Hydrolysis Of Cyclohexanone Oxime To Hydroxylamine Catalyzed By HZSM-5 Molecular Sieve

Hydroxylamine?NH₂OH?is an important chemical raw material that plays key roles in the production of?-caprolactam,pharmaceutical,pesticide,rubber,dye and military,etc.In this paper,one-step synthesis of hydroxylamine from hydrolysis of cyclohexanone-oxime was studied using solid acid as catalyst.The catalytic performance of HZSM-5 zeolite solid acid catalysts was investigated in kettle reactor and tubular reactor,respectively.And several metholds including Gaussian calculation chemistry were used to simulate and analyze the thermodynamics of hydrolysis cyclohexanone-oxime to synthesis hydroxylamine.Based on the studies,ionic liquid modified HZSM-5 catalyst was prepared and its catalytic performance was explored preliminary.Traditional thermodynamic calculations as well as Gaussian simulation were performed in this paper.It was found that Gibbs free energy change of the hydrolysis is a positive number??G>0?and the equilibrium constantis a extremely smallvalue.In the kettle reactor,single factor experimental design was used to the hydrolysis reaction of cyclohexanone-oxime.Various parameters including type of solid acid,reaction temperature and time,were investigated for optimization of the hydrolysis.The results showed that when the HZSM-5 zeolite with SiO₂/Al₂O₃ molar ratio of 25 was used as catalyst,the optimal conditions investigated were cyclohexanone-oxime 1 g,cyclohexanone-oxime:catalyst mass ratio 1:6,cyclohexanone-oxime:H₂O molar ratio1:62,conducted at 15?for 1 h.Under the optimum conditions,the conversion of cyclohexanone-oxime was 17.75%,and the concentration of hydroxylamine was 0.19 wt%.Further optimization revealed that hydroxylamine concentration was increase to 0.71 wt%as the mass ratio of cyclohexanone-oxime to catalyst was 1.5.When HZSM-5 zeolite with SiO₂/Al₂O₃ molar ratio of 38 and 50 were employed,the hydroxylamine aqueous solution concentrations were 0.77 wt%and 0.45 wt%,respectively.Furthermore,the reusability of the catalyst HZSM-5 was studied,and the reason of deactivation of the catalyst was analyzed and characterized by thermogravimetry,elemental analysis,and pyridine infrared.It was found that the hydroxylamine produced is a weakly alkaline substance,which is easy to combine with acidic catalysts,forming an acid-base adsorption.This causes the inactivation of the catalyst.After calcination at high-temperature,the HZSM-5 catalyst was reused five times without obvious decrease of catalytic activity.In the tubular reactor,the catalytic performance of the HZSM-5 zeolite with SiO₂/Al₂O₃ molar ratio of 25 was investigated.The results showed that the suitable reaction conditions were catalyst particle size 5¹0 mesh,the WHSV of raw material 1.25 h^-1?concentration 3.8 mol/L?,catalyst amount 22 g,the WHSV of water 0.45 h^-1?feed rate 10mL/h?and the concentration of NH₂OH aqueous solution obtained 1.2 wt%.The advantages of this process are mild reaction conditions,continuous feed of cyclohexanone-oxime and production of hydroxylamine,recycling of unreacted raw materials.Based on the above studies,a series of ionic liquid-modified HZSM-5 catalysts were prepared.The results showed that the suitable ionic liquid precursor was selected as N-sulfobutylpyridine hydrogen sulfate.Under the same reaction conditions,cyclohexanone-oxime 1 g,cyclohexanone-oxime:catalyst mass ratio 1:2,cyclohexanone-oxime:H₂O molar ratio 1:62,conducted at 60?for 1 h,and the conversion of raw material was increased from 2.60%to 7.71%,and the concentration of hydroxylamine aqueous solution was increased to 0.12 wt%.