Study On Polyoxometalates Catalytic The Oxidation Reaction

Oxidation reaction is one of the important reactions in organic synthesis field. A wide range of applications is applied to oxidation products in every branch of the chemical industry. With the development of the green oxidation technology, research and development of environmental friendly catalyst oxidant especially is of vital significance.In this paper, oxidative degradation of aromatic compounds, selective oxidation of alcohols and the oxidation of pyrazine were studied in detail with polyoxometalates as catalysts. Specific research contents include the following aspects:Catalytic wet air oxidation (CWAO) process, enable to eliminate organic pollutants with non toxic by-product formation, was investigated in micellar system under room condition. Degradation of a series of aromatic compounds, including aromatic hydrocarbons, benzyl alcohol, benzaldehyde, benzoic acid, and some N-containing compounds was carried out based on molybdovanadophosphoric polyoxometalates [(Ci6H33)N(CH3)3]3+xPVxMo12-xO40(x=1,2,3) catalysts and surfactants. Outstanding results (60%-96%degradation efficiencies) were achieved for most of the tested substrates. And the POM micellar catalysts have an excellent stability and can be used as heterogeneous catalysts for about six times.A series of polyoxometalate (POM)-based metal-organic framework (MOF) was synthesized and used in selective oxidation of alcohols. The catalyst with uniform size and morphology offered easy accessibility between substrates and catalyst. At the same time, MOF ensured that POM was encapsulated, which could dramatically prevent the assembly of catalyst. With CTAB aqueous solution as solvent, both improved reaction efficiency and simple recycling of the catalytic system were achieved to afford a green oxidation process.A new catalytic system was applied to the oxidation reactions involved in the synthesis of LLM-105, in which protonated peroxotungstate were immobilized into the network of cross-linked chitosan with the superparamagnetic Fe3O4core (Fe3O4/CS/HWO) used as catalyst.With H2O2as oxidant, good to excellent yields could be achieved with pyrazine,2,6-dimethoxypyrazine,2,6-dichloropyrazine and2-chloro-6-methoxypyrazine as substrates without any addition of trifluoracetic acid, which provided a significant exploration towards novel and environmental synthetic route for LLM-105. A representative procedure for the oxidation process is as following:substrate (10mmol), CH3CN (30mL), Fe3O4/CS/HWO (0.1mmol, about0.1g), and30%H2O2(5mL) was added with5times equably at60℃ temperature. The oxidation process was monitored by TLC. Product could be obtained with yields of60-73%.Theoretical studies were also carried out with Gaussian03to evaluate the oxidation process. All of the calculated data matched well with our experimental results.