Insight into H2S production from CS2 hydrolysis for heavy metals treatment: In-situ FT-IR and DFT studies over crystalline phase-dependent ZrO2

Abstract

H2S is an efficient vulcanizing reagent for heavy metals treatment in nonferrous smelting industries, yet these industries lack of H2S source is a well known problem. In this study, CS2 was hydrolyzed to a high concentration of H2S (>20 vol%) with different crystalline phase zirconium oxide catalysts. The metastable tetragonal ZrO2 (t-ZrO2) exhibited a sunk octahedron structure was successfully synthesized by calcination of MOF-808. Compared to monoclinic ZrO2 (m-ZrO2), it obtained excellent H2S production performance, which can reach near-perfect 100 % at 450 °C. Furthermore, experimental results shown that KOH modified t-ZrO2 could increase CS2 hydrolysis activity due to it is a base catalytic reaction. The in-situ FT-IR demonstrated that reaction sequences followed the order of CS2 → COS → H2S, in which CS2/H2O adsorption and CO2 desorption would influence the hydrolysis efficiency. t-ZrO2 obtained better CS2 adsorption, hydrophobicity, and CO2 desorption than m-ZrO2, which were attributed to intrinsic structure and abundant surface defects. Subsequently, DFT results profiled that cleave of the first CS bond in CS2 was rate-determining step with the activation energy about 63 kJ/mol over t-ZrO2.