SBA-15 supported benzoxazolium-based ionic liquids: Synthesis, characterization, and application in the adsorptive desulfurization

Abstract

In this study, organosilane-modified S-aryl/alkyl-substituted benzoxazolium-based ionic liquids ([S-RBOx][Cl]; R = benzyl or methyl) were synthesized and immobilized on SBA-15 silica support to afford supported ionic liquids (SILs). The structure elucidation of SILs was done by using SEM, SAXS, BET, TEM, EDS, and NMR spectroscopy. Moreover, the adsorbent role of SILs and SBA-15 was studied in the adsorptive desulfurization by taking model and real gasoline samples. In contrast to SBA-15, both SIL adsorbents were found more efficient because of the π-π interactions, induced between supported [S-RBOx][Cl] and thiophene compounds. The Freundlich adsorption isotherm was found more suitable to fit the experimental adsorption data in comparison to the Langmuir isotherm. SBA-15@[S-BzBOx][Cl] was obtained with maximum adsorption capacity (328 mg/g) in comparison to SBA-15 (109.1 mg/g) and SBA-15@[S-MeBOx][Cl] (256.6 mg/g). The maximum adsorption was obtained by SBA-15@[S-BzBOx][Cl] at 45 °C within 100 min by using an adsorbent quantity of 600 mg from model gasoline having a sulfur content of 250 ppm and provided removal of TS, TN, and DBT with the percentage of 57.2%, 63.6%, and 78.9% respectively. All the SILs were reused ten times and obtained with almost constant adsorption efficiency.