与气相分子相比,在支持的氧化瓦纳催化剂上将甲醇氧化为甲
Jens Döbler1, Marc Pritzsche, Joachim Sauer
1Institut für Chemie der Humboldt Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany.
Journal of the American Chemical Society
|August 4, 2005
概括
密度函数理论研究了甲醇氧化成甲在氧化物支持的氧化物上的甲醇氧化. 速度限制步骤涉及转移,对充电物种的激活能量要低得多.
科学领域:
- 催化剂是一种催化剂.
- 表面科学是一门学科.
- 计算化学计算化学
背景情况:
- 甲醇氧化成甲是一种关键的工业过程.
- 在这种反应中,广泛使用的是在二氧化上支的氧化催化剂.
- 了解分子水平的反应机制对于催化剂设计至关重要.
研究的目的:
- 用计算方法阐明在二氧化上甲醇氧化成甲的机制,支持氧化.
- 为了识别限制速度的步骤和过渡状态.
- 为了评估催化剂模型系统和电荷对反应路径的影响.
主要方法:
- 使用密度函数理论 (DFT) 的计算.
- 用于孤立的氧化瓦纳物种,使用了silsesquioxane类型的模型.
- 破碎对称的方法被用来治疗比拉基卡洛伊德过渡状态.
- 计算了不同模型系统的激活能量.
主要成果:
- 甲醇的分离吸附形成了CH3O(O=) V(O-) 2表面复合体.
- 速度限制的步骤是从甲氧基向瓦纳基氧转移气.
- 激活能被计算为O=V(OCH3) 3 (147 kJ/mol) 和丝素模型 (154 kJ/mol).
- 对于O=V(OCH3) 3(*+) 基离子,发现激活障碍明显较低 (80kJ/mol).
结论:
- 这项研究提供了对支持的氧化瓦纳甲醇氧化机制的详细见解.
- 氧化瓦纳物种的电荷状态强烈影响反应的激活能量.
- 气相集群研究可能无法完全反映受支持的催化剂的行为,因为充电效应.
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