Effect of B2O3 modified Ag/TiO2-Al2O3 adsorbents on the adsorption desulfurization of diesel

Ag/TiO2-B2O3-Al2O3 adsorbents with different B2O3 loadings (e.g. 5%–20% (w)) were prepared by impregnation. Static adsorption tests were carried out by contacting the adsorbents with commercial diesel containing 245.36 mg(S)/L sulfur at ambient conditions to investigate the adsorption desulfurization activity. The results show that Ag/TiO2-Al2O3 modified by B2O3 exhibits a great enhancement for the adsorption desulfurization activity. When B2O3 (15% (w)) was loaded, 2%Ag/4%TiO2-15%B2O3-Al2O3 (w) could achieve the best desulfurization activity with a saturation capacity of 2.36 mg(S)/g adsorbent. This is a significant achievement regarding the desulfurization efficiency, especially for commercial diesel without pretreatment. The effects of B2O3 on the textural properties, crystal structure and surface acidity properties of the adsorbent were studied by N2-physisorption, O2-chemisorption, X-ray diffraction (XRD), temperature-programmed desorption of ammonia (NH3-TPD), Fourier transform infrared spectrometer (FT-IR spectra) and 11B nuclear magnetic resonance (11B-NMR) techniques. Correlating the characterizations with the desulfurization activity, it is found that the adsorption desulfurization activity is well related with the amounts of weak acid sites on the adsorbents. B2O3 modification induces larger amounts of BO4 species and improves the surface weak acidity, resulting in a higher adsorption desulfurization activity.