In-Depth Understanding of Highly Active Silicotungstic Acid Catalysts for Ethanol Dehydration to Ethylene under Industrially Favorable Conditions

A series of SiO2-supported silicotungstic acid (STA/SiO2) catalysts were prepared by the incipient impregnation method and utilized in dehydration of ethanol to ethylene. The catalysts were characterized through X-ray diffraction (XRD), N2 physical adsorption, transmission electron microscopy (TEM), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), pyridine-adsorbed FTIR (Py-FTIR), Raman spectroscopy, and thermogravimetry/differential scanning calorimetry (TG/DSC). The influence of loading amount and calcination temperature on the properties and catalytic activities were investigated. The yield of ethylene was 93.9% at an ethanol conversion of 96.9% over the 36-STA/SiO2(250) catalyst at 240 °C and 1.0 MPa. The kinetics study indicated that diethyl ether was an intermediate under the investigated reaction conditions. A consecutive slow decrease in ethanol conversion and ethylene yield was observed after the 800-h run, which was due to the decreased Brønsted amount caused by carbon deposition, rather than the change of crystal phase or leaching of active sites.