Effect of catalytic esterification on the friction and wear performance of bio-oil

The tribological response of bio-oil derived from Spirulina algae has been assessed, according to the choice of catalyst during esterification. The bio-oil was upgraded over the selected catalysts of KF/HZSM-5 and KF/Al2O3 with ethanol. Physical and chemical properties were assessed throughout with the crystal structure of the catalysts was characterized by X-ray diffraction (XRD), chemical groups and components of the bio-oil by Fourier Transform infrared spectroscopy (FTIR) and Gas Chromatograph-Mass Spectroscopy (GC-MS). Tribological experiments were conducted using a bespoke piston ring-on-cylinder liner tribometer. Worn surfaces were observed by Scanning Electron Microscope (SEM), and the elemental contents and valences were tested by X-ray Energy Dispersive Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). It is shown that choice of catalyst used during the upgrading of the bio-oil has a significant effect on tribological performance. Catalytic esterification improved friction resistance and the anti-wear properties of the bio-oil. KF/Al2O3 was a better catalyst for doing this than KF/HZSM, a result of the ester and organic groups present in the KF/Al2O3 upgraded bio-oil. These groups acted to form a protective tribo-film between surfaces.