Modeling carbon dioxide adsorption on polyethylenimine-functionalized TUD-1 mesoporous silica

Samples of porous, foam-like TUD (Technische Universität Delft)-1 mesoporous silica were functionalized with polyethylenimine and were used as a substrate for CO(2) adsorption. Produced solids were characterized by means of electron microscopy, thermogravimetric analysis, and N(2) adsorption/desorption at 77K, in order to prove that polymer chains efficiently filled the pores of functionalized samples. CO(2) adsorption isotherms on polyethylenimine-containing TUD-1 were evaluated at T=298, 313, 328, and 348 K for pressures up to 100 kPa by means of a volumetric technique. The CO(2) adsorption capacity proved to be significantly dependent on temperature, with the highest capacity encountered at T=348 K. The experimental data for CO(2) adsorption were satisfactorily described by means of the Langmuir isotherm, and the dependence of the isosteric heat on the fractional coverage of the adsorbent was evaluated by means of the van't Hoff equation, showing values in the order of 80 kJ/mol for a fractional coverage of about 50%.