Effects of polyvinylpyrrolidone on the preparation of supported La 2O3 catalysts by a modified impregnation method for the oxidative coupling of methane

摘要

The direct transformation of methane, such as oxidative coupling of methane (OCM), is a long-standing challenge in methane utilization. Keeping this objective in mind, we explored the dispersion and acid-base effects of the catalysts on OCM. Herein, we prepared a series of La2O 3/MgO catalysts by using a modified impregnation method with polyvinylpyrrolidone added to impregnated solutions. The BET, XRD, SEM, and TEM characterizations of the samples confirm that La2O3 dispersion on MgO increases with the addition of polyvinylpyrrolidone and the particles become smaller in size and more uniform in distribution. High catalytic performances (e.g., the C2 yield 16 %) of the well-dispersed La2O3/MgO catalysts for OCM are demonstrated at a lower temperature (e.g., 550°C) and a lower loading (e.g., 1.9 wt %). In addition, with the modification of acid-base properties of the supports, we find that base properties of the supports are responsible for C2 formation and acidic properties of the supports are responsible for COx formation. These properties establish a good correlation of the dispersion and basicity of the catalysts with the catalytic performances of the catalysts for OCM. Disperse and couple! The addition of polyvinylpyrrolidone (PVP) into an impregnated solution can effectively increase the dispersion of active components during the preparation of the supported catalysts; the acid-base properties of the supports have great influences on the selectivity for the oxidative coupling of methane. MO=Metal oxide. Copyright ? 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.