A liquid mixture comprising at least one readily volatile and at least one sparingly volatile component is separated in a film evaporator by a process in which (i) a continuous stream of a liquid starting material mixture is provided, (ii) a liquid film is produced from the continuous stream and is brought into contact with a heat exchange surface of the Mm evaporator, (ii) the liquid film is partly evaporated, a gas stream enriched with the at least one readily volatile component and a liquid stream enriched with the at least one sparingly volatile component being obtained, wherein (iv) the heat exchange surface is coated with a catalytically active material which (v) catalyzes, in the liquid film, a chemical reaction in which at least one readily volatile component is formed.