Low-temperature conversion of phenol into CO, CO₂ and H₂ by steam reforming over La-containing supported Rh catalysts

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• 作者：Domna A. Constantinou^a ; M. Consuelo Á ; lvarez-Galvá ; n^b ; José ; Luis G. Fierro^b ; Angelos M. Efstathiou^a ; ^{efstath@ucy.ac.cy}
• 关键词：Phenol steam reforming ; Hydrogen production ; Supported-Rh catalysts ; HRTEM ; XPS ; CO2-TPD ; CO-TPD ; CO2-DRIFTS ; H2O-DRIFTS ; Operando DRIFTS-mass spectrometry WGS
• 刊名：Applied Catalysis B ; Environmental
• 出版年：2012
• 期刊代码：4_09263373
• 类别：ce
• 出版时间：18 May, 2012
• 卷：117-118
• 期：Complete
• 页码：81-95
• 文件大小：1376 K

摘要

The steam reforming of phenol in the low-temperature range of 350-550 掳C was studied over 0.5 wt%Rh supported on Ce_0.15Zr_0.85O₂, Zr_0.93La_0.07O₂, and Ce_0.13Zr_0.83La_0.04O₂ mixed metal oxides. The reforming specific activity (per gram of catalyst basis) was found to depend on (a) Rh dispersion, (b) the concentration (渭mol g^鈭?) of labile oxygen species of support, as determined by 鈥渙xygen storage capacity鈥?measurements, and (c) the promotion of the water-gas shift (WGS) reaction rate, all of which largely influenced by the support chemical composition. The addition of 4 atom%La³⁺ into the Ce_0.15Zr_0.85O₂ crystal structure was found to largely promote the dispersion of Rh, to increase significantly (by a factor of 1.75) the concentration of surface basic sites (渭mol m^鈭?) of Ce_0.13Zr_0.83La_0.04O₂ compared to Ce_0.15Zr_0.85O₂ support, to prevent to a large extent the inhibiting role of hydrogen in the rate of WGS reaction, and to influence significantly the concentration and structure of surface reaction intermediates of the WGS, namely: formate (HCOO-) and -OH groups formed on the support, and adsorbed CO formed on the Rh metal. The 0.5 wt%Rh/Ce_0.13Zr_0.83La_0.04O₂ catalyst led to a significantly better performance towards steam reforming of phenol in terms of phenol conversion, H₂-yield, and CO/CO₂ product ratio in the 350-450 掳C range compared to a commercial Ni-based catalyst (44 wt%Ni) used for steam reforming reactions. At 400 掳C, the 0.5 wt%Rh/Ce_0.13Zr_0.83La_0.04O₂ catalyst exhibited approximately 54%and 50%, respectively, higher phenol conversion and hydrogen yield, compared to the Ni-based industrial catalyst. The significantly lower CO/CO₂ product ratio obtained in the case of Rh/Ce_0.13Zr_0.83La_0.04O₂ compared to that obtained in the other supported-Rh catalysts is in agreement with the higher kinetic rate for the WGS reaction observed in the former catalyst.