A kinetic study of methane and carbon dioxide interconversion over 0.5%Pt/SrTiO₃ catalysts

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• 作者：A. Topalidis ; D.E. Petrakis ; A. Ladavos ; L. Loukatzikou ; P.J. Pomonis
• 关键词：Dry reforming of methane ; Kinetics of dry reforming ; Reverse water gas shift reaction ; Pt/SrTiO₃ catalysts
• 刊名：Catalysis Today
• 出版年：2007
• 期刊代码：13_09205861
• 类别：ce
• 出版时间：30 September 2007
• 卷：127
• 期：1-4
• 页码：238-245
• 文件大小：692 K

摘要

The kinetics of interconversion of methane with carbon dioxide was studied over a 0.5%Pt/SrTiO₃ solid catalyst in the temperature range 813–893 K and partial pressure range 0.083<P_CH4,P_CO2<0.667. The fitting of the experimental data for the rate of methane conversion, R_CH4, using the empirical equation R_CH4=k₁(P_CH4)^m(P_CO2)ⁿ showed that both reaction orders n and m are steady and obtain values equal to m ≈ 1 and n ≈ 0. The results are explained using Langmuir–Hinshelwood kinetics with the reactants adsorbed on distinct and discreet active sites of the solids, namely the methane is weakly adsorbed on the metallic phase and the carbon dioxide is strongly adsorbed on the oxidic phase of the catalyst. The apparent activation energy for the reforming of methane was estimated to be 123 kJ mol⁻¹.

The rate of conversion of the carbon dioxide, R_CO2, was also fitted using a similar empirical equation R_CO2=k₂(P_CH4)^m(P_CO2)ⁿ. The results indicate that there is a positive but variable dependence on both reaction orders which increases in the temperature range 813–893 K from m ≈ 0.0 to m ≈ 0.30 and from n ≈ 0.3 to n ≈ 0.6. This variation is attributed to the variable participation of the rate of the reverse water gas shift reaction, R_rwgs, to the overall rate R_CO2 of CO₂ conversion. The dependence of R_rwgs on the partial pressure of CO₂ appears similar to that of R_CH4 on the same reactant but shows strong inhibition by the reaction products. The results are discussed using Langmuir–Hinshelwood kinetics with the reactants and products adsorbed competitively on similar active sites of the catalyst.