在Rh16/In2O3催化剂上催化二氧化碳加氢合成甲醇的机理:密度泛函理论与微动力学模型的联合研究

Mechanism of methanol synthesis from CO2 hydrogenation over Rh16/In2O3 catalysts: A combined study on density functional theory and microkinetic modeling

  • 摘要: 本研究采用密度泛函理论 (DFT) 和微动力学模型分析了 Rh16/In2O3 催化剂上二氧化碳 (CO2) 氢化成甲醇 (CH3OH) 的情况;研究了 Rh16/In2O3 界面上 H2 的自发解离和 CO2 的有效吸附,其中, In2O3 中的氧空位提供了有利的效果。此外,Bader 电荷分析显示 Rh16 上带有轻微的正电荷,这对于理解催化剂的电子特性和活性非常重要。证实了RWGS+CO-Hydro 途径是甲醇合成的主要途径,其特点是经过一系列中间转化:CO2*→COOH*→CO*+OH*→HCO*→CH2O*→CH2OH*→ CH3OH*。在不同温度 (373−873 K) 和压力 (10−2−103 bar) 下进行的反应速率控制程度分析 (DRC) 揭示了两个关键的动力学现象,在较低温度和较高压力下,转化步骤 CO* + H* → HCO * 显著影响总体反应速率;而在较高温度下,CH2O* + H* → CH3O* 的步骤占主导地位。

     

    Abstract: In this study, the hydrogenation of carbon dioxide (CO2) to methanol (CH3OH) over Rh16/In2O3 catalyst was studied through Density Functional Theory (DFT) and microdynamics modeling. The spontaneous dissociation mechanisms of H2 and CO2 adsorption at the Rh16/In2O3 interface were investigated. The oxygen vacancies in In2O3 enhanced the adsorption process. Bader charge analysis revealed a marginal positive charge on Rh16, elucidating the critical insights into the electronic characteristics and catalytic activity. The study established the RWGS+CO-Hydro pathway as the predominant mechanism for methanol synthesis, characterized by a sequential transformation of intermediates: CO2*→COOH*→CO*+OH*→HCO*→CH2O*→CH2OH*→ CH3OH*. Furthermore, degree of Reaction Rate Control (DRC) analysis conducted in the range of 373−873 K and 10−2 to 103 bar identified two principal kinetic phenomena: at lower temperature and higher pressure, the conversion of CO* + H* to HCO* significantly impacted the overall reaction rate. Conversely, at higher temperature, the step from CH2O* + H* to CH3O* was dominate.

     

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