Patent ID: 8841481

Claim:
A process for preparing unsaturated aldehydes or unsaturated carboxylic acids by heterogeneous catalytic gas phase oxidation of unsaturated or saturated hydrocarbons, comprising the process steps of: i) providing a gas mixture at least comprising a saturated hydrocarbon and catalytically dehydrogenating the at least one saturated hydrocarbon in the gas phase to obtain a gas mixture comprising an unsaturated hydrocarbon in a dehydrogenation reactor having a dehydrogenation catalyst material; or ii) providing a gas mixture at least comprising oxygen and at least one unsaturated hydrocarbon wherein unsaturated hydrocarbon has a space velocity of at least 150 liters/hr; iii) catalytically oxidizing the unsaturated hydrocarbon obtained in process step i) or provided in process step ii) in the gas phase to obtain a gas mixture comprising an unsaturated aldehyde in a first oxidation reactor having a first oxidation catalyst material; iv) catalytically oxidizing the unsaturated aldehyde obtained in process step iii) in the gas phase to obtain a gas mixture comprising an unsaturated carboxylic acid in a second oxidation reactor having a second oxidation catalyst material; wherein at least one of the reactors selected from the dehydrogenation reactor, the first oxidation reactor and the second oxidation reactor comprises at least one open-cell foam body and the foam body is characterized by a cell width within a range of from 10 to 40 ppi, and wherein the foam bodies are present in the form of random packings, such random packings are characterized in that they have a diameter which is at most 50% and at least 5% of the diameter of the reactor, in the case of a tube bundle reactor, of the diameter of the particular reaction tubes, and, in the case of a wall reactor, of the distance between two adjacent plates, or in the form of blocks, such blocks are characterized in that they have a diameter which is at least 90% of the diameter of the reactor, in the case of a tube bundle reactor, of the diameter of the particular reaction tubes, and, in the case of a wall reactor, of the distance between two adjacent plates.