Study On Synthesis Process Of Limonene-1,2-epoxide Catalyzed By Heteropolytungstoborate Catalyst

Limonene-1,2-epoxide, the molecular formula was C10H16 O, with active response characteristics, which could obtain a series of important organic compounds through ring-opening reaction with various nucleophilic reagents. It was a rare chiral material and important pharmaceutical intermediates.Recently, limonene-1,2-epoxide was syntheticed by limonene as raw material under the condition with solvents that the yield was not high and the purity was low. Thus, aim to green chemistry, the article chose heteropolytungstoborate with high catalytic activity as catalyst without solvents. The optimal conditions for preparation of heteropolytungstoborate were investigated by orthogonal array design and heteropolytungstoborate were charaterized in a variety of ways.Then, it was applied to limonene epoxidation reaction, through the orthogonal array design to explore the optimum conditions of synthesis of limonene-1,2-epoxide. Also, the reaction products were separated through the high speed counter-current chromatograghy in order to obtain high purity of limonene-1,2-epoxide. The main conclusions of the study were as follows:(1) The conditions for preparation of heteropolytungstoborate were determined.According to single factor experiment and orthogonal array design, the optimum preparation conditions of heteropolytungstoborate were obtained, with which the yield of limonene-1,2-epoxide as reference indexes. Results showed that when the molar ratio of dilute sulphuric acid and sodium tungstate at 1.5:1, the molar ratio of sodium tungstate and boric acid at 3:1, the molar ratio of CTMA and sodium tungstate at 1:3, synthesis temperature 80 ℃ and synthesis time 1 h, the yield of limonene-1,2-epoxide reached up to 4.35%.(2) The formula and structure of heteropolytungstoborate were determined.According to the infrared spectra(IR), X-ray powder diffraction(XRD) analysis,themogracimetric analysis(TG) and specific surface area analysis(BET), it determined that the prepared catalyst in this paper was heteropolytungstoborate which kept the kegginstructure with certain crystalline phase and high catalytic activity, and the molecular formula was C19H44W3BNO18.(3) The effect of inorganic salts as co-catalyst was explored.Results showed that inorganic salts as co-catalyst could alternate dichloroethane and other toxic solvents using in limonene epoxidation reaction, which had an effect on easing the hydrolysis and improving the yield.The sodium chloride was the best choice and the amount was 0.15 g.(4) The conditions for reaction technology of limonene epoxidation were determined. According to single factor experiment and orthogonal array design, the optimum reaction conditions of limonene epoxidation were obtained, with which the yield of limonene-1,2-epoxide as reference indexes. Results showed that when the reaction temperature 40 ℃, the the mass ratio of catalyst and hydrogen peroxide solution at 0.07:1, the molar ratio of hydrogen peroxide and limonene at 2:1 and the reaction time18 h, the yield of limonene-1,2-epoxide reached up to the best which was 6.82%. Using heteropolytungstoborate as catalyst effectively shortened the reaction time of limonene epoxidation, reduced the reaction temperature and improved the reaction efficiency.(5) The two-phase solvent system of high speed counter-current chromatography for separating limonene epoxidation products was determined. According to suitable K value and alpha value, it screened aqueous two-phase solvent system n-hexane-ethyl acetate-methanol-water(6:1:6:1) and non aqueous two-phase solvent system ligarine-acetonitrile-acetone(5:4:1) for separating limonene epoxidation products.Using ligarine-acetonitrile-acetone(5:4:1) solvent system, the purity of limonene-1,2-epoxide was 78.3%. Using n-hexane-ethyl acetate-methanol-water(6:1:6:1) solvent system, the purity of limonene was 95.5%. High speed counter-current chromatography was an effective way to separate and pure limonene epoxidation products.