Synthesis And Application Of Rhenium(Molybdenum,Tungsten)-Containing Functional Catalysis Compounds

As a kind of rare and scattered metal, rhenium has vast applications in chemical industry and catalysis fields. On the basis of our previous work, we will continuously explore new green catalysis system of rhenium-based compound. Five novel types of rhenium-based compounds were synthesized from rhenium powder on standard Schlenk operation condition:pyridinium perrhenate(C5H6NReO4), N-methylimidazolium perrhenate(C4H7N2ReO4), morpholinium perrhenate(C4H10NORe04), quinolinium perrhenate(C9H8NReO4), piperidinium perrhenate (C5H12NReO4). In addition, the five compounds were characterized by IR,1HNMR, Raman spectrum and ESI-MS, and then measured their four crystal structure.Five Re-based compounds mentioned above were taken as catalyst in the epoxidation of cyclooctene. The effects of the quantities of the catalyst, oxidant, solvent, as well as reaction time and temperature of the reaction were investigated, which confirmed the optimum reaction conditions of the five catalyst system. Using this catalytic system, the oxidation reactions proceed on mild conditions with fast reaction rate, moreover, the experimental procedure was quite simple and exhibited high yields and high selectivities. Through the spectroscopic and Density Functional Thcory(DFT) studies of cyclooctene epoxidation reaction mechanism catalyzed by Re-based compounds, the prevailing activated species was identified. The Re-based catalysts can also be used in Baeyer-Villiger oxidation with excellent catalysis effects. We have confirmed the optimum reaction conditions of2-adamantane oxidation in the different five catalyst systems by mono-factor experiments, which showed high yields and high selectivities in the every catalysis system. Thus, the five Re-based catalysts were verigied as efficient and with wide application.On this basis of the perfect effects of Re-based compounds, we were looking forward a kind of catalyst to adapt the requirements of industrial production, which has similar catalyst effect and moderate price. As rare metals, molybdenum and tungsten have not only similar physical and chemical properties as rhenium, but also unique catalytic performance and price advantage. For further research, Three new Mo-W mixed-coordinated polyoxometalates (POMs) with different organic countercations were synthesized and characterized. They were3-(1-heptyl-3-methyl-imidazolium) heteropolyoxomolybdotungstates [Smim]3[PMoW3O24],3-(1-propyl-pyridinium) heteropolyoxomolybdotungstates [PPy]3[PMoW3O24] and3-(triethylbutylammonium) heteropolyoxomolybdotungstates [N2224[PMOW3O24]. The three types of POMs are used as catalyst respectively, together with UHP as oxidant and ionic liquid [Smim]PF6as solvent, in the epoxidation reaction of cyclooctene and cyclohexene. Effects of quantities of the catalyst, the oxidant, reaction time and temperature were studied, then the optimizing conditions of each catalytic system were confirmed with excellent results.The five types of rhenium-based catalysts in this paper showed higher activity and stability. The catalysts could be easily recovered by column chromatography and reused after reaction; the recycled catalyst could still be used with favourable effects. The catalytic system of Mo-W mixed-coordinated polyoxometalate in the epoxidation reaetion of olefin has many advantages, For example, high yields and selectivities, quite simple procedure, mild reaction conditions, cost-effective. Moreover, the catalytic system can be reused for5times without losing its catalytic activity. The efficient and environmentally benign catalytic system showed their potential application in industry.