Highly selective oxidative dehydrogenation of ethane to ethene over layered complex metal chloride oxide catalysts

Abstract

Complex metal chloride oxides consisting of bismuth, alkali, alkaline earth, chlorine, and oxygen, were synthesized, characterized structurally, and tested as catalysts for the oxidative dehydrogenation of ethane to ethene with molecular oxygen. The catalysts were prepared by high-temperature solid-state reaction of appropriate mixtures of bismuth chloride oxide, bismuth oxide, alkali chloride, and alkaline earth chloride. We found that the catalysts containing strontium as the alkaline earth constituent and potassium as the alkali constituent were highly active and selective for the oxidative dehydrogenation of ethane. SrBi₃O₄Cl₃, which is a fundamental phase of the catalysts, was characterized by single and double chlorine sheets in its layer structure. The catalyst having the composition of KSr₂Bi₃O₄Cl₆ showed an extremely high ethene selectivity, more than 90%, even under high oxygen partial pressure conditions and at high molar ratios of oxygen to ethane, and gave 70% yield of ethene at 640°C under an optimized feed gas composition.