Patent GB-647467-A (GB)
Title: Improvements in or relating to gasoline hydrocarbons and process for the manufacturethereof
IPC: C07C1/04
Filed: 1946-11-27
Abstract: Gasoline hydrocarbons are obtained by generating a synthesis gas consisting essentially of carbon monoxide and hydrogen, passing said synthesis gas in contact with a fluidized synthesis catalyst comprising iron in a synthesis reaction zone under superatmospheric pressures and at elevated temperatures to effect substantial conversion into normally liquid hydrocarbons with formation of oxygen-containing compounds, withdrawing an effluent stream of reaction products from the synthesis reaction zone, separating from the effluent a normally liquid fraction rich in gasoline hydrocarbons and containing a substantial amount of oxygen-containing compounds, subjecting this fraction to contact with a solid contact agent of the mineral type to effect dehydration in a treating zone in the presence of a substantial amount of carbon dioxide at a temperature generally in the range of 700 DEG  to 950 DEG  F., thereby converting the hydrocarbons into gasoline hydrocarbons of improved anti-knock value, removing from the contact treating zone a product mixture containing improved gasoline hydrocarbons, gaseous hydrocarbons and gas including carbon dioxide, and recovering gasoline hydrocarbons therefrom. The synthesis gas is obtained from normally gaseous hydrocarbons, e.g. natural gas and refining waste gases preferably by treatment with oxygen at about 2000 DEG  to 2400 DEG  F. and a pressure of about 250 lbs. or in the range of about 100-500 p.s.i. gauge.  Other materials specified for the production of synthetis gas are coal, coke, lignite, peat, shale and heavy fuel oils. Advantageously the hydrocarbon gas and oxygen are separately preheated to at least 600 DEG  F., preferably as high as possible. Preferably the synthesis gas is passed up through a mass of powdered catalyst so that the latter is maintained fluidized without appreciable quantities being carried out of the reactor.  The reactor may be fitted with cooling tubes in which case the remaining reaction channels should have an internal radius of not less than about 0.5 inches and not more than about 4 inches, preferably not less than 1 nor more than 2 inches.  The catalyst comprises iron containing promoters such as the oxides of magnesium, thorium or alumina. The reaction may be effected at about 500 DEG  to 700 DEG  F. and under pressures of 100-500 p.s.i.g.  Dehydration catalysts instanced are synthetic cracking catalysts, acid treated clays, actuated alumina and bauxite, and when this stage of the reaction is effected at about 700-750 DEG  F. water is removed from alcohols and other oxygenated compounds obtained in the synthesis, at about 950 DEG  F., however, the fraction is not only dehydrated but also reformed so that heavy hydrocarbons present are converted to lighter hydrocarbons. Temperatures used in this process are 700-950 DEG  F., preferably 800 DEG  to 900 DEG  F.  The dehydration catalyst is regenerated with substantially pure oxygen at above about 800 DEG  F. but below deactivation temperature, e.g. about 1100 DEG  F. to give a flue gas of carbon mon- and di-oxide which may be recycled to the gas generator or reactor.  A diesel oil fraction may be removed from the products before dehydration treatment.  It is an advantage to include a polymerization stage for polymerization of olefines recovered from the product mixture or contained in a fraction of the product mixture gaseous hydrocarbons then remaining being recycled.  In an illustration, natural gas containing 90 per cent methane is reacted with oxygen at about 2000 DEG  F. and approximately 250-275 p.s.i.g. in the presence or absence of recycle gases to produce a synthesis gas containing about 85-95 per cent carbon monoxide and hydrogen in the ratio of about 2 mols. of hydrogen to 1 mol. of carbon monoxide which is cooled to about 600 DEG  F. before entry to the reactors where synthesis is effected at about 650 DEG  F. and about 250 p.s.i.g. in the presence of a powdered iron catalyst suspended as a relatively dense mass in an upward flowing stream of reactants.  The gases are advisably passed at about 1 ft. per sec. with a contact time of 30-50 secs.  A desirable catalyst is one containing 2-3 per cent of potassium oxide and alumina as promotors and preferably all should pass a 200-mesh screen and about 85 per cent a 325-mesh screen.  From the reactor gases are passed to a separator where entrained catalyst is removed and injected into recycle gases to the reactor.  The effluent gases are cooled and flashed under pressure at about 70-150 DEG  F. to effect a crude separation, an aqueous layer containing alcohols and other dissolved oxygenated compounds being drained off.  The upper oil layer contains about 10-15 per cent of absorbed carbon dioxide and is about 80-85 per cent a naphtha fraction boiling below about 400 DEG  F. containing about 40-50 per cent olefines.  Uncondensed gases containing carbon dioxide, hydrogen, hydrocarbons of 1 to about 5 carbon atoms and a small quantity of carbon dioxide are in part recycled to the reactor and in part passed to an absorber where they may be mixed with gases from the polymerization stage described below and where they are treated in countercurrent with lean oil the residual gas being vented or passed to the generator or reactor and the enriched oil after treatment with steam is recycled as lean oil the gases from this stage being condensed to give an aqueous layer which is drawn off, an oil layer which is recycled to the enriched oil, and gaseous hydrocarbons containing carbon dioxide which is combined with the upper oil layer from the flash separation.  This mixture is heated to about 900 DEG  F. and treated with a fluidized mass of catalyst such as bauxite at a velocity of about 1 ft. per sec. with a contact time of about 20-30 secs. in a conversion zone, the catalyst being regenerated in a contiguous combustion zone with oxygen cyclic flow of catalyst through the two zones being maintained.  Here oxygenated compounds are dehydrated and e.g. aldehydes, ketones and acids decompose to give carbon dioxide and monoxide.  The carbon dioxide present in this stage acts as a diluent and so undesirable side reactions are avoided.  About 2-10 mols. of carbon dioxide should be present per mol. of hydrocarbons treated.  The reaction products together with those of combustion are fractionated to separate a fraction comprising gases and motor fuel hydrocarbons from a residue of gas oil boiling above 400 DEG  F. which contains any entrained catalyst from the treatment zone.  The distillate is cooled and separated uncondensed gases being removed and passed to the top of a gasoline stabilizer and an aqueous layer drained off from an oil layer which is partly returned to the fractionator, the remainder being sent to the lower portion of the stabilizer where gasoline is withdrawn from the bottom and a gas removed at the top which is condensed, any oil forming being returned to the stabilizer.  The uncondensed gases containing olefines are passed to an absorber where they are treated in counter-current with lean oil in a similar fashion to that described in connection with synthesis stage.  The recovered hydrocarbon gases are cooled and separated, water removed, oil recycled to the oil steam treatment stage and uncondensed gases heated and polymerized by contact with, e.g. a phosphoric acid type catalyst at 375-500 DEG  F. and 500-2000 lbs. pressure.  Excess carbon dioxide may be vented or recyled prior to this stage.  The reaction products pass to a stabilizer where polymer gasoline is separated from light hydrocarbon gases and is withdrawn as an end-product.  A gas fraction removed from the stabilizer is cooled and separated the condensate being recycled and the gases recycled to the first absorber as above indicated, returned to the generator or used as a diluent for the polymer feed.  Various other recycling stages are described.  Oxygenated compounds may be recovered from the aqueous phase obtained in the separation before dehydration.  The catalyst in the treatment zone may be of the fixed bed type.  The generator may contain catalysts for the production of synthesis gas from methane, carbon dioxide and steam.