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Toward Sustained Product Formation in the Liquid-Phase Hydrogenation of Mandelonitrile over a Pd/C Catalyst.

ABSTRACT: The liquid-phase hydrogenation of the aromatic cyanohydrin mandelonitrile (MN, C6H5CH(OH)CN) over a carbon-supported Pd catalyst to produce the primary amine phenethylamine (PEA, C6H5CH2CH2NH2) is investigated with respect to the transition from operation in single-batch mode to repeat-batch mode. While a single-batch reaction returns a complete mass balance, product analysis alongside mass balance measurements for a six-addition repeat-batch procedure shows an attenuation in the rate of product formation and an incomplete mass balance from the fourth addition onward. This scenario potentially hinders possible commercial operation of the phenethylamine synthesis process, so it is investigated further. With reference to a previously reported reaction scheme, the prospects of sustained catalytic performance are examined in terms of acid concentration, stirrer agitation rate, catalyst mass, and hydrogen availability. Gas-liquid mass transfer coefficient measurements indicate efficient gas ? liquid transfer kinetics within the experimental constraints of the Henry's law limitation on hydrogen solubility in the process solvent (methanol). Deviations from the optimized product selectivity are attributed to mass transport constraints, specifically the H2(solv) ? 2H(ads) transition, which is ultimately restrained by the availability of H2(solv). Finally, in an attempt to better understand the deactivation pathways, inelastic neutron scattering measurements on a comparable industrial-grade catalyst operated in an analogous reaction in fed-batch mode indicate the presence of an oligomeric overlayer postreaction. This overlayer is thought to be formed via oligomerization of hydroxyimine or imine species via specific pathways that are identified within a postulated global reaction scheme.

SUBMITTER: McAllister MI

PROVIDER: S-EPMC7309435 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Toward Sustained Product Formation in the Liquid-Phase Hydrogenation of Mandelonitrile over a Pd/C Catalyst.

McAllister Mairi I MI Boulho Cédric C Brennan Colin C Parker Stewart F SF Lennon David D

Organic process research & development 20200504 6

The liquid-phase hydrogenation of the aromatic cyanohydrin mandelonitrile (MN, C6H5CH(OH)CN) over a carbon-supported Pd catalyst to produce the primary amine phenethylamine (PEA, C6H5CH2CH2NH2) is investigated with respect to the transition from operation in single-batch mode to repeat-batch mode. While a single-batch reaction returns a complete mass balance, product analysis alongside mass balance measurements for a si ...[more]

PMID: 32587453

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Project description:Methanol synthesized from carbonate hydrogenation is of great importance for CO2 utilization indirectly. Herein, a series of Cu/Zn/Al heterogeneous catalysts were prepared by co-precipitation with a synchronous aging step, and were applied for hydrogenation of diethyl carbonate (DEC) to produce methanol. Furthermore, the catalysts were characterized by physicochemical methods, such as N2 adsorption, ICP-OES, N2O titration, SEM, TEM, XRD, H2-TPR and XPS in detail. Higher copper concentration led to a higher ratio of bulk CuOx species in the calcined samples, which resulted in different copper species distribution after the reduction process. Structure activity relationship analysis indicated that the balance of surface Cu0 and Cu+ species influenced the formation rate of methanol. A higher proportion of Cu+ to (Cu+ + Cu0) was conductive to methanol formation, while excessive Cu0 site density played a negative influence on the methanol synthesized from DEC. Cu/Zn/Al with a 45.2% weight fraction of copper showed better performance with a total methanol formation rate of 131.0 mg gcat. -1 h-1. The reaction temperature and reaction time could obviously affect the reaction performance and the results suggested that 200 °C and 6 h were suitable. Furthermore, the long-term stability and activity of the catalyst was also studied on a fixed bed, and the yield of total methanol reached to 88.5% and the selectivity of total methanol gradually decreased to 74.0% within 200 h, which could be attributed to the detrimental influence derived from the increase of Cu0. The reaction pathways involved in the hydrogenation of DEC process were proposed. The substance scope was also extended to other carbonates and the catalyst exhibited superior catalytic performance toward linear carbonates. This work provided insights into carbonate hydrogenation over an effective Cu/Zn/Al catalyst, which could be utilized into upgrading CO2 indirectly to produce commodity methanol under relatively mild reaction conditions.

Dataset Information

Toward Sustained Product Formation in the Liquid-Phase Hydrogenation of Mandelonitrile over a Pd/C Catalyst.

Publications

Toward Sustained Product Formation in the Liquid-Phase Hydrogenation of Mandelonitrile over a Pd/C Catalyst.

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