(370h) Magnesium Vanadate Catalyzed Oxidative Dehydrogenation of Ethane to Ethylene Using CO2 As a Soft Oxidant

In the United States, ethylene is produced by non-catalytic steam cracking of shale gas at temperatures as high as 800°C to yield ethylene, propylene, hydrogen, water, and other by-products. An alternative route for ethylene production is low temperature, highly selective, catalytic oxidative dehydrogenation (ODH) of ethane to ethylene in the presence of oxygen. The primary cost drivers for conventional ODH chemistry are the prices of inert gases and the use of pure oxygen. Our research has been focused on improving the process by lowering or eliminating the inert requirement and replacing oxygen with cheaper and safer CO₂. In this research, we examined the catalytic activity of various phases of supported magnesium vanadate catalysts for the CO₂ mediated ODH reaction. In addition, the effect of adding various promoters such as Mo, Co, Cr, and Fe were analyzed. Our studies indicate that magnesium pyrovanadate (Mg₂V₂O₇) is more active phase of the catalysts compared to magnesium metavanadate (MgV₂O₆) and orthovanadate (Mg₃V₂O₈) phase, which provides 12% ethane conversion, 48% ethylene selectivity, and 13% CO₂ conversion at 550°C. Chromium (Cr) has no effect on ethane conversion, whereas molybdenum (Mo) increase the selectivity. The combined effect of Mg, V, Cr and Mo provides 8% ethane conversion, 65% ethylene selectivity and 5% CO₂ conversion at 550°C without using any inert gas. The presentation will include detailed catalyst structure-activity correlations, reaction mechanisms, the effects of adding promoters and process economics.