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.

中文翻译：

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在Pd / C催化剂上实现Mandelonitrile液相加氢中的持续产物形成。

碳载Pd催化剂上芳香族氰醇扁桃腈（MN，C ₆ H ₅ CH（OH）CN）的液相加氢生成伯胺苯乙胺（PEA，C ₆ H ₅ CH ₂ CH ₂ NH ₂针对从单批处理模式到重复批处理模式的过渡进行了研究。虽然单批反应返回了完整的质量平衡，但对于六次添加的重复批生产程序，产品分析以及质量平衡测量显示，从第四次添加开始，产品形成速率有所降低，并且质量平衡不完全。这种情况可能会阻碍苯乙胺合成工艺的商业运行，因此需要进一步研究。参考先前报道的反应方案，根据酸浓度，搅拌器搅拌速率，催化剂质量和氢的可用性检查了持续催化性能的前景。气液传质系数的测量结果表明，在亨利定律对工艺溶剂（甲醇）中氢溶解度的限制的实验约束范围内，有效的气体→液体传输动力学。与最佳产品选择性的差异归因于传质限制，特别是H₂（solv）→2H（ads）的跃迁，最终受H ₂（solv）的存在限制。最后，为了更好地理解失活途径，在以类似的分批进料模式进行反应的可比工业级催化剂上进行的非弹性中子散射测量表明存在低聚层后反应。该覆盖层被认为是通过假定的整体反应方案中确定的特定途径通过羟基亚胺或亚胺物种的低聚形成的。