K-doped LaAlO3 A-sites: Regulating surface basicity and oxygen species composition for highly efficient organosulfur hydrolysis

Catalytic hydrolysis technology is a promising solution for carbonyl sulfide (COS) treatment, but it is still difficult to scale up due to the poor selectivity of H₂S and low stability of the catalyst. Developing an efficient catalyst, therefore, remains a significant challenge. Although perovskite-based catalysts are widely utilized in various applications, they are less commonly applied to carbonyl sulfide hydrolysis. Moreover, the effects of doping modification and the hydrolysis reaction mechanism remain to be fully elucidated. Through extensive testing and evaluation of various lanthanide perovskite materials, LaAlO₃ has demonstrated excellent catalytic hydrolysis performance. At 100 °C, LaAlO₃ exhibits a COS removal efficiency of 37 % and an H₂S selectivity of 52 %. After modification via potassium doping at the A-site, the catalyst achieves near-complete conversion of COS to H₂S and maintains stable operation for extended periods under high space velocity. The adsorption energies of various adsorption sites were calculated using DFT, confirming the optimal adsorption sites for reactants COS and H₂O. Water undergoes dissociative adsorption on the catalyst to form -OH groups, which then adsorb COS through the Eley-Rideal (E-R) mechanism, leading to the formation of the hydrolysis intermediate HSCO₂⁻. Reactive oxygen species, on the other hand, facilitate the dissociative adsorption of H₂O, leading to the formation of more surface hydroxyl groups. Meanwhile, calculations indicate that K doping significantly enhances the adsorption energy of the reactants. The structure and properties of the catalysts have been characterized using a variety of techniques. The results have shown that K doping increases the content of weak basic sites and O₂⁻ in LaAlO₃. Consequently, the catalytic activity of La_0.8K_0.2AlO₃ prepared by the sol-gel method is enhanced, showing higher selectivity and stability. This work provides new solutions and insights for the application of perovskites in the field of environmental catalysis. Owing to its simple preparation method, low cost, and high efficiency, the modified LaAlO₃ catalyst exhibits excellent environmental and economic benefits.