Patent GB-513545-A (GB)
Title: Improvements relating to the conversion of mineral oils into gasoline
IPC: C10G50/00
Filed: 1938-04-12
Abstract: 513,545. Gasoline motor fuel. STEYENS, A. H. (Standard Oil Co. (Indiana)). April 12, 1938, No. 11248. Addition to 510,155. [Class 2 iii)] A modification of the process for producing a high yield of anti-knock motor fuel of desired volatility according to the parent Specification, is characterized by fractionating the hydrocarbons of less than 5 carbon atoms per molecule into a fraction containing ethylene as the predominating olefinic constituent, and a second fraction containing higher boiling normally gaseous olefins and butane, subjecting the first fraction to thermal polymerization at elevated temperatures and pressures to convert a portion thereof to liquid hydrocarbons including gasoline, subjecting the second fraction to catalytic polymerization to convert olefins therein to liquid products including gasoline, and recovering the gasoline from the thermal and catalytic polymerization steps. Preferably, the total liquid products from both polymerization steps are combined .and returned to the cracking system whereby products heavier than gasoline are cracked and polymerization products of gasoline boiling range are recovered with the cracked gasoline. Cold crude oil introduced by line 10 is preheated in coils 11, 13 and heat exchanger 16 and is fractionalised in tower 12 into light virgin naphtha and gases removed by line 17a, heavy virgin naphtha withdrawn through line 20, and unvaporized residue which passes through line 21 to evaporator 23. where gas oil is vaporized while the heavy residue is withdrawn by line 27 and passed to viscosity breaker furnace 30 where it is heated to 850-925‹F. under a pressure of 100-750 lbs./sq. in. and then returns to the lower section of evaporator 23. Gasoline and gas oil vapours leave evaporator 23 by line 32 and pass bubble tower 14 when gas oil is condensed and passed to gas oil furnace 37 to be cracked at 900-1050‹F. and 100-750 lbs./ sq. in. pressure. The cracked products pass,'if desired, to reaction drum 40 and then to evaporator 23. Heavy virgin naphtha withdrawn through line 20 from the crude flash tower is cracked in furnace 49 at 950‹-1100‹F.. and 200- 1500 lbs./sq. in. pressure, the products passing to evaporator 23. Unvaporized cracked residue and tar frcm evaporator 23 passes to the bottom 24 of the crude flash tower when any remaining gas oil is distilled and passed via line 25 to section 19 while heavy residual fuel oil is withdrawn from the system by line 53. Gasoline vapours and gas leave tower 14 by line 54 and pass preferably to clay towers 56, 57 where gum-forming constituents are polymerized and returned as liquids to the cracking system. Vapours pass via condensers and coolers to separator 68 whence uncondensed gases are removed, the liquid passing to fractionator 72. A gasoline deficient in volatile light ends is withdrawn from the latter and hydrocarbons with less than 5 carbon atoms in the molecule pass overhead and are separated in fractionator 78 into a fraction comprising mainly ethane and ethylene and another comprising propane, propylene, butane and butylene. The latter fraction is catalytically polymerised in chamber 92. Suitable catalysts are of the aluminium halide stable double salt type, the other metallic halide being, for example, sodium, lithium or cuprous chloride or sodium or antimony bromide. Polymerization takes place at 200- 550‹F. and 200-1000 lbs./sq. in. pressure. The products pass to fractionator 96 which separates butane and lighter unconverted gases from gasoline and heavier hydrocarbons which are returned to the cracking process, the polymer gasoline then being processed with the cracked gasoline and recovered therewith via line 75 as gasoline deficient in light ends. Materials heavier than gasoline are re-cracked. Gases from fractionator 96 may be removed from the system or may be treated with gases and light virgin naphtha from the crude oil flash tower 12; passing to separator 108 which removes fixed gases, the residue passing to stabiliser 111 from the bottom of which stabilized light virgin naphtha is removed while gases may be withdrawn from the system by line 116 or may be fractionated at 119 into butane as a bottom product and gases which are removed from the system or sent to a gas cracking furnace 126, operated at 1350-1650‹F. and 0-100 lbs./sq. in. pressure to produce olefine from gases containing mainly ethane and propane. Alternatively, gases from fractionator 96 may pass to fractionator 133 for separation into butane, preferably used for blending with the gasoline withdrawn from stabilizer 72, and gases which may be removed from the system, or sent to fractionator 111 or fractionator 119 or direct to gas cracking furnace 126. In a modification gas oil only is withdrawn from the bottom of fractionator 96, and gasoline vapour and gases pass to fractionator 133 whence polymer gasoline is obtained as a bottom product, which is stabilized to a higher vapour pressure than the cracked gasoline from stabilizer 72, and may be used to produce, by blending, a normal gasoline. Excess butane and lighter gases pass to fractionator 142 whence butane is removed as bottom product and gases may be eliminated or passed to the gas cracking furnace. The gas fraction containing predominantly ethylene which is removed from stabilizer 78 is polymerized at 850-1100‹F. and 1000- 3000 lbs./sq. in. pressure in furnace 152. Fixed gases are removed from the products in separator 155 and the liquid products may be returned to the evaporator 23 or bubble tower 14 or passed to fractionater 162 whence gasoline gas oil and heavier constituents return to the cracking system while gases, if desired, after a preliminary separation in fractionator 176 are eliminated, or sent either to gas cracking furnace 126, or back to the catalytic polymerization step for polymerization of any propylene or butylene present. In a modification gases of less than 5 carbon atom/molecule separated in stabilizer 72 may all be passed to the catalytic polymerization step and the ethylenic fraction recovered from the products then subjected to thermal polymerization.