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首页> 外文期刊>Green chemistry >Production of lactic acid esters catalyzed by heteropoly acid supported over ion-exchange resins
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Production of lactic acid esters catalyzed by heteropoly acid supported over ion-exchange resins

机译：负载在离子交换树脂上的杂多酸催化的乳酸酯的生产

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摘要

The heterogeneous liquid-phase esterification reaction of lactic acid with ethyl alcohol accompanied with lactoyllactic acid hydrolysis over heteropoly acid supported on ion exchange resin catalysts was investigated at 343 K with ethanol to lactic acid molar ratio of 1:1. The catalysts with 5-20% of tungstophosphoric (H_3PW_(12)O_(40)·xH_2O) and molybdophosphoric (H_3PMo_(12)·xH_2O) acid type of heteropoly acids over Lewatit S100 showed higher activities than the resin itself. DRIFTs and XRD analysis indicated the formation of amorphous heteropoly acid layer, which is strongly bonded to the resin surface with hydrate structure. Reaction experiments showed molybdophosphoric acid has slightly higher activity than the tungstophosphoric acid, which yields slower deactivation. The reaction model was established by considering the hydrolysis reaction of lactoyllactic acid under the reaction conditions and the esterification step. Reaction rate constants for homogeneous self catalyzed, ion exchange resin catalyzed, and kinetic contribution of heteropoly acid loading were calculated. Kinetic analysis of the reaction data revealed that the active proton sites do not increase proportionally with the amount of heteropoly acids over the resin surface and proton efficiency of the catalysts decreases with increasing loading. It was observed that molybdophosphoric acid loaded S100 catalysts have higher proton efficiency than the tungstophosphoric acid loaded counterpart.
机译：研究了乳酸与乙醇的异相液相酯化反应，以及在离子交换树脂催化剂上负载的杂多酸上乳酸-乳酸的水解，在343 K下乙醇与乳酸的摩尔比为1：1。在Lewatit S100上，钨磷（H_3PW_（12）O_（40）·xH_2O）和钼磷（H_3PMo_（12）·xH_2O）酸类型的杂多酸催化剂的活性比树脂本身高。 DRIFT和XRD分析表明形成了非晶杂多酸层，该杂多酸层牢固地结合到具有水合物结构的树脂表面上。反应实验表明，钼磷酸比钨磷酸具有更高的活性，而钝化活性较慢。考虑反应条件下乳基乳酸的水解反应和酯化步骤，建立反应模型。计算了均相自催化，离子交换树脂催化的反应速率常数以及杂多酸负载量的动力学影响。反应数据的动力学分析表明，活性质子位点不会随树脂表面杂多酸的含量成比例增加，并且催化剂的质子效率会随着负载量的增加而降低。观察到负载钼磷酸的S100催化剂比负载钨磷酸的对应物具有更高的质子效率。

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