Preparation Of Resin-derived Activated Carbon Spheres For Desulfurization Of Fuels

Selective adsorption has favorable application in production of "zero sulfur" transportation fuel owning to its mild operation condition and low-energy consumption. In this paper, a resin-derived activated carbon was prepared. The influence of pore structure and surface chemistry on the adsorption performance towards dibenzothiophene (DBT) in model fuel was investigated.A polystyrene-based ion-exchange resin was employed as the precursor for preparation of the resin-derived carbon spheres (RCS) through KOH activation. Carbon spheres under various KOH impregnation ratios were characterized by SEM, N2adsorption and Boehm titration and their adsorption performance towards DBT were investigated. The optimism preparation condition is carbonizing at600℃for0.5h and then activating at800℃for0.5h. Result indicates microporous structure predominated in the derived samples. The samples with large surface areas and total pore volumes exhibited larger adsorption capacities than a commercial activated carbon, F400. Polanyi-Dubinin-Mane (PDM) model was applied to fit the adsorption data. Moreover, a good linear relationship was observed between the extra-micropore volume and adsorption capacity, which proved that micropore filling was involved during the adsorption process. Intra-particle diffusion model was used to describe the kinetic data of DBT onto the adsorbents. The adsorption processes were divided into three stages according to the different diffusion parameter. The existence of mesopores enhanced the adsorption rate. The selective adsorption towards DBT in the presence of competing compounds was also investigated and high selectivity of the RCS towards DBT was attained.Adsorption capacity of RCS towards DBT was affected by the surface chemistry as well. Nitric acid was used here for oxidation of RCS. The effects of oxidation time, temperature and concentration on the adsorption performance towards DBT were studied. The carbons were characterized by N2adsorption, Boehm titration and DTG. Results showed that the modification had an unnoticeable effect on the surface area and total pore volume of the modified carbons. Pore structure was destroyed to some extent at high oxidation temperatures. An appropriate condition was oxidizing with10mol/L nitric acid at60℃for1h. The polarity and surface acidic groups of carbon spheres increased after oxidation. The adsorption isotherms of DBT were fitted well with the Freundlich model. Adsorption capacity was increased due to the enhancement of surface chemistry.In a word, the resin-derived carbon spheres with regular shape and high intensity was prepared in this paper. Pore structure and surface chemistry of the samples were adjusted under different conditions. Compared to the commercial activated carbon, the carbon spheres exhibited higher adsorption capacity and selectivity towards DBT in model fuel.