| Molybdenum is a kind of mineral resources which is non-renewable, the resources reserves of molybdenum is the second place in China of the world. With the development of the industrialization, the application of molybdenum expands unceasingly. The molybdenum catalysts are widely applied in industrial areas, such as oil hydrogenation desulfurization, catalytic reforming and the synthesis of acrylonitrile etc. At the same time, they have a widely application in chemical fields. Molybdenum catalyst is often used as catalyst for olefin epoxidation reaction, it is be widely attention for its non-toxic, low price, high catalytic activity and selectivity. The traditional catalyst of olefin epoxidation was loaded molybdenum compound, which often uses organic solvent, such as methylene chloride and ethyl ether, hydrogen peroxide, sodium hypochlorite and urea peroxide are usually used as the oxidant. Although had the system a good catalytic activity, the activity of the catalyst component was easily lost, and it was not conform to green chemistry in recent years because of the organic solvents flammable, volatile, easy to pollute the environment. This paper used ionic liquids which were synthesized by ourselves as reaction solvent, hydrogen peroxide as oxidant to establish a pollution-free reaction system.First, we synthesized a series of octamolybdates which is substituted by nitrogen Heterocyclic,including [Cnmor]4Mo8O26(n=5,8), [Cnquin]4Mo8O26(n=2,4,5,8), [Cnmim]4Mo8O26(n=2,5), these octamolybdates have been characterized through IR, NMR, elemental analysis, thermal analysis and so on, which indicated that the relatively pure octamolybdates have been synthesized. We got three crystals with the volatile solvent method, respectively was[C5mor]4Mo8O26, [C2mim]4Mo8O26, [C5mim]4Mo8O26, and characterization by X-ray single crystal diffraction.Complex of C40H88Mo8N4O30([C5mor]4Mo8O26):colorless, Triclinic, Space group P I, a= 11.361(2) A,b=11.621(2)A, c=13.513(3)A, Z=1,V=1510.2(5)A3, F(000)=932, R,= 0.0271, wR2= 0.0713.Complex of C24H44Mo8N8O26([C2mim]4Mo8O26):colorless, Orthorhombic, Space group Pbca, a=15.716(2)A,b=16.265(3)A,c=17.988(3)A,Z=4,V=4597.9(13)A3, F(000)=3152,R1= 0.0224, wR2= 0.0556.Complex of C36H68Mo8N8026([C5mim]4Mo8026):colorless,Monoclinic,Space group P2(1)/n,a=10.953(2)A,b=16.166(3)A,c=15.948(3)A,Z=2,V=2821.5(10)A3 F(000)=1768, R1= 0.0259, wR2= 0.0575.Second, at the condition of [C4quin]4Mo8O26 as catalysts, H2O2 as oxidant, ionic liquids [C8mim]BF4 as solvents, we used the single factor analysis to study the epoxidation of cyclooctene and we obtained the best reaction conditions. When the substrate was lmmol, oxidant was 2.5 mmol and solvent was 0.6 mL, catalyst 20 μmol, reaction 4 h at 70 ℃, the production rate yield of epoxy cyclooctane was 93.4 %. Under the best reaction conditions, the yield of cyclooctene epoxidation can reach 95.0% of using other octamolybdates as catalysts. We also test the cycling of catalyst under the optimal experimental conditions, the results showed that the series of catalysts still had high catalytic activity after being used five times. In the view of the energy conservation and environmental protection, this kind of catalyst is advantage catalyst.Third, on the basis of the optimum reaction conditions of cyclooctene, we used [Cnmor]4Mo8O26(n=5,8), [Cnquin]4Mo8O26(n=2,4,5,8), [Cnmim]4Mo8O26(n=2,5) as catalyst, UHP as oxidant, ionic liquids [C8mim]BF4 as solvent,we studied the epoxidation reaction of cyclohexene, cyclopentene, styrene and 1-hexene catalytic, the optimum reaction conditions are obtained. Cyclohexene:the substrate was 1 mmol, catalyst was 20 μmol, oxidant was 2.5 mmol and solvent was 0.6 mL, reaction time was 4 h at 50 ℃,, the epoxidation yield can reach 93.4%. Cyclopentene: the substrate was 1 mmol, catalyst was 20 μmol, oxidant was 2.5 mmol and solvent was 0.6 mL, reaction time was 4 h at 35 ℃, the epoxidation yield can reach 98.4%. Styrene:the substrate was 1 mmol, catalyst was 20 μmol, the amount of oxidant was 2.5 mmol and the amount of solvent was 0.6 mL, reaction time was 10 h at 50 ℃, the epoxidation yield was 48.2%.1-hexene:the substrate was 1 mmol. catalyst was 20μmol. the amount of oxidant was 2.5 mmol and the amout of solvent was 0.6 mL. reaction time was 18 h at 50 ℃, the epoxidation yield can reach 33.6%.In a word, we used a series of octamolybdates as catalyst which were substituted by nitrogen heterocyclic to study the epodition of cyclooctene, cyclohexene, cyclopentene and 1-hexene styrene. The advantages of the system are low reaction temperature, high catalytic activity, high selectivity, etc. In the system of cyclooctene epoxidation, it has the advantages of green environmental protection and a higher value of practical application. |
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