Oxygen vacancy-engineered titanium-based perovskite for boosting H₂O activation and lower-temperature hydrolysis of organic sulfur.

Abstract

Modulation of water activation is crucial to water-involved chemical reactions in heterogeneous catalysis. Organic sulfur (COS and CS₂) hydrolysis is such a typical reaction involving water (H₂O) molecule as a reactant. However, limited by the strong O-H bond in H₂O, satisfactory CS₂ hydrolysis performance is attained at high temperature above 310 °C, which is at the sacrifice of the Claus conversion, strongly hindering sulfur recovery efficiency improvement and pollution emissions control of the Claus process. Herein, we report a facile oxygen vacancy (V_O) engineering on titanium-based perovskite to motivate H₂O activation for enhanced COS and CS₂ hydrolysis at lower temperature. Increased amount of V_O contributed to improved degree of H₂O dissociation to generate more active -OH, due to lower energy barrier for H₂O dissociation over surface rich in V_O, particularly V_O clusters. Besides, low-coordinated Ti ions adjacent to V_O were active sites for H₂O activation. Consequently, complete conversion of COS and CS₂ was achieved over SrTiO₃ after H₂ reduction treatment at 225 °C, a favorable temperature for the Claus conversion, at which both satisfying COS and CS₂ hydrolysis performance and improved sulfur recovery efficiency can be obtained simultaneously. Additionally, the origin of enhanced hydrolysis activity from boosted H₂O activation by V_O was revealed via in-depth mechanism study. This provides more explicit direction for further design of efficacious catalysts for H₂O-involved reactions.