Glycerol carbonate (GC) was synthesized by transesterification of glycerol with dimethyl carbonate (DMC) using calcium oxide (CaO) derived from eggshell as a catalyst. The best results of 96% glycerol conversion and 94% GC yield were achieved under the following reaction conditions: 0.08 mole ratio of CaO to glycerol, 1:2.5 mole ratio of glycerol to DMC, 60°C reaction temperature, and 3 hours reaction time. As expected, CaO showed deteriorated catalytic performance when recycling as observed by a rapid decrease in GC yield. This research showed that the active CaO phase first was converted to calcium methoxide (Ca[OCH₃]₂) and calcium diglyceroxide (Ca[C₃H₇O₃]₂) and finally to carbonate phase (CaCO₃) which can be confirmed by XRD patterns. According to the phase transformation, the basicity decreased from 0.482 mmol/g to 0.023 mmol/g, and basic strength altered from strong basic strength (15.0 < H_ < 18.4) to weak basic strength (7.2 < H_ < 9.8), resulting in the lower catalytic activity of the consecutive runs. Despite the fact that the GC selectivity was almost 100%, the reaction products (methanol and GC) were not obtained in their stoichiometric ratio and their extents corresponded with that of the catalyst phase transformation to CaCO₃. The mechanism of CaO catalyzed transesterification based on the condensation reaction of glycerol and catalyst was proposed, and in situ formation of water-derivative species was hypothesized as a cause of CaO transformation. CaO could react with DMC and water, generating methanol and CaCO₃. This enabled unconventional monitoring of catalyst deactivation by checking if the mole ratio of methanol to GC was higher than 2:1 of its reaction stoichiometric ratio. It was also demonstrated that calcination of post-run catalyst at 900°C to CaO exhibited almost constant catalytic activity, and the mole ratio of methanol to GC was constant at its reaction stoichiometry (2:1) for at least 4 times use.

中文翻译：

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甘油与碳酸二甲酯酯交换生产甘油碳酸酯的非常规监测方法对CaO催化剂失活的机理

甘油碳酸酯 (GC) 是通过甘油与碳酸二甲酯 (DMC) 的酯交换反应合成的，其中使用来源于蛋壳的氧化钙 (CaO) 作为催化剂。在以下反应条件下获得了 96% 甘油转化率和 94% GC 收率的最佳结果：CaO 与甘油的摩尔比为 0.08，甘油与 DMC 的摩尔比为 1:2.5，反应温度为 60°C，反应时间为 3 小时. 正如预期的那样，通过 GC 产率的快速下降观察到，CaO 在再循环时表现出恶化的催化性能。该研究表明，活性 CaO 相首先转化为甲醇钙 (Ca[OCH ₃ ] ₂ ) 和甘油二氧化钙 (Ca[C ₃ H ₇ O ₃ ] ₂)，最后是碳酸盐相(CaCO ₃ )，这可以通过XRD图谱确认。根据相变，碱度从 0.482 mmol/g 降低到 0.023 mmol/g，碱度从强碱度（15.0 < H_ < 18.4）变为弱碱度（7.2 < H_ < 9.8），导致连续运行的催化活性较低。尽管 GC 选择性几乎为 100%，但反应产物（甲醇和 GC）并未按其化学计量比获得，其程度与催化剂相转变为 CaCO _{3的程度相对应}. 提出了基于甘油和催化剂缩合反应的CaO催化酯交换反应机理，并假设水衍生物的原位形成是CaO转化的原因。CaO可以与DMC和水反应，生成甲醇和CaCO ₃。这可以通过检查甲醇与 GC 的摩尔比是否高于其反应化学计量比的 2:1 来非常规地监测催化剂失活。还证明，在 900°C 下煅烧后催化剂对 CaO 的催化活性几乎恒定，并且甲醇与 GC 的摩尔比在其反应化学计量 (2:1) 下至少使用 4 次是恒定的。