Process for the conversion of normally gaseous hydrocarbons into hydrocarbon liquids

摘要

To polymerize normally gaseous hydrocarbons to hydrocarbons of gasoline boiling range solid phosphoric acid catalysts are used, prepared by mixing phosphoric acid with an inert absorbent such as kieselguhr, heating the pasty mass to 288-400 DEG C., grinding to uniform size and hydrating with superheated steam to a desired extent which approximates to the pyrophosphoric acid composition. Particles of regular size and shape may be produced, e.g. by extruding the pasty mass before heating. To reactivate the used catalyst, combustion gases are generated under pressure sufficient to ensure flow through the catalyst beds. Hydrocarbon fuel mixed with air and water or steam to regulate the temperature during reactivation is admitted at 152 to a combustion chamber 156. A minimum of excess air is used to give combustion gases of low oxygen content. The combustion gases are withdrawn through a water-cooled metal box 158 welded to the chamber 156 and pass to a water-wash tower 163 in which they are finally cooled with injected water. The gas mixture then passes with the desired amount of air to heater 171 and thence to the used catalyst where it burns the carbonaceous deposit. Initially, the oxygen content of the gases is low and the temperature during reactivation should not exceed 538 DEG C. Gas is passed until a gas with an oxygen content substantially that of pure air produces no rise of temperature in the catalyst bed. During subsequent steaming at 266 DEG C. under atmospheric pressure to attain maximum catalytic activity, the temperature is maintained, e.g. by a flow of separately generated combustion gases through the jackets surrounding the catalyst chambers.ALSO:Normally gaseous hydrocarbons, e.g. from oil cracking operations and containing substantial quantities of olefine are subjected to a catalytic polymerization treatment to form hydrocarbons of gasoline boiling range, the total products of polymerization being cooled, preferably by contact with a liquid absorption medium to provide a liquid comprising the polymers of gasoline and higher boiling range and dissolved lower boiling hydrocarbons, which liquid, after a stabilizing fractionation to remove all hydrocarbons of less than 4 carbon atoms per molecule and a substantial portion or all of those with 4 carbon atoms per molecule, is separated by distillation into polymers of gasoline boiling range, and products of higher boiling point. If desired the preliminary gas mixtures may be treated with basic materials such as alkaline or alkaline earth hydroxides, or amines to reduce their sulphur content. Starting mixtures which are completely liquid or gaseous are fed in at 1 by pump 3, while mixtures in mixed phase are fed in at 28 to a separator 30, the two phases being separated for treatment. Liquid mixtures of relatively high sulphur content are freed therefrom by contact with basic solution in mixing tower 15, while gaseous mixtures pass upwards through tower 25 counter current to the basic solutions, and the sulphur free mixtures pass to heating coil 9. Mixtures initially low in sulphur content pass directly to heater 9. A suitable initial mixture contains 17,4 per cent of propene and butenes. A controlled amount of water, e.g. 2-5 per cent may be introduced at 45 just before the heater to prevent dehydration of the catalytic polymerizing agent. From the heater the olefine containing mixtures pass down catalyst containing towers used in series or parallel relation. Preferably three towers are used in series, while the catalyst in a fourth is being reactivated. The catalyst in each tower is arranged in a number of beds of limited thickness. The towers are jacketed to permit control of temperature for polymerization or catalyst reactivation. The products from the polymerization step pass into header 64 where caustic soda solution is added to neutralize acid extracted from the catalyst beds and prevent corrosion of the lines. This alkali together with water added initially to the gas mixture is withdrawn as a lower layer in separator 60. It may be utilized further to neutralize acid concentrates occurring during reactivation of the catalysts. The hydrocarbon products pass from separator 60 through condenser 67 to absorber 69 where debutanized polymers absorb all the products of the polymerization with the exception of gases boiling below the boiling point of propane which escape to be used as fuel through line 70, with valve 71 set to maintain a desired pressure on the polymerization step. The liquid products from the bottom of absorber 69 pass to drum 74, and thence by pump 77 to column 80 where gases boiling below the butane are driven off. These gases are condensed at 83 and pass to tank 86 whence some of them as liquid may be returned to the top of tower 80 as refluxing liquid. Some of the gaseous phase from tank 86 may be returned via line 97 to the initial heater inlet line 4 to maintain the volume of gases entering the polymerizing plant uniform. Gases may be removed also via line 921 and valve 931 which is set to maintain the desired pressure on column 80. The liquid product from the bottom of tower 80 passes to column 101 whence butanes are removed as overhead product, and pass via condenser 104 to receiver 107. A portion of the condensed butane is returned to the top of tower 101 as refluxing liquid. The remainder of the butane is removed to storage via line 114. Column 101 may be operated to remove all the butanes or a controlled amount may be left in to give a final gasoline product of desired vapour pressure. If desired the products from condenser 67 may be passed direct to tank 74 and column 101, absorber 69 and column 80 being byepassed. The liquid product from the bottom of column 101 passes, if desired via pump 118, and cooler 123 to a sweetening plant (not shown) where its mercaptan content is reduced by known methods, and thence via heater 128 to tower 131 where products of gasoline boiling range are distilled from higher boiling polymers. The vaporous product from column 131 is condensed at 134 and received at 137 provided with a pressure controlling valve 149. A portion of the liquid may be returned to the top of column 131 as refluxing liquid. The main bulk of the product passes through branch line 143 and cooler 145 to storage. The catalyst used is preferably of the solid phosphoric acid type, prepared by mixing a phosphoric acid with inert absorbent such as kieselguhr, heating the pasty mass to 288-400 DEG C., grinding the cake produced to particles of uniform size and hydrating with superheated steam to a desired extent which approximates to the pyrophosphoric acid composition. Particles of regular size and shape may be produced by forming, e.g. by extrusion of the pasty mass before calcining. For reactivation of the catalyst, combustion gases are generated under pressure sufficient to ensure flow through the catalyst beds. Hydrocarbon fuel is admitted at 152, mixed with air and water or steam to regulate the temperature produced during reactivation, to a combustion chamber 156. A minimum of excess air is used to give combustion gases with low oxygen content. The combustion gases are withdrawn through a water-cooled metal box 158 welded to the chamber 156 and pass to a water wash tower 163 in which they are finally cooled with injected water. The gas mixture then passes via line 168 together with a desired amount of air to adjust the oxygen content to heater 171 and thence to the catalyst to be reactivated where it burns the carbonaceous deposit thereon. Initially the oxygen content of the reactivating gases is low, and the temperature during reactivation should not exceed 538 DEG C. Passage of combustion gas mixture is continued until a mixture with an oxygen content substantially equivalent to pure air produces no temperature rise in the catalyst bed. During the subsequent steaming to ensure maximum catalytic activity the temperature is maintained, e.g. by a flow of separately generated combustion gases through the jackets 52 surrounding the catalyst chambers, at 266 DEG C. at atmospheric pressure. Specification 437,188 is referred to.