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Simultaneous determination of adsorption coefficients and surface reaction mechanisms using initial reaction rates
Reaction Kinetics, Mechanisms and Catalysis ( IF 1.7 ) Pub Date : 2021-08-15 , DOI: 10.1007/s11144-021-02049-x
Jeffrey C. Gee 1 , Karen W. Fulbright 1
Affiliation  

Initial reaction rate data for the direct esterification of 1-tetradecene with heptanoic acid on dry Amberlyst®15 catalyst permitted the identification of the surface reaction mechanism, as well as the adsorption coefficients of all reactants and products. Three different surface reaction mechanisms were considered, a two-site Langmuir–Hinshelwood mechanism and two single-site Eley–Rideal mechanisms. All the mechanisms considered competitive adsorption by all reactants and products. For each model, an error surface was calculated above the two-dimensional space of possible reactant adsorption coefficients. The error surface identified the best adsorption coefficients for each model and revealed the most likely mechanism for the surface reaction. The best mechanism was Eley–Rideal with adsorbed tetradecene reacting with heptanoic acid in the bulk phase. To explain initial rate responses to changes in initial reactant concentrations, both tetradecene and heptanoic acid must adsorb strongly to the active sites, and heptanoic acid must rapidly equilibrate between monomer and dimer forms. Data also revealed that adsorption and desorption rates were sometimes competitive with the rate of the surface reaction; equilibrium between adsorbed species and those in solution was not always maintained during short reaction times. Proper distinction between Langmuir–Hinshelwood and Eley–Rideal mechanisms required initial rate data for extreme ranges of initial reactant concentrations.



中文翻译:

使用初始反应速率同时测定吸附系数和表面反应机制

1-十四烯与庚酸在干燥 Amberlyst®15 催化剂上直接酯化的初始反应速率数据允许识别表面反应机理,以及所有反应物和产物的吸附系数。考虑了三种不同的表面反应机制,一种是双中心 Langmuir-Hinshelwood 机制,另一种是两种单中心 Eley-Rideal 机制。所有机制都考虑了所有反应物和产物的竞争吸附。对于每个模型,在可能的反应物吸附系数的二维空间上方计算误差面。误差表面确定了每个模型的最佳吸附系数,并揭示了表面反应最可能的机制。最好的机制是 Eley-Rideal,吸附的十四烯与本体相中的庚酸反应。为了解释初始反应物浓度变化的初始速率响应,十四烯和庚酸都必须强烈吸附到活性位点,并且庚酸必须在单体和二聚体形式之间快速平衡。数据还显示,吸附和解吸速率有时与表面反应速率相竞争;在较短的反应时间内,吸附物质与溶液中物质之间的平衡并不总是能保持。Langmuir-Hinshelwood 和 Eley-Rideal 机制之间的正确区分需要初始反应物浓度极端范围的初始速率数据。十四烯和庚酸都必须强烈吸附到活性位点,并且庚酸必须在单体和二聚体形式之间快速平衡。数据还显示,吸附和解吸速率有时与表面反应速率相竞争;在较短的反应时间内,吸附物质与溶液中物质之间的平衡并不总是能保持。Langmuir-Hinshelwood 和 Eley-Rideal 机制之间的正确区分需要初始反应物浓度极端范围的初始速率数据。十四烯和庚酸都必须强烈吸附到活性位点,并且庚酸必须在单体和二聚体形式之间快速平衡。数据还显示,吸附和解吸速率有时与表面反应速率相竞争;在较短的反应时间内,吸附物质与溶液中物质之间的平衡并不总是能保持。Langmuir-Hinshelwood 和 Eley-Rideal 机制之间的正确区分需要初始反应物浓度极端范围的初始速率数据。在较短的反应时间内,吸附物质与溶液中物质之间的平衡并不总是能保持。Langmuir-Hinshelwood 和 Eley-Rideal 机制之间的正确区分需要初始反应物浓度极端范围的初始速率数据。在较短的反应时间内,吸附物质与溶液中物质之间的平衡并不总是能保持。Langmuir-Hinshelwood 和 Eley-Rideal 机制之间的正确区分需要初始反应物浓度极端范围的初始速率数据。

更新日期:2021-08-19
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