Boosting carbonyl sulfide catalytic hydrolysis performance over N-doped Mg-Al oxide derived from MgAl-layered double hydroxide

Carbonyl sulfide (COS), the organic sulfur generated in the chemical industry, has been receiving more attention due to its environmental and economic influence. In this study N-doped MgAl-LDO catalyst was successfully prepared and tested for the COS hydrolysis reaction at low temperature, it was observed that the N species can be formed both in surface and bulk. Moreover, the basicity property and the H2O adsorption-desorption property were remarkably improved due to the N-doping. Besides, the hydroxyl group can be formed more easily and more abundantly on N modified catalyst surface, which was beneficial to the COS adsorption and the remarkable improvement of catalytic performance. The catalytic hydrolysis performance can proceed for almost 1440 min without any deactivation at 70 °C. However, further increase of temperature was not beneficial to improve the catalytic performance due to the occurrence of H2S oxidation side reaction. Furthermore, it was revealed that the surface hydroxyl groups were responsible for the adsorption of COS and then the formed surface transitional species reacted with the H2O molecules. Hydrogen thiocarbonate and bicarbonate were the main reaction intermediate. The rate-determining step was IM6→IM7 i.e., a type transformation of bicarbonate.