MgO/La2O2CO3催化剂上的低温甲烷氧化偶联

Low-temperature oxidative coupling of methaneover MgO/La2O2CO3 catalysts

摘要:

共沉淀法制备的MgO/La2O2CO3催化剂使甲烷氧化偶联 (OCM) 在炉温460 oC时开始反应，且使反应在50 oC炉温下进行至少24 h。助剂Ni的加入降低了起始和最低反应温度，使催化剂在380 oC的炉温下开始反应，之后在无热源的情况下可使反应进行至少24 h。助剂Zn 的加入提高了反应活性，使C2的选择性提高了6%，但同时对低温反应不利，反应在炉温100 oC下6 h后自动停止。OCM体系中的强放热的副反应为OCM温和反应提供了热源。催化剂中的La2O2CO3组分是维持低温甲烷氧化偶联反应的关键。

Abstract:

MgO/La2O2CO3 catalyst prepared by thermal decomposition of the precursors obtained from coprecipitation method was tested in low-temperature OCM (oxidative coupling of methane). The result showed that such catalyst could hold the reaction for at least 24h at Tex=50 oC (external furnace temperature). The addition of Ni2 to the catalyst caused lower Ti (ignition temperature) and Tm(minimum reaction temperature) of OCM reaction, which was due to the enhancing catalytic performance of Ni2 on COx selectivity in OCM. The addition of Zn2 promoted the C2 selectivity, but brought negative impacts on the reaction exothermicity, which led to the lower stability of the catalyst. The thermal effects of the OCM accompanying side reactions to produce COx played great role on the process of the low temperature OCM reaction. The component La2O2CO3 was believed to provide the main active species for the reaction.