Volatile organic compounds (VOCs) are the main air pollutants emitted from the combustion of fossil fuels in many industry processes and transportation activities. VOCs are associated with various health-related problems. Catalytic combustion was commonly used for the abatement of VOCs in the past decades. The involved catalysts are normally composed of noble metals such as Au, Pt and Rh. Noble metals generally exhibit good catalytic performance, but they are expensive and easy to be poisoning. In the past few decades, transition metal oxides (TMOs) have captured increasing attention due to their attractive performance as active catalysts for VOCs treatment. Moreover, TMOs own the advantages of facile synthesis, good thermo stability and low cost. To obtain catalysts with high activity and stability, it is necessary to develop new tailored synthesis strategy and explore the catalytic mechanism of functional TMOs.

Recently, laboratory of Circulating Fluidized Bed in the Institute of Engineering Thermophysics, Chinese Academy of Sciences, developed a new pulsed spray evaporation chemical vapor deposition (PSE-CVD) system combined with cold-wall stagnation point-flow CVD reactor for the synthesis of TMOs. As shown in Fig.1, liquid feedstock was delivered into the hot evaporation chamber by a PSE unit. Then, the resulting vapor was transported into the deposition chamber and the TMOs thin films were formed on different substrates. Finally, the waste vapor was collected by a liquid nitrogen trap. The as-deposited films were comprehensively characterized in terms of structure, morphology and composition by XRD, SEM and XPS, respectively. The catalytic performances of the TMOs films for VOCs conversion were investigated by a fixed bed quartz reactor, as displayed in Fig.2. The results indicate that the TMOs synthesized by the home-made PSE-CVD system leads the complete oxidation of VOCs towards low temperature dramatically relative to the non-coated mesh. The reproduced results also demonstrate that the prepared TMOs have good reusability. Up to now, a series of excellent TMOs (Fe₂O₃, Co₃O₄, Cu₂O, Cr₂O₃, Mn₃O₄, CuO and binary oxides) were synthesized by PSE-CVD for the complete oxidation of aliphatic hydrocarbon, alcohols, aldehydes, ketones and aromatic hydrocarbons. This novel approach can guide a doorway to develop new functional catalysts for real applications.

This work was supported by the Recruitment Program of Global Youth Experts and the results have been published on Proceedings of the Combustion Institute, Faraday Discussions, Chemical Engineering Journal, RSC Advances, Physica Status Solidi C: Current Topics in Solid Physics and Physica Status Solidi A: Applications and Materials Science.

Fig. 1 Schematic diagram of the PSE-CVD system.

Fig. 2 Experimental setup of catalytic test.