Study On Partial Hydrogenation Of Adiponitrile To Aminocapronitrile Over Nickel-based Catalysts

The partial hydrogenation of adiponitrile to aminocapronitrile is a key step in the route of synthesis of caprolactam using butadiene as raw material, and it is practically significant to develop a new catalyst with high catalytic performance for partial hydrogenation of adiponitrile.A series of supported nickel-based catalysts for the partial catalytic hydrogenation of adiponitrile to aminocapronitrile were prepared by the incipient impregnation method. The effects of calcinations temperature ofγ-alumina, promoters, reduction conditions and reaction conditions on the physico-chemical properties of catalysts were investigated by means of nitrogen adsorption-desorption (BET), X-ray diffraction (XRD), temperature-programmed reduction (TPR) and the performance evaluation with a fixed-bed reactor or an autoclave reactor. The catalyst deactivation and regeneration were also investigated.The nickel catalyst supported onα-Al₂O₃ derived fromγ-Al₂O₃ calcined at 1473 K showed good catalytic performances for adiponitrile partial hydrogenation to aminocapronitrile, which was due to its large pore diameter and absence of acidic sites. Among the catalysts modified with different promoters, the catalyst supported onα-Al₂O₃ and modified with K₂O and La₂O₃ copromoter had the best performance.The partial hydrogenation of adiponitrile to aminocapronitrile was performed on alumina supported nickel catalysts modified with potassium, lanthanum and magnesium in a high pressure stainless steel reactor. In the presence of ammonia, under the reaction conditions of 4.4 MPa and 377 K, the conversion of adiponitrile and the selectivity of aminocapronitrile reached 73.5% and 78.6% after reaction for 6h, respectively. Keeping the mass ratio of catalyst and adiponitrile as 0.13⁰.16 and increasing the concentration of adiponitrile could enhance the capacity of the reactor.The catalyst deactivation was mainly due to carbon species deposition, and the calcinations-reduction treatment was an effective regeneration method for the deactivated catalyst.