An investigation into cyclohexanone ammoximation over Ti-MWW in a continuous slurry reactor

In the present study, the liquid-phase ammoximation of cyclohexanone with ammonia and hydrogen peroxide was studied using a MWW-type titanosilicate (Ti-MWW) catalyst in a continuous slurry reactor to develop a clean process for producing cyclohexanone oxime. The reaction parameters, which governed the cyclohexanone conversion, oxime selectivity and catalyst deactivation, were investigated by simulating the operating conditions of an industrial process. Under optimized reaction conditions, Ti-MWW produced a cyclohexanone conversion and oxime selectivity over 96% and 99%, respectively. Moreover, Ti-MWW was extremely robust and showed a longer lifetime than the conventional titanium silicalite-1 catalyst. The causes of deactivation were elucidated to be the coke deposition and partial dissolution of the zeolite framework of Ti-MWW during ammoximation. The deactivated Ti-MWW catalyst was regenerated effectively by a combination of acid treatment and cyclic amine-assisted structural rearrangement.

.Figure optionsDownload high-quality image (256 K)Download as PowerPoint slideResearch highlights▶ The liquid-phase ammoximation of cyclohexanone has been studied for the first time with Ti-MWW as a catalyst in a continuous slurry reactor. The effects of reaction parameters on the catalytic performance of Ti-MWW in the ammoximation, the catalyst deactivation behavior as well as the regeneration method for the deactivated Ti-MWW were investigated in detail. ▶ Ti-MWW showed a much longer catalyst lifetime than TS-1 when it maintained a cyclohexanone conversion of >96% and an oxime selectivity of >99%. The deactivation of Ti-MWW was clarified to be due to the coke formation and a partial desilication of the zeolite framework. ▶ A combination of acid treatment and structure rearrangement assisted by cyclic amine is proposed to regenerate the deactivated Ti-MWW catalyst effectively. The results would be meaningful for developing cleaner processes of ketone ammoximation.