Plasma-catalytic oxidation of diluted formaldehyde over Cu-Ce oxide catalysts

Summary form only given. With the rapid development of industry and economy, the emission of volatile organic compounds (VOCs) is becoming a global focus because of its negative impact on both human health and environment ¹. The combination of cold plasma and catalysis (plasma-catalysis) provides an attractive alternative to the conventional thermal catalytic route for the removal of low concentration of gas pollutants in high volume waste gas streams ². Catalyst is a key factor affecting the performance of a plasma-catalytic process ³. Cu-based catalysts have been investigated in thermal catalytic oxidation of VOCs due to its high catalytic activity and relative low cost. The addition of promoter CeO₂ could further improve the performance for VOC oxidation. However, the use of Cu-Ce catalysts in plasma-catalytic gas cleaning process for the oxidation of VOCs has not been studied before. The synergy resulting from the combination of cold plasma and Cu-Ce catalysts is still not clear. In this study, a coaxial dielectric barrier discharge (DBD) reactor has been developed for the plasma-catalytic oxidation of formaldehyde over Cu-Ce oxide catalysts. It is found that the process performance has been significantly enhanced when using binary oxide catalysts compared to pure CuO and CeO₂ catalysts. A maximum removal efficiency (94.7%) and CO₂ selectivity (97.3%) has been achieved when the Cu-Ce catalyst (CuO/CeO₂=1:1) is directly placed in the DBD reactor. The combination of Cu and Ce oxides results in larger specific surface area and pores, and smaller crystalline size, which favors the oxidation of formaldehyde. In addition, two redox cycles of Cu and Ce could facilitate the formation of active oxygen atoms and contribute to the plasma-catalytic oxidation reactions.