Physicochemical Studies of Adsorptive Denitrogenation by Oxidized Activated Carbons

A commercially available activated carbon was oxidized by concentrated sulfuric acid, saturated ammonium persulfate solution, and mixed sulfuric acid and ammonium persulfate, respectively. The original carbon and the modified carbons were evaluated by batch adsorption using model diesel fuels. The pore structure and surface chemistry of adsorbents were characterized with N2 adsorption/desorption, Fourier transform infrared spectroscopy, and Boehm's titration. Both physical and chemical aspects of the selectively adsorptive denitrogenation of oxidized activated carbons were investigated. Appropriate oxidation can promote the carbon's ability to adsorb nitrogen-containing compounds. The effect of the density of acidic oxygen-functional groups on the adsorption of nitrogen-containing compounds was demonstrated by the regression method and quantum chemistry calculations. The capacities due to physisorption were also estimated. The behaviors of N-containing compounds in a competitive adsorption system were dependent on the molecular size and the properties of adsorbates.