Mitigating catalyst deactivation in selective hydrogenation by enhancing dispersion and utilizing reaction heat effect

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.