An analysis of the Mars–van Krevelen rate expression
An analysis of the Mars–van Krevelen rate expression
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DOI：
10.1016/j.cattod.2007.02.002
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发表时间：
2007-05
期刊：
影响因子：
5.3
通讯作者：
M. Vannice
中科院分区：
文献类型：
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作者：
M. Vannice
对多相催化氧化反应的马尔斯-范克雷文速率公式的推导中包含的“机理”和假设的分析揭示了一些不一致之处。所导出的表达式只适用于分子氧吸附在单一位置上的反应；然而，该模型假设晶格O离子(或原子)与被氧化的底物反应。此外，描述模型的步骤不是基本步骤，此外，没有考虑中间体和产品的竞争吸附。因此，原始推导是不正确的，并且该速率表达式必须仅被视为数学数据拟合函数。替代的Langmuir-HinShelwood，Hougen-Watson类型的催化序列通常可以提供类似的，有时是相同的速率方程，该速率方程可以比Mars-van Krevelen表达式更好地拟合速率数据，或者至少是一样好。后一种模型还提供了可用于热力学一致性评估的速率参数。
An analysis of the “mechanism” and the assumptions incorporated into the derivation of the Mars–van Krevelen rate expression for heterogeneously catalyzed oxidation reactions reveals a number of inconsistencies. The expression as derived is properly applicable only for a reaction involving molecular oxygen adsorbed on a single site; however, the model assumes that lattice O ions (or atoms) react with the substrate being oxidized. Furthermore, the steps describing the model are not elementary steps and, in addition, the competitive adsorption of intermediates and products is not considered. Consequently, the original derivation is incorrect and this rate expression must be viewed only as a mathematical data-fitting function. Alternative Langmuir–Hinshelwood, Hougen–Watson-type catalytic sequences can typically provide similar, and sometimes identical, rate equations which can fit rate data better than, or at least as well as, the Mars–van Krevelen expression. These latter models also provide rate parameters that can be evaluated for thermodynamic consistency.