Regulation on mesoporous structure of Ag doped SiO2 aerogel by microdroplet template method for adsorption desulfurization

Abstract

A series of Ag(I) doped silica (Ag/SiO₂-tem-x/y) aerogel composites were prepared by microdroplet template method with different amount of template, whose physical and chemical properties were characterized by XRD, XPS, SEM-mapping, BET and XRF methods, and the sorption ability for thiophenics in model fuels was investigated, compared with Ag/SiO₂ prepared by conventional sol-gel method. The results showed that compared with conventional sol-gel method, the use of microdroplet template method could obviously improve the regularity of pore structure, the specific surface area and the actual doped rate of Ag species, however, did not change the chemical state of Ag species in aerogel composites. Both Ag/SiO₂-tem-x/y and Ag/SiO₂ adsorbed thiophenics mainly through the π-complexion between thiophenics and Ag(I) species. However, compared with Ag/SiO₂, the changes in physical and chemical properties of Ag/SiO₂-tem-x/y generated more highly dispersed Ag(I) species on the surface and the quicker diffusion velocity of thiophenics in the pore channels, consequently, leading to a higher sorption uptake for thiophenics. Among Ag/SiO₂-tem-x/y sorbents, Ag/SiO₂-tem-20/1 had the maximal sorption uptake for thiophene, up to 10.7 mg-S/g_ads. Upon four regeneration cycles by solvent washing, the sorption uptake of Ag/SiO₂-tem-20/1 could recover 74.11 % of fresh one, being better than that of Ag/SiO₂-50 (59.67 %), owing to the lower loss rate of Ag(I) species in former. The sorption process of thiophene on Ag/SiO₂-50 and Ag/SiO₂-tem-20/1, which was spontaneous and exothermic with a decreased disorder, could be better described by the pseudo-second-order kinetics mode and Langmuir adsorption isotherm model, respectively.