Adsorption of Sulfur Compounds by Hydrodesulfurization Catalysts

Abstract

The adsorption of benzene and dibenzothiophene by hydrodesulfurization catalysts in oxidic and sulfided states has been measured. The equilibrium isotherms were Langmurian, with the adsorption capacity depending on the size of the adsorbate molecule and determined by the area of the adsorbing surface. Sulfidation created an increase in the adsorbing area and in the adsorption capacity. It also caused a strengthening of the adsorption bond involving the heteroatom and inhibition of bonds involving the benzene ring. The kinetics were in agreement with a model based on activated surface diffusion in the pores. The energy of activation for diffusion was related to the strength of the adsorption bond when the adsorbate was taken up from the gaseous phase. The adsorption of dibenzothiophene from the liquid phase was too slow to be measurable when the catalyst was in an oxidic state but proceeded at a measurable rate on the sulfided catalyst.