Low-temperature plasma-catalytic oxidation of formaldehyde in atmospheric pressure gas streams

Formaldehyde (HCHO) is a typical air pollutant capable of causing serious health disorders in human beings. This work reports plasma-catalytic oxidation of formaldehyde in gas streams via dielectric barrier discharges over Ag/CeO₂ pellets at atmospheric pressure and 70 °C. With a feed gas mixture of 276 ppm HCHO, 21.0% O₂, 1.0% H₂O in N₂, ∼99% of formaldehyde can be effectively destructed with an 86% oxidative conversion into CO₂ at GHSV of 16500 h⁻¹ and input discharge energy density of 108 J l⁻¹. At the same experimental conditions, the conversion percentages of HCHO to CO₂ from pure plasma-induced oxidation (discharges over fused silica pellets) and from pure catalytic oxidation over Ag/CeO₂ (without discharges) are 6% and 33% only. The above results and the CO plasma-catalytic oxidation experiments imply that the plasma-generated short-lived gas phase radicals, such as O and HO₂, play important roles in the catalytic redox circles of Ag/CeO₂ to oxidize HCHO and CO to CO₂.