| Ester synthetic oil is a kind of lubricating oil base oil with excellent application performance and environmental protection performance,which has become the main component of high-end environmental friendly lubricating oil at present,and has been widely used in various fields.In this paper,a kind of high viscosity polyol ester was synthesized from neopentyl polyol,adipic acid and mono-fatty acid.Firstly,the stannous oxide was selected as the catalyst for the esterification reaction in this paper through literature review and experimental investigation,this kind of catalyst has the advantages of easy separation from reacting mixture,recyclability and high catalytic activity,and could make the esterification reaction reach a high conversion of hydroxyl.Secondly,the trimethylolpropane and pentaerythritol esters were synthesized by using stannous oxide as catalyst.In the synthesis experiments of trimethylolpropane ester,the proper feed style and molar ratio of raw material were determined by orthogonal tests,that is,the first step was to add all trimethylolpropane and hexanedioic acid according to the molar ratio of 1.7:1,and then add the corresponding amount of catalyst and react 1 hour.In the second step,n-heptanoic acid and iso-octanoic acid were added according to the molar ratio of 7:3,and the corresponding amount of catalyst was added to react 4 hours.Then the proper reacting conditions of trimethylolpropane ester were determined by the single factor experiments and orthogonal experiments.The experimental results illustrated that the suitable reacting conditions were 1.5 wt.%dosage of catalyst,2.15 m L·min-1·g-1 flux?The flow rate of nitrogen per gram of reacting mixture,the same below?of N2,170?reaction temperature,2 hours for the first step reaction,7 hours for the second step reaction.Under above conditions,the kinematic viscosity of the final synthesed trimethylolpropane ester at 40?and 100?was 198 mm2·s-1 and 23 mm2·s-1respectively,and its viscosity index was 136,the hydroxy conversion of esterification reaction could be more than 95%.For the synthesis experiments of pentaerythritol ester,the appropriate feed style and molar ratio of raw material were also determined by orthogonal tests,that is,all pentaerythritol and adipic acid were added at the molar ratio of 2.0:1,and n-heptanoic acid and iso-octanoic acid were added at the molar ratio of 7:3,and the corresponding amount of catalyst was added to react 5 hours.Then,based on the single factor experiments and orthogonal test results,the proper reaction conditions were determined for the synthesis of pentaerythritol ester,i.e.,the dosage of catalyst was 1.5 wt.%,the flux of N2 was 1.45 m L·min-1·g-1,the reaction temperature was 170?,the total reaction time was 7 hours.Under the suitable reacting conditions,the kinematic viscosity of synthesed pentaerythritol ester at 40?and 100?was about 165 mm2·s-1and 20 mm2·s-1 respectively,its viscosity index was close to 140,the hydroxy conversion of esterification reaction could be more than 97%.Finally,synthesed pentaerythritol ester was selected as the crude ester product to be deacidified and refined by the combination of N2 stripping and molecular distillation.After deacidification refining by N2 stripping and two-stage molecular distillation,the acid value of the crude ester product decreased from the initial 11.2mg KOH·g-1 to0.048mg KOH·g-1,and the deacidification rate could be up to 99.57%.The physicochemical properties of the ester product were measured after the deacidification refining.The analysis results demonstrated that the ester product which was synthesized and refined by this work could basically meet the performance requirements of high viscosity lubricant base oils,and could be used to blend high-end environment-friendly lubricating oil products. |
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