HYDROLYSIS OF CARBON SULFIDES ON TITANIA AND ALUMINA CATALYSTS - THE INFLUENCE OF WATER

The influence of the amount of water on the rate of CS2 hydrolysis over gamma-alumina and titania catalysts was studied using infrared, adsorption-desorption, and activity measurements. Especially with the titania catalyst the amount of water present on the surface appeared to affect the activity decisively. At low temperatures water can block CS2 adsorption sites and thus decreases the CS2 hydrolysis rate. At temperatures between 525 and 600 K the amount of water on the surface drops and the order with respect to water becomes positive, while at temperatures above 600 K the order approaches zero. At temperatures above 600 K the normal hydrogen thiocarbonate intermediated mechanism does not operate any more. Instead, a sequential sulfidation-hydrolysis mechanism is evidenced to be responsible for the activity. The influence of the water coverage on the activity is of great importance in view of the use of titania and alumina catalyst in Claus plants.