B2 O3对Ag/TiO2-Al2 O3吸附剂的柴油吸附脱硫性能影响

摘要

Ag/TiO2-B2 O3-Al2 O3 adsorbents with different B2 O3 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-Al2 O3 modified by B2 O3 exhibits a great enhancement for the adsorption desulfurization activity. When B2 O3 ( 15%) 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 B2 O3 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 11 B nuclear magnetic resonance ( 11 B-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. B2 O3 modification induces larger amounts of BO4 species and improves the surface weak acidity, resulting in a higher adsorption desulfurization activity.%采用浸渍法制备了不同 B2 O3负载量( e. g.5%~20%( w ))的 Ag/TiO2-B2 O3-Al2 O3吸附剂。以含硫量为245.36 mg(S)/L 的商业柴油作为考察对象,常温常压下采用静态评价进行吸附脱硫性能研究。结果表明,B2O3改性后的Ag/TiO2-Al2 O3吸附剂的柴油吸附脱硫活性有了较大提高,当B2 O3的负载量为15%时,吸附剂的吸附脱硫活性最高,2%Ag/4%TiO2-15%B2O3-Al2O3(w)的饱和吸附硫容达到2.36 mg(S)/g 吸附剂。这对于未经预处理的商业柴油而言,吸附脱硫活性已经达到较高水平。采用N2物理吸附、O2化学吸附、X射线衍射( XRD)、NH3程序升温脱附( NH3-TPD)、傅里叶红外光谱( FT-IR spectra)、11 B核磁共振(11 B-NMR)等表征手段对不同负载量B2 O3改性Ag/TiO2-Al2 O3吸附剂的织构性质、晶相结构和表面酸性的影响进行研究。关联活性测试和表征结果发现,吸附剂的吸附脱硫活性主要与吸附剂的表面弱酸性有关,而B2 O3改性在吸附剂表面引入了较多的四配位的BO4物种,能显著增加吸附剂表面弱酸性位点数量,提高吸附剂的吸附脱硫活性。