| Heteropolyacid has a unique structure and property.If the heteropolyacid is used as a catalyst,its anion-cation structure can be adjusted as needed.Thus it is widely used to catalyze the redox,alkylation,photocatalytic and hydrodesulfurization reaction,also it gets a good catalytic effect.In the reaction system of using heteropolyacid catalyst for catalyzing redox reaction,the commonly used catalyst include phosphorus molybdenum,phosphotungstic and PTMA acid;the common oxidant include hydrogen peroxide,carbamide peroxide and cheap oxygen;the heteropoly acid that contains phosphorus,tungsten,molybdenum is the research focus of catalysis area.The three kinds of PTMA heteropoly acid that contain[Smim]3[PMoW3O24]?[PPy]3[PMoW3O24]and[N2224]3[PMoW3O24]are compounded,and 1-methyl-3-heptyl imidazole,N-n-propyl-pyridine and N,N,N,N-triethyl ammonium are the main cation elements;they are characterized by IR,NMR and mass spectrum,which showing the synthesis of the pure target catalyst.While using three kinds of catalysts,the cyclooctene and cyclohexene are respectively used as substrate;carbamide peroxide(UHP)as oxidant in the olefin oxidation experiment,which achieve a desirable effect.The reaction result of epoxide alkane yield are influenced by different reaction system temperature,reaction time,the amount of catalyst,oxidizing agent and solvent,which are respectively studied in the single factor experiment,resulting in the optimum condition for the reaction.In addition,cyclooctene is used as substrate,and[Smim]3[PMoW3O24]heteropolyacid as catalyst in studying the recycling operation of this reaction system;as a result,it is founded that after reusing for five times,the catalyst still maintains a high activity and its reaction yield remain at more than 80%.If heterpoly acid[Smim]3[PMoW3O24]is used as catalyst,UHP as oxidant,and[Amim]PF6 ionic liquid as solvent,then the optimal reaction condition of catalyzing cyclooctene epoxidation will be as following:the reaction temperature is 65 degree centigrade,the amount of cyclooctene substrate is 1mmol,1.5mmol UHP oxidant,20mg catalyst and 0.6mL ionic liquid solvent[Amim]PF6;the reaction for reflux stir needs forty minutes,yield of epoxy cyclooctane is 99.50%.The optimal reaction condition of catalyzing cyclohexene epoxidation are as following:the amount of cyclothexene substrate is 1mmol,the reaction temperature is 55 degree centigrade;the amount of catalyst is 40mg,2.0 mmol UHP oxidant and 0.6mL ionic liquid solvent[Amim]PF6;reaction for reflux stir need three hours,yield of epoxy cyclohexane is 95.73%.If heteropoly acid[PPy]3[PMoW3O24]is used as catalyst,UHP as oxidant,and ionic liquid[Amim]PF6 as solvent,then the optimal reaction condition of catalyzing cyclooctene epoxidation will be as following:the reaction temperature is 70 degree centigrade,the amount of cyclooctene substrate is 1mmol,2.5mmol UHP oxidant,20mg catalyst and 0.6mL ionic liquid solvent[Amim]PF6;the reaction for reflux stir needs thirty minutes,yield of epoxy cyclooctane is 98.91%.The optimal reaction condition of catalyzing cyclohexene epoxidation are as following:the amount of cyclothexene substrate is lmmol,the reaction temperature is 55 degree centigrade;the amount of catalyst is 40mg,2.0 mmol UHP oxidant and 0.6mL ionic liquid solvent[Amim]PF6;reaction for reflux stir needs four hours,yield of epoxy cyclohexane is 95.15%.If heteropoly acid[N2224]3[PMoW3O24]is used as catalyst,UHP as oxidant,and ionic liquid[Amim]PF6 as solvent,then the optimal reaction condition of catalyzing cyclooctene epoxidation will be as following:the reaction temperature is 70 degree centigrade,the amount of cyclooctene substrate is 1mmol,1.5mmol UHP oxidant,20mg catalyst and 0.6mL ionic liquid solvent[Amim]PF6;the reaction for reflux stir needs thirty minutes,yield of epoxy cyclooctane is 98.31%.The optimal reaction condition of catalyzing cyclohexene epoxidation are as following:the amount of cyclothexene substrate is 1mmol,the reaction temperature is 55 degree centigrade;the amount of catalyst is 40mg,2.0 mmol UHP oxidant and 0.6 mL ionic liquid solvent[Amim]PF6;reaction for reflux stir needs four hours,yield of epoxy cyclohexane is 94.49%.In conclusion,if 1-methyl-3-heptyl imidazole,N-n-propyl-pyridine and N,N,N,N-triethyl ammonium are used as the main cation elements in the three kinds of PTMA heteropoly acid[Smim]3[PMoW3O24],[PPy]3[PMoW3O24]and[N2224]3[PMoW3O24],the epoxidation reaction for catalyzing cyclooctene and cyclohexene will work very well;the catalyst has a high activity in the reaction system;the yield of epoxide alkane is also very high;the selectivity of epoxidation product is better.Moreover,after the entire reaction system is reused for several times,the catalyst still maintains a high activity;loss of ionic liquid solvent is less,yield of epoxidation reaction remain at a high level.Therefore;the above elements are the ideal catalyst of epoxidation reaction. |
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