The nature and kinetics of the adsorption of dibenzothiophene in model diesel fuel on carbonaceous materials loaded with aluminum oxide particles

Abstract

The resulted environmental and industrial problems from presence of sulfur compounds such as dibenzothiophene (DBT) in some fuel led to attract greater interest in research on the removal of these compounds. In this study the adsorption isotherms of dibenzothiophene (DBT) in model diesel fuel were obtained and desulfurization kinetics was carried out. The adsorbents used were commercial coconut activated carbon (AC), multiwall carbon nanotubes (CNT) and synthesized graphene oxide (GO) loaded with 5% and 10.9% aluminum (Al) in the form of aluminum oxide (Al2O3) particles to improve the chemical properties of their surface. The physicochemical properties for these adsorbents were characterized using thermal gravimetric analysis (TGA), N2 adsorption–desorption surface area analyzer, scanning electron microscope (SEM), energetic dispersive X-ray diffractogram (EDX), field emission electron microscope (FE-TEM) and X-ray photoelectron spectrometer (XPS). The adsorption capacities for DBT on the aluminum oxide modified adsorbents are improved by about twofold, which is attributable to introduction of Al2O3 Lewis acid as an additional adsorption site. The highest adsorption capacity for DBT (85 ± 1 mg/g) with high selectivity factor relative to naphthalene (54 mg/g) was achieved using loaded activated carbon with 5% Al. The adsorption capacities, removal selectivity and efficiencies with which the other prepared adsorbents remove DBT from model fuel are reported. The adsorption isotherms fitted both the Langmuir and Freundlich models. The adsorption rate for DBT follows pseudo-second order kinetics with correlation coefficients close to 1.00. The adsorbents are stable and reusable for at least 5 times. Keywords: Selectivity, Adsorptive desulfurization, Adsorption isotherms, Thiophenic compounds, Model fuel