Studies On Preparation Of P-methoxybezaldehydes By Direct Electro-oxidation And Its Antioxidant Properties

P-methoxybezaldehyde（p-MBA）is widely applied in spices,medicines,cosmetics and food additives because of its special properties and aroma.Consequently,the environment-friendly and efficient technique for the preparation of p-MBA has always been a hot research topic on the preparation of food essences and fragrances.Currently,electrochemical synthesis technology has attracted more and more attentions to the preparation of p-MBA,which is of great theoretical and practical significance.In this dissertation,three nano-composite materials,such as MnO₂/CNTs,GR/CNTs and MnO₂/GR/CNTs,were synthesized with carbon nanotubes（CNTs）,graphene（GR）and MnO₂ and their composition,microstructure and morphology were determined by using FT-IR,SEM,EDS,TEM,XRD and XPS characterization methods.The results showed that CNTs and GR have formed a three-dimensional network structure by interlaced growth pattern,and the lamellar MnO₂ with a diameter of14 nm loaded on it,which resulted in the formation of a good structural composite.Furthermore,the electrochemical properties of three composite materials were investigated by cyclic voltammetry.It was found that MnO₂/CNTs/GR nano materials had the advantages of high stability and catalytic activity and could be used as excellent electrode materials and catalysts.In this study,the H type of electrolytic cell was designed,which comprises MnO₂/CNTs/GR nano-composite electrode（anode）,Pt electrode（cathode）and H₂SO₄/C₃H₆O（electrolyte）.Furthermore,p-MBA has been successfully synthesized by direct electro-oxidation,using p-methoxytoluene（p-MT）as raw material.Besides,based on single-factor experiment to investigate the influences of electrolytic conditions such as p-MT concentration,acid concentration,co-electrolyte concentration,electrolytic voltage and acetone volume on anode current efficiency,the optimal electrolytic parameters were determined through response surface method,that is,when p-MT concentration is 0.05 mol/L,H₂SO₄concentration is 1.5 mol/L,electrolyte concentration is 0.015 mol/L,acetone volume is 31%,electrolytic time is 1 h and electrolytic voltage is 1.70 V,and the current efficiency could reach 87.57%.Moreover,the composition and structure of p-MBA were determined through HPLC and FT-IR,and its antioxidant properties were evaluated through measuring its DPPH and ABTS removal abilities.Results suggested that the p-MBA,prepared by direct electro-oxidation,has high selectivity,conversion rate,current efficiency and great vitro antioxidant capacity,which shows high value in food applications.In conclusion,the technique for preparing p-MBA by direct electro-oxidation possesses some advantages of environmental protection,high efficiency,low energy consumption and energy conservation,which is expected to be widely used in practical production.In the research,the exploration of electrochemical process and evaluation of products performance establish a theoretical basis for the large-scale production in the future.