Effect of Mg, Ca, and Sr on CeO2 Based Catalysts for the Oxidative Coupling of Methane: Investigation on the Oxygen Species Responsible for Catalytic Performance

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• 作者：Víctor J. Ferreira ; Pedro Tavares ; José L. Figueiredo ; Joaquim L. Faria
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2012
• 出版时间：August 15, 2012
• 年：2012
• 卷：51
• 期：32
• 页码：10535-10541
• 全文大小：328K
• 年卷期：v.51,no.32(August 15, 2012)
• ISSN：1520-5045

文摘

CeO₂ catalysts modified with earth alkaline metals (M = Mg, Ca, and Sr) were prepared by the citrate method in a M:Ce molar ratio of 1:1. Different analytical techniques including diffuse reflectance Ultraviolet鈥揤isible (DR UV鈥搗is) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and temperature programmed desorption of CO₂ (TPD-CO₂) were used for the characterization of the catalysts. The materials were tested in the oxidative coupling of methane (OCM). The results of calcined samples revealed that the charge transfer from cerium to oxygen ions is shifted when CeO₂ is doped, indicating defects on the catalyst surface. A linear correlation was found between the amount of surface basic sites and the ratio of the oxygen species O₂^{鈥?/sup> and O₂2鈥?/sup> to lattice oxygen. This behavior is crucial for the CH₄ conversion and selectivity to C₂H₆ and C₂H₄ at 700 掳C. Ca-doped CeO₂ catalyst revealed the best performance in the OCM, which can be attributed to the similar ionic radii of Ca2+ and Ce4+.}