Preparation Of Hydroxylamine By Cyclohexanone Oxime Hydrolysis Catalyzed By Porous SiO₂ Supported Acidic Ionic Liquid

Hydroxylamine（NH₂OH）is an important chemical raw material,usually in the form of inorganic salts（such as hydroxylamine hydrochloride,hydroxylamine sulfate.）,or in the form of aqueous solution.It is mainly used for synthesis of caprolactam（production of nylon-6）,drug intermediate hydroxylamine-o-sulfonic acid,and synthetic pesticides,medicine,spices,fuel,etc.In this paper,a supported acid functionalized ionic liquid catalyst supported by silica was used to catalyze the one-step hydrolysis of cyclohexanone oxime into hydroxylamine.The thermodynamics of the hydrolysis reaction of cyclohexanone oxime was analyzed by quantitative calculation.The results showed that the gibbs free energy change Δ_rG_m^θof cyclohexanone oxime hydrolysis is positive（>0）,and the equilibrium constant（K^Θ）is a very small value.It means that the reaction does not occur spontaneously under the standard conditions,and the oxime hydrolysis reaction is mainly controlled by thermodynamics.The single-factor experimental method was used to investigate the effects of catalyst type,catalyst preparation method,reaction temperature and time on the cyclohexanone oxime hydrolysis reaction.The catalyst was characterized by elemental analysis,infrared spectroscopy,and thermogravimetric analysis.Based on the calculation of density functional theory,the structure of the supported IL was initially explored,and the micro-mechanism of the hydrolysis reaction was proposed.The results show that:（1）The supported acid functional catalyst prepared by the impregnation method shows some activity for the cyclohexanone oxime hydrolysis reaction,with[SPIPTES]CF₃SO₃/SiO₂（15wt.%）as the catalyst,the amount of cyclohexanone oxime added is 0.1 g,the mass ratio of hexanone oxime to catalyst was 1:10,the amount of ultrapure water added was 30 m L,the conversion of cyclohexanone oxime was 37.13%,and the yield of hydroxylamine was36.69%when reacted at 60℃for 1 h,but the catalyst recycling is not good.（2）The addition of solvents toluene and ethanol can promote the hydrolysis reaction of cyclohexanone oxime to a certain extent,but the effect is not obvious.（3）The process of preparing supported catalyst by sol-gel method is particularly important for the activity of catalyst.It was found that the supported ionic liquid catalyst[SPIPTES]CF₃SO₃@SiO₂-6prepared by the gel sol method is a suitable hydrolysis catalyst,and the preparation conditions are as follows.The template agent polyethylene oxide-polypropylene oxide-polycyclohexene Oxyethane triblock copolymer,molecular formula is PEO-PPO-PEO（P123）4.95 g,ultrapure water 45 m L,pre-hydrolysis time 7 h,sol-gel time4 h.（4）the suitable reaction conditions for hydrolysis:[SPIPTES]CF₃SO₃@SiO₂-6:cyclohexanone oxime（mass ratio）=10:1（1 h,60℃）.Under this condition,cyclohexanone oxime conversion was 17.40%,and hydroxylamine yield was 17.23%,the catalyst[SPIPTES]has a relatively high reusability.（5）the possible catalyst structure was suggested by the calculation of density functional theory.（6）the hydrolysis reaction mechanism of protonated cyclohexanone oxime was proposed,through comprehensive experiments and density functional theory calculation.