TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Feedstock: The hydrocarbonaceous feedstock is a hydrocarbon stream having an average of at least 2C. The feed mixture additionally comprises steam.Preferred Gas: The oxygen-containing gas is air.    TECHNOLOGY FOCUS - METALLURGY - Preferred Catalyst Carrier: The catalyst carrier comprises a metal alloy, preferably an aluminum-containing alloy, more preferably an alloy comprising iron, chromium and aluminum. The metal alloy is coated with stabilized or partially stabilized zirconia. The metal catalyst carrier is a metal foam or an arrangement of metal gauze, foil or wire.    TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Arrangement: The fixed arrangement of catalyst comprises layers (1,2) spaced apart from each other. Layer (1) is located upstream of layer (2).Preferred Property: Length of layer (1) is smaller than length of layer (2). The void fraction of layer (1) is higher than void fraction of layer (2). Fixed arrangement of catalyst or layer (1) of the fixed arrangement of catalyst has a void fraction of 0.6-0.98, preferably 0.7-0.95. Ratio of diameter of the upstream surface of the catalyst and the inner diameter of the nozzle is at least 5, preferably at least 7. Flow of the feed mixture is parallel to the upstream surface of the catalyst or swirling in the direction parallel to the upstream surface of the catalyst.Preferred Method: Flow of the feed mixture is ejected from a nozzle to the upstream surface of the fixed arrangement of catalyst in such a way that the flow impinges on almost half, preferably on at most a third, more preferably on at most a fifth of the total area of upstream surface of the catalyst. Temperature of the upstream surface of the fixed arrangement is below 1100 degreesC. A portion of the conversion product formed in layer (1) flows back to the feed supply chamber. At least 5% (v/v), preferably at least 20% of the conversion product flows back to the feed supply chamber. Flow of the feed mixture in the feed supply chamber is such that the flow sucks in portion of the conversion product. EXAMPLE - 3 kg/h of gaseous flow of feed mixture of temperature 300 degreesC and consisting of naphtha, air and stream was injected from a nozzle to the upstream surface of the catalyst. The nozzle had an inner diameter of 3.5 mm and was placed at 17 mm from the upstream surface of the arrangement of knitted and pressed fecralloy wire. The amounts of air and steam in the feed mixture was such that the oxygen-to-carbon ratio was 0.45 and the steam-to-carbon ratio was 0.9. The temperature in the top layer of the catalyst bed was 960 degreesC and the gas mixture composition in the feed supply chamber contained hydrogen, carbon dioxide and carbon monoxide.