The hydrogenation of mandelonitrile over a Pd/C catalyst: towards a mechanistic understanding

Abstract

A carbon supported Pd catalyst is used in the liquid phase hydrogenation of the aromatic cyanohydrin mandelonitrile (C6H5CH(OH)CH2CN) to afford the primary amine phenethylamine (C6H5CH2CH2NH2).

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

“…205680) was almost exclusively used (sections –). Characterization of this catalyst is reported elsewhere . Because of the large sample size required for INS (≥10 g), a technical-grade 5 wt % Pd/C catalyst was soley used for the INS measurements (Section ).…”

“…Mechanistic aspects of the single-batch liquid-phase hydrogenation reaction of mandelonitrile (MN) over a carbon-supported palladium catalyst (5 wt % Pd/C) have previously been investigated. , Alongside the desired product, phenethylamine (PEA), the byproduct 2-amino-1-phenylethanol (2-APE) was produced (Scheme ). These prior studies indicated that while the reaction was not completely selective toward phenethylamine ( S = 87%), a closed mass balance was achieved, indicating efficient catalysis under the stated conditions …”

“…In order to evaluate whether catalytic turnover could be sustained over multiple cycles for the specified reaction, a repeat-batch procedure was adopted. Here numerous aliquots of the mandelonitrile starting material and the sulfuric acid auxiliary reagent were made for a single catalyst charge. − This procedure effectively represents a series of batch reactions. In this case, six sequential additions of the reagents (mandelonitrile and sulfuric acid) were studied.…”

“…The study highlights the importance of maintaining the hydrogen supply throughout all components of this multistage process, which includes both hydrogenation and hydrogenolysis steps . Furthermore, within this reaction system, reactive imine and enamine intermediates may participate in coupling reactions with the amine products to form the corresponding secondary and tertiary amines, − thus providing additional routes to those previously described, , which may compromise product selectivity. Thus, deactivation pathways via oligomer formation are possible.…”

Preparation and catalytic performance of active metal sintered membrane reactor anchored with Pt atoms

“…tricklebed reactor, bubble column reactor) and stirred tank slurry reactors are usually employed for gas-liquid-solid, three-phase reaction systems. [12][13][14][15][16] However, these traditional reactors possess a few intrinsic problems: (i) the diffusion of reactants and/or products is hindered by limited diffusion channels within the catalytic zone, which result in decreased reaction rates and poor product selectivity. [17][18][19][20] (ii) poor thermal conductivity and mechanical strength in catalyst supports can lead to catalyst sintering and structural degradation during these reactions.…”