Process for heterogeneously catalyzed partial dehydrogenation of at least one hydrocarbon to be dehydrogenated

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, and
• the 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° 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;
• and
• g) a ratio X:d, of the length of the bed X and a distance d is greater than 0.1 and less than 5.