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

Authors: 
Sun, X., Auburn University
Tatarchuk, B. J., Auburn University

Organic sulfur compounds in liquid hydrocarbon fuels are converted into SOx 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.
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