Pt-MOx/CeO2水相重整催化剂上氧化物助剂对于水气变换反应的促进作用研究

Investigation of the promotion effect of metal oxides on the water-gas shift reaction activity over Pt-MOx/CeO2 catalysts for aqueous phase reforming

  • 摘要: 甲醇水相重整是一种在相对温和条件下的有效产氢路径。采用分步浸渍法制备Pt/CeO2和Pt-MOx/CeO2 (M = Fe、Cr、Mg、Mn)系列催化剂,并对其反应性能进行了研究。采用XPS、XRD、TEM、CO-TPD、NH3-TPD、CO2-TPD等表征手段对催化剂的金属价态、氧空位数量、金属粒子分布、CO吸附性能和催化剂的酸/碱性等性质进行表征和分析。通过关联结果表明,MOx的加入削弱了Pt-CeO2间的相互作用,促进了价态较低的Ptδ + 的生成,这有助于C–H键的裂解,促进甲醇的转化。Pt-MgO/CeO2上的产氢量最高(164.78 mmol),CO和CH4选择性相对较低,而Pt-CrOx/CeO2上的CH4选择性最高(2.21%)。对于Pt/CeO2和Pt-MOx/CeO2 (M = Fe、Cr、Mg、Mn)催化剂的产物选择性而言,CO2/CH4比与催化剂碱度相关性较好,说明碱度促进了水分子的解离吸附和水气变换反应活性,降低了甲烷化活性。

     

    Abstract: Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO2 and a series of Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH3-TPD, CO2-TPD, etc. It was found that the addition of MOx weakened the Pt-CeO2 interaction and promoted the generation of Ptδ + species with lower valence state, which contribute to the C−H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH4 selectivities were obtained over the Pt-MgO/CeO2, while the highest CH4 selectivity was obtained over the Pt-CrOx/CeO2 (2.21%). Over the Pt/CeO2 and Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts, CO2/CH4 ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H2O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.

     

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