The invention relates to a method of separating and purifying products from a high pressure processing system adapted for processing a feed stream comprising carbonaceous material at a pressure of at least 150 bar and a temperature of at least 300° C., where the converted feed stream (product mixture) is cooled to a temperature in the range 50 to 250° C., and depressurized to a pressure in the range 1 to 150 bar, the method comprising separating the depressurized product mixture in gas phase, an oil phase (liquid hydrocarbon), and a water phase comprising water soluble organics, dissolved salts and optionally suspended particles in a first phase separator and purifying the oil phase from the first phase separator by mixing it with one or more washing agents, at least one of which comprises water, and separating the oil phase from the one or more washing agents in a further separation step.