TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The bio-oil is oils or oily components obtained from thermal processing of biomass, from supercritical fluid treatment of biomass, from molten salt treatment of biomass, from ionic liquid treatment of biomass, pyrolysis oils, and/or fractions of bio-oils. The pyrolysis oil is subjected to treatment with an aqueous media to obtain a water-soluble fraction and water-insoluble fraction and the water-insoluble fraction is subjected to the oxidation. In the process at least one polar solvent (30) is used in the oxidation and after the oxidation the solvent is separated from the oxidation product and recycled to the oxidation. The water-soluble fraction is subjected to fractionation to give an organic phase and aqueous phase, and the organic phase is recycled to the condensation and the aqueous phase is recycled to the aqueous media. In the process a catalyst comprising a metal including groups 3-11 of the periodic table of elements is used in the oxidation. The oxidation is carried out at 20-200 degrees C, preferably 80-150 degrees C. The oxidation is carried out under a pressure from normal atmospheric pressure normal temperature and pressure to 40 bar. The oxidation is carried out under a pressure of 5-20 bar. The condensation is carried out at 300-450 degrees C. The condensation is carried out under a pressure of normal temperature and pressure to 20 bar. Preferred Components: The polar solvent is aqueous media and/or acetic acid. The oxidant is oxygen, ozone and hydrogen peroxide. The basic catalyst is silicates, aluminates, zeolites, alkalimetal hydroxides alkaline earth oxides, alkali metal oxides, rare earth oxides, preferably thorium dioxide, zirconium dioxide, zinc dioxide, titanium dioxide, alkali ion-exchanged zeolites, alkali ion-added zeolites, alkali metal ions on alumina, alkali metal ions on silica, alkali metals on alkaline earth oxides, alkali metals and alkali metal hydroxides on alumina, on hydrotalcite, on chrysotile, on sepiolite, potassium fluoride supported on alumina, lanthanide imide and nitride on zeolite. EXAMPLE - No suitable example given.