An Efficient Method for the Production of Cyclohexylamine from Cyclohexanone and Ammonia over Cu-Cr-La/γ-Al₂O₃

Abstract

ABSTRACT. The reductive amination of cyclohexanone with ammonia over Cu-Cr-La/γ-Al2O3 was investigated. It was found that a proper solvent with high solubility of ammonia and 4Å molecular sieves for the elimination of generated water contributed to the formation of cyclohexylamine in the premixing process. In addition, the addition of ammonia in the fixedbed reactor could obviously improve the conversion of cyclohexanone to cyclohexylamine. Finally, reaction conditions including reaction temperature, hydrogen pressure and charging rate of the premix were optimized. Under the optimized conditions, cyclohexylamine was obtained in 83.06% yield.

Amination of Cyclohexanol over a Ni‐Based Catalyst – Part II: Catalyst Stability and Reaction Pathway

“…Furthermore, the formation of by‐products has also been verified in this work, which results from reactions with the formed primary amines as aminating agents, in this case the reaction between CHOL intermediaries and CHA and/or aniline 2, 7, 8, 14–16, 24. In order to fully understand how side reactions occur and which species are involved, CHOL conversion was varied by changing its WHSV at a constant temperature of 200 °C and NH 3 :H 2 :CHOL molar ratio of 2.2:2.2:1.…”

“…DICHA is a secondary amine, which means that its formation involves the presence of a primary amine as aminating agent, in this case CHA. So, the side reaction of DICHA formation can be assumed to follow the BHM but with CHA as aminating agent, as also proposed elsewhere 16. Based on the obtained results presented in Figs.…”

“…The study of the reductive amination reaction pathway, with NH 3 as aminating agent, is scarce in the available literature 14–16, but for the dehydrogenation reaction of CHOL into CHONE a few results have been reported 31–33. From those works, CHONE, phenol, benzene, and cyclohexene are pointed as the dehydrogenation products of CHOL.…”

“…Alcohols are quite stable compounds, so secondary alcohols like cyclohexanol (CHOL) necessitate some type of activation into more electrophilic species to react in condensation reactions with NH 3 to synthesize amines, cyclohexylamine (CHA) in this case 12–20. A possible route towards activation of CHOL and consequent direct reductive amination into CHA can be through the borrowing hydrogen methodology (BHM), also called hydrogen autotransfer process 7, 13, 19, 21–23.…”

“…The formed ketone can also undergo further reaction with the produced amines, since those are more nucleophile species than NH 3 , yielding secondary and/or tertiary amines, namely, dicyclohexylamine (DICHA), N ‐cyclohexylaniline (CHANIL), N ‐cyclohexylcyclohexylimine, and cyclohexylcyclohexanol. Therefore, the selective synthesis of primary amines can be quite a cumbersome task, but some satisfactory results have already been achieved for the synthesis of CHA from CHOL in the presence of metal and mixed‐metal oxide catalysts 14–16, 19, 25–27.…”