Carbon aerogels (CAs) were studied as adsorbents for the desulfurization of liquid hydrocarbon fuels for fuel cell applications. A synthetic mixture of dibenzothiophene (DBT) and n-hexadecane (n-HD) was used as a model for sulfur contaminated diesel fuel. Carbon aerogels with two different average pore sizes (4 and 22 nm) were synthesized, characterized, and tested for adsorption of DBT at ambient temperature and atmospheric pressure. The approach-to-equilibrium was monitored, and adsorption isotherms were measured. The CA with the larger average pore size had a higher sulfur adsorption rate and a higher capacity for DBT. The isotherms were best represented by the Freundlich model. According to the Langmuir isotherm, the adsorption capacities of the 4 nm CA and 22 nm CA were 11.2 and 15.1 mg S/g dry CA, respectively. The CAs were found to selectively adsorb DBT over naphthalene, which is a chemically similar but non-sulfur containing organic compound, when both are present in solution. However, the presence of naphthalene slightly reduced the amount of DBT adsorbed.

Surface and textural properties of Zr-doped silica [xZrO2-(100 − x)SiO2] have been investigated as a function of zirconium content in the range of x = 5 to 50 (mol % Zr) via heating their respective xerogels (prepared with a novel sol−gel route developed recently) in air at 500 °C for 4 h. Nitrogen adsorption−desorption investigations (BET/BJH) on the 500 °C-heated samples show a maximum specific surface area of 484 m2g-1 at x = 20, and a minimum of 105 m2g-1 at x = 50. With increase of zirconium content, porosity of the Zr-doped silica can be tuned conveniently from the mesoporous (100 Å) to the microporous (≤ 20 Å) region with unimodal (or nearly unimodal) pore size distributions. Material issues such as thermal reactions, oxide mixing level and formation mechanisms have also been investigated with FTIR, XRD, DTA/TGA, and XPS methods. It is found that silica networks have been significantly modified with the introduction of zirconium, and crystallization of ZrO2 in the doped silica occurs only at 903−953 °C. Moreover, surface analysis shows that there is no appreciable element enrichment in the surface region, whereas significant changes in binding energies of Zr 3d, Si 2p, and O 1s have been detected. The above observations are indications that a good mixing has been attained.