GB740634A - Method of carrying out catalytic reactions - Google Patents

Abstract

In a cyclic catalytic process involving heating a stationary catalyst zone containing an easily oxidisable metal by the passage of hot gases therethrough, and then passing reactants through the catalyst to effect an endothermic reaction, heat is supplied by passing free oxygen through the catalyst zone to convert the metal to its oxide, and then passing an oxidisable gas through the zone to reduce the oxide to metal, the amount of oxygen used being controlled so that the temperature difference between the entrance and exit portions of the catalyst zone is less than about 475 DEG F and the maximum temperature reached is below the sintering temperature of the catalyst. The hot gases may be produced by burning a fuel, e.g. natural gas, liquid hydrocarbons, water gas, producer gas, or oil gas; if the gases contain excess oxygen they are suitable for the oxidation step in the process, while if they are the result of combustion with insufficient air, they may be used in the reduction step. Reduction may also be carried out with hydrogen, carbon monoxide, or gaseous hydrocarbons, e.g. methane; nitrogen or carbon dioxide may be present as a diluent. A suitable catalyst is nickel or cobalt supported on a porous carrier; alumina, silica, magnesia, calcium oxide, titanium oxide, chromium oxide, thoria, ceria, and chromates or silicates, e.g. zirconium silicate, may also be present in the catalyst. The invention is described with reference to the reaction of hydrocarbons and steam to form a combustible gas containing hydrogen and carbon monoxide; in this case the volume of oxygen used in the oxidation step is 15-180 cubic feet per 1000 cubic feet of hydrogen and carbon monoxide produced. The hydrocarbon reactant may be natural gas, refinery oil gas, methane, ethane, propane, butane, gasoline, or gas oil and may contain ethylene, propylene, or butylene; air may be present during the reaction which takes place at 1500 DEG F or higher for methane, or at a lower temperature for higher hydrocarbons. Reduction of the catalyst can be effected with the hydrocarbon reactant. An example describes the reaction of natural gas and steam in the presence of nickel-coated spheres of aluminium oxide, using varying amounts of oxygen for the oxidation. Reference is also made to processes for the desulphurisation of hydrocarbons, cracking of liquid hydrocarbons to gaseous hydrocarbons, cracking of heavy liquid hydrocarbons into light liquid hydrocarbons such as gasoline, and the conversion of paraffinic hydrocarbons into aromatic hydrocarbons.