Unraveling the sulfur poisoning mechanism of N-doping KAl2O3 catalyst in simultaneous hydrolysis of COS and CS2 via experimental and theoretical study

Abstract

The short lifetime and poor resistance to poisoning of hydrolysis catalysts restricted their application in the desulfurization of blast furnace gas. N doping was applied to enhance the low-temperature hydrolytic activity and stability of the catalysts, and the poisoning mechanisms of COS and CS2 were explored by a series of characterizations and DFT theoretical calculations. The results revealed that the N-modified catalyst could maintain 100 % COS conversion and more than 40 % CS2 conversion after 120 h reaction. The characterization results certified that reduced surface area, weakened surface basicity, and weakened COS and CS2 adsorption capacity were the main causes of catalyst poisoning. The deposited sulfur species on the catalyst were mainly monomeric sulfur and sulfate (Al2(SO4)3). The incorporation of N significantly reduced the production of Al2(SO4)3 and enhanced the protection of the Al active site by K, which in turn enhanced the resistance to poisoning. DFT theoretical calculations exhibited that the oxidation products of COS were mainly COSO2- and CO2SO-, while CS2 was easily converted to COS first and then further be oxidized. The addition of N made the oxidation intermediate species more difficult to generate, while the oxidation product SO2 was easier to desorb, which explained the improved catalyst resistance to poisoning.