Ketone Ammoximation Over Ti-MWW In A Continuous Slurry Reactor

The discovery of titanium silicalite-1 (TS-1)has opened up new possibilities of developing zeolites-based green catalytic processes. The high selectivity of TS-1 makes the water as the sole by-product. But TS-1 suffers constraints and mass transfer limitations due to its typical of medium pores. The manufacturing cost of TS-1 is generally high because of using expensive tetrapropylammonium hydroxide as a structure-directing agent. In addition, TS-1 catalyst should be prepared in small particles to achieve a high performance, which causes difficulty in membrane separation for a slurry-bed reactor. Ti-MWW is a promising catalyst for clean synthesis of oximes. Nevertheless, the production of bulk chemicals like cyclohexanone oxime in a large scale favours a continuous slurry-bed reactor which is equipped with membrane separator to save the labor needed by batchwise processes.In this study, from the viewpoint of simulating commercial process, we have applied Ti-MWW to the ammoximation of ketones in a continuous slurry-bed reactor, and investigated the effects of reaction parameters, deactivation behavior and catalyst regeneration by comparing with conventional TS-1.First, cyclohexanone conversion and oxime selectivity is over 96% and 99% in the ammoximation of cyclohexanone, respectively. Moreover, Ti-MWW showed a longer duration of lifetime than TS-1.The causes for the deactivation of Ti-MWW catalyst in the ammoximation have been investigated in details. The deactivation was mainly owing to the coke formation and partial dissolution of framework. A combination of acid treatment with structural arrangement was found to be an effective way to regenerate the catalyst.Second, methyl ethyl ketone conversion and oxime selectivity is over 95% and 99% in the ammoximation of methyl ethyl ketone, respectively. Ti-MWW also showed a longer duration of lifetime than TS-1.