(417r) UV-Assisted Adsorptive Desulfurization (ADS) of Liquid Fuels Using TiO2 Based Adsorbents

Organic sulfur compounds in liquid hydrocarbon fuels are converted into SO_x during combustion, which may cause severe environmental pollution such as acid rain and smog. Sulfur compounds can also damage the electrodes of fuel cells. As a result, desulfurization has attracted much attention nowadays. The conventional hydro-desulfurization (HDS) process cannot meet the stringent environmental regulation. Thus several alternative technologies have been investigated in order to replace HDS. Among these technologies, adsorption desulfurization (ADS) is one of the most promising methods to achieve an ultra-low sulfur level under ambient operating conditions. Ag/TiO₂ and Ag/TiO₂—Al₂O₃ adsorbents developed by our research group showed high selectivity and capacity and can be regenerated. The desulfurization mechanism was investigated by previous work based on the interaction between sulfur compounds and surface hydroxyl groups. In the present work, UV assisted adsorptive desulfurization technique was developed for the first time by applying TiO₂/UV system into dynamic desulfurization (breakthrough) process. According to our acknowledgement, sulfur removal assisted by UV using TiO₂ and Ag-TiO₂ is unique in adsorptive desulfurization area. Experimental results showed that sulfur capacities of TiO₂ based adsorbents were improved during UV-assisted breakthrough experiments using model fuels and jet fuel. The breakthrough capacity of blank TiO₂ increased from 2.45 mgS/g to 4.05 mgS/g under UV irradiation. H₂O impurities can decrease the activity of TiO₂ based adsorbents. The sulfur capacity of Ag/TiO₂ decreased from 5.84 mgS/g to 4.63 mgS/g in the presence of H₂O. However, the capacity was increased to 6.40 mgS/g upon UV illumination using H₂O as fuel additive. No photo-oxidative reactions were observed during sulfur removal process. Relative concentrations of active OH radicals on TiO₂ under UV were measured by fluorescence technique using terephthalic acid. Photo-induced charge carries on TiO₂ surface were characterized by in situ infrared (IR) spectroscopy. The effect of UV irradiation on surface hydroxyl groups and possible desulfurization pathway were discussed based on research results.