Enhanced performance and DFT study of sulfur poisoning mechanism of modified Al2O3 catalyst in COS hydrolysis

Abstract

The sulfur poisoning mechanism of Al2O3 catalysts in COS hydrolysis is still controversial. The modified K0.1Al2O3-PA catalyst exhibited enhanced anti-poisoning performance, which maintained 100 % conversion and 85 % H2S selectivity after 150 h of reaction. The results illustrated that the decrease of activity was related to the reduced specific surface area, basicity, oxygen vacancies and weakened adsorption ability of COS. The sulfur species on the Al2O3 and Al2O3-PA catalyst was Al2(SO4)3 and elemental S, respectively. After adding K, the sulfur species existed stably in the form of K2SO4. The DFT calculation results suggest that the trapping of H2S by K weakens the adsorption of H2S on Al, which protects the Al sites. The results suggested that COS and H2S are difficult to be oxidized by lattice oxygen, especially after adding K. In the presence of O2, H2S is more easily oxidized to generate S and OH– through a two-step dehydrogenation reaction.