Preparation Of Glutaraldehyde From Cyclopentene Oxidation By Phase Transfer Catalysis Of Organic-Inorganic Polyoxometallates

Glutaraldehyde is an important fine chemical with important applications in various fields such as chemicals,medicine and health.Hydrogen peroxide as an oxidant is a cheap and easily available clean energy source,and the preparation of glutaraldehyde from cyclopentene by one-step oxidation with hydrogen peroxide is simple,mild,clean and pollution-free,and has high industrial application value.The current domestic and international studies on cyclopentene oxidation are mainly divided into homogeneous and non-homogeneous systems.The catalysts for homogeneous systems are generally traditional heteropolyacid salts catalysts,which are difficult to be recovered after the reaction and have poor recyclability;the catalysts for non-homogeneous catalytic systems that have been widely studied are mainly loaded with active components such as tungsten sources into molecular sieves or metal skeletons to overcome the problem of difficult catalyst recovery in homogeneous systems.Although non-homogeneous catalysts have excellent performance in reusability,they still suffer from a series of problems such as loss of active components and slow reaction rate.In this thesis,a series of new systems for the preparation of glutaraldehyde from cyclopentene oxidation by phase transfer catalysis of organic-inorganic polymetallic oxides were created to achieve efficient recovery of catalysts while maintaining high catalytic activity.The specific research is as follows:（1）Preparation of glutaraldehyde from cyclopentene oxidation by phase transfer catalysis of molybdenum-containing polyoxometallates.Seven molybdenum-containing polyoxometallate catalysts were designed and synthesized for the preparation of glutaraldehyde by cyclopentene oxidation using N-n-hexyl pyridine,octyl pyridine,cetyl pyridine,1-methyl-3-butylimidazole and 1-methyl-3-octylimidazole as cations and octamolybdic acid or vanadomolybdic acid as anions,respectively.The catalytic activities of the catalysts were investigated under solvent-free,single-phase organic solvent,and organic/water two-phase solvent conditions,respectively.The catalyst[C₈H₁₇N₂C₃H₃（CH₃）]₅VMo₇O₂₆ with high catalytic activity was screened under solvent-free conditions,and only 26.1%glutaraldehyde yield was obtained under optimized conditions.The non-homogeneous catalytic oxidation of cyclopentene by[C₄H₉N₂C₃H₃（CH₃）]₅VMo₇O₂₆ in the 1,2-dichloroethane system for the preparation of glutaraldehyde was obtained in 43.2%yield of glutaraldehyde under optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:50:80,T=40°C,t=8 h）with complete catalyst recovery.It was found that[C₄H₉N₂C₃H₃（CH₃）]₅VMo₇O₂₆ has a phase transfer catalytic process in the two systems of ethyl acetate,and ethyl acetate/water（volume ratio 4:1）.The reaction in ethyl acetate gave 40.1%glutaraldehyde yield and the catalyst was recycled four times to maintain high catalytic activity.A glutaraldehyde yield of 55.1%was obtained in ethyl acetate/water two-phase solvent under optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:170:41.6,T=45°C,t=6 h）,and the catalyst maintained good catalytic activity after six cycles.（2）Keggin-type polyoxometallates for phase transfer-catalyzed oxidation of cyclopentene for the preparation of glutaraldehyde.Twenty-four catalysts were prepared using N-n-hexyl pyridine,octylpyridine,dodecylpyridine and 1-methyl-3-octylimidazole as cations,combined with Keggin-type silicotungstic acid,phosphotungstic acid,phosphomolybdic acid,silicomolybdic acid and doped polyoxometallate as anions,and used in the reaction of cyclopentene oxidation for the preparation of glutaraldehyde.Firstly,the solubility performance of the catalyst in various solvents was investigated.[C₆H₁₃NC₅H₅]₆PMo₉V₃O₄₀ exhibited good phase transfer catalytic performance in the two-phase system of tributyl phosphate/water（volume ratio 4:1）,and 50.9%glutaraldehyde yield was obtained under the optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:130:100,T=40°C,t=12 h）.The catalyst[C₈H₁₇N₂C₃H₃（CH₃）]₆PMo₉V₃O₄₀ achieved the phase transfer catalysis in the two-phase system of toluene/water（volume ratio 4:1）,and 59.4%glutaraldehyde yield was obtained under the optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:100:25,T=40°C,t=8 h）,and the catalyst maintained high catalytic activity after four cycles.（3）Dawson type polyoxometallates for phase transfer-catalyzed oxidation of cyclopentene for the preparation of glutaraldehyde.Eighteen catalysts were prepared using 1-methyl-3-octylimidazole,1-methyl-3-butylimidazole,1-methyl-3-dodecylimidazole and octylpyridine as cations,combined with Dawson type phosphotungstic acid,phosphomolybdic acid,silicotungstic acid,silicomolybdic acid and their doped polyoxometallate as anions.The solubility performance of various solvents on Dawson type polyoxometallate catalysts and the catalytic activity of the catalysts in different solvents were investigated.The catalyst[C₈H₁₇N₂C₃H₃（COOH）]₉P₂W₁₅V₃O₆₂ catalyzed the reaction in non-homogeneous chloroform system to obtain 49.3%glutaraldehyde yield with a catalyst recovery close to 100%.In the 1,2-dichloroethane system,[C₁₂H₂₅N₂C₃H₃（CH₃）]₁₀P₂W₁₄V₄O₆₂ could perform the homogeneous catalysis of cyclopentene,and 76.9%glutaraldehyde yield was obtained under the optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:200:100,T=40°C,t=4 h）,but the catalyst recovery efficiency was poor,and only 47%of the catalyst was recovered.It was found that the catalyst[C₈H₁₇N₂C₃H₃（CH₃）]₁₀P₂W₁₄V₄O₆₂could achieve good phase transfer catalytic performance in the two-phase system of tributyl phosphate/water（volume ratio 4:1）.Under the optimized conditions（n（Cat.）:n（H₂O₂）:n（CPE）=1:135:50,T=40°C,t=6 h）,the conversion of cyclopentene reached 92.1%and the yield of glutaraldehyde reached 72.6%,and the catalysts had excellent stability and reusability,and maintained high catalytic activity after five cycles.In this paper,we successfully created several new routes for the preparation of glutaraldehyde from cyclopentene oxidation by phase transfer catalysis of organic-inorganic polyoxometallates,and achieved efficient recovery of the catalyst while maintaining high catalytic activity.This paper provides a certain theoretical basis for the development of a new efficient and clean glutaraldehyde synthesis process,which is not only of theoretical importance,but also has potential application prospects.