Preparation Of Chromium And Cobalt Oxide Films And Their Characteristic Of Catalytic Combustion

Volatile organic compounds (VOCs) are recognized as one of the major contributors to air pollution, which come from boiler combustion, automobile exhaust and garbage power generation. VOCs are harmful to humans and can lead to the increase of photo-chemical smog and PM 2.5. Catalytic combustion is widely seen as one of the most effective pollution treatment technologies for consuming less energy and creating no secondary pollution. The catalysts play a very important role in the catalytic oxidation system. It is very necessary and important to search a kind of catalysts with relatively high activity, themal stability, poison resistance and less expensive.For many traditional methods, production costs were very expensive and most of them required complex treatments. In addition, the purity of the acquired samples was usually difficult to ensure. So we designed the pulsed-spray evaporation chemical vapor deposition (PSE-CVD) experimental device, which owns the advantages of relatively low cost, tailored composition and easy control of the quality, thickness and morphology of the samples.Chromium oxide (Cr2O3) and cobalt oxide (CoO) thin films were controllably synthesized by PSE-CVD for deep oxidation of propene. The prepared samples were comprehensively characterized with respect to structure, morphology and surface composition with X-Ray powder diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. An in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was involved to reveal the surface mechanism occurred on Cr2O3 and CoO. The structural analysis indicated that a pure phase of Cr2O3 was obtained at 425 ℃. Smooth and evenly distributed spherical particles were observed. And to CoO, pure spinel was obtained when the temperature is 350 ℃. A homogeneous grain distribution was observed. With water addition into the feedstock, agglomeration was observed on the surface. Based on the DRIFTS observations, the Langmuir-Hinshelwood (L-H) mechanism was proposed for C3H6 over Cr2O3 and CoO films.The catalytic performance of the Cr2O3 and CoO grown on mesh of stainless of steel was investigated with respect to the complete oxidation of C3H6. The background effect of the stainless steel element on the experiments was tested by carrying out the oxidation of C3H6 on non-coated mesh under the same conditions. The results show clearly that Cr2O3 and CoO enable the oxidation of C3H6 at lower temperatures relative to the non-coated mesh; The catalyst prepared without water shows better activity than the one prepared with water. Compared to the T50 which refers to the temperature at 50% of C3H6 conversion, CoO shows much better catalytic properties than Cr2O3. Simultaneously T50 obtained with Cr2O3 is quite close to the values of the noble metal and pervoskite.