Participation of linear methoxy species bonded to Ti⁴⁺ sites in the methanol carbonylation catalyzed by TiO₂-supported rhodium: An infrared investigation

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• 作者：Gerardo A. Flores-Escamilla ; Juan C. Fierro-Gonzalez ; ^{jcfierro@iqcelaya.itc.mx}
• 关键词：Methanol carbonylation ; Supported rhodium ; Infrared spectroscopy
• 刊名：Journal of Molecular Catalysis A ; Chemical
• 出版年：2012
• 期刊代码：57_13811169
• 类别：ch
• 出版时间：July, 2012
• 卷：359
• 期：Complete
• 页码：49-56
• 文件大小：1006 K

摘要

TiO₂-supported rhodium samples synthesized from the Rh₆(CO)₁₆ complex were catalytically active and selective for the gas-phase methanol carbonylation at 140 掳C and atmospheric pressure in the presence of methyl iodide as promoter. Infrared (IR) spectra recorded during catalysis allowed the identification of molecularly adsorbed methanol, together with linear, doubly, and triply-bridged surface methoxy species on Ti⁴⁺ sites of the support. IR bands characteristic of rhodium complexes that might be regarded as reaction intermediates were also observed, in addition to bands assigned to surface acetate species attributed to the formation of methyl acetate. Our results reveal that only linear methoxy species on Ti⁴⁺ sites react with flowing CO in the presence of CH₃I to give methyl acetate, whereas bridged methoxy species and molecularly adsorbed methanol are only spectators in methanol carbonylation.