Ultrasonic-Assisted Impregnation as an Efficient Tool for the Manufacture of Cu-Containing Faujasite as an Active Catalyst for the Oxidation of Cyclohexene

In this study, a method was developed to prepare active catalysts for cyclohexene oxidation by using ultrasonic-assisted impregnation of faujasite zeolites (in protonic or sodium forms) with copper. This reaction is important for producing valuable chemicals such as surfactants, polymers, agrochemicals, and pharmaceuticals. All catalysts were thoroughly characterized, mainly using spectroscopic techniques. The results showed that the chemical form of copper was influenced by the use of ultrasound. The effects were more pronounced when sodium-form zeolites were used and when the ultrasound treatment lasted longer. In these cases, copper tended to form clusters. Notably, the ultrasound treatment did not cause structural damage (amorphization) to the zeolite framework. Catalytic tests revealed that using ultrasound to prepare copper-loaded protonic faujasites significantly increased cyclohexene conversion from 1% to 13%, with a selectivity of 55% toward 2-cyclohexen-1-one. In contrast, for catalysts based on sodium-form zeolites, the conversion dropped sharply from 75% to 7%, while selectivity increased from 53% to 71%. This suggests that copper clusters formed during ultrasound treatment promote the formation of 2-cyclohexen-1-one.