GB817127A - A process for the catalytic conversion of hydrocarbons or hydrocarbon mixtures - Google Patents

Abstract

<PICT:0817127/III/1> Hydrocarbon catalytic conversion reactions, such as the dehydrogenation for example of butane to butenes and butadiene and of butanes to butadiene, the catalytic reforming of straight-run hydrocarbons and catalytic cracking of petroleum distillates boiling above gasoline, are carried out by transferring hydrocarbon feed vapours, finely divided catalyst particles and finely divided solid particles of an inert refractory heat transfer medium into the lower end of an upright reaction zone having a length-to-inside diameter ratio of at least 6, the inert particles being of such a size and density that when suspended in a slowly moving gaseous medium with the catalyst particles they tend to settle out and being at a temperature above the reaction temperature and sufficient to heat and maintain the feed and catalyst at reaction temperature, the feed being introduced at such a rate that the catalyst and inert particles are carried through the reactor in a dispersed phase the residence time being less than 12 seconds, passing the materials from the top of the reactor to a stripping zone where they are mixed with an inert stripping and quenching material to cool them and where the solid particles separate, withdrawing gaseous and vaporous products, passing catalyst and inert particles suspended in a small amount of gas to a regeneration zone where a dense bed of separate layers of catalyst and inert particles with a diffuse interface is formed, introducing an oxygen-containing gas to burn off coke and heat the particles to a temperature at least 38 DEG C. below the temperature of the inert solids entering the reactor and such that the catalyst is not damaged, transferring inert particles to a separate heating zone where they are further heated by introduction of a combustible gas and an oxygen-containing gas and returning catalyst from the regeneration zone and inert particles from the heating zone to the reactor. In a preferred embodiment hydrocarbon feed from line 1 is pumped to the heater 3 where it is at least partially vaporized if not already a gas and heated to a temperature 38-150 DEG C. below reaction temperature. Thence it is passed to the reactor 5 which may have an inside diameter of 60-180 cms. and a length-to-inside diameter ratio of 15-50. Catalyst and inert particles are also passed to the reactor, the inert particles being at least 38 DEG C. hotter than the catalyst or feed and high enough to maintain a reaction temperature of e.g. 538-650 DEG C. at the bottom of the reactor 38 DEG C. less at the top. The gases pass upwards at a velocity of at least 4.5 metres per second and up to 15 or more metres per second. Mounted on top of the reactor is a stripper 6 provided with baffles and a cyclone to separate the solids from the gases and fed with low-pressure steam, e.g. at 0.35-3.5 atmospheres gauge from line 8 to cool the reactants and strip product gas from the solids. Product gas leaves by line 7 for recovery. The solids pass, preferably by gravity, to regenerator 11 which is fed with air by line 12 to burn off coke and heat the particles which separate into two layers. The catalyst leaves, preferably by gravity, by line 30 to the bottom of a pretreater 32 to which is fed a reducing gas, such as carbon monoxide, hydrogen or a hydrogen-containing gas such as process (e.g. reforming) tail gas, by line 33. Thence the catalyst is fed, preferably by gravity, to the reactor by line 35. The inert solids pass, preferably by gravity, from the regenerator to heater 21 to which is fed the reducing gas from the pretreater by line 37 together with other fuel, if necessary, by line 23 and air by line 22. Combustion gas passes to the gas space in the regenerator and through the cyclone therein for recovery of catalyst fines. Inert particles pass, preferably by gravity, to the reactor by line 26. Suitable catalysts referred to are chromia-alumina, activated if desired by potassia, for dehydrogenation, platinum or molybdena-alumina for reforming and silica-alumina for cracking, suitable particle sizes being 0.05-0.15 mm. The inert material may be sintered magnesia, sintered alpha-alumina, carborundum or zirconia in particle sizes of 0.075-0.4 mm.ALSO:<FORM:0817127/IV (b)/1> Hydrocarbon catalytic conversion reactions, such as the dehydrogenation for example of butane to butenes and butadiene and of butenes to butadiene, or the catalytic reforming of straight-run hydrocarbons are carried out by transferring hydrocarbon feed vapours, finely divided catalyst particles and finely divided solid particles of an inert refractory heat transfer medium into the lower end of an up-right reaction zone having a length-to-inside diameter ratio of at least 6, the inert particles being of such a size and density that when suspended in a slowly moving gaseous medium with the catalyst particles they tend to settle out and being at a temperature above the reaction temperature and sufficient to heat and maintain the feed and catalyst at reaction temperature, the feed being introduced at such a rate that the catalyst and inert particles are carried through the reactor in a dispersed phase, the residence time being less than 12 seconds, passing the materials from the top of the reactor to a stripping zone where they are mixed with an inert stripping and quenching material to cool them and where the solid particles separate, withdrawing gaseous and vaporous products, passing catalyst and inert particles suspended in a small amount of gas to a regeneration zone where a dense bed of separate layers of catalyst and inert particles with a diffuse interface is formed, introducing an oxygen-containing gas to burn off coke and heat the particles to a temperature at least 38 DEG C. below the temperature of the inert solids entering the reactor and such that the catalyst is not damaged, transferring inert particles to a separate heating zone where they are further heated by introduction of a combustible gas and an oxygen-containing gas and returning catalyst from the regeneration zone and inert particles from the heating zone to the reactor. In a preferred embodiment hydrocarbon feed from line 1 is pumped to the heater 3 where it is at least partially vaporized if not already a gas and heated to a temperature 38-150 DEG C. below reaction temperature. Thence it is passed to the reactor 5 which may have an inside diameter of 60-180 cms. and a length-to-inside diameter ratio of 15-50. Catalyst and inert particles are also passed to the reactor, the inert particles being at least 38 DEG C. hotter than the catalyst or feed and high enough to maintain a reaction temperature of e.g. 538-650 DEG C. at the bottom of the reactor and 38 DEG C. less at the top. The gases pass upwards at a velocity of at least 4.5 metres per second and up to 15 or more metres per second. In dehydrogenating butane the reaction time should be less than 5 seconds. Mounted on top of the reactor is a stripper 6 provided with baffles and a cyclone to separate the solids from the gases and fed with low pressure steam, e.g. at 0.35-3.5 atmospheres gauge from line 8 to cool the reactants and strip product gas from the solids. Product gas leaves by line 7 for recovery. The solids pass, preferably by gravity, to regenerator 11 which is fed with air by line 12 to burn off coke and heat the particles which separate into two layers. The catalyst leaves, preferably by gravity, by line 30 to the bottom of a pretreater 32 to which is fed a reducing gas, such as carbon monoxide, hydrogen or a hydrogen-containing gas such as process (e.g. reforming) tail gas, by line 33. Thence the catalyst is fed, preferably by gravity, to the reactor by line 35. The inert solids pass, preferably by gravity, from the regenerator to heater 21 to which is fed the reducing gas from the pretreater by line 37 together with other fuel, if necessary, by line 23 and air by line 22. Combustion gas passes to the gas space in the regenerator and through the cyclone therein for recovery of catalyst fines. Inert particles pass, preferably by gravity, to the reactor by line 26. Suitable catalysts referred to are chromia-alumina, activated if desired by potassia, for dehydrogenation, and platinum or molybdena-alumina for reforming, suitable particle sizes being 0.05-0.15 mm. The inert material may be sintered magnesia, sintered alpha-alumina, carborundum or zirconia in particle sizes of 0.075 - 0.4 mm. Slightly reduced pressures may be used in dehydrogenating butane.