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 heterocycle specificity and saturation capacity of TiO2 adsorbents. 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 study presents valuable evidence in support of the enhancement produced by UV irradiation is due to photocatalytic reactions between adsorbed water and anatase TiO2 by tracking the UV-induced conversion of adsorbed water and lattice oxygen into surface hydroxyls as monitored by XPS. Two different types of commercial TiO2 adsorbents (@163 and 70 m2/g) were investigated at different hydration levels as determined by TGA. The qualitative and quantitative analysis of the deconvolution details of the photoelectron peaks demonstrated the following conversion stoichiometry, where one adsorbed water and one lattice oxygen is converted into two surface hydroxyls. O2-(lattice) + H2O(ads)===&gt;2OH- Eight examinations of eight different reaction cases for both 160 and 70 m2/g TiO2 at 4 various hydration levels each. The measured conversion ratio for the above analysis varied from 1.83 to 2.15 with an average value of 1.98 and a standard deviation of 0.10. The XPS analysis of the samples removed from the XPS chamber and stored in laboratory conditions showed that photo-generated surface hydroxyls can persist for over 2 weeks with or without handling.

Quantitative XPS examination of UV induced surface modification of TiO2 sorbents for the increased saturation capacity of sulfur heterocycles

2019 Fall National Meeting

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