engleski

VOC oxidation over copper doped ceria nanocatalysts

Excessive emissions of volatile organic compounds (VOCs) into the environment, which mainly result from different industrial plants and motor vehicles, greatly affect the quality of the air and thus the quality of life. There are currently many technologies that keep the concentration of volatile organic compounds in the atmosphere below the allowed limits. The catalytic oxidation of volatile organic compounds has been intensively investigated since the 1970s with the aim of finding efficient catalysts and suitable reactors. Traditional noble metal catalysts, like Pt or Pd, although the most active for the oxidation of hydrocarbons, are expensive and extremely susceptible to poisoning, especially when employed at moderate working temperatures. Cerium(IV) oxide or ceria (CeO2) is a very good alternative due to its low cost, good mechanical properties, thermal stability, poisoning resistance, and, most importantly, high oxygen storage and release capacity stemming from the fast and facile reversible redox reaction between cerium(IV) and cerium(III) cations inside the ceria crystal lattice. Many studies have shown that it is not easy to predict the behaviour of a mixture based on the oxidation process of a single component, because the performance of the catalyst is influenced by several factors. Some authors state that during catalytic oxidation of a mixture of volatile organic compounds, the process may be inhibited, while others believe that certain molecules of volatile organic compounds may be activated if mixed with other molecules and may change the selectivity [1]. Therefore, in this work, pure and copper doped ceria (CuxCe1-xO2, x = 0, 0.1, 0.3 and 0.4) nanoparticles were prepared using the hydrothermal method, thermally treated at 500 °C for 2 hours and thoroughly characterized. The catalytic activity of powder catalysts was tested in the fixed bed reactor at various working conditions using single VOC compound, toluene, and VOC mixture BTEX (benzene, toluene, ethylbenzene, and o-xylene). Catalytic oxidation was carried out at atmospheric pressure, at different temperatures, with a constant total flow rate of the reaction mixture and constant inlet toluene (210 ppm), and BTEX (each compound ca 45 ppm) concentrations. Copper doped ceria shoved higher activity compared to pure ceria, as was expected. Characteristic temperature, T90, at which 90% VOC conversion was achieved indicates that generally higher temperatures were needed for single toluene oxidation than for individual compounds in BTEX mixture, except for benzene (on copper doped ceria catalysts) which showed to be the most difficult BTEX component to oxidize due to its known stable structure (Table 1.). This could indicate that toluene oxidation is greatly improved when BTEX mixture was oxidised rather than individual toluene compound.

VOC oxidation ; copper doped ceria nanocatalysts

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