Highly selective synthesis of methyl ethyl ketone oxime through ammoximation over Ti-MWW

The liquid-phase ammoximation of methyl ethyl ketone (MEK) with ammonia and hydrogen peroxide was conducted on Ti-MWW, TS-1, Ti-MOR and Ti-Beta catalysts in order to produce methyl ethyl ketone oxime (MEKO) cleanly. Compared with other titanosilicates, Ti-MWW produced MEKO more efficiently and selectively, achieving a conversion and selectivity both over 99% under optimized conditions. Ti-MWW was particularly superior to TS-1 in MEKO selectivity, as TS-1 co-produced easily 2-nitrobutane byproduct as a result of consecutive oxidation of MEKO unless the ammonia/MEK molar ratio was increased to 4. The catalyst deactivated in repeated ammoximation, mainly owing to a partial dissolution of framework silicon in basic reaction media. Efforts were thus made in order to develop practicable regeneration methods. By adding a controlled amount of silica source into the reaction mixture, we could suppress the deactivation of Ti-MWW catalyst and then the lifetime was prolonged effectively.