Photo-assisted adsorptive desulfurization of hydrocarbon fuels over TiO2 and Ag/TiO2

Photo-assisted adsorptive desulfurization (ADS) of hydrocarbon fuels using TiO2 and Ag/TiO2 adsorbents under mild conditions has been investigated. UV irradiation (λ = 365 nm) was directly introduced into the adsorbent packed bed. Typical UV flux at 1 cm from the UV lamp was 1.8-2.0 mW/cm2. Sulfur removal performance was evaluated by breakthrough experiments in the presence of UV and H2O. Results indicated that the sulfur removal capacity of TiO2 was increased by 50% during UV-assisted ADS. Ag/TiO2 adsorbents showed the highest UV-assisted capacity which was 6.35 mg S/g adsorbent using a model fuel containing 3500 ppmw sulfur (benzothiophene in n-octane) and 1000 ppmw H2O. In situ IR analysis were applied to study the effects of H2O and UV molecules on surface OH groups. The chemical state change of Ag caused by UV irradiation was characterized by X-ray Photoelectron Spectrometer (XPS). Based on IR data, the enhanced desulfurization capacity of TiO2 under UV irradiation was attributed to the increase in the total number of terminal Ti(IV)OH groups. Multi-cycle experiments will be carried out later to study the stability of UV-activated sulfur removal sites and the photo-assisted sulfur removal mechanism will be investigated in the future.