Effect of Sodium on the Catalytic Properties of VOx/CeO2 Catalysts for Oxidative Dehydrogenation of Methanol

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• 作者：Yan Li ; Zhehao Wei ; Junming Sun ; Feng Gao ; Charles H. F. Peden ; Yong Wang
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 21, 2013
• 年：2013
• 卷：117
• 期：11
• 页码：5722-5729
• 全文大小：354K
• 年卷期：v.117,no.11(March 21, 2013)
• ISSN：1932-7455

文摘

A series of VO_x/CeO₂ catalysts with various sodium loadings (Na/V ratio from 0 to 1) have been studied for oxidative dehydrogenation (ODH) of methanol. The effect of sodium on the surface structure, redox properties, and surface acidity/basicity of VO_x/CeO₂ was investigated using hydrogen temperature-programmed reduction (H₂-TPR), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The experimental results indicate that the effect of sodium on VO_x/CeO₂ is highly dependent on the Na/V ratio. At a low Na/V ratio (Na/V < 0.25), sodium addition only slightly decreases the redox ability of VO_x/CeO₂ and has little effect on its activity and selectivity to formaldehyde, even though the Br枚nsted acidity is almost completely eliminated at a Na/V ratio of 0.25. At a high Na/V ratio (Na/V > 0.25), sodium addition greatly alters the nature of the active sites by V鈥揙鈥揅e bond cleavage and V鈥揙鈥揘a bond formation, leading to significantly reduced activity of the VO_x/CeO₂ catalysts. At Na/V > 0.25, the selectivity to formaldehyde also decreases with increasing Na/V ratio due to (1) the suppressed reducibility of VO_x and (2) increased basicity leading to increased CO₂.