Patent GB-815332-A (GB)
Title: Dehydrogenation of hydrocarbons
IPC: B01J8/18
Filed: 1956-04-11
Abstract: <PICT:0815332/IV (b)/1> A process for the dehydrogenation of two or more hydrocarbons, requiring dehydrogenation conditions of differing severity, in a single vessel with a single catalyst, comprises passing a suspension of hot, finely divided dehydrogenating catalyst in a gas continuously, upwardly through a long narrow reaction chamber, passing the hydrocarbon requiring the severest conditions into the lower portion of the chamber, passing one or more other hydrocarbons into the chamber at one or more successively spaced stages along the path of the stream of catalyst suspension in order of decreasing severity requirements and in such quantities and at such temperatures as to quench the products from the preceding stage to a temperature below that at which the hydrocarbon introduced at the preceding stage is dehydrogenated but above that at which the hydrocarbon introduced is dehydrogenated, separating the catalyst from the product stream and recovering the desired products.  This may be particularly applied to butene as a more difficulty dehydrogenatable material and butane as a more easily dehydrogenatable material.  Butane is heated in the heater 1 and when commencing operations is fed via lines 9 and 6 into the reactor 2. The catalyst is introduced by line 14 and the reactants pass into the cyclone separator 10 where the catalyst is removed.  The products pass out by line 30 and butene is recycled to the heater 4 and thence by lines 5 and 6 to the reactor.  Butane is now fed by line 3 to the reactor at a point where the dehydrogenation of butene to butadiene is complete.  In the upper part of the reactor butane is converted to butene which is separated from the product butadiene and recycled. Catalyst separated from the products in the separator 10 falls into the stripper 8 where it is maintained as a fluidized bed by hydrogen supplied at line 12 which also strips any entrained product from the catalyst, the resultant mixture is mixed with the product before recovery processes.  Part of the catalyst is led by line 16 to the regenerator 18, where again it is maintained as a fluidized bed. Carbonaceous deposits are burned off the catalyst by introducing an oxidizing gas such as air through line 20.  Any further heat to reheat the catalyst may be supplied by introducing hydrogen or a fuel gas through line 22.  The gases pass out through line 24 and may be partially recycled through line 26.  Regenerated catalyst is returned to the stripper by line 28 or may be returned direct to the reactor. If preferred a transfer-line regenerator may be used instead of a fluidized bed. Suitable catalysts include nickel, alumina, alumina with chromium, tungsten or molybdenum, oxides of copper, cobalt and nickel and a mixture of magnesium and iron oxides with potassium carbonate and copper oxide.  The catalyst is introduced to the reactor at a temperature of 1150-1550 DEG  F., and the butene in line 5 such that the temperature in the lower part of the reactor is 1300-1500 DEG  F.  The gas velocity in the reactor is between 5 and 100 ft./sec. being sufficient to ensure that catalyst and gas pass through the reactor at the same velocity and that the catalyst density is 0.5-10 lb./ft.3, the catalyst particle size being 80-400 mesh with a tempperature of 1300-1550 DEG  F.  The butene reaction time is 0.1 to 0.5 second; the butane is introduced to reduce the temperature to 1150-1300 DEG  F. and a further reaction period of 0.1-0.5 second allowed.  The pressure may be reduced to between 100 and 400 mm. of Hg or steam added as a diluent to lower the partial pressure of hydrocarbons.  Other combinations of hydrocarbons are (1) butene-butane-ethylbenzene, (2) isobutane-ethylbenzene, (3) isopentene-isopentane. Specification 779,380 is referred to.