Adsorptive desulfurization of model gasoline by using modified bentonite

This work involved the investigation on the removal of organic sulfur compounds from the model liquid fuels by using adsorption desulfurization (ADS) method. For this purpose, removal of 4-methyl dibenzothiophene (4-MDBT) in model gasoline streams with raw bentonite, nanobentonite and nanobentonite modified by nanomagnetite, active carbon and Ni(NO3)2.9H2O was considered. Various factors influencing the desulfurization capability, including loading and baking temperature were investigated. Thermo-gravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) showed that the ability of modified bentonite to adsorb 4-MDBT depends strongly on surface chemistry, particularly on the presence of basic oxygen-containing groups and acid content. The adsorbents tested for desulfurization capacity at breakthrough followed the order: 30wt% Fe3O4/30wt% Active carbon/40% Na -Nanobentonite > 30wt% Fe3O4/30wt% Active carbon/40% Ca – Nanobentonite > 30wt % Fe3O4/70% Ca-Nanobentonite > 15wt % Fe3O4/15wt% Ni/70% Ca– Nanobentonite. The results of preliminary tests for raw bentonite and nanobentonite were not significant in comparison with the modified nanobentonites: a, b, c, d samples, (about 40% lower than the four sample models). The optimum calcination temperature was 800°C. The multivariate methods were used for optimization of acceptance parameters. A Plackett–Burman design (PBD) was chosen as a screening method to estimate the relative influence of the factors that can be affected on the analytical response. Results show that surface area, pore size and pore volume of the bentonite can be increased several times using the impregnation method by 30wt% Fe3O4/30% active carbon. Also, the surface morphology of the bentonite is changed with this modification.