Novel in situ tribo-catalysis for improved tribological properties of bio-oil model compound

A novel in situ tribocatalytic esterification reaction has been developed driven by frictional processes, to alleviate the corrosion wear induced by the high content of organic acid in bio-oil. Solid superacid (SO42−/γ-Al2O3) was formulated and prepared as the catalyst. Acetic acid was as the base for the bio-oil, and glycerol was used as a modifying agent. The tribological properties of the bio-oil with varying amounts of solid superacid were evaluated on a HDM-20 end-face tribometer. Scanning electron microscope and X-ray photoelectron spectroscopy were employed to measure the micro-morphologies and elemental contents on the worn surfaces after sliding. The effect of tribocatalysis on the composition of the bio-oil was analyzed by Fourier transform infrared spectrometer and Gas chromatography-Mass spectrometry. The results show that when lubricated by pure bio-oil the worn surfaces showed severe furrows and bulk exfoliation of the surface material. With the solid superacid added to the bio-oil, abrasive wear and material exfoliation were alleviated. The reason for the improved tribological properties is that the solid superacid not only could roll on the friction surface and act as lubricating particles, but also catalyzed esterification between acetic acid and glycerol, which simultaneously improved the tribological properties of bio-oil.