TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The step (b) is carried out before the step (c), or the step (c) is carried out before the step (b). The catalyst support is dried after the impregnation of the catalyst support with the solution of the ruthenium precursor compound in step (b) and/or after the impregnation of the catalyst support with the precipitating agent in step (c). The method further comprises transferring the precipitated ruthenium component into the oxidation step. The catalyst support is calcined after the precipitation of the ruthenium component for transferring the precipitated ruthenium component into the oxidation step. The catalyst support is impregnated with the solution of the ruthenium precursor compound by soaking the catalyst support with the solution of the ruthenium precursor compound or spraying the solution of the ruthenium precursor compound on the catalyst support. The catalyst support is heated during the impregnation with the solution of the ruthenium precursor compound. Preferred Components: The catalyst support contains zirconium oxide in an amount of at least 90 wt.%. The catalyst support has a specific surface area of 50-160 m2/g. The proportion of ruthenium in the shell catalyst is 0.01-20 wt.%. The ruthenium-containing shell of the catalyst support is free from a further active metal and/or a promoter metal. The shell has a thickness of less than 500 mu m. The catalyst support has an integral pore volume of greater than or equal to 0.2 ml/g to 0.2-0.6 mg/l. At least 85% of the integral pore volume of the catalyst support is formed of mesopores and macropores. The catalyst support has a mean pore diameter of 8-80 nm. The catalyst support is formed as molding. The molding is a pressed body. The molding is a sphere or a cylinder. The maximum dimension of the molding is 1-25 mm. The catalyst support has a hardness of greater than or equal to 20 N. The ruthenium precursor compound is halides, nitrates, nitrosyl nitrates, nitrites, formates, propionates, oxalates, acetates, nitrosyl acetates, carbonates, hydrogen carbonates or organic complexes of ruthenium. The ruthenium precursor compound is chlorides of ruthenium, preferably ruthenium(III) chloride. The solution of the ruthenium precursor compound is an aqueous solution. The precipitating agent is an aqueous alkaline solution. The aqueous based solution is an aqueous solution of an alkali metal- or alkaline earth metal-hydroxides, preferably an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution or an aqueous solution containing sodium hydroxide and potassium hydroxide. EXAMPLE - Zirconium oxide pellets (10 g) with a diameter of 3 mm were taken in a rotating flask. A mixture of ruthenium(III) chloride (3.11 g) and distilled water (0.05 g) was added to the flask. After the complete absorption of the solution by zirconium oxide pellets, the pellets were immersed in 3.5M sodium hydroxide solution (10.49 g) and left standing for 2 hours to precipitate the ruthenium as ruthenium hydroxide. Then the resulting shell catalyst precursor was washed with deionized water until chloride-free, and then dried to obtain the shell catalyst, and the mean shell thickness of the catalyst was 459 microns.