Study on Heterogeneous Catalytic Aqueous Nitrate over Cu-Pd/Titanate Nanotubes
Date Issued
2009
Date
2009
Author(s)
Chen, Hsiu-Yu
Abstract
Nitrate contamination is widespread due to over-fertilization in agriculture. Once taken into the body, nitrates are converted into nitrites, which can interfere with the oxygen-carrying capacity of the blood. This study examined the removal of aqueous nitrates (NO3-) by catalytic hydrogenation over microwave-induced titanate nanotubes supported bimetallic Pd-Cu catalysts (Pd-Cu/TNTs), and used Pd-Cu/TiO2 to be the contrast.ecause acid-treating step are the key factor affecting the physical property of TNTs, three different acid reagents were used to treat TNTs, and the effect of loading amount of bimetallic metals was also studied. In terms of the selectivity to N2 and the degradation kinetic of nitrate, the optimum loading amount located at 20% w.t., and HCl was the best reagent to assist in TNT synthesis.ith an intention to explore the sustainability of Pd-Cu/TNTs, a multi-spiking test was also carried out and the selectivity to N2 decreased only at the 6th cycle. But for Cu-Pd/TiO2, the selectivity to N2 yield decreased with each cycle. Based on the Cu 2p and Pd 3d spectra analyzed by Electron Spectroscopy for Chemical Analysis (ESCA), a relatively more shift to higher binding energy was observed in the case of Cu-Pd/TiO2. And TNTs were the electron donor so that a trivial shift to higher binding energy was observed after reactions. That means almost no oxidation process occurred for bimetals supported TNTs after reaction. In other words, TNTs can be considered as a sacrifice material to prevent the supported bimetallic catalysts from being oxidized.atalyst can be deactivated due to the oxidant in the air, but only partial metals on the TNTs’ surface were oxidized. This result is probably owing to its tube shape so that metals inside TNTs could not contact with air. In the contrary, metals of Pd-Cu/TiO2 were oxidized more. Therefore, TNTs can prevent metals from oxidation in the air.lthough Pd-based catalysts provide efficient reduction, it requires successful approaches for catalyst regeneration in terms of fouling by constituents in nature water. Therefore, this study also focused on the effect of sulfide-fouled catalysts and found applicable regeneration process. Catalysts were severely deactivated after sulfide poisoning. Nevertheless, Pd-Cu/TNTs were deactivated slighter than Pd-Cu/TiO2. Sulfide-fouled catalysts were studied with oxidative and reductive regenerative conditions. However, only heated air along with sodium borohydride provided efficient recovery of nitrate degradation. On the contrary, Pd-Cu/TNTs were deactivated more after oxidative regeneration.
Subjects
nitrate
titanate nanotubes
sulfide fouling
regeneration
Electron Spectroscopy for Chemical Analysis
Type
thesis
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