VOC oxidation and CO2 adsorption on dual adsorption/catalytic system based on fly ash zeolites

Zeolite NaX was prepared by conversion of coal ash residue, collected from the electrostatic precipitator of a thermal power plant supplied with lignite coal, by treatment with alkaline solution. Three different synthesis procedures, namely hydrothermal activation, double stage fusion-hydrothermal activation, and atmospheric aging, were applied. Formation of zeolite NaX, accompanied by iron oxides or Fe2+/3+ ions incorporated in the zeolite matrix was found. The zeolite crystallites are with uniform size around 1-2 mu m. The obtained materials showed the formation of a micro-mesoporous composite with relatively high specific surface area (between 220 and around 500 m(2)/g). Fly ash zeolites (FAZ) showed high capacity for CO2 adsorption depending on the state of iron in the zeolite structure. Cobalt-modified fly ash zeolites (Co-FAZ) were prepared by incipient wetness impregnation technique with 6 wt. % cobalt loading. The initial and cobalt modified FAZ showed high activity in degradation of different VOCs (acetone, n-hexane, toluene and 1,2 dichlorobenzene). It was established that the extent of zeolitization and the state of iron in FAZ are critical parameters for the catalytic activity. The obtained initial and modified fly ash zeolites are promising candidates for development of a dual catalytic/adsorption system for VOCs and CO2 elimination.