Preparation Of Catalysts For Selective Hydrogenation Of Benzonitrile To Benzylamine

Benzylamine is a kind of important primary aromatic amines and is one ofimportant organic chemical raw materials and fine chemical intermediates. With thestrong developments of fine chemical products, it plays an important role in theincreasing gradually market demand for benzylamine. It’s worth to search for a newtechnology to improve the quality and quantity of benzylamine which cannot met thedemand of the developing market now, especially the new high-efficient technologyof research on catalytic hydrogenation of benzonitrile to benzylamine, by continuousfixed bed reactor, which attracts the most of researchers’ interest.In this paper, we mainly focus on the performance of supported metal catalysts inthe continuous hydrogenation of benzonitrile to benzylamine. The catalysts werecharacterized by XRD, BET, TPR and TPD et al. There does many explore researchexperiments to find out the optimal reaction condition and the effects on catalystperformance of the active metal species, the carrier type, solvent, catalyst preparation,reaction temperature, pressure, WHSV, and molar ratio of hydrogen on benzonitrile.The reaction evaluation indicated that0.5%Pd/γ-Al2O3prepared byimpregnation exhibited excellent activity. The conversion of benzonitrile reachedabout97.1%and the selectivity of benzylamine is up to75.5%(the yield reached73.3%) at optimized reaction condition (ethanol as solvent, the mass ratio of ethanoland benzonitrile is4:1; reaction temperature,100oC; pressure,1MPa; WHSV,0.6h-1;the molar ratio of hydrogen and benzonitrile,20).The catalytic hydrogenation products were analyzed. The possible reactionmechanism for hydrogenation of benzonitrile to benzylamine was proposed.Benzylamine is the primary products and dibenzylamine is the secondary product.The two reactions are parallel competing reactions. Toluene is another product bydepth hydrogenation of benzonitrile. The results showed that high reactiontemperature is favorable to get depth hydrogenation products toluene. The more acidicsites the catalyst has, the easier benzonitrile turned to dibenzylamine, whichbenzonitrile has polymerization reaction to dibenzylamine. Benzonitrile tended to delaminate to toluene when strong alkaline additives were added to the catalyst. It wasindicated that the acid-base of catalyst has significant impact on the performance ofcatalyst.