The Cyclopentanone Self-condensation Over Calcined and Uncalcined TiO.sub.2-ZrO.sub.2 with Different Acidic Properties

• Published in: Catalysis letters 2022-03, Vol.152 (3), p.806
• Main Authors: Wan, Jinmeng, Yang, Haixia, Fu, Lin, Lin, Wenjing, Hu, Qing, Xi, Fengcao, Pan, Langsheng
• Format: Article
• Language: English
• Subjects: Adsorption; Comparative analysis; Pyridine
• ISSN: 1011-372X
• DOI: 10.1007/s10562-021-03655-z

The self-condensation of cyclopentanone has been studied over calcined and uncalcined TiO.sub.2-ZrO.sub.2. The catalyst properties were examined by XRD, FTIR, SEM, N.sub.2 adsorption-desorption, and pyridine FTIR. Compared with calcined TiO.sub.2-ZrO.sub.2, uncalcined TiO.sub.2-ZrO.sub.2 exhibited superior catalytic performance (94% conversion of cyclopentanone and 86% yield of dimer). This might be because uncalcined TiO.sub.2-ZrO.sub.2 has both Lewis and Brønsted acids, while calcined TiO.sub.2-ZrO.sub.2 only contains Lewis acids. Kinetics analysis indicated that C-C coupling was the rate-limiting step on the two catalysts. For uncalcined TiO.sub.2-ZrO.sub.2, the C-C coupling occurred between the two species on the catalyst surface. Through the H bond, the cyclopentanone was firmly adsorbed on the catalyst surface by Brønsted acid sites, then the enol intermediate could attack another cyclopentanone polarized by adjacent Lewis acid sites. As a consequence, the coexistence of Brønsted and Lewis acids in catalysts exhibited enhanced activity in cyclopentanone self-condensation. Graphical