在Rh16/In_(2)O_(3)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 CO_(2)hydrogenation over Rh16/In_(2)O_(3)catalysts:A combined study on density functional theory and microkinetic modeling

本研究采用密度泛函理论(DFT)和微动力学模型分析了Rh16/In_(2)O_(3)催化剂上二氧化碳(CO_(2))氢化成甲醇(CH_(3)OH)的情况;研究了Rh16/In_(2)O_(3)界面上H_(2)的自发解离和CO_(2)的有效吸附,其中,In_(2)O_(3)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:CO_(2)→COOH→CO+OH→HCO→CH_(2)O→CH_(2)OH→CH_(3)OH。在不同温度(373−873 K)和压力(10^(−2)−10^(3)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,CH_(2)O+H→CH_(3)O的步骤占主导地位。

In this study,the hydrogenation of carbon dioxide(CO_(2))to methanol(CH_(3)OH)over Rh16/In_(2)O_(3)catalyst was studied through Density Functional Theory(DFT)and microdynamics modeling.The spontaneous dissociation mechanisms of H_(2)and CO_(2)adsorption at the Rh16/In_(2)O_(3)interface were investigated.The oxygen vacancies in In_(2)O_(3)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:CO_(2)→COOH→CO+OH→HCO→CH_(2)O→CH_(2)OH→CH_(3)OH.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 CH_(2)O+H to CH_(3)O was dominate.