US2327973A - Conversion of hydrocarbon oils - Google Patents

Description

Aug. 24, 1943. c. L. THOMAS CONVERSION oF HYDRocAnBoN oILs Filed Aug. 25, 1939 Patented Aug. 24, 1943 CON-'VERSION 0F HYDBOCARBON OILS Charles L. Thomas, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, lll.,

. Va corporation of Delaware Application August 25, 1939, serial No. 291,890 i s' claims. (ci. 19e-52) 'I'his invention relates to the conversion of crude petroleum into substantial yields of motor fuel products and is a continuation-impart of my cb-pending application Serial No. 166,570, filed September 30, 1937. The process may also be applied to similar hydrocarbon distillates from other sources, such as shale oils, coal tars, etc.

More specifically, the invention concerns a combination of catalytic and non-catalytic cracking witha denite interrelation of steps s o that maximum benefits are obtained, not only in respect to yields and antiknock value of the finished gasoline, but also in respect to thel life of the catalytic masses employed in the catalytