Preparation Of Copper Catalysts By Dielectric Barrier Discharge Plasma Decomposition

Environmental problems and energy crisis become more serious with the development of industry. Developing highly efficient Cu-based catalysts for one-step synthesis of methyl formate from the syngas and CO catalytic oxidation is very important for properly using fossil resources, alleviating pollution, decreasing energy consumption and developing new fuels.In the present work, the air dielectric-barrier discharge (DBD), which is initiated and operated at atmospheric pressure, has been applied to decompose the Cu-Zn and Cu hydroxycarbonates. DBD is one of the cold plasmas and characterized by high electron energy and high electric field intensity. Radical and excimer can be formed in DBD easily. The experiments indicated that the Cu-Zn and Cu hydroxycarbonates can be decomposed into corresponding oxide by DBD. The morphology and particle size of the Cu and Cu-Zn oxides prepared by DBD are different from those prepared through the conventional calcination method. Compared to the CuO-ZnO catalyst prepared by the conventional calcination method, on the DBD-prepared catalyst, the size of the particle is smaller and the dispersion of the particle is higher. This may be resulted from the lower caloric effect in DBD. On the DBD-prepared CuO-ZnO catalyst, CuO stayed on the surface and was reduced to Cu2O more easily. Diffuse reflectance infrared Fourier transform analyses indicated that the DBD-prepared CuO-ZnO catalyst is more active to the formate hydrogenation step. The catalysts tests confirmed that more methoxy was formed on DBD-prepared CuO-ZnO.The structure of the DBD-prepared CuO is different from that of the CuO prepared using the calcination method. It was found that the DBD-prepared CuO is hexagonal thin film. After treating with NaHCO3 solution, the hexagonal thin film CuO can be turned into nanowire CuO. These results indicated that DBD could be a novel and promising technology for preparing materials with nano-structure. The DBD-prepared CuO with different nano-structures showed different activity to the catalytic oxidation of CO. On the nanowire CuO, CO can be oxidized into CO2 at 220℃. Moreover, the nanowire CuO exhibited higher stability.Electron bombardment resulted in the decomposition of the hydroxycarbonates in DBD. The strong electronic and magnetic fields in DBD could be the origin of the change in the morphology of the obtained oxides. The ozone formed during the discharge should benefit to improve the ability of the catalysts to adsorb oxygen. These may be the reasons for the more excellent performance of the DBD-prepared catalyst than the catalyst prepared via conventional calcination method.