Study On The Antioxidant Mechanism And Combustion Characteristics Of Jatropha Curcas Biodiese

In the context of"carbon peaking and carbon neutrality",biodiesel has received widespread attention due to its excellent environmental performance,fuel performance,and renewable raw materials.However,biodiesel is prone to oxidation and deterioration during storage and application,which limits its potential for application.Adding antioxidants as a highly efficient way to improve the oxidation stability of biodiesel can effectively address the issue of oxidative degradation of biodiesel.However,due to the unclear oxidation mechanism of biodiesel,the unclear antioxidant mechanism of antioxidants,and the unclear impact on combustion flames,the improvement of biodiesel oxidation stability and the application of antioxidants are restricted.Therefore,this thesis uses a combination of theoretical analysis,quantum computation,and experimental research to systematically study the oxidation/oxidation of biodiesel.A new type of ionic liquid antioxidant with dual functions of oxidation and corrosion inhibition was synthesized,and the effects of oxidation and antioxidant on the combustion characteristics of biodiesel were explored.In response to the unclear oxidation mechanism and reaction pathway of biodiesel in complex environments,the oxidation evolution mechanism of unsaturated fatty acid methyl esters in biodiesel under different conditions was systematically studied.Unsaturated fatty acid methyl esters in biodiesel undergo a chain reaction of highly active carbon radicals,peroxide radicals,hydroxyl radicals,and secondary oxidation products under thermal,light,and metal ion environments.The core steps of the initial oxidation process are H dissociation reaction,oxygen ³O₂activation reaction,and synergistic metal deprotonation reaction.As the oxidation chain reaction gradually deepens,biodiesel and its blended fuels will generate a large number of highly polar oxidation products with strong hydrophilicity such as alcohols,aldehydes,ketones,carboxylic acids,etc.,leading to the formation of oxidized insoluble substances in blended fuels.In response to the problem of large amounts and poor effects of traditional antioxidants in biodiesel,two new ionic liquid antioxidants with different cationic structures[Im0,2][C₆H₂（OH）₃COO]and[Mim Y2,11][C₆H₂（OH）₃COO]were synthesized.The new ionic liquid antioxidant has three phenolic hydroxyl functional groups,and the dissociation energies of phenolic hydroxyl H are 325.5 k J/mol,300.2 k J/mol,and 325.7 k J/mol.The conjugation effect of polyphenol hydroxyl groups enhances the ability of O-H to scavenge free radicals,releasing H,interrupting the lipid peroxidation chain reaction,thereby inhibiting the oxidation of biodiesel.The new antioxidant can form a stable metal ion chelate with Fe³⁺and form an adsorption film on the metal surface with a corrosion inhibition efficiency of 93.3%,improving the corrosion inhibition and lubrication performance of biodiesel on metals.In response to the issue of biodiesel being prone to catalytic oxidation with metal materials during the preparation,transportation,and storage processes,it is proposed for the first time to improve the oxidation stability of biodiesel by inhibiting the catalytic oxidation activity of transition metal ions through the cross complexation of phenolic（ionic liquid antioxidant）amine（TEPA）type antioxidants.The combination of[Im0,2][C₆H₂（OH）₃COO]and TEPA can form stable chelates with Fe³⁺and Cu²⁺metal ions,respectively,reducing the rates of C-H catalytic bond breaking and Fenton like reactions,while releasing H free radicals to interrupt the oxidation process chain reaction,effectively improving the oxidation stability of biodiesel metal container storage.In response to the unclear impact of biodiesel oxidation and the addition of antioxidants on combustion flame,the kinetic mechanism of biodiesel combustion reaction,the pyrolysis gas component overflow characteristics,OH group distribution,spectral characteristics,and pollutant emissions of biodiesel before and after oxidation and biodiesel with the addition of composite antioxidants were studied.After oxidation,the OH,CH,C2 free radical intensity and NOx emissions of biodiesel combustion flames increase,while CO emissions and soot particle size gradually decrease;There was no significant difference between the combustion flame of biodiesel with the addition of complex antioxidants and the blank group.The CO emission concentration of the combustion pollutants was 74.6%of the blank group,the NOx emission concentration was 84.7%of the blank group,and the soot particle size was86.34%of the blank group.This study revealed the key roles and main reaction mechanisms of heat,light,and metal ions in the oxidation process of biodiesel.Based on this,a new type of biodiesel specific antioxidant with dual functions of oxidation and corrosion inhibition was developed,revealing the mechanism of cross complexation of phenolic amine antioxidants to inhibit the catalytic oxidation activity of transition metal ions.And using this mechanism,the oxidation stability of biodiesel was significantly improved,the amount of antioxidants was reduced,and the effect of[Im0,2][C₆H₂（OH）₃COO]and TEPA composite antioxidants on the combustion flame of biodiesel was clarified.We have improved the theoretical system of biodiesel oxidation and antioxidant oxidation,providing theoretical and technical support for the large-scale application of biodiesel ionic liquid antioxidants.