Process for the dehydrogenation of dehydrogenatable hydrocarbons

Claim 1

In a process for the dehydrogenation of a dehydrogenatable hydrocarbons with separate and intermediate selective oxidation of hydrogen which comprises the steps of: (a) contacting said hydrocarbon with a dehydrogenation catalyst comprising an alkaline metal-promoted iron compound in a first-reaction dehydrogenation zone in the presence of steam at dehydrogenation conditions to produce a first-reaction dehydrogenation zone effluent stream comprising a mixture of unconverted hydrocarbons, dehydrogenated hydrocarbons, hydrogen and steam; (b) removing said first-reaction dehydrogenation zone effluent from said first-reaction dehydrogenation zone; (c) passing said effluent of step (b) to a second-reaction oxidation zone, which is separate and discrete from said first-reaction dehydrogenation zone; (d) contacting said first-reaction dehydrogenation zone effluent in said second-reaction oxidation zone with an oxygen-containing gas to selectively oxidize said hydrogen within said first-reaction zone effluent to the substantial exclusion of oxidation of unconverted and dehydrogenated hydrocarbons in the presence of an oxidation catalyst consisting essentially of a Group VIII noble metal, a Group IVA metal and a Group IA or IIA metal composited on a metal oxide support at oxidation conditions wherein the exothermic selective oxidation of said hydrogen provides additional heat and thereby raises the temperature of said unconverted and dehydrogenated hydrocarbons; (e) withdrawing said unconverted and dehydrogenated hydrocarbons from said second-reaction oxidation zone having an increased temperature with respect to the temperature of said first-reaction dehydrogenation zone effluent; (f) passing said removed second-reaction oxidation zone product stream of step (e) to a third-reaction dehydrogenation zone containing a dehydrogenation catalyst comprising an alkaline metal-promoted iron compound at dehydrogenation conditions to produce dehydrogenated hydrocarbons; and, (g) withdrawing and recovering said dehydrogenated hydrocarbons, the improvement which comprises utilizing as said support a shaped particle having one or more channels wherein the channels have an outside diameter, d o , to inside diameter, d i , ratio greater than 1.10 and less than 8.0 where d i is the largest transverse dimension taken across the inside of any channel and d o is the dimension to the outside walls of the walls surrounding the channel, taken along the line of d i and the entire particle having a ratio of shape surface to gross volume greater than [4/C. +2/L] in which D is the average overall diameter of the particle in a direction transverse to the axis of the channels and L is the average channel length.