Physical and chemical surface modification of carbon nanotubes for adsorptive desulfurization of aromatic impurities in diesel fuel

Due to some environmental problems of sulfur compounds, it is necessary to eliminate these impurities from hydrocarbon fuels. To achieve effective removal of aromatic sulfur compounds such as benzothiophene and dibenzothiophene, different surface modification of carbon nanostructures, physical and chemical surface modifications, were utilized to reach the adsorptive desulfurization and oxidative desulfurization processes. The acid treatment by H2SO4/HNO3 and polymer-wrapping technique by polyethylene glycol were used for chemical and physical surface modification, respectively. Additionally, we tried to control the intensity and types of functional groups on the surface of carbon nanotubes. Besides, the efficiency of sulfur removal was measured. Both single-walled and multi-walled carbon nanotubes were utilized, and prepared samples have been investigated by FTIR, UV-Visible, TEM, Raman, and TGA techniques. The adsorption capacity values of each sample were evaluated by the temperature, time, and concentration parameters. The result shows that this surface modification can significantly improve the impurity removal of hydrocarbon fuel. Polymer-coated complexes showed higher removal values due to better dispersion than surface-oxidized carbon nanotubes. It was demonstrated that 90% of sulfur impurities with aromatic structure could be removed using an insignificant amount of the synthesized complex at moderate conditions. Besides, a comparison of laboratory data by conventional adsorption isotherms was investigated, and finally, the best operating conditions for maximum adsorbent performance were evaluated.