ABSTRACT
In this study, ZnO-TiO2 binary oxide catalysts were successfully prepared by a solid-state dispersion. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller and photoluminescence techniques. It was observed that the interaction between ZnO and TiO2 affected the photocatalytic efficiency of binary oxide catalysts. 20 wt% ZnO-TiO2 photocatalyst exhibited much higher photocatalytic activity than pure TiO2, ZnO and P-25 in the degradation of 4-chlorophenol under low UV irradiation. The chemical interaction between ZnO and TiO2 in the form of the Zn-O-Ti- bond may affect the photoefficiency of binary oxide catalysts. The profound effect of binary oxide catalyst for 4-chlorophenol degradation was generally considered due to small particle size, lower band gap energy and the presence of more surface OH groups than that of the pure TiO2 and ZnO photocatalyst. It was concluded that in the case of 20 wt% ZnO-TiO2 catalyst, the main intermediates of degradation were phenol, 2-chlorophenol, hydroquinone and catechol, while with P-25 the main intermediates were ring-opening products, suggesting that different reaction mechanisms may have taken place depending on the nature of the catalyst.
Subject(s)
Chlorophenols/chemistry , Nanoparticles/chemistry , Titanium/chemistry , Water Pollutants, Chemical/chemistry , Zinc Oxide/chemistry , Catalysis , Microscopy, Electron, Transmission , Nanoparticles/radiation effects , Nanoparticles/ultrastructure , Particle Size , Photoelectron Spectroscopy , Photolysis , Spectroscopy, Fourier Transform Infrared , Titanium/radiation effects , Ultraviolet Rays , X-Ray Diffraction , Zinc Oxide/radiation effectsABSTRACT
The aim of this work was to study combustion of toluene (1000ppm) over MnO(2) modified with different supports. α-Al(2)O(3) and γ-Al(2)O(3) obtained from Boehmite, γ-Al(2)O(3) (commercial), SiO(2), TiO(2) and ZrO(2) were used as commercial support materials. In view of potential interest of this process, the influence of support material on the catalytic performance was discussed. The deposition of 9.5MnO(2) was performed by impregnation over support. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and oxidation (TPR/TPO) and thermogravimetric analysis (TGA). The catalytic tests were carried out at atmospheric pressure in a fixed-bed flow reactor. 9.5MnO(2)/α-Al(2)O(3)(B) (synthesized from Boehmite) catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of 289°C. Considering all the characterization and reaction data reported in this study, it was concluded that the manganese state and oxygen species played an important role in the catalytic activity.
Subject(s)
Manganese Compounds/chemistry , Oxides/chemistry , Toluene/chemistry , Catalysis , Microscopy, Electron, Scanning , Oxidation-Reduction , Photoelectron Spectroscopy , Thermogravimetry , X-Ray DiffractionABSTRACT
Catalytic hydrodechlorination of 2,4-dichlorophenol was studied over 0.97% Pd/C, 0.98% Rh/C and 0.8% Pd-0.19% Rh/C catalysts. The catalysts were prepared by incipient wetness impregnation of support and characterized by BET surface area, temperature programmed reduction (TPR) and X-ray diffraction (XRD). The 0.97% Pd/C catalyst, which had the largest crystallite size, was the most active and selective towards the formation of 2- and 4-chlorophenols among three catalysts in liquid phase. Hydrodechlorination activity of carbon-supported catalysts were in the order of Pd/C>Pd/Rh/C>Rh/C. The kinetic equation explained experimental data well and kinetic parameters of three catalysts were provided and discussed.
