Kinetics of carbonyl sulfide hydrolysis. 1. Catalyzed and uncatalyzed reactions in mixtures of water plus propane

Carbonyl sulfide (COS), which occurs as an impurity in commercial sources of propane, can hydrolyze in the presence of water to form hydrogen sulfide (H2S) and carbon dioxide (CO2). Whereas COS is not itself corrosive, the hydrolysis product H2S is corrosive, especially in the presence of water. In this paper, we summarize the results from studies that address the issue of COS hydrolysis in propane, thought to be a major problem in the liquefied petroleum gas industry. A series of kinetics measurements were made of COS in a propane-water system. Reaction rates were determined from chromatographic monitoring of the decrease in COS and the appearance of H2S in the vapor phase as a function of time. The hydrolysis rate was measured for 500 and 1000 ppm mixtures of COS in propane at 38, 65, and 85 degreesC. COS hydrolysis was not observed in propane at 16 degreesC. In addition, rate constants were measured for the hydrolysis reaction catalyzed by potassium hydroxide and alkanolamines. The rate of hydrolysis of COS in the aqueous propane system is several orders of magnitude lower than that in pure water.