Patel Anish, Patel Anjali
Polyoxometalates and Catalysis Laboratory, Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda Vadodara India
RSC Adv. 2019 Jan 11;9(3):1460-1471. doi: 10.1039/c8ra08419j. eCollection 2019 Jan 9.
The present work describes for the first time, the synthesis and characterization of a bi-functional catalyst consisting of nickel and supported 12-tungstophosphoric acid as well as its application in one pot oxidative esterification of benzaldehyde and benzyl alcohol to benzoate ester. The said reactions were operated without any base at a low temperature and atmospheric pressure. The influence of reaction parameters such as nickel concentration, molar ratio of substrate to HO as well as methanol, catalyst amount, reaction temperature and reaction time were investigated to optimize the conditions for maximum conversion with good selectivity towards the desired product. The superiority of the present work lies in obtaining higher conversion as well as higher selectivity of the desired product with a high TON for both the systems under sustainable reaction conditions. Moreover, the catalyst could be recovered and reused for up to three cycles without any significant loss in its selectivity. The obtained conversion as well as selectivity were discussed with a number of control experiments and based on the obtained results, mechanisms for both the reactions were proposed. Furthermore, the difference in activity towards oxidative esterification of benzaldehyde and benzyl alcohol was also correlated with the proposed mechanism.
本研究首次描述了一种由镍和负载型12 - 钨磷酸组成的双功能催化剂的合成与表征，以及其在一锅法中将苯甲醛和苯甲醇氧化酯化制备苯甲酸酯中的应用。所述反应在低温和常压下无任何碱存在的条件下进行。研究了镍浓度、底物与HO以及甲醇的摩尔比、催化剂用量、反应温度和反应时间等反应参数的影响，以优化条件，实现最大转化率并对所需产物具有良好的选择性。本研究的优势在于，在可持续反应条件下，两种体系均能获得较高的转化率以及所需产物的高选择性和高TON。此外，该催化剂可以回收并重复使用多达三个循环，其选择性没有任何显著损失。通过一系列对照实验对获得的转化率和选择性进行了讨论，并根据所得结果提出了两种反应的机理。此外，苯甲醛和苯甲醇氧化酯化活性的差异也与所提出的机理相关。
