Mechanism-guided design of sulfur-modified platinum catalysts for selective hydrogenation of nitrobenzene

Sulfur modification can effectively modulate the electronic properties of the active sites on the metal catalysts and thus tune the catalytic performance. In this paper, sulfur-modified Pt/C catalysts were prepared by impregnation with a certain amount of thiourea as the precursor for the selective hydrogenation of nitrobenzene (NB) to p-aminophenol (PAP). Under reaction conditions, the highest conversion achieved was 99.5% and the selectivity was 72.5%. The effects of sulfur source type and sulfur content on the structure and physicochemical properties of catalyst support and active site were investigated. Results of XPS, H2-TPD-Mass and IR indicated the presence of strong inter-electron interaction between S and Pt. The sulfur modified catalyst not only reduces the dissociation and adsorption strength of hydrogen by Pt, but also inhibits the adsorption strength of phenylhydroxylamine on the catalyst surface, preventing excessive hydrogenation of phenylhydroxylamine, and prompting Bamberger rearrangement to p-aminophenol.