Investigating role of sulphur specific carbon adsorbents in deep desulphurization

Abstract

Adsorptive desulphurization of model fuel (thiophene in isooctane) was studied by using sulphur specific carbon based adsorbents, SHIRASAGI GH2x 4/6 and SRCx 4/6, in an attempt to obtain insight into the adsorptive behaviour of sulphur moiety on the modified surfaces. Both adsorption equilibria and adsorption kinetics have been reported. Characterization of the modified adsorbents was carried out using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction (XRD) and surface area analyser. Adsorption experiments along with characterization results highlight potential for higher sulphur adsorption on the modified adsorbents. Substantially higher capacities for adsorption of thiophene were obtained, ∼5.5 and ∼20mgg−1 of sulphur for SHIRASAGI GH2x 4/6 and SRCx 4/6 respectively. Experimental investigations reveal possible influence of Al/Si ratio, 12.46 and 9.35 in GH2x and SRCx respectively that can have implication in adsorption behaviour. It was found that surface modification plays important role in enhancing sulphur removal capacity as compared to conventional carbon adsorbents. A plausible mechanism to account for surface interactions and role of surface modification has been proposed. The higher mesopore volume along with higher oxygen content is believed to influence preferential adsorption of thiophenic sulphur by SRCx. The work also indicated specific role of Al and Si content in the carbon matrix. The utility of these adsorbents and higher sulphur removal capacity has also been confirmed using synthetic mixture of refractory sulphur compounds such as benzothiophene, dibenzothiophene along with thiophene.