Study On The Catalytic Performance Of The Developed Catalysts For Adiponitrile Hydrogenation

Adiponitrile is a very important chemical raw material,and its hydrogenation product of hexamethylene diamine is widely used in various fields.In addition,the hydrogenation of adiponitrile is a key step for the hydrogenation of butane to caprolactam.Therefore,the development of catalyst which is environment-friendly,simple in preparation,efficient for the selective hydrogenation of ADN is of great significance.In this paper,the Ni-K2O/γ-Al2O3 and Ni-K2O/TiO2 showed high activity for the selective catalytic hydrogenation of adiponitrile under mild reaction conditions.We discussed the impact of the ultrasound and the preparation condition of TiO2 nanotube on the nature of the catalyst.The main achievements are shown below:1.The catalyst of Ni-K2O/γ-Al2O3 was prepared by method of incipient-wetness impregnation assisted by ultrasound.We made a thorough inquiry about the effects of ultrasound on the nature of the catalyst.The results showed that ultrasonic effectively reducesthe time of catalyst preparation,and increases the dispersion of the active ingredient Ni on the surface of the carrier,while the carrier particles have a certain degree of refinement and exhibit a larger surface area.In addition,the ultrasound strengthens the interaction between the active ingredient and the carrier,so most of NiO have a weakly interaction with the carrier which reduces the loss of Ni.2.Ni-K2O/γ-Al2P3,which was prepared by ultrasound-assisted method,was used as catalyst for the hydrogenation of adiponitrile.The optimal reaction conditions is as followed:the catalyst was reducted at 450 ℃ for 2h,ADN 1g,ethanol 15g,catalyst 0.6g,reaction temperature 75 ℃,H2 pressure 2MPa,stirring speed 800rmp.The catalyst shows the highest performance,specifically the connversion rate of adiponitrile is 67.1%and the selectivity of hexamethylene diamine and 6-aminocapronitrile was 19.6%and 64.7%respectively.3.TiO2 nanotubes were prepared by hydrothermal method.We explored the affect of the post-processing on the structure of TiO2 nanotubes and the nature of the Ni-K2O/TiO2 catalyst.The results show that TiO2 nanotubes are formed during the pickling process.With the decrease of residual sodium,the particle size of NiO decreases firstly and then increases.When the amount of residual sodium was 0.67%,the conversion rate of ADN is 92%and the selectivity HMDA and ACN are 36.3%and 59.2%respectively.With the carrier calcination temperature increasing,the specific surface area of catalyst decreases and NiO particle size gradually increases,so the catalyst activity is gradually decreased.When the carry was calcined at 350 ℃ for 2h,the corresponding catalyst exhibited the best activity,specifically the conversion rate of ADN is 94.6%and the selectivity of ACN and HMDA is 49.3%and 49.6%respectively.With the amount of chromium increasing,the particle size of NiO decreases firstly and then increases.When the doped chromium is 0.8%,the conversion rate of AND is 83.5%and the selectivity of ACN and HMDA are 30.0%and 66.4%respectively.4.The reduction temperature of NiO is lowered for catalyst which is modified by silane,and the dispersion of NiO is increased.After burning off surface modifiers,the conversion of adiponitrile and the selectivity of hexamethylene diamine is improved.SBA-15-R1-Ni’-K2O shows the best activity.The conversion of adiponitrile is 98.3%,the selectivity of HMDA and ACN are 74.2%and 20.2%,respectively.