Study On Plasma Catalytic Removal Of Formaldehyde From Indoor Air And Its Byproducts

The indoor air pollutants, such as formaldehyde, has been attracted more and more attentions in recent years. In plasma chemistry reaction, the plasma catalytic method is the significant way to reduce the energy cost and improve the removal efficiency. In this paper, we studied the plasma catalytic removal of formaldehyde adsorbed on the catalysts.And we also mainly studied the two byproducts containing CO derived from formaldehyde conversion and N₂O produced by the N₂ and O₂ discharges. The results are as follows.We studied the effect of the position of the catalyst CeO₂ on the removal of formaldehyde and the byproduct CO derived from formaldehyde conversion under simulated air and pure oxygen discharge conditions.The position of the catalyst CeO₂ are including one stage method-A,one stage method-B,two stage method-A and two stage method-B.It is shown from the results that the position of the catalyst CeO₂ has no effect on the byproduct CO under the two discharge conditions.Using the two stage method-A, the CO selectivity in pure oxygen discharge and simulated air discharge are 1% and 4%, respectively .7%ZnO/γ-Al₂O₃,7%CeO₂/γ-Al₂O₃,7%NiO/γ-Al₂O₃,7%MnO₂/γ-Al₂O₃, 7%Fe₂O₃/γ-Al₂O₃, 7%CuO/γ-Al₂O₃ and 7%Co₃O₄/γ-Al₂O₃ supported metal oxide catalysts were prepared by the incipient wetness impregnation technique using a cheap sphericalγ-Al₂O₃ as carriers. The results revealed that the CO selectivity is the lowest and the time needed to completely remove formaldehyde is the shortest with 7%CeO₂/γ-Al₂O₃ catalyst.NO_X may be formed in N₂ and O₂ discharges, so the formation of N₂O in N₂ and O₂ DBD plasmas was studied at room temperature and atmospheric pressure in the paper, after studying the removal of formaldehyde from the simulated air. The effects of the total flow rate, N₂/O₂ ratio, discharge voltage, water content and catalysts on the formation of N₂O were investigated. It was shown that the concentration of N₂O decreases with increasing the total flow rate, but the amount of N₂O formation hardly change with the total gas flow rate at high flow rate(≥120 ml/min in this experiment).The concentration of N₂O decreases with the ratio of N₂/O₂. Much N₂O can be produced at high voltage. Water and the catalysts can inhibit the formation of N₂O to some extent.