Adsorptive desulfurization of thiophene over Ti0.9Ce0.1O2 mixed oxide: A mechanistic study on the basis of XPS, in-situ FT-IR and TPD characterizations

Abstract

The adsorption of thiophenic compounds over Ti0.9Ce0.1O2, an oxidatively regenerable sulfur adsorbent, was studied by XPS, DRIFT, and TPD-MS. Effect of the oxidative pretreatment on thiophene adsorption over Ti0.9Ce0.1O2 adsorbent, the adsorption site for thiophenic compound, and the role of surface Ce and Ti cations in the adsorptive desulfurization (ADS) were investigated. The results suggest that the surface oxygen plays an essential role in ADS and is a major active site for chemical adsorption of the thiophenic compounds. The surface Ce and Ti were further oxidized by the surface oxygen in the oxidative pretreatment, and then reduced during the adsorption of thiophenic compounds. This phenomenon is attributed to an electron transfer from the adsorbates to the surface Ce and Ti. It appears that the role of the surface Ce and Ti can accept electrons from adsorbate, and also contributes to producing the active oxygen to oxidize the sulfur atom of thiophenic compounds. An oxidative pretreatment, including oxidative regeneration, activates the surface oxygen to forms active oxygen species and oxidizes the surface Ce and Ti. Based on the results obtained, a possible mechanism was proposed for the chemical adsorption, dissociation and surface reaction of thiophene on Ti0.9Ce0.1O2 mixed metal oxide adsorbent.