Sulfur Vacancies are the Active Sites in the Iron Sulfide Catalyst for the Hydrogenation of Naphthalene

Abstract

Iron sulfide catalysts could boost the hydrogenation of polycyclic aromatic hydrocarbons, and have been widely employed in direct coal liquefaction owing to their low price and good activity. In the past, the Fe deficient structure on Fe1‐xS was normally considered as the active site. Herein, the promotion effect of S vacancies on the performance in the naphthalene hydrogenation reaction was revealed. Additional S vacancies on the prepared Fe1‐xS catalyst were introduced by a heat‐treatment under H2. Multiple characterization techniques verified that the density of S vacancies on catalyst surface increased with the prolonged H2 treatment time, while the Fe deficient structure displayed an opposite trend. The performance in the hydrogenation of naphthalene to tetralin was used to evaluate the catalyst activity. It was found that the sequence of naphthalene conversion over catalysts was consistent with the corresponding content of S vacancies, indicating that S vacancies were more efficient active sites. DFT calculation results revealed that both molecular H2 and naphthalene exhibited a pronounced inclination towards adsorption on S vacancies as compared to intact surface of Fe1‐xS. The increasing amount of S vacancies facilitated the adsorption of reactants and the weakening of naphthalene C‐C bonds.