Fabrication And Catalytic Performance Of Nanoporous Catalysts And Photocatalysts

Due to the existence of synergistic effect and bifunctional mechanism, the composite metal catalysts usually exhibit a better catalytic performance than the single-metal catalysts, such as the selectivity, activity and stability for the reactions. In the past several years, the porous metallic materials have been developed rapidly, especially the materials with several kinds of metals, as they are a category of novel engineering materials with the dual properties both in function and structure.In this thesis, the researches mainly focus on the preparation, characterization and catalytic oxidation of alcohols (mainly benzyl alcohol and D-glucose) of the nano-porous catalysts (including Raney-Cu, Au/Raney-Cu, Au@Raney-Cu, Pt/NPG, Pd/NPG, Cu/NPG, and so on). Besides, there is also the preparation of Bi-Ti-O based photocatalyst and its photocatalytic properties.The main information is as follows:First of all, the preparation of a series of Raney-Cu-based catalysts.First, we prepared two kinds of Raney-Cu based samples (Au/Raney-Cu and Au@Raney-Cu) through a spontaneous irreversible redox procedure. The structural and chemical properties of the samples were characterized using X-ray diffraction (XRD),scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).The catalytic activities of the catalysts were tested by gas-phase selective oxidation of benzyl alcohol to benzaldehyde using oxygen as the oxidants.From the results, it was found that in the sample Au/Raney-Cu, gold was in the form of Au0, while in the sample Au@Raney-Cu, gold was in the form of Auα+. If Au was in the form of the above cases, the catalytic activities to the oxidation of benzyl alcohol over these two samples could be 2～3 times higher than the Raney-Cu samples. However, before heat-treatment, gold in the sample Au/Raney-Cu was in the form of Auδ+(α<δ<3), and this sample performed a much lower catalytic activity. In addition, the catalytic activity could also be improved with the existence of Cu2O in the samples. Second, It was found that the self made sample (s-Raney-Cu) which was made by dealloying Cu-Al alloys was in the form of slender rod-like structure, and the rods possessed a hollow structure with a quite rough surface. However, the morphology of the purchased Raney-Cu was quite different, and it had a bi-continuous 2D nanoporous structure. While using these two kinds of catalysts for the gas-phase oxidation of benzyl alcohol, the catalytic activity over the s-Raney-Cu could be four times of the purchased one, but its selectivity towards benzaldehyde was much lower, because of the advanced oxidation to CO2, and the color of the products was also very dark.Second, two kinds of catalysts (Pt/NPG and Pd/NPG) were prepared by electrochemical oxido-reduction to deposite a small amount of Pt or Pd on the NPG surface, and the catalytic activities of the catalysts were tested by the aerobic oxidation of D-glucose to D-gluconic acid under mild conditions. The results of the Pt/NPG indicated that a little amount of Pt could enhance the stability of NPG for the aerobic oxidation of D-glucose to D-gluconic acid. To some extent, Pt could make up the weaknesses of NPG, such as the relative poor stability and and easy to inactivation. Pt/NPG fit for the long-time-run aerobic oxidation of D-glucose to D-gluconic acid. However, the activity of Pd/NPG was lower for the aerobic oxidation of D-glucose than the NPG sample, so Pd was not helpful for the conversion of D-glucose to D-gluconic acid. Moreover, we prepared the nano-porous gold (NPG) samples by dealloying, and prepared the Cu/NPG samples by utilizing under potential deposition of Cu onto the NPG surfaces. The activity to the gas-phase selective oxidation of benzyl alcohol over the Cu/NPG sample was improved while comparing with the NPG sample; and the conversion of benzyl alcohol could be increased about 50%.Third, to make high-performance and cheap photocatalysts, which can be used in clean energy and environmental modification, is always the difficulty and hotspot of study. In this thesis, Bi-Ti-O based photocatalysts were made by dealloying Ti-Bi alloys (Ti:Bi=1:2) in nitric acid and subsequently heat treatment. By controlling the erosion time, the residue of bismuth in alloy was regulated. After being treated at different temperatures, the samples with special topography and crystal form were obtained, such as nanocrystals of 50nm (α-Bi2O3, TiO2/a-Bi2O3, TiO2) and 100 nm bismuth titanate (Bi12TiO20/Bi4Ti3O12). Furthermore, the photocatalytic activities of those materials were studied by the degradation of methyl orange under UV illumination, and TiO2/α-Bi2O3, TiO2 and bismuth titanate exhibited good photocatalytic activity.