Preparation And Catalytic Performance On Formaldehyde Of Ag/MnO₂ Nanomaterials

Formaldehyde is one of the dominant indoor air pollutants, which severely affect human health, Complete catalytic oxidation is an efficient way for the elimination of formaldehyde. Supported noble metal catalysts are promising catalytic materials because it possess excellent catalytic activities of formaldehyde at room temperature. However, the high cost and limited supply of noble metals have been hampering widespread application. Among them, silver displays more suitable for the catalytic oxidation of formaldehyde due to its relatively low-cost and excellent catalytic performance in comparison with gold and platinum. Therefore, silver is a suitable active component for the complete catalytic oxidation of formaldehyde. Its well-known that the catalytic performance of silver nanoparticles(NPs) are highly depend on their surface structure, surface active sites, size and shape, which are rely on the preparation method, reaction conditions and supporter.In this thesis, on the basis of 3D-hollow hedgehog-like α-Mn O2 nanostructures as supports, Ag/ Mn O2 nano materials were fabricated through varying synthetic methods and reagent concentrations, which were characterized by scanning electron microscopy(SEM), transmission electron microscope(TEM), high-resolution TEM(HRTEM), inductively coupled plasma-atomic emission spectrometry(ICP-AES), Brunauer–Emmett–Teller(BET) surface area, X-ray diffraction spectrum(XRD) and hydrogen temperature programmed reduction(H2-TPR). Their catalytic activity of formaldehyde on the Ag/Mn O2 nano-catalysts were evaluated. The main results of this thesis are follows:1. Four nano-catalysts were synthesized by hydrazine reduction, sodium borohydride reduction, ultraviolet reduction and impregnation methods. Among them, the nano-catalysts fabricated by the hydrazine reduction method exhibited highest catalytic performance, the formaldehyde conversion of which was up to 100% at 110 ℃, this complete conversion temperature is much lower than that of pure Mn O2 supporter(230 ℃).2. A series of Ag/Mn O2 catalysts with different silver loading were synthesized by hydrazine reduction method through varying reagent and coating agent concentrations. The catalytic activity of Ag/Mn O2 nano-catalysts gradually increased and then decreased with the increase of the silver loading. The Ag/Mn O2 nano-catalyst showed the highest catalytic activity when its silver loading was up to 15 wt%, at 70 ℃,the formaldehyde conversion and specific reaction rate of which were 53% and 4.3 nmol/(m2·s). This specific reaction rate was 2.3 times higher than the previous supported silver catalysts.