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Catalytic oxidization of indoor formaldehyde at room temperature – Effect of operation conditions

Wang, Zhiqiang / Pei, Jingjing / Zhang, Jianshun

Abstract Catalytic oxidization has been studied for elimination of formaldehyde, which is a common and toxic indoor pollutant. However, most of previous studies were conducted at temperature and concentration level much higher than typical room condition. The current paper is to determine the effectiveness of catalytic oxidization of formaldehyde at room condition. The performance of one noble metal catalyst (Pd/γ-Al2O3) and two transition metal oxide catalysts (Fe2O3–MnO2 and CuO–MnO2) were studied at room temperature (23–25 °C). The effect of concentration (0.5–5 ppm), relative humidity (20–80%) and air velocity (0.2–1.0 m/s) were studied with single-pass breakthrough method. The major conclusions are: (1) Under room temperature and much lower concentration levels than in previous studies, the noble metal catalyst also demonstrated significantly better removal performance than metal oxide, maintaining a constant efficiency with time; (2) For different concentration levels, the efficiency of Pd/γ-Al2O3 did not change significantly at concentrations below 5 ppm, while the efficiency increased as concentration decreased for Fe2O3–MnO2; (3) the effect of relative humidity on the catalysts performance was not consistent for different type of catalysts; (4) Regarding the mass transfer mechanism, the importance of external mass transfer process was revealed by tests at different velocity for surface coated catalyst and dimensionless analysis, while both internal diffusion and external mass transfer are influential for homogeneously formed catalyst pellet. (5) The effect of multi-pollutants existence was also investigated, and it was found that the presence of other VOCs slightly decrease the performance of Pd/γ-Al2O3, but not Fe2O3–MnO2.

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Highlights • Noble metal and metal oxide catalyst are compared for indoor formaldehyde removal. • Single pass efficiency is higher at lower concentration for Fe2O3–MnO2. • Effect of relative humidity is dependent on catalyst property. • The process is internal diffusion limited; external mass transfer is vital for surface-coat media. • Metal oxide has great potential for formaldehyde control considering catalyst cost.