Cr2O3催化合成气转化至甲醇的微观动力学研究

Cr₂O₃是双功能催化合成气转化的重要氧化物组分，其可将合成气转化为重要的中间物种甲醇. 结合密度泛函理论计算和微观动力学模拟，本文系统研究了干净Cr₂O₃(001)和(012)表面，以及氢覆盖或含有氧空位的还原(012)表面的结构及催化合成气转化至甲醇的活性. 本文探讨了合成气转化为甲醇的分步或协同反应路径，并确定CO或CHO氢化是决速步骤. 微观动力学分析表明，Cr₂O₃(001)表面难以催化合成气转化为甲醇，在673 K 时，两个还原性(012)表面的反应速率(25∽28 s^-1)比干净的(012)表面(4.3 s^-1)高出约五倍. 计算结果表明了Cr₂O₃表面还原性对催化活性的重要性，或许可以为双功能催化体系中氧化物组分的设计提供参考.

Insights into Syngas to Methanol Conversion on Cr2O3 Oxide from First-Principles-based Microkinetic Simulations

Cr₂O₃ has been recognized as a key oxide com-ponent in bifunctional catalysts to produce bridging intermediate, e.g., methanol, from syngas. By combining density functional the-ory calculations and microkinetic modeling, we computationally studied the surface structures and catalytic activities of bare Cr₂O₃ (001) and (012) surfaces, and two reduced (012) surfaces covered with dissociative hydrogens or oxygen vacancies. The reduction of (001) surface is much more difficult than that of (012) surface. The stepwise or the concerted reaction path-ways were explored for the syngas to methanol conversion, and the hydrogenation of CO or CHO is identified as rate-determining step. Microkinetic modeling reveals that (001) surface is inactive for the reaction, and the rates of both reduced (012) surfaces (25-28 s^-1) are about five times higher than bare (012) surface (4.3 s^-1) at 673 K. These theoretical re-sults highlight the importance of surface reducibility on the reaction and may provide some implications on the design of individual component in bifunctional catalysis.