Epoxidation of ethylene over silver catalysts in loe-temperature corona discharge

Abstract

The production of ethylene oxide via partial ethylene oxidation, so-calledthylene epoxidation, is currently indispensable for obtaining valuable chemical feedstock or intermediate to be used for manufacturing several kinds of chemicals, such as solvents, adhesive, surfactant, and foam polyurethane. In this study, the epoxidation of ethylene in a low-temperature corona discharge system in the presence of ditterent catalysts, namely Ag/(low-surface-area, LSA)a-Al2O3, Ag/(high-surface-area, HSA)a-Al2O3, Au-Ag/(HSA)a-Al2O3, and Au/TiO2, was studied. In a comparison among the studied catalysts, Ag(LSA)a-Al2O3 catalyst was found to offer the highes selectivity of ethylene oxide, as well as the lowest selectivities of carbon dioxide and carbon monoxide. The selectivity of ethylene oxid increased with increasing applied voltage, while the selectivity of ethylene oxide remained unchanged when the frequency was varied in the range of 300-500 Hz. Nevertheless, the selectivity of ethylene oxide increased with increasing frequency beyond 500 Hz. The optimum Ag loading on (LSA)a-Al2O3 was found to be 12.5 Wt%, at maximum ethylene oxide selectivity of 12.98% was obtained at the optimum applied voltage and input frequency of 15 kV and 500 Hz, respectively. Under these optimum conditions, the power consumption was found to be 12.6x10-16 W s/molecule of ethylene oxide produced. In addition, low oxygen to ethylene molar ration and low feed gas flow rate were also experimentally found to be beneficaial for the ethylene epoxidation.