La doped silica aerogel as selective adsorbent for the desulfurization of model fuel

Abstract

La doped silica aerogel composites (La2O3/SiO2-n) with different Si/La molar ratio were synthesized through sol-gel method and atmospheric drying technology, which were used to adsorb thiophenic compounds from model fuels. Compared with the pure SiO2 aerogel, the adsorption capacities of La2O3/SiO2-n obviously increased, owing to adding La species led to the appearance of the weak Lewis acid sites on the surface. The adsorption mechanism of La2O3/SiO2-n for thiophenics included the direct S-La bond and weak π-La acid-base interaction between La3+ and thiophenics, and the former was primary. Among La2O3/SiO2-n, the La2O3/SiO2-200 not only had the highest adsorption capacity for thiophene, up to 8.16 mg S/gads (i.e., 138.31 mg-S/mmol La), but also exhibited an excellent anti-aromatics competitive adsorption ability and a good regeneration performance. The adsorption kinetic and adsorption isotherms were well described by pseudo-second-order (PSO) and Langmuir models, respectively, indicating the adsorption of La2O3/SiO2-200 for TH was dominated by chemisorption, which was a spontaneous and endothermic process. The present of aromatics in model fuels had a slightly negative effect on the adsorption of La2O3/SiO2 for thiophene.