Surface-modified TS-1 with enhanced activity for cyclohexanone ammoximation in a Pickering emulsion and increased stability in hot aqueous ammonia

Abstract

Functional TS-1, partially hydrophobilized with organosilanes, was found to be more active and stable in a Pickering emulsion. In this work, TS-1 behaved simultaneously as a catalyst and solid emulsifier favoring the cyclohexanone ammoximation reaction in organic solvent-free conditions. The composition, structure, formed emulsion morphology, and surface morphology were characterized by Fourier-transform infrared (FT-IR) spectroscopy, conductometer, optical microscope with high speed CCD camera, Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It indicated that hydrophobilization provided TS-1 a moderate wettability, allowing the formation of a stable Pickering emulsion, thus promoting the performance in catalyzing the cyclohexanone/H₂O₂/NH₃·H₂O reaction in the absence of organic solvents. What is more, due to alkyl groups grafted to TS-1, the zeolites were comparatively exclusive to the aqueous phase and they are more capable of enduring severe environment, i.e., 200 °C, under autogenic pressure.