Catalyst Deactivation for Enhancement of Selectivity in Alcohols Amination to Primary Amines

Abstract

Selective synthesis of valuable primary amines is an important target in modern industry. Amination of alcohols with ammonia is an economically efficient and environmentally friendly process for primary amine synthesis. This consecutive reaction yields a mixture of primary, secondary, and tertiary amines. High selectivity to primary amines is an important challenge of alcohol amination. Carbon deposition on the catalyst surface is conventionally considered an undesirable process, which leads to poor catalytic performance. In this paper, carbon deposition produced by catalyst pretreatment with alcohols under the optimized conditions has been employed for major enhancement of the selectivity of alcohol amination to primary amines (from 30 to 50 to 80–90%). This extremely positive effect of carbon deposition on the amination selectivity arises from steric hindrance in hydrogenation of bulky secondary imines as intermediate products over partially carbon-decorated cobalt nanoparticles.

A multifaceted role of a mobile bismuth promoter in alcohol amination over cobalt catalysts

“…Steric hindrance during hydrogenation of secondary imine induced by Bi on the surface of Co results in suppression of hydrogenation of bulky secondary imine with shift of the reaction selectivity to primary amine. The similar effect has been observed during amination of alcohols over Co nanoparticles after their pretreatment with alcohol resulting in carbon deposition [14][41,42,43].…”

“…Ni [13] and Co [14], under hydrogen can be achieved via so called hydrogen borrowing or hydrogen auto transfer methodology [15,16,17,18], which consists of dehydrogenation and hydrogenation processes. The one-pot alcohol amination generally consists of three consecutive steps: (i) dehydrogenation of an alcohol to a reactive aldehyde (or ketone); (ii) imine formation by coupling of a carbonyl compound with ammonia; (iii) amine formation by hydrogenation of the imine over the catalyst.…”

“…Different approaches have been used to control the activity and selectivity in amination of alcohols. In our previous work [14], intentional deposition of polymeric carbonaceous species on the surface of Co/Al 2 O 3 catalysts was used to considerably improve the selectivity of primary amines in the gas and liquid-phase amination of aliphatic alcohols with NH 3 . The selectivity enhancement was attributed to the suppression of primary amine self-coupling because of hindering of secondary imine hydrogenation.…”

Organonitrogen Chemicals from Oxygen-Containing Feedstock over Heterogeneous Catalysts

“…Carbon deposition on the catalyst surface was conventionally considered negative as it reduces the catalytic activity. Nevertheless, Khodakov and Ordomsky deposited polymeric carbonaceous species on a Co/Al 2 O 3 catalyst, which enhanced the selectivity of primary amines from 30–50% to 80–90% in amination of alcohols, including 1-butanol, 1-octanol, and benzyl alcohol . The reduced Co/Al 2 O 3 catalyst was treated in an alcohol/nitrogen gas flow at 250 °C for several hours before reaction.…”

Direct Amination of Biomass‐based Furfuryl Alcohol and 5‐(Aminomethyl)‐2‐furanmethanol with NH3 over Hydrotalcite‐derived Nickel Catalysts via the Hydrogen‐borrowing Strategy

“…[7] As a consequence, the amination of alcohols by this strategy can also be termed "hydrogen transfer amination". Additionally, the amination of alcohols can be catalyzed by heterogeneous metal catalysts, mostly based on Ni, [8] Co [9] and Ru, [3b] following the "dehydrogenation-iminization-hydrogenation" process. [10] In contrast to the former process, this reaction process is generally carried out under a mixture of ammonia and hydrogen.…”