High efficient synthesis of methyl ethyl ketone oxime from ammoximation of methyl ethyl ketone over TS-1 in a ceramic membrane reactor

The liquid-phase ammoximation of methyl ethyl ketone (MEK) with ammonia (NH₃), hydrogen peroxide (H₂O₂) over titanium silicalite-1 (TS-1) was attempted to efficiently produce methyl ethyl ketone oxime (MEKO) in a ceramic membrane reactor where a ceramic membrane was used to distribute H₂O₂. Under optimized conditions, the MEK conversion and MEKO selectivity could reach 99.6% and 99.0%, respectively. Compared with the general ammoximation of MEK which took tert-butyl alcohol (TBA) as an organic solvent, the higher conversion of MEK and selectivity of MEKO were obtained at lower molar ratio of NH₃ to MEK in the ceramic membrane reactor. This was related to the change of feeding mode of NH₃ and the introduction of membrane distributor in the reactor to provide micron-sized drops of H₂O₂ into the reaction system and enhance the mass transfer of phases. The stability of TS-1 was also explored and results showed that TS-1 catalysts deactivated rapidly among ammoximation. Efforts were thus made in order to find out the dominating reason of catalyst deactivation. The results showed that the absence of TBA aggravatingly resulted in the deposition and pore blocking of TS-1, resulted in catalyst deactivation. Through high-temperature calcination, the lifetime of catalyst activity could be prolonged effectively.