A multiphase reaction medium including pressurized carbon dioxide and water for selective hydrogenation of benzonitrile with a Pd/Al2O3 catalyst

Abstract

The hydrogenation of benzonitrile was studied with a Pd/Al 2 O 3 catalyst in the presence of pressurized CO 2 and water. This multiphase reaction system was effective for the selective production of the desired primary amine of benzylamine with no deactivation of the catalyst. The enhanced selectivity to the primary amine resulted from its transfer into water phase, which prevented the primary amine from reacting with an intermediate of imine into the secondary amine in the organic phase (benzonitrile). In addition, interactions of CO 2 molecules with the primary amine could also increase its selectivity. In the absence of water, the catalyst was deactivated by the accumulation of a carbamate salt on the surface of catalyst. But this deactivation was avoided by the addition of water because the salt was soluble in water and it did not deposit on the catalyst existing at interfacial layer between the water and organic phases.

Multiphase reaction media including dense phase carbon dioxide and/or water: A case study for hydrogenation of phenol with a Pd/Al2O3 catalyst

“…In our recent work, the effects of CO 2 and/or water have been investigated on selective hydrogenation of benzonitrile with Pd/Al 2 O 3 catalyst [15]. The selectivity to primary amine increased from 85% to more than 96% by the presence of CO 2 and water with no catalyst deactivation.…”

Selective hydrogenation of benzyl cyanide to 2-phenylethylamine over a Pd/Al2O3 catalyst promoted by synergistic effects of CO2 and water

“…The carbamate salt is insoluble in BC organic phase, resulting in high selectivity to PEA. The formation of the carbamate salt from benzylamine and CO2 was reported by Chatterjee et al 15 and Yoshida et al 12 The formation of carbamate salt in hydrogenation of BN using NiCl2/NaBH4 in CO2 expanded ethanol at 303K was shown by Xie et al and they also observed an enhanced benzylamine selectivity.…”

“…The temperature of the cell was controlled by a temperature controller and a heating jacket containing rod heaters. 12,19 The FTIR spectra were collected for a mixture of CO2 dissolved in liquid benzyl cyanide at different pressures.…”

“…Very recently, Chen et al 11 and Yoshida et al 12 investigated the hydrogenation of benzonitrile in different multiphase media using a Ni/Al2O3 catalyst and a Pd/Al2O3 one, respectively. These authors indicated the effectiveness of dense phase CO2 on the selective production of the desired primary amine of benzylamine in the absence of water.…”

Selective Hydrogenation of Nitriles to Primary Amines Catalyzed by a Polysilane/SiO2‐Supported Palladium Catalyst under Continuous‐Flow Conditions

“…[11] Relativelym ild conditions were achievedw ith Pd catalysts; however,t here is still much room for improvement with respect to both yield and selectivity. [12] Although, with the exception of gaseous reactions, [13] most previousm ethods with homogeneous and heterogeneous catalysts have been conducted in batch systems, continuous-flow systemsh ave several advantages over batch systemsi nt erms of environmental compatibility, efficiency,a nd safety. [14,15] High productivity and saving of energya nd space can be attained by using flow systems, and it is possible to adjust the quantity of production by controlling the rate of introductiono fs tarting materials ("just-in-time" production).…”