Influence of support acidity on CO₂ reforming of ethane at high temperature

CO₂ reforming of ethane (CRE) is an important reaction that produces syngas by utilizing CO₂ and shale gas as raw materials. For the industrial production of syngas via CRE, a high temperature reaction is pivotal to secure high productivity and an efficient separation process. The catalytic properties required for high temperature CRE are different from those in low temperature CRE, since ethane is thermally decomposed over 600 ℃. In this study, the CRE reaction was conducted using Ni/Al₂O₃, Ni/MgAl₂O₄, and Ni/MgO catalysts at 800 ℃. The blank test revealed that C₂H₆ was mostly decomposed into C₂H₄ and H₂ at 800 °C, indicating CO₂ reforming of C₂H₄ is the actual reaction pathway. Ni/MgAl₂O₄ and Ni/MgO exhibited high activity and stability in CRE, while Ni/Al₂O₃ was deactivated rapidly with a large amount of coke deposition. The various characterizations and coke formation/removal experiments demonstrated that coke deposition during CRE was mainly attributed to C₂H₄ cracking on the acidic sites of the catalysts, and thus coke deposition increased as acidic sites increased. An interesting observation is that the rate of C₂H₄ cracking was similar in the Ni doped support and the bare support, indicating that severe coke deposition of Ni/Al₂O₃ was caused by the C₂H₄ cracking over the support itself. Mg doped Al₂O₃ support was prepared to suppress the support acidity. Increasing Mg contents alleviated coke deposition and enhanced catalyst durability. Therefore, suppression of acidic sites of the supports will be an important factor in designing a stable catalyst for the high temperature CRE reaction.