Synthesis Of Trimethylolpropane Esters Of Oleic Acid Using Br(o|¨)nsted Acid Ionic Liquid As Catalysts And Lubricanting Performance Analysis

As a replacement for mineral based lubricant, biodegradable lubricant brings hope fordefusing critical crisis faced by the ecological environment. Traditionally, acid catalysts(phosphoric acid, sulfuric acid, p-toluenesulfonic acid) were used for the production ofbiolubricant. However, there are some disadvantages, such as equipment corrosion,side-reactions (dark color for the base oil) and the separation process is quite troublesome.Although heterogeneous catalysts can be recycled easily, they have other shortcomings such asdeactivation from coking, high costs and some of them still have the tendency to causesaponification. Br nsted ionic liquids (ILs) have been shown as promising catalysts foresterification owing to their negligible volatility, excellent thermal stability and the variety ofstructures available.A series of Keggin heteropolyacid (HPA) salts as catalysts were prepared and their catalysisperformance in the reaction were studied. Compared with heteropolyacid catalysts and otherKeggin heteropolyacid (HPA) salts, the pyridinium with PW12O403-as the anion ([PyBS]3PW12O40) showed the best catalytic performance. The results of orthogonal experiment showedthe primary and secondary factors in the esterification of trimethylolpropane and oleic acid forbiolubricant production: reaction time> catalyst dosage> temperature> molar ratio of reatants.Under the optimal reaction conditions (temperature:100℃, reaction time:3h, reactant molarratio:3.6:1, and catalyst amount, high conversion rate of trimethylolpropane (99.0%) andselectivity of trimethylolpropane triester (92.1%) were obtained. The ionic liquid was reused6times after the removal of water and no obvious change in catalytic activity was detected (thecatalyst lost in the recycling process was neglected). The effect of fatty acid with different alkylchain on the reaction was studied, and the results proved that the fatty acids with a long alkylchain demanded relatively longer reaction time. The effect of the presence of water in the[PyBS]3PW12O40catalyzed reaction system was studied.The probable mechanism for the esterification was deduced according to experiments. Itwas proved that the esterification between trimethylolpropane and oleic acid was a consecutivereaction, and the experimental results confirmed with second order reaction characteristic. It waspresumed that the reaction mechanism bared a resemblance to the protonic acid.The produced esters were refined through vaccum distillation, alkali lye and so on. The basisphysicochemical properties of rheological property, antioxidant stability, and thermal stabilityhave been investigated. The trimethylolpropane esters’ viscosity was49mm2/s at40℃,8.9mm2/sat100℃, viscosity index was165, solidifying point was lower than-27℃, the decomposition temperature was around300℃.