Liquid-Phase Adsorption of Multi-Ring Thiophenic Sulfur Compounds on Carbon Materials with Different Surface Properties

Abstract

This work examines the effects of structural and surface properties of carbon materials on the adsorption of benzothiophene (BT), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) in the presence of 10 wt % of aromatics in liquid alkanes that simulate sulfur compounds in diesel fuels. The equilibrium-adsorption capacity varies significantly, from 1.7 to 7.0 mg-S/g-A. The results show that different carbon materials have significantly different sulfur-adsorption capacities and selectivities that depend not only on textural structure but also on surface functional groups. The adsorption of multi-ring sulfur compounds on carbon materials was found to obey the Langmuir isotherm. On the basis of adsorption tests and the characterization of carbon materials by BET and XPS, the oxygen-containing functional groups on the surface appear to play an important role in increasing sulfur-adsorption capacity. The adsorption-selectivity trend of the carbon materials for various compounds increases in the order of BT < naphthalene < 2-methylnaphthalene < DBT < 4-MDBT < 4,6-DMDBT, regardless of carbon material types. This selectivity trend for sulfur compounds is dramatically different and almost opposite from that previously observed for adsorption over nickel-based adsorbents. The regeneration of spent activated carbons was also conducted by solvent washing. The high-adsorption capacity and selectivity for methyl DBTs indicate that certain activated carbons are promising adsorbents for selective adsorption for removing sulfur (SARS) as a new approach to ultra deep desulfurization of diesel fuels.

Role of phosphorus in carbon matrix in desulfurization of diesel fuel using adsorption process

“…Scientific efforts focus on oxidation [1,2], photoxidation [3,4] or adsorption . The adsorption based methods applied activated alumina [7,8], zeolites [9], and activated carbons [7,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] as adsorbents. The results obtained on the latter materials seem promising [12,22,[26][27][28].…”

Adsorption and Ultrasound-Assisted Sorbent Regeneration

“…As discussed elsewhere, 32 the original H-K model underestimates the total interaction energy of the adsorbate molecules, and after correction, the pore sizes are shifted toward higher (and correct) values. 32 After impregnation, the pores sizes were still large enough for the sulfur molecules to adsorb.…”

“…32 The effects of the substrate on the metal salt, if any, are much weaker. Thus, any electronic effect as the reason for the strong synergistic effect discussed above is ruled out.…”

“…1,4,32 Although various carbons could selectively adsorb thiophenic sulfur, the selectivity was not high enough because early breakthrough of small sulfur concentration occurred. 1 However, the sulfur capacities were high because of their large surface areas.…”

“…32 The model diesel contained over 10 different compounds, and will not be compared here. Comparing the results in Figures 2 and 3 with that on aerogels, it is seen that the amounts adsorbed DBT were significantly higher on the π-complexatrion sorbents.…”