Alcoholysis of urea with 1,2‐propylene glycol (PG) is a potential industrial process for the synthesis of propylene carbonate (PC) with many advantages. However, the preparation of industrial catalysts such as Zn‐Al oxide by the co‐precipitation method will inevitably produce a large amount of salty water and building desalting equipment will increase the investment cost. The present work attempts to use a mechanically mixed catalyst consisting of commercial ZnO and Al₂O₃ to solve these problems. This type of catalyst was capable of catalyzing the reaction more than 5 times. The PC yield was gradually increased with each use. The best PC yield of 96.7% is comparable to the co‐precipitated Zn‐Al oxide catalysts and was achieved during the third use. In the reaction, ZnO and Al₂O₃ were dissolved into the reactants to form complexes, which homogenously catalyzed the reaction. It was found that the dissolved Zn and Al complex significantly influenced the PC yield and re‐precipitated in the late stage of the reaction. Furthermore, the partial dissolution of Al assisted the dissolution and precipitation of Zn, which improved the PC yield. After several dissolution‐precipitation cycles, ZnO‐Al₂O₃ was homogeneously mixed at the atomic scale. Interestingly, there was an adequate linear relationship between the amount of dissolved Zn and Al in each reaction, the linear correlation coefficient improved after each reaction, and the slope of the line (the ratio of dissolved Zn/Al) was 7.26 in the third use.

中文翻译：

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机械混合的ZnO-Al2O3催化剂通过尿素的醇解合成碳酸亚丙酯

尿素与1,2-丙二醇（PG）的醇解是合成碳酸亚丙酯（PC）的潜在工业方法，具有许多优点。但是，通过共沉淀法制备工业催化剂（如Zn-Al氧化物）将不可避免地产生大量的盐水，并且建筑脱盐设备将增加投资成本。本工作试图使用由商业ZnO和Al ₂ O ₃组成的机械混合催化剂来解决这些问题。这种类型的催化剂能够催化反应超过5次。每次使用都会逐渐提高PC产量。最佳PC产率为96.7％，可与共沉淀Zn-Al氧化物催化剂相媲美，并且是在第三次使用中获得的。在反应中，ZnO和Al_将2 O ₃溶解在反应物中以形成络合物，从而均匀地催化反应。结果发现，溶解的锌和铝配合物会显着影响PC的收率，并在反应后期重新沉淀。此外，Al的部分溶解有助于Zn的溶解和沉淀，从而提高了PC产量。经过几个溶解-沉淀循环后，ZnO-Al ₂ O ₃在原子尺度上均匀混合。有趣的是，在每个反应中锌和铝的溶解量之间具有足够的线性关系，在每个反应后线性相关系数得到改善，在第三次使用中，线的斜率（溶解锌/铝的比率）为7.26 。