AbstractThe upgrading of bio-oil in supercritical ethanol was investigated using furfural and acetic acid as model compounds with the aim of exploring the reaction pathways. The effects of catalysts, temperature, cold H2 pressure, and the presence of other compounds were studied. Based on products analysis, upgrading with Pt/HZSM-5 improved performance over Pd/HZSM-5 and Ru/HZSM-5. Moreover, the catalytic performance of Pt/HZSM-5 could be enhanced by adding Ni as a second metal. Complete conversion of acetic acid and 83.06% conversion of furfural were achieved at 320 °C and 1.0 MPa of cold H2 pressure. The presence of acetone was found to increase the conversion of furfural. Through gas chromatography–mass spectrometry (GC-MS) analysis, the reaction pathways of furfural and acetic acid were clarified. It was concluded that it is possible to combine different reactions including esterification, hydrogenation, ring opening, isomerization, aldol condensation, and acetalization in supercritical ethanol.