The catalyst of environmental catalysis 英语论文.doc
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1、The catalyst of environmental catalysis Molecular chemisorption at manganese oxide/liquid interfaces has attracted increased interest due to its importance in the development of heterogeneous catalysts, microbial fuel cells and selective adsorption. Recently, inexpensive manganese oxide based cataly
2、sts instead of noble metal catalysts have been investigated in the catalytic wet oxidation (CWO) of phenolic wastewater. However, the adsorption of organic compounds on manganese oxide surfaces, which plays an important role in electron transfer and oxygen reduction, has not fully been explored. Phe
3、nol has attracted more attention in wastewater treatment because of its toxicity and wide occurrence in wastewater. Several conversion processes, currently under development for the production of synthetic fuel from coal, discharge substantial amounts of phenol (0.2-0.5g/L). Moreover, phenol is take
4、n as a model compound for the study of adsorption and oxidation because phenol is an intermediate product in the oxidation of higher-molecular-weight aromatic compounds and phenol also converts to a series of intermediates on oxidation.Cryptomelane-type manganese oxide is an octahedral molecular sie
5、ve (OMS) composed of 2x2 edge-shared Mn06 octahedral chains, which are corner shared to form onedimensional tunnels. Potassium ions and water are located in the tunnels (designated K-OMS-2). Mixed-valent manganese ions (Mn2+ and Mn3+) are situated in the octahedral sites of cryptomelane. Transition
6、metal ions can be incorporated into the framework or tunnel sites. Sizes and charges of M determine which sites are occupied. The synthetic counterpart of metal ion doped cryptomelane is known asoctahedral molecular sieve M-K-OMS-2 (M doped metalions). In recent years, some work has been published o
7、n the syntheses of cryptomelane-type manganese oxides and their applications in the oxidation of benzene, carbon monoxide, and other hydrocarbons. K-OMS-2 was found to possess excellent hydrophobicity and strong affinity for volatile organic compounds in the oxidation of benzene. Little has been rep
8、orted on doping effects on the adsorption of substrates or on catalytic properties.This research focuses on structure-property relationships for doped cryptomelane. These doped porous cryptomelane materials have high surface areas (40-100m2/g), more oxygen vacancies compared with undoped K-OMS-2, an
9、d more surface bonded OH groups. The substitution of framework Mn2+ with bivalent (Cu2+) and trivalent ions (Co3+) can create more oxygen vacancies to maintain an overall charge. Surface bonded OH groups on OMS-2 react with solute molecules and increase the adsorption of phenolic compounds. Solute m
10、olecules tend to attach to oxygen vacancies. Subsequently, electron and/or oxygen transfer between the metal oxide surfaces and solutes take place at these sites.Doped K-OMS-2 materials have dual roles in the removal of aqueous phenol, including adsorption and oxidation of phenol at moderate tempera
11、tures (298-423 K), pressures (80-150 psi), and pH (6-9). When phenol is adsorbed, phenol is oxidized to CO2 and H2O in the catalytic wet oxidation with oxygen. The advantages of this process over microbial activated sludge processes are that this process withstands high phenol loading rates and the
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