Sr-doped calcium and barium manganites as catalysts in heterogeneous oxidation of volatile organic compounds
ŽUžIC A. 1, CAR F. 1, MACAN J. 1, TOMAšI? V. 1, GAJOVIC A. 2
1 University of Zagreb, Faculty of Chemical Engineering and Technology, Zagreb, Croatia; 2 Ru?er Boškovi? Institute, Zagreb, Croatia
Volatile organic compounds (VOCs), often referred to as organic solvents, are compounds that evaporate easily under normal conditions (atmospheric pressure and room temperature). High VOC emissions can lead to the formation of ground-level ozone responsible for photochemical smog and damage of atmospheric ozone layer. Apart from the environmental impacts, VOC exposure can also cause harmful health effects like respiratory diseases, lung function damage and gene mutation [1-2].
Catalytic oxidation is one of the most promising techniques for volatile organic compounds removal from industrial outlet gas streams. Sr-doped CaMnO3 (CSMO) and BaMnO3 (BSMO) were investigated as potential catalysts in catalytic oxidation of a model VOC mixture composed of benzene, toluene, ethylbenzene and o-xylene (BTEX). CSMO and BSMO catalysts with different Sr concentrations (x = 0, 0.3 and 0.5) were synthesized using autocombustion (CNA) and coprecipitation procedures.
The catalytic activity of prepared materials was tested in a temperature range from 373 to 723 K using constant catalyst mass in a fixed bed reactor. Toluene, ethylbenzene and o-xylene were completely removed using all prepared catalysts. All catalysts had average pore diameters ranging from 4.5 to 7.5 nm, which resulted in good diffusion of reactants and products. The highest benzene conversion of 86.43 % at 723 K was obtained for BSMO (x = 0.3) catalysts prepared by CNA synthesis. Generally, the highest catalytic activities were obtained for CSMO catalysts prepared by coprecipitation and BSMO catalysts prepared by CNA synthesis due to their oxygen vacancies and specific surface areas.