Ammoximation Of Cyclohexanone In Pickering Emulsion And The Synthesis Of Magnetic TS-1

Cyclohexanone oxime is usually produced by cyclohexanone ammoximation process developed by Enichem Company.Tertiary butyl alcohol is usually used as solvent to make homogeneous between two immiscible reactants of cyclohexanone and aqueous H2O2,which makes the separation difficult and increases the energy consumption.By modifying the surface of TS-1,thus adjusting its surface wettability,we made the modified titanium silicon molecular sieve TS-1.The modified TS-1 can be used as solid emulsifier to make the Pickering emulsion as well as catalyst to intensify the mass transfer and the reaction.By constructing the stable Pickering emulsion reaction system,the use of organic solvents such as Tertiary butyl alcohol can be avoided.In our work,we modified the surface of TS-1 with octadecyltrichloro silane(OTS),aiming at gaining a moderate wettability of TS-1.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier-transform infrared(FT-IR)spectroscopy and Brunauer–Emmett–Teller(BET)were used to characterize TS-1 molecular sieve.Optical microscopy and conductivity meter were used to observe the morphology of Pickering emulsion and to test the stability of Pickering emulsion.A gas chromatography(GC)was used to exam the results of cyclohexanone ammoximation carried out in Pickering emulsion stabilized by modified TS-1.It is indicated that modified TS-1 can be used as solid emulsifier to form stable Pickering emulsion with decreased drop size and improve the reaction efficiency.The results showed that modified TS-1 had good performances in the reaction of cyclohexanone ammoximation.Among a series of functionalized TS-1,TS-1 that modified by mass ratio of 12.5 mg octadecyltrichloro silane/(1 g TS-1)exhibited the best catalytic activity.The best result lied in 97.5% conversion of cyclohexanone,and 94.2% selectivity of cyclohexanone oxime.Also,we tested the stability of TS-1,both functionalized and unmodified,in hot aqueous ammonia under their self-generated pressure.X-ray diffraction(XRD)was used to check the changes of relative crystallinity.Scanning electron microscopy(SEM)was taken to investigate the surface morphology.Transmission electron microscopy(TEM)was employed to observe the channel and structure inside TS-1 sieve.All these results evidenced the better toleration of TS-1 functionalized.To well solve the separation and recycling problems of catalyst used in reactions,we synthesized TS-1 by loading a magnetic center inside it.And the so-synthesized molecular sieve is named ?sandwich? attributing to the three layer TS-1@SiO2@?-Fe2O3 structure.The results showed that the "sandwich" type molecular sieve TS-1@SiO2@?-Fe2O3 had good catalytic activity on the reaction of cyclohexanone ammoximation.Moreover,it brings convenience to the separation and recycling of catalysts.