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A process for heterogeneously catalyzed partial dehydrogenation of a hydrocarbon, in which a reaction gas mixture input stream comprising the hydrocarbon to be dehydrogenated is conducted through a fixed catalyst bed disposed in a shaft and the reaction gas mixture input stream is obtained in the sh

A process for heterogeneously catalyzed partial dehydrogenation of a hydrocarbon, in which a reaction gas mixture input stream comprising the hydrocarbon to be dehydrogenated is conducted through a fixed catalyst bed disposed in a shaft and the reaction gas mixture input stream is obtained in the shaft by metering an input gas II comprising molecular oxygen upstream of the fixed catalyst bed into an input gas stream I which comprises molecular hydrogen and the hydrocarbon to be dehydrogenated and is flowing within the shaft toward the fixed catalyst bed.

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1. A process for heterogeneously catalyzed partial dehydrogenation of at least one hydrocarbon, the process comprising: passing through a fixed catalyst bed the entirety of a reaction gas mixture input stream comprising molecular oxygen, molecular hydrogen and the at least one hydrocarbon to be dehy

1. A process for heterogeneously catalyzed partial dehydrogenation of at least one hydrocarbon, the process comprising: passing through a fixed catalyst bed the entirety of a reaction gas mixture input stream comprising molecular oxygen, molecular hydrogen and the at least one hydrocarbon to be dehydrogenated,wherein the fixed catalyst bed is disposed in a shaft with a given cross section and comprises in the flow direction of the reaction gas mixture input stream an inert bed of the length X of inert shaped bodies followed by a catalytically active bed,wherein the catalytically active bed comprises at least one shaped catalyst body which in the reaction gas mixture input stream causes, at least in the entrance region of the catalytically active bed, a lower activation energy to conduct a combustion reaction of molecular hydrogen with molecular oxygen to yield water and/or a combustion reaction of hydrocarbon with molecular oxygen to yield carbon oxides and water followed by the dehydrogenation of the at least one hydrocarbon to at least one dehydrogenated hydrocarbon,with the proviso that a portion of the at least one hydrocarbon to be dehydrogenated is dehydrogenated to the at least one dehydrogenated hydrocarbon, andthe reaction gas mixture input stream is obtained in the shaft by metering an input gas II, comprising molecular oxygen with a total volume flow rate V2, upstream of the fixed catalyst bed to an input gas stream I which comprises molecular hydrogen and the at least one hydrocarbon to be dehydrogenated and flows within the shaft toward the fixed catalyst bed with a volume flow rate V1 and a flow rate W,wherein the input gas II is metered in the form of input gas II streams flowing out of a plurality of exit orifices A of a line system disposed upstream of the fixed catalyst bed in flow direction of the input gas stream I such that: a) directions of the majority M of all input gas II streams exiting from the exit orifices A in the theoretical absence of the input gas stream I enclose an angle α of 90±60°90±30° with the flow direction of the input gas stream I;b) a distance D of the majority M of all exit orifices A from the fixed catalyst bed, based on the flow rate W of the input gas stream I in the shaft, is less than or equal to the induction time J of the reaction gas input mixture multiplied by 2·W;c) a projection of the centers of the majority M of all exit orifices A in flow direction of the input gas stream I into the projection plane E at right angles to the flow direction of the input gas stream I within the projection plane E gives rise to a number ZA of the exit orifice centers present in any m2 of ≧10 for at least 75% of the projection area covered by the input gas stream I;d) the individual input gas II streams exiting from the exit orifices A corresponding to the number ZA of exit orifice centers deviate from their numerical mean by not more than 50%;e) among the number ZA of exit orifices, the distance d from one exit orifice center to the closest exit orifice center is not more than 2√{square root over (1m2/ZA)};f) the V1:V2 ratio is ≧8; andg) a ratio X:d, of the length of the bed X and a distance d is greater than 0.1 and less than 5. 2. The process according to claim 1, wherein the input gas II comprises: from 0 to 80% by volume of steam,from 10 to 97% by volume of N2 andfrom 3 to 25% by volume of O2. 3. The process according to claim 1 or 2, wherein the input gas II comprises: from 15 to 80% by volume of H2O,from 20 to 85% by volume of N2 andfrom 5 to 25% by volume of O2. 4. The process according to claim 1, wherein the V1:V2 ratio is ≧15. 5. The process according to claim 1, wherein the V1:V2 ratio is ≧20. 6. The process according to claim 1, wherein the longest dimension L of one exit orifice A is from ≧0.1 mm to ≦5 cm. 7. The process according to claim 1, wherein the longest dimension L of one exit orifice A is from ≧1 mm to ≦5 mm. 8. The process according to claim 1, wherein the directions of the majority M of all input gas II streams exiting from the exit orifices A in the theoretical absence of the input gas stream I enclose an angle α of 90±30°90±20° with the flow direction of the input gas stream I. 9. The process according to claim 1, wherein the directions of the majority M of all input gas II streams exiting from the exit orifices A in the theoretical absence of the input gas stream I enclose an angle α of 90±10° with the flow direction of the input gas stream I. 10. The process according to claim 1, wherein the majority M of all exit orifices A fulfills the condition D≦0.5·W·J. 11. The process according to claim 1, wherein the majority M of all exit orifices A fulfills the condition D≦0.2·W·J. 12. The process according to claim 1, wherein ZA≧30. 13. The process according to claim 1, wherein ZA≧50. 14. The process according to claim 1, wherein ZA≧100. 15. The process according to claim 1, wherein the distance d is not more than 1.5√{square root over (1m2/ZA)}. 16. The process according to claim 1, wherein the distance d is not more than √{square root over (1m2/ZA)}. 17. The process according to claim 1, wherein the individual input gas II streams exiting from the exit orifices A corresponding to the number ZA of exit orifice centers deviate from their numerical mean by not more than 30%. 18. The process according to claim 1, wherein the individual input gas II streams exiting from the exit orifices A corresponding to the number ZA of exit orifice centers deviate from their numerical mean by not more than 10%. 