Catalytic hydrolysis of COS over unsupported Al2O3: New insights into the influence of hydroxyl characteristics on hydrolysis efficiency

H 2 O molecules are challenging to dissociate at low temperatures to produce hydroxyl groups for heterogeneous carbonyl sulfide (COS) hydrolysis. Utilizing the inherent hydroxyl groups on Al 2 O 3 surfaces for catalytic COS hydrolysis is effective; however, the relationship between the hydroxyl nature and hydrolysis efficiency remains unclear. In this study, we investigated the effects of crystal structure, surface morphology, specific surface area, and hydroxyl characteristics of Al 2 O 3 on COS hydrolysis efficiency. Results showed that the content, stability, and activity of hydroxyl groups significantly impacted the efficiency. Catalysts prepared from commercial alumina (Al 2 O 3 -C) exhibited superior COS hydrolysis efficiencies under both dry and humid conditions compared to pseudo-boehmite derived Al 2 O 3 (Al 2 O 3 -S) and boehmite derived Al 2 O 3 (Al 2 O 3 -B) owing to the higher, more stable, and active hydroxyl content in Al 2 O 3 -C. Although Al 2 O 3 -S contained a sufficient amount of surface hydroxyl, its lower activity reduced the hydrolysis efficiency. The catalytic COS hydrolysis mechanism over hydroxyl-rich Al 2 O 3 was elucidated through various characterization methods, providing new insights into the correlation between Al 2 O 3 surface hydroxyl properties and COS hydrolysis efficiency.