated by XRD, BET, SEM, EDX, XPS and NH3-TPD. Upon the reaction temperature between 200 to 400°C, it was found that the conversion increased with increasing of temperature for all catalysts. The Pd incorporated into catalysts enhanced the ethanol conversion depending on the sequence of impregnation. At low temperature (ca. 200 to 300°C), diethyl ether is a major product and the Pd modification over W/TiO2 catalyst resulted in increased diethyl ether yield. This is because an increase of ethanol conversion was obtained with Pd modification, while diethyl ether selectivity did not change. This can be attributed to the higher amount of weak acids sites present after Pd modification into catalyst. Among all catalysts, the PdW/TiO2 catalyst (coimpregnation) achieved the highest diethyl ether yield of 41.4% at 300℃. At high temperature (ca. 350 to 400°C), ethylene is the major product. The W/Pd/TiO2 catalyst (with sequential impregnation of Pd on TiO2 followed by W) exhibited the highest ethylene yield of 68.1% at 400°C. It can be concluded that the modification of Pd onto W/TiO2 upon different sequence of Pd and W impregnation can improve the diethyl ether and ethylene yield in catalytic ethanol dehydration.