Preparation of Molybdenum Carbides Using Butane and Their Catalytic Performance

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• 作者：Tian-cun Xiao ; Andrew P. E. York ; V. Cliff Williams ; Hamid Al-Megren ; Ahmad Hanif ; Xi-ya Zhou ; and Malcolm L. H. Green
• 刊名：Chemistry of Materials
• 出版年：2000
• 出版时间：December 2000
• 年：2000
• 卷：12
• 期：12
• 页码：3896 - 3905
• 全文大小：355K
• 年卷期：v.12,no.12(December 2000)
• ISSN：1520-5002

文摘

The synthesis of high surface area molybdenum carbides from molybdenum oxide andbutane has been studied via temperature-programmed reaction (TPRe), X-ray diffraction(XRD), scanning electron microscopy (SEM), ¹³C solid-state NMR, infrared (IR), and Ramanspectroscopy (LR). The molybdenum oxygen/carbon system passes through four phasetransitions before transforming into the pure Mo₂C carbide. Carbon exists in two forms withinhigh surface area molybdenum carbide. The initially produced molybdenum carbide has aface-centered-cubic (fcc) structure but is gradually converted into the hexagonal-close-packed(hcp) structure with increasing carburization temperature, and eventually at high temperature coke is deposited. During the early stages, MoO₃ is reduced by H₂, but at highertemperatures, butane also takes part in the reduction and, besides being consumed in theformation of carbide, is catalytically converted into methane, ethane, propane, and benzene.The high surface area of the molybdenum carbide materials is a consequence of preliminarycracking of oxide crystallites during reduction with hydrogen and later from the depositionof amorphous carbon. Catalytic activity tests indicate that molybdenum carbide material,prepared at 823 K, is a good catalyst for the dehydrogenation of butane. The carbide obtainedbetween 923 and 973 K has excellent performance for pyridine HDN with good selectivity.