Pd catalysts with different particle size were investigated in a strongly exothermic acetylene hydrogenation by changing space velocity. It was found that larger Pd nanoparticles provoked the significant amounts of oligomers and accumulated reaction heat although space velocity had been greatly improved. When Pd particle size was reduced, the number of active sites increased, which contributed to a decrease in heat produced on a single active site, thereby hindered formation of hot spots over catalyst leading to lesser deactivation. Furthermore, by utilizing the features of highly dispersed catalyst without instantaneous heat accumulation, the target acetylene hydrogenation (exothermic) was coupled with acetylene dissociation (endothermic) by sharing reaction heat to construct supported Pd carbide catalysts. Modification of subsurface carbon inhibited the generation of green oil and thus further enhanced selectivity and stability. This work provides an alternative and counter-intuitive concept where more highly dispersed metal nanoparticles may in fact be more stable.

中文翻译：

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通过增强分散和利用反应热效应减轻选择性加氢催化剂失活

通过改变空速在强放热乙炔加氢反应中研究了不同粒径的 Pd 催化剂。结果发现，尽管空速已大大提高，但较大的 Pd 纳米颗粒会引发大量的低聚物并积累反应热。当 Pd 粒径减小时，活性位点的数量增加，这有助于减少单个活性位点产生的热量，从而阻碍催化剂上热点的形成，从而减少失活。此外，利用催化剂高度分散且无瞬时蓄热的特点，目标乙炔加氢（放热）与乙炔解离（吸热）通过共享反应热来构建负载型碳化钯催化剂。地下碳的改性抑制了绿油的产生，从而进一步提高了选择性和稳定性。这项工作提供了一个替代的和反直觉的概念，其中更多高度分散的金属纳米粒子实际上可能更稳定。