Abstract

Kinetics for the reaction between 1-tetradecene and heptanoic acid to make tetradecyl heptanoates on dry Amberlyst^® 15 catalyst at 90 °C are extremely complex. Observed kinetics of simultaneous double bond isomerization and esterification cannot be reconciled with a single type of catalytic site. Esterification and most of the double bond isomerization must occur on separate sites. Relative rates of esterification for tetradecene isomers suggest that adsorption coefficients on the esterification sites follow 1-tetradecene > 2-tetradecene > 3+-tetradecenes. These relative adsorption coefficients imply that, on this esterification site, 2-tetradecene isomerizes to 3-tetradecene faster than 3-tetradecene isomerizes to 2-tetradecene or 4-tetradecene, a truly novel finding not previously reported for any other acidic site. The site where most of the double bond isomerization occurs does not display this behavior, and isomerization of linear tetradecenes proceeds to thermodynamic equilibrium. Kinetic data indicate that esters form when carboxylic acid traps rapidly isomerizing carbenium ions on the catalyst’s surface. Competition is fierce for esterification sites among olefins, carboxylic acid, and esters, and olefins occupy few esterification sites. Contrastingly, olefins triumph in competition for isomerization sites, and olefin isomerization is much faster than esterification. Heptanoic acid exists primarily in dimer form, but the monomer form reacts to make esters. A complex kinetic model fit experimental data for double bond isomerization, conversion of olefin to esters, and the distribution of secondary esters that formed over 22 h.

Graphic abstract

中文翻译：

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在Amberlyst®15催化剂上进行烯烃酯化：酯化部位是否违反了热力学？

摘要

对于1-十四碳烯和庚酸之间的反应动力学，以使在干燥的Amberlyst十四庚^® 15催化剂在90℃下是极其复杂的。观察到的同时双键异构化和酯化反应的动力学不能与单一类型的催化位点相协调。酯化和大多数的双键异构化必须发生在不同的位置。十四碳烯异构体的相对酯化速率表明，在酯化位点上的吸附系数遵循1-十四碳烯> 2-十四碳烯> 3 +-十四碳烯。这些相对吸附系数表明，在该酯化位点上，2-十四碳烯异构化为3-十四碳烯的速度比3-十四碳烯异构化为2-十四碳烯或4-十四碳烯的速度更快，这是一个真正新颖的发现，以前没有任何其他酸性位置报道过。大多数双键异构化发生的位置不显示此行为，并且线性十四碳烯的异构化达到热力学平衡。动力学数据表明，当羧酸陷阱迅速使催化剂表面上的碳正离子异构化时，就会形成酯。烯烃，羧酸和酯之间的酯化位竞争激烈，而烯烃几乎不占酯化位。相反，烯烃在竞争异构化位点上胜出，并且烯烃异构化比酯化快得多。庚酸主要以二聚体形式存在，但单体形式反应生成酯。复杂的动力学模型拟合了双键异构化，烯烃转化为酯以及22小时形成的仲酯分布的实验数据。

图形摘要