Adsorption of carbon dioxide on the chemically modified silica adsorbents

Abstract

Silica adsorbents were chemically modified to have base sites on their surfaces and the adsorption characteristics of carbon dioxide on them were investigated. Base sites were introduced either by impregnation of silica gels with calcium acetate salt or by synthesizing silica xerogels using a sol-gel method from alcoholic solution of TEOS and calcium acetate salt. The salt in gels was transformed to calcium oxide by calcination at 700°C for 2 h. The chemically modified adsorbents possess irreversible surfaces, resulting in chemisorption of carbon dioxide on calcium oxide. However, the adsorbents showed reversible adsorption-desorption cycles of carbon dioxide after one dose of carbon dioxide chemisorption. Interaction between carbon dioxide and base site increased adsorptivity for carbon dioxide at 100°C and 250°C. Adsorptivity of carbon dioxide represented by Henry's constant (μmol/m2/atm) increased by the chemical modification from 0.4 to maximum 1.5 at 100°C and from 0.032 ∼ 0.17 to maximum 0.7 at 250°C.