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Two imidazole carbene ligands immobilized palladium catalyzed aromatic halogenated hydrocarbons dehalogenation

Author: ZhangChunMin
Tutor: LiZiYan
School: Kunming University of Science and Technology
Course: Environmental Engineering
Keywords: imidazole carbine SBA-15 Pa catalyst catalytic dehalogenation aryl halides
CLC: TQ203.2
Type: Master's thesis
Year: 2010
Downloads: 31
Quote: 0
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Abstract


Organic halides pollutants in the environment are mainly come from industrial emission and pesticide uses in agriculture, and there organic halides caused area pollution. The main features of these pollutions are:①Most of them are persistent organic pollutants (POPs), which get into all spheres thought volatilization, rain cleaning, surface runoff, bioconcentration, bioamplification by all kinds of physical, chemical and biologic process. And there organic halides cause environmental pollution, ecological damages and damages to people;②Because of pollutions transfer and transfor, there are microcrystalline or trace in the environment. Especially for pesticide which caused area pollution. The concentration range of them in water is 0-100ng/L, and 0-2μg/g in sediment. But there also caused serious environment problems. So many degradation methods for organic halides were focus research in resent years, includes: phytoremediation, biological remediation, chemical remediation, and so on. This research use immobilized imidazole carbene ligand Pd catalyst to degrade organic halides, find out chemical remediation method and technology for polluted water in mild environment.The organic halides in this research are mainly aryl halides, and the dehalogenation chemical equation isAdvantages in this research are that catalytic dehlogenation reaction is in water, the condition is mild and hydrogen donor is water-solubility. So works were done as follows:(1) Two kinds of catalysts were synthesized which take imidazole carbene as ligand (immobilized different silica). These catalysts were characterized elemental analysis and FTIR. And taken loss study, the results showed that the metal Pd was immobilized in the silica though chemical bond. And the metal Pd in the catalyst was not easy loss though loss experiment.(2) Dehalogenation experiments of aryl halides were taken for the two catalysts, and controlled experiment was taken without catalyst. The results indicated that the catalysts synthesized have perfect catalytic activities. However, aryl halides do not remove the halogen without catalyst. By comparison experiment, the catalytic activity of catalyst immobilized nano-silica was higher than the catalyst immobilized silica, the time for dehalogenation could be shorten for more than 3 times. And groups and ring in the benzene ring effect dehalogenation.(3) Research was also taken for screening hydrogen donor of dehalogenation. Take formic acid, methanol, ethanol and hydrazine hydrate as hydrogen donor, the results of catalytic dehalogenation showed that hydrazine hydrate was the best hydrogen donor.(4) This paper investigated the reusable of the catalysts. And the results showed that the catalysts synthesized could reuse.(5) Finally, This paper investigated the mechanism of catalytic dehalogenation. A possible pathway for catalytic dehalogenations is a oxidative addition-reductive elimination process.

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