Study On The Process Of Hydrogenation Of Adiponitrile And Nitrocyclohexane

Caprolactam is an important organic petrochemical material. At present, the raw materials for the production of caprolactam in industry mainly are benzene, toluene and phenol. And cyclohexanone-hydroxylamine route to cyclohexanone oxime occupys predominant position in industry, then it undergoes by Beckmann rearrangement to obtain the caprolactam. However, these methods are complex, low atomic economic benefit, it is usually by-product large quantity lower economic ammonium sulfate and it has serious environment problems. Therefore the research for producing the caprolactam focus on the way to reduce the consumptions of energy, cut the production cost and develop new simple and green technology. Butadiene hydrocyanation and nitrocyclohexane hydrogenation methods are two new technologies for producing caprolactam, which have shortened the reaction process and avoided the cyclohexane oxidation process, and these two routes have higher value and better prospect application. In this paper, adiponitrile hydrogenation to 6-aminocapronitrile and nitrocyclohexane hydrogenation route are discussed.As to adiponitrile hydrogenation, Ni-B/SiO2, Ni-B/α-Al2O3 and Ni-B-K/SiO2 were prepared by chemical reduction method. The prepared catalysts are characterized by nitrogen absorption-desorption, XRD, SEM and SAED. It reveals that with the introduction of potassium, it can reduce the specific surface area of catalyst and get higher dispersion of the amorphous phase Ni-B. The prepared catalysts have been tested in the liquid phase hydrogenation of adiponitrile without ammonia under mild condition. It has been found that the catalyst of Ni-B-K/SiO2 shows better catalytic performance than Ni-B/SiO2, with the selectivity of 6-aminocapronitrile is 84.9% and the selectivity of 6-aminocapronitrile and hexamethylenediamine reaching 99.3% at the adiponitrile conversion of 63.5%.As to nitrocyclohexane hydrogenation, the catalysts of single-wall carbon nanotubes supported palladium were prepared by methanol impregnation method, water impregnation method, two-step water impregnation method, ion exchange method and chemical reduction method with the reductant of formaldehyde and KBH4. The prepared catalysts are characterized by nitrogen absorption-desorption, XRD, XPS, TEM and H2-TPR. The results show that Pd/SWCNTs prepared by water impregnation method provide a smaller particle size of palladium. The reduction conditions have great influence on the valence state of palladium on the support. The catalyst with smaller particle size, better dispersion and higher content of monovalent palladium exhibits better catalytic performance in nitrocyclohexane hydrogenation to cyclohexanone oxime. Pd/SWCNTs-2 prepared by water impregnation method and reduced at 723 K gives 96.4% selectivity to cyclohexanone oxime at the 96.0% conversion of nitrocyclohexane under mild conditions of 0.3 MPa and 323 K.A series Ni supported activated carbon catalysts were prepared by impregnation method and characterized by nitrogen absorption-desorption, XRD and H2-TPR. The different kinds of activated carbon and the pretreatment way have been studied. The results show that specific surface area and pore size have great influence on the catalytic performance. When the activated carbon was treated by CO2, the catalyst shows the smallest average pore size and the lowest selectivity to cyclohexanone oxime, and when the activated carbon was treated by the steam, the catalyst shows the largest average pore size and the best selectivity to cyclohexanone oxime. Furthermore, the influence of the amount of iron on the steam treatment of activated carbon was studied. The introduction of iron can enlarge the average pore size of the catalyst and improve the selectivity to cyclohexanone oxime. When the amount of iron was 4%, the selectivity to cyclohexanone oxime reaches to 88.9%.The research on the gas phase hydrogenation nitrocyclohexane process was based on the palladium supported catalyss. It has been found that the main product of the gas phase nitrocyclohexane hydrogenation was cyclohexylamine due to the higher temperature.Finally, the possible reaction route of nitrocyclohexane hydrogention process was proposed based on the experiment.