The basicity of ZnAl hydrotalcite type materials was modified through the incorporation of Ce into their structure and used as heterogeneous catalysts in the transesterification of soybean oil. A series of novel ZnAl–Ce(X) catalysts was synthesized by the co-precipitation method varying the loading of Ce (X = Ce/Al molar ratio). The larger ionic radius of Ce 3+ (1.01 Å) compared with Al 3+ (0.53 Å) and Zn 2+ (0.72 Å), hinders the appropriate incorporation of Ce 3+ in the brucite-like structure, causing a small segregation of Ce 3+ as CeO 2 . However, the concentration of basic sites (acid–basic Lewis pairs) and specific surface area of the ZnAl–Ce(0.0) sample were enhanced with the incorporation of Ce, improving its catalytic activity. The most appropriate Ce loading was obtained with a Ce/Al molar ratio of 0.03, which was attributed to its large surface area, along with a higher amount of acid–basic Lewis pairs related to the presence of aluminum in pentahedral coordination. Thus, the total amount of basic sites ( − OH and M–O − ) of ZnAl–Ce(0.03) was triplicated, leading to a FAME yield of 80% with this catalyst, which represents an increase of 11.3% when compared with the ZnAl hydrotalcite without Ce. Graphic Abstract

中文翻译：

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Ce改性ZnAl水滑石的基本性质在豆油酯交换反应中的应用

ZnAl水滑石类材料的碱性通过将Ce掺入其结构中而得到改善，并用作大豆油酯交换中的多相催化剂。通过改变Ce负载量（X=Ce/Al摩尔比）的共沉淀法合成了一系列新型ZnAl-Ce（X）催化剂。与 Al 3+ (0.53 Å) 和 Zn 2+ (0.72 Å) 相比，Ce 3+ (1.01 Å) 的离子半径较大，阻碍了 Ce 3+ 在类水镁石结构中的适当结合，导致小部分偏析Ce 3+ 作为CeO 2 。然而，ZnAl-Ce(0.0) 样品的碱性位点浓度（酸碱路易斯对）和比表面积随着 Ce 的掺入而增加，从而提高了其催化活性。在 Ce/Al 摩尔比为 0.03 时获得最合适的 Ce 负载量，这归因于其较大的表面积，以及与铝在五面体配位中存在相关的更多酸碱路易斯对。因此，ZnAl-Ce(0.03) 的碱性位点 (-OH 和 M-O-) 的总量是三次重复，导致使用该催化剂的 FAME 产率为 80%，与催化剂相比增加了 11.3%。不含 Ce 的 ZnAl 水滑石。图形摘要