(395d) Adsorption Desulfurization of Liquid Fuel Using Ag/TiO2 and Ag/Tiox—Al2O3 Assisted By Ultraviolet Irradiation

Organic sulfur compounds in liquid fuels are converted into SO_x during combustion, which cause severe environmental pollution such as acid rain and smog. Also sulfur is considered as a poison for catalysts in fuel cells. As a result, desulfurization has attracted much attention nowadays. The conventional hydrodesulfurization (HDS) process becomes more complicated for removing the refractory sulfur heterocycles from commercial fuels. Thus several alternative technologies have been investigated in order to supplement HDS. Among those technologies, adsorption desulfurization (ADS) is one of the simplest and efficient methods to achieve ultra-low sulfur level under ambient temperature and pressure. Previously, Ag/TiO₂ and Ag/TiO_x—Al₂O₃ adsorbents developed by our group showed high selectivity, capacity and regenerability. Our recent research interests focus on the photocatalytic property of TiO₂ material on desulfurization. In the present work, the desulfurization performance of these two adsorbents treated by ultraviolet (UV) irradiation was studied by both saturation and breakthrough tests using model fuels (e.g. 3500 ppmw S as benzothiophene in n-octane). Low power input UV sources at a longer wavelength (λ=365 nm) were applied to treat our sulfur adsorbents. Our research results showed that the desulfurization capacities of both Ag/TiO₂ and Ag/TiO_x—Al₂O₃ were improved apparently via photo-irradiation. The breakthrough capacity of blank TiO₂ increased from 1.83 mgS/g to 3.06 mgS/g with UV treatment. And the saturation capacity of 4wt% Ag/TiO₂ increased from 4.87 mgS/g to 6.42 mgS/g with UV treatment. UV source can produce more active sites on support materials’ surface while loading Ag can further lower down the band gap of TiO₂ and also inhibit the the recombination of electron-hole pair. The characteristics of the adsorbents and possible mechanisms were investigated by X-ray Photoelectron Spectroscopy (XPS) and UV diffuse-reflectance spectroscopy (DRS). The UV photooxidation effects on organic sulfur compounds were also studied using gas chromatography (GC-PFPD).