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Volatile organic compounds (VOCs) have relatively high vapor pressure and thus easily vaporize under ambient conditions. VOCs are known to cause air pollution and compared with various solutions, catalytic combustion has advantageous features for VOCs removal: (i) complete combustion of dilute fuel proceeds stably at low temperatures; (ii) extremely low emission of NOx and unburned fuels can be achieved. In general, supported precious metal catalysts exhibit high activity for low-temperature oxidation of VOCs. Among supported precious metal catalysts, platinum catalysts are known to be active for various catalytic reactions.
The aim of this study is to develop composite titanium dioxide CeO2–ZrO2–Bi2O3 catalyst with destruction efficiency for acetaldehyde at room temperature. Several CeO2–ZrO2–Bi2O3 catalysts were prepared, including by co-precipitation calcined at different temperature, blending with TiO2 and loading few amount of platinum by impregnated method. For the reaction test, methylene blue aqueous solution was used as organic pollutant for photocatalytic activity test and catalytic oxidation of acetaldehyde was examined.
The samples were characterized in detail. The XRD patterns showed high crystalline for both CeO2–ZrO2–Bi2O3 catalysts calcined at 550 and 800 oC, respectively. No platinum peaks were observed in 2wt%Pt/19.6wt% Ce68Bi17Zr15(550)+TiO2 which present that the particle size of Pt was too small to detect. The BET analysis showed that the surface area of Ce68Bi17Zr15(550) was about the same as that of Ce68Bi17Zr15(800), indicating the formation of well crystalline oxide compound. The TEM images indicate that the average particle size of Ce68Bi17Zr15(550) was smaller than that of Ce68Bi17Zr15(800) and the particle size of platinum was 2.69 - 3.52 nm which is in agreement with the results of XRD. From the result of HR-TEM, the crystalline lattice fringes of CeO2-ZrO2-Bi2O3 solid solution was observed both in Ce68Bi17Zr15(550) and Ce68Bi17Zr15(800) and could observe the Pt particle disperse well on the support.
For the photocatalytic activity test, methylene blue was decomposed by 20wt%Ce68Bi17Zr15(550)+TiO2, 20wt%Ce68Bi17Zr15(800)+TiO2 and 2wt%Pt/19.6wt% Ce68Bi17Zr15(550)+TiO2 under UVC illumination at room temperature respectively and the 20wt%Ce68Bi17Zr15(800)+TiO2 catalyst showed the highest photocatalytic activity. Compared the UV light illuminated direction, as the entire surface could be exposed under UVC light, it was observed that the rate constant of reactor illuminated by top was larger, indicating higher conversion of methylene blue. Illuminated under UVC light, Ce68Bi17Zr15(550) and Ce68Bi17Zr15(800) catalysts were observed that the removal of acetaldehyde increased and the Ce68Bi17Zr15(800) catalyst showed the higher activity than Ce68Bi17Zr15(550) catalyst with or without UVC light illumination. For 2wt%Pt/19.6wt% Ce68Bi17Zr15(550)+ TiO2 catalyst, it could improve the oxidation activity to remove acetaldehyde at room temperature compared with TiO2. Acetaldehyde could be remove under Ce-Zr-Bi catalysts at room temperature and we expect the catalyst could be extended to oxidize formaldehyde that has relatively strong reduction. | en_US |