(33b) XPS Characterization of TiO2 Photo-catalytic Adsorptive Desulfurization
Due to the stringent requirements about the maximum sulfur emissions have been put into effect by governments, ultra-deep desulfurization has been paid more and more attention recently. UV induced photo-assisted adsorptive desulfurization (PAD) technique has been proven to be capable to enhance the sulfur removal capacity of anatase TiO2 adsorbent. XPS characterization of TiO2 adsorbents before and after UV treatment can provide precise evidence to reveal the mechanism of the enhancement by UV irradiation. This work presents valuable evidence in support of the enhancement produced by UV irradiation is due to photo-catalytic reactions between adsorbed water and anatase TiO2. 2 types of anatase TiO2 adsorbents were applied to study the effect of UV irradiation and adsorbed H2O on the UV induced PAD. Thermogravimetric Analysis (TGA) results showed the relative amount of adsorbed H2O on each TiO2 adsorbent. XPS results illustrated that UV irradiation caused a photo-catalytic reaction between adsorbed H2O and anatase TiO2 to form additional hydroxyl groups, and the relative amount of adsorbed H2O on TiO2 is the key to determine how much additional hydroxyls can be produced. The photo-catalytic produced OH groups help improve the desulfurization capacity of TiO2 adsorbent.
Keywords: Desulfurization, Adsorption, Titanium dioxide, Photo-catalysis, UV, XPS, TGA