Electrochemical Oxidation Synthesis Of Aromatic Aldehyde Compounds In Different Ionic Liquids

Aromatic aldehydes are important organic chemical raw materials,which are widely used in pesticides,medicines,spices,food,electroplating and other fields.Traditional chemical synthesis of aromatic aldehydes needs complex process and produces a large amount of organic waste which causes huge pressure on the environment.In this thesis,the effects of different ionic liquids containing various cation and anion structures on synthesis of aromatic aldehydes through the direct electrochemical oxidation of aromatic compounds were studied.Firstly,potential windows,conductivities,and pH values of MIMBF4,EMIMBF4,PrMIMBF4,BPyBF4,BMIMBF4,BMIMHSO4,BMIMAc ionic liquids and their aqueous were studied.Ionic liquids which were suitable for electrochemical oxidation systems were selected by comparing the nature of ionic liquids with different anions and cations.The interactions between different solvents and p-methoxy toluene(p-MT)were investigated by ultraviolet spectroscopy.The red shift of absorption peak was obviously observed in ionic liquid solutions which indicated the strong interactions between the ionic liquids and p-MT.Secondly,the electro-oxidation behavious of p-MT were studied in ILs with different ions structure on platinum electrode by cyclic voltammetry(CV),chronoamperometry(CP)and potentiostatic electrolysis.The results showed that the electro-oxidation process of p-MT was irreversible and controlled by diffusion.The diffusion coefficient of p-MT were:MIMBF4>PrMIMBF4>BPyBF4>EMIMBF4>BMIMBF4>BMIMHSO4>BMIMAc.The highest yield and selectivity of methoxybenzaldehyde were reached to 88.6%and 92.9%respectively by potentiostatic electrolysis in PrMIMBF4 ionic liquid aqueous.Thirdly,Electrochemical reduction behavior of methoxybenzoic acid in ionic liquid aqueous was studied by CV.There was a reduction peak at-100 mv in the CV curve,but its diffusion coefficient was small and electrolytic conversion rate was low.Therefore it is unsuitable for the synthesis of benzaldehyde by electrochemical reduction of methoxybenzoic acid in this system.Lastly,the electrochemical behavior of aromatic compounds containing nitro group in ionic liquid aqueous solutions were researched by CV.Aromatic compounds with electron withdrawing group were difficult to be electro-oxidized and there was electro-oxidation peak in acid ionic liquids.