Supported transition-metal oxide catalysts for reduction of sulfur dioxide with hydrogen to elemental sulfur

Abstract

This work is for the purpose to find a high performance catalyst for the catalytic reduction of SO 2 with H 2 as a reducing agent. NiO/γ-Al 2O 3 catalyst was found to be the most active catalyst among the seven γ-Al 2O 3-supported metal-oxide catalysts tested. With NiO as the active species, of the supports tested, γ-Al 2O 3 was the most suitable one and the optimal Ni content was 16 wt%. Using this NiO/γ-Al 2O 3 catalyst, we found that the optimal feed ratio of H 2/SO 2 is 2:1 and the catalyst presulfided with H 2 + H 2S exhibits a higher performance than that pretreated with H 2 or He. XRD patterns reveal that the nickel oxide experienced a transformation to Ni 3S 2 and NiS, and then to NiS 2, the most active nickel sulfide, during the reaction process. The reason for the highest catalyst activity of 16 wt% Ni was attributed to the largest amount of NiS 2. Water vapor in the feed gas reactant caused inhibition of catalyst activity, whereas H 2S promoted the reduction of SO 2. These phenomena were rationalized with the aid of Claus reaction.