COS-Forming Reaction between CO and Sulfur: A High-Temperature Intrinsic Kinetics Study

Carbonyl sulfide (COS) is formed in the front end of Claus plants, which are used to recover sulfur from acid gases. This study aims to fill the knowledge gap regarding the kinetics of the reaction between carbon monoxide (CO) and sulfur for COS formation. An experimental investigation was conducted to measure the intrinsic kinetics of this homogeneous gas-phase reaction across a temperature range of 600-1150 °C and a residence time of 0.5-2.0 seconds. The results indicate that the overall reaction follows second-order kinetics, with a reaction rate constant defined as kf = (3.18 ± 0.36) × 10^5 exp[-(6700 ± 108 K)/T] m³/(kmol·s). Additionally, a kinetic model was developed to account for both COS formation and decomposition. The rate constant for the reverse reaction, COS decomposition, was regressed to fit equilibrium data from high-temperature experiments, yielding a rate constant of kr = (2.18 ± 1.12) × 10^9 exp[-(21630 ± 160 K)/T] m³/(kmol·s). These findings provide critical insights into the kinetic behavior of COS reactions in industrial processes.