Alkali and alkaline metal (Li, Na, K, Ca, and Mg)-loaded zirconium oxide catalysts were prepared by the wet impregnation method. All the prepared catalysts were employed as active heterogeneous catalysts for the transesterification of glycerol (GL) with dimethyl carbonate (DMC) producing glycerol carbonate (GLC). The catalyst with 20 wt % loading of Li on ZrO₂ showed a maximum catalytic activity with 100% selectivity toward GLC. The structure and basic properties of the prepared catalysts were studied by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and CO₂-temperature programmed desorption techniques. The effect of various reaction parameters like catalyst concentration, reaction temperature, and the molar ratio of reactants on the GLC yield was also studied. For the first time, the reaction product was quantified using the ¹H NMR technique. Considering the less availability of the kinetic study of the transesterification of GL with DMC, kinetic parameters were also studied. The Li/ZrO₂-catalyzed transesterification reaction appeared to follow second-order kinetics with an activation energy (E_a) of 93.7 kJ mol^–1. Thermodynamic parameters like enthalpy (ΔH^⧧), entropy (ΔS^⧧), and Gibbs free energy (ΔG^⧧) of the reaction were also determined.

中文翻译：

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锆酸锂作为生产碳酸甘油酯的选择性且经济高效的混合金属氧化物催化剂

通过湿法浸渍法制备了负载碱金属和碱金属（Li，Na，K，Ca和Mg）的氧化锆催化剂。所有制备的催化剂均用作活性多相催化剂，用于甘油（GL）与碳酸二甲酯（DMC）的酯交换反应，生成碳酸甘油酯（GLC）。Li在ZrO ₂上负载20 wt％的催化剂表现出最大的催化活性，对GLC的选择性为100％。通过X射线衍射，高分辨率透射电子显微镜，X射线光电子能谱和CO ₂研究了制备的催化剂的结构和基本性能。程序升温脱附技术。还研究了催化剂浓度，反应温度和反应物摩尔比等各种反应参数对GLC收率的影响。首次使用¹ H NMR技术对反应产物进行定量。考虑到用DMC进行GL酯交换反应动力学研究的可能性较小，还研究了动力学参数。Li / ZrO ₂催化的酯交换反应似乎遵循二级动力学，活化能（E _a）为93.7 kJ mol ^–1。热力学参数等焓（Δ ħ ^⧧），熵（Δ小号^⧧），和吉布斯自由能（Δ ģ ^⧧反应）也进行了测定。