Study on the Synthesis and Lubricating Properties of Trimethylolpropane Palmitoleate

Abstract

To replace mineral based lubricants and prepare vegetable oil-based lubricants with good stability, easy degradation and environmental friendliness, trimethylolpropane palmitoleate(TMPTO) was synthesized using natural product palmitoleic acid and trimethylolpropane as raw materials, and acidic cation resin Amberlyst as a heterogeneous catalyst. The effects of preparation conditions on the esterification rate of TMPTO were studied, and the optimal synthesis parameters were determined. The physical properties of TMPTO, including kinematic viscosity, viscosity index and flash point were tested. The structure and thermal oxidative stability of TMPTO were characterized using nuclear magnetic resonance(NMR), fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC) and thermogravimetric analysis(TG). The anti-wear performance, wettability and anti-aluminum corrosion properties of TMPTO were evaluated using a four-ball testing machine, contact angle goniometer and X-ray fluorescence spectrometer(XRF), respectively. Results showed that under the conditions of a reaction temperature of 180 ℃, a vacuum degree of 0.09 MPa, an alcohol-to-acid molar ratio of 1.0∶3.1, a reaction time of 5 h, and a catalyst amount of 0.2%(mass fraction), the esterification rate of palmitic acid reached 81.53%. After four uses of the catalyst, the esterification rate remained at 81.15%. The synthesized trimethylolpropane palmitoleate had an acid value of only 1.87 mg KOH/g, a high flash point(238 ℃), and exhibited excellent anti-aluminum corrosion performance, wettability, thermal oxidative stability and extreme pressure anti-wear properties: the maximum non-seizure load(PB) was ≤88 kg, and the maximum sintering load(PD) was ≤620 kg.

Keywords

• palmitoleic acid; trimethylolpropane palmitoleate; acid cationic resin; thermal oxidation stability; lubrication