19. The process according to claim 1, wherein the majority M of all exit orifices A and of the individual input gas II streams exiting from them is understood to mean those exit orifices A and the individual input gas II streams exiting from them from which a total of more than 70% of the total volume flow rate V2 exit, with the proviso that the individual input gas II streams exiting from them, among the entirety of all individual input gas II streams, do not comprise a stream which is smaller than the largest of the individual input gas II streams not included in this majority M. 20. The process according to claim 1, wherein the majority M of all exit orifices A and of the individual input gas II streams exiting from them is understood to mean those exit orifices A and the individual input gas II streams exiting from them from which a total of just more than 90% of the total volume flow rate V2 exit, with the proviso that the individual input gas II streams exiting from them, among the entirety of all individual input gas II streams, do not comprise a stream which is smaller than the largest of the individual input gas II streams not included in this majority M. 21. The process according to claim 1, wherein a projection of the centers M of all exit orifices A in the flow direction of the input gas stream I into the projection plane E at right angles to the flow direction of the input gas stream I within the projection plane E gives rise to a number ZA of the exit orifice centers present in any m2 of ≧10 for at least 85% of the projection area covered by the input gas stream I. 22. The process according to claim 1, wherein a projection of the centers M of all exit orifices A in flow direction of the input gas stream I into the projection plane E at right angles to the flow direction of the input gas stream I within the projection plane E gives rise to a number ZA of the exit orifice centers present in any m2 of ≧10 for at least 95% of the projection area covered by the input gas stream I. 23. The process according to claim 1, wherein the reaction gas mixture input stream is conducted through the fixed catalyst bed with the proviso that at least 2 mol % of the at least one hydrocarbon to be dehydrogenated present therein is dehydrogenated to the at least one dehydrogenated hydrocarbon. 24. The process according to claim 1, wherein the reaction gas mixture input stream is conducted through the fixed catalyst bed with the proviso that at least 5 mol % of the at least one hydrocarbon to be dehydrogenated present therein is dehydrogenated to the at least one dehydrogenated hydrocarbon. 25. The process according to claim 1, wherein the reaction gas mixture input stream comprises at least 5% by volume of the at least one hydrocarbon to be dehydrogenated. 26. The process according to claim 1, wherein the reaction gas mixture input stream comprises at least 10% by volume of the at least one hydrocarbon to be dehydrogenated. 27. The process according to claim 1, wherein the molar content of molecular oxygen in the reaction gas mixture input stream is not more than 50 mol % of a molar amount of molecular hydrogen present therein. 28. The process according to claim 1, wherein, as the reaction gas mixture input stream passes through the fixed catalyst bed, at least 95 mol % of the total amount of molecular oxygen present in the reaction gas mixture input stream is consumed for the combustion of the molecular hydrogen present in the reaction gas mixture input stream. 29. The process according to claim 1, wherein the temperature of the reaction gas mixture input stream on entry into the fixed catalyst bed is from 300 to 700° C. 30. The process according to claim 1, wherein the loading on the fixed catalyst bed, based on the total amount of a catalyst present therein, with the at least one hydrocarbon to be dehydrogenated is from 100 to 10 000 1 (STY)/l·h. 31. The process according to claim 1, wherein the induction time J is ≦2000 ms. 32. The process according to claim 1, wherein the induction time J is ≦100 ms. 33. The process according to claim 1, wherein the cross section of the lines conducting the input gas II is polygonal where the exit orifices A are disposed. 34. The process according to claim 1, wherein the cross section of the lines conducting the input gas II is tetragonal where the exit orifices A are disposed. 35. The process according to claim 1, wherein the exit orifices A are round. 36. The process according to claim 1, wherein the temperature difference ΔTIII between the temperature of the input gas stream I and the temperature of the input gas II is not greater than 300° C. 37. The process according to claim 1, wherein the at least one hydrocarbon to be dehydrogenated is propane. 38. The process according to claim 1, wherein the at least one dehydrogenated hydrocarbon is propylene. 39. The process according to claim 1, which is performed in a shaft reactor configured as a tray reactor. 40. The process according to claim 1, wherein the process for heterogeneously catalyzed partial dehydrogenation of the at least one hydrocarbon is followed by a process for heterogeneously catalyzed partial oxidation of the at least one dehydrogenated hydrocarbon. 41. The process according to claim 40, wherein the downstream process for heterogeneously catalyzed partial oxidation of the at least one dehydrogenated hydrocarbon is a process for heterogeneously catalyzed partial oxidation of propylene to acrolein and/or acrylic acid. 42. The process according to claim 41, wherein the acrylic acid is removed from the product gas mixture of the heterogeneously catalyzed partial oxidation in such a way that the product gas mixture which may, if appropriate, have been cooled beforehand by direct and/or indirect cooling is fractionally condensed in a column comprising separating internals with a side draw removal of crude acrylic acid and/or subjected to an absorption with water or an aqueous solution. 43. The process according to claim 42, which is followed by a process for suspension crystallization of the crude acrylic acid. 44. The process according to claim 43, which is followed by a process for washing the acrylic acid suspension crystals formed in a wash column. 45. The process according to claim 44, which is followed by a process in which washed acrylic acid suspension crystals are melted and polymerized to polymers. 46. The process according to claim 42, where the product gas mixture is cooled beforehand by direct and/or indirect cooling before removal of acrylic acid from the product gas mixture of the heterogeneously catalyzed partial oxidation.