Synthesis Methods Of Amine/phenolic Antioxidants And Mechanism Of Their Thermal-oxidative In Ester Oil

With sequential improvement of requirements for high-temperature resistance,heavy load resistance,long-period performance of mechanical components in the fields of automobiles,aerospace,and large ships,to achieve high reliability and efficiency lubrication in harsh conditions,researchers have taken improvement the performance of synthetic lubricants as breakthrough target for lubricant within mechanical systems.Meanwhile,the development of anti-oxidation additives for synthetic lubricating oils and the research on the anti-oxidation properties of synthetic lubricating oils are of the key work,and are of great significance.Based on the National Basic Research Program of China“Anti-friction and Antioxidant Characteristics of Lubricant Additives and Its Effect on the Performance of Synthetic Lubricants”,this paper take trimethylolpropane oleate?TMPTO?as synthesize ester base oils,synthesizing amine and phenolic antioxidant additives,studying the influence of additives on physical chemical properties and thermal-oxidation performance of synthetic ester base oils,hope to provide experimental data and basic theory for the development of high performance synthetic lubricants and their antioxidant additives.In this paper,a novel method of alkyl diphenylamine antioxidants by using ionic liquid as catalystandanone-stepsynthesismethodof3,5-bis?1,1-dimethylethyl?-4-hydroxybenzenepropanoic acid octadecyl ester are proposed respectively.The study have examined effects of additives on the main physical chemical properties,functional group structure and tribological properties of TMPTO through different thermal oxidation conditions.The results show that amine-phenol combine antioxidant have a slightly better inhibitory effect on TMPTO viscosity growth and Butyl-octyl-diphenylamine couldgetbestsuppressionoftotalacidvalueat135?for480h,meanwhile,Butyl-octyl-diphenylamine could have obvious advantage on viscosity inhibiting and amine-phenol combine antioxidant have a slightly better suppression of total acid on TMPTO under thermal oxidation at 200?for 96 h.The FT-IR and Raman spectroscopy characterizations show that the addition of antioxidants could protect basic structure of TMPTO in the early stage of thermal oxidation,and the-CH₂ on the carbon chain is gradually consumed.Under the action of butyl octyldiphenylamine,the dehydrogenation of TMPTO easily occurs alkenyl hydrogen=C-H bond in the unsaturated C=C.When3,5-bis?1,1-dimethylethyl?-4-hydroxybenzenepropanoic acid octadecyl ester protect TMPTO,the unsaturated C=C bond in the base oil molecule should easily break down to transition.Tribological testing show that the developed antioxidants have a relatively small effect the friction coefficient and wear scar diameter on ester oil TMPTO under thermal oxidation conditions.Based on the principles of typical thermal analysis?TG,DTA and DSC?reaction kinetics activation energy calculation equations,theoretical method for evaluating thermal oxidation performance of lubricating oils was established.The TG and DTA analysis methods focus on accelerating thermal oxidation and causing quality loss,of which the calculation results show that 3,5-bis?1,1-dimethylethyl?-4-hydroxybenzenepropanoic acid octadecyl ester has the best thermal oxidation resistance and thermal decomposition ability in TMPTO.The DSC analysis method could accurately reflect the heat exchange of thermal oxidation reaction.The calculation shows that the amine-phenol combine antioxidant have the best thermal oxidation resistance..What`s more,the initial oxidation temperature and reaction activation energy of lubricating oils are measured by PDSC analysis.It is shown that initial oxidation temperature of the amine-phenolic combine antioxidant is 226°C and the initial oxidation reaction energy is 140.545 KJ/mol,which is higher than the other two antioxidants.The verification results are consistent with the conclusions from DSC.The thermal oxidation process of antioxidants acting on TMPTO base oils have been simulated to Molecular dynamics method,combining with properties test results of antioxidants in lubricating oils,the thermal oxidation reaction mechanism of base oil TMPTO and antioxidants are summarized.The main changes in the characteristics of the base oil TMPTO molecules:intramolecular decomposition occurs to produce oleic acid and ethane cyclopropane methyl oleate firstly.Ethylcyclopropane methyl oleate is oxidized by heat to form ethane alkyl cyclopropane methyl peroxide or ethane alkyl cyclopropane methyl hydroperoxide,furthermore is oxidized to hexanol.The oleic acid radicals are easily thermally decomposed to form 17-alkenyl radicals,which transform into the 17-oxide transition state of peroxides.The effect of butyl octyl diphenylamine is characterized by the fact that dehydrogenation of the secondary amine at 1273 K mainly,and forms butyl octyl diphenylamine resonator at 1473 K.That is advantage to TMPTO slowed down the deep oxidation and decomposition,meanwhile,mainly forming more long carbon chain diene free radicals or polyalkylene hydroperoxides.During thermal oxidation of TMPTO,3,5-bis?1,1-dimethylethyl?-4-hydroxybenzenepropanoicacidoctadecylestereasily decomposes into 18-hydrogen peroxide and 2,6-di-tert-butyl 4-propionylphenol group,which could been converted into 2-tert-butyl-4-peroxyethyl-6-hydroperoxy tert-butylphenol after1273K,150ps;It also could be converted into 2,6-di-tert-butyl-4-hydroperoxyethyl-phenol resonator at 1473K,which eventually decomposes into the stable substance2,6-di-tert-butyl-4-ethylphenol.While 18 alcohol should be dehydrogenated to 18-ene.It could slow down the deep decomposition and oxidation of the base oil molecules.The main feature is that TMPTO tend to form more short carbon alkenyl,alkenyl hydroperoxide or other oxides.The combination of amine and phenol antioxidants exhibited synergistic effects,delaying the increase of molecular products in the base oil molecular system and the progress of chain growth reactions.