Nitrocyclohexane Hydrogenation Over Ni-based Catalyst Modified With Metal Promoter

Cyclohexanone oxime is a key intermediate for the production of ?-caprolactam,which can produce polyamide by the polymerization process.And polyamide can produce fibers and engineering plastics.Moreover,?-caprolactam is used as medical supplies widely.The methods presently employed in the manufacture of cyclohexanone oxime are cyclohexanone-hydroxylamine route or ammoximation of cyclohexanone which cannot avoid complex operation by production of ammonium sulfate and wastes.With the development of nitro technology,the route of choosing cyclohexane as raw materials to produce nitrocyclohexane,then hydrogenation of it to produce cyclohexanone oxime receives much concern.Especially,liquid phase hydrogenation process with simple operation under mild process conditions has higher value and better prospect application.In this paper,we aim to replace old nitrocyclohexane hydrogenation route with new catalyst to decrease casts and increase cyclohexanone oxime yield.Non-noble metal Ni/AC catalysts were prepared and applied in nitrocyclohexane hydrogenation.The reaction raw material nitrocyclohexane is made unprofessional,and purified to more than 93%.We used GC-MS to detect the products of nitrocyclohexane hydrogenation which contained cyclohexanone oxime ? cyclohexane and tiny cyclohexyl hydroxylamine.And we quantify of products by GC using the dimethyl phthalate as internal standard.In this paper,we prepared a set of Ni/AC catalysts and applied them to nitrocyclohexane hydrogenation to examine the impact of different active carbons,different nickel precursors,different Ni loadings or different reduction methods on nitrocyclohexane hydrogenation.We found wooden activated carbon loaded with nickel showed better catalytic performance.Over those catalysts the conversion of raw material nitrocyclohexane 35.94%,and the cyclohexanone oxime selectivity at 60.47%.Moreover,the nickel precursor and Ni loading had impact on dispersion of active component.When we chose nickel acetate as precursor and keep loading at 20%,the catalyst had good catalytic performance with conversion of 56.78%,and cyclohexanone oxime selectivity of 42.20%.And we find that catalysts reduced by hydrogen show good catalystic performance.To improve the catalytic performance of Ni/AC,we tried to add some promoters such as Pd?Fe?Cu to modify Ni/AC.This paper examined the impact of different promoters,different promoter loading and reduction temperatures,on nitrocyclohexane hydrogenation.And we optimized the process conditions of nitrocyclohexane hydrogenation.Through XRD?hydrogen chemisorption?XPS?TEM detect,we found promoters modify Ni/AC catalyst mainly through promoting reduction of nickel,improving hydrogen uptake quantity,lager metal surface area and higher nickel dispersion,which may be in favor of the nitrocyclohexane hydrogenation.Then we optimized the process conditions using 1.5%Cu-20%Ni/AC catalyst,finally we found the optimal conditions: reaction temperature at 60?,reaction pressure at 0.3MPa,reaction time at 7h,and carried out nitrocyclohexane hydrogenation under this condition the conversion of nitrocyclohexane was 99.55%,the selectivity of cyclohexanone oxime was 77.73%.