Oxygen vacancy-engineered titanium-based perovskite for boosting H 2 O 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 CS 2 ) hydrolysis is such a typical reaction involving water (H 2 O) molecule as a reactant. However, limited by the strong O-H bond in H 2 O, satisfactory CS 2 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 H 2 O activation for enhanced COS and CS 2 hydrolysis at lower temperature. Increased amount of V O contributed to improved degree of H 2 O dissociation to generate more active -OH, due to lower energy barrier for H 2 O dissociation over surface rich in V O , particularly V O clusters. Besides, low-coordinated Ti ions adjacent to V O were active sites for H 2 O activation. Consequently, complete conversion of COS and CS 2 was achieved over SrTiO 3 after H 2 reduction treatment at 225 °C, a favorable temperature for the Claus conversion, at which both satisfying COS and CS 2 hydrolysis performance and improved sulfur recovery efficiency can be obtained simultaneously. Additionally, the origin of enhanced hydrolysis activity from boosted H 2 O activation by V O was revealed via in-depth mechanism study. This provides more explicit direction for further design of efficacious catalysts for H 2 O-involved reactions.