A process for the preparation of an aliphatic hydroxycarbonyl compound etherified with an aliphatic group, by catalytic oxidation of an etherified hydroxyalcohol in the presence of a metal catalyst, wherein an aliphatic hydroxyalcohol, etherified with an aliphatic group, is oxidized with an oxygen-containing gas, at from 450.degree. to 700.degree. C., in the presence of a catalyst arranged according to particle size in an upper or front region, middle region and a lower or rear region which have a total thickness of from 5 to 100 millimeters and comprise:
- (a) at least three layers of silver crystals of different particle size, with at least one of the layers of silver crystals constituting the lower or rear region of the catalyst from which the oxidized mixture is discharged containing particles of size from 1 to 2.5 mm and constituting from 30 to 85 percent by weight of the catalyst, at least one of the layers of silver crystals constituting the middle region of the catalyst containing particles of size from 0.75 to 1 mm and constituting from 2 to 30 percent by weight of the catalyst and at least one of the layers of silver crystals constituting the upper or front region of the catalyst facing the mixture to be oxidized containing particles of size from 0.2 to 0.75 mm and constituting from 8 to 50 percent by weight of the catalyst, and at least one layer of copper crystals arranged above or below one of said layers of silver crystals and containing particles of size from 0.2 to 0.75 mm and constituting from 1 to 40 percent by weight of the catalyst, or
- (b) at least three layers of silver crystals of different particle size, with at least one of the layers of silver crystals constituting the lower or rear region of the catalyst from which the oxidized mixture is discharged containing particles of size from 1 to 2.5 mm and constituting from 30 to 85 percent by weight of the catalyst, at least one of the layers of silver crystals constituting the middle region of the catalyst containing particles of size from 0.75 to 1 mm and constituting from 2 to 30 percent by weight of the catalyst and at least one of the layers of silver crystals constituting the upper or front region of the catalyst facing the mixture to be oxidized containing particles of size from 0.2 to 0.75 mm and constituting from 8 to 50 percent by weight of the catalyst, and at least one layer of copper crystals arranged above or below one of said layers of silver crystals containing particles of size from 0.2 to 0.75 mm and constituting from 0.5 to 40 percent by weight of the catalyst, and at least one layer of catalyst particles comprising from 70 to 99 percent by weight of copper, from 0.9 to 20 percent by weight of tin and from 0.1 to 10 percent by weight of phosphorus, based on the total weight of these elements in these particles, with these layers of catalyst particles containing particles of size from 0.2 to 0.75 mm and constituting from 0.5 to 10 percent by weight of the catalyst, or
- (c) at least three layers of silver crystals of different particle size, with at least one of the layers of silver crystals constituting the lower or rear region of the catalyst from which the oxidized mixture is discharged containing particles of size from 1 to 2.5 mm and constituting from 30 to 85 percent by weight of the catalyst, at least one of the layers of silver crystals constituting the middle region of the catalyst containing particles of size from 0.75 to 1 mm and constituting from 2 to 30 percent by weight of the catalyst and at least one of the layers of silver crystals constituting the upper or front region of the catalyst facing the mixture to be oxidized containing particles of size from 0.2 to 0.75 mm and constituting from 13 to 68 percent by weight of the catalyst.