Adsorption of organic vapors on single-walled carbon nanotubes

Adsorption properties of single-walled carbon nanotubes (SWNTs) were investigated using standard gravimetric techniques. Equilibrium vapor-phase adsorption isotherms were measured for three fundamentally different molecules on SWNTs of two different diameters (12 and 16.8 Å). SWNT interactions with aromatic (benzene), aromatic and heterocyclic (thiophene), and nonaromatic (cyclohexane) molecules were investigated, as well as the effects of diameter on adsorption. Stronger adsorption was observed for the smaller SWNTs. Isosteric heats of adsorption were calculated from the adsorption isotherms and followed the order thiophene > benzene > cyclohexane. Furthermore, batch adsorption experiments were performed to investigate the feasibility of desulfurization of fuels using SWNTs. Batch experiments were performed to verify preferential adsorption of thiophene over benzene using a model fuel. Selectivity for thiophene over benzene was demonstrated, and a test with a commercial diesel sample was performed. Heat treatments were found to increase the sulfur capacity. Removal of sulfur species was comparable to that of BPL activated carbon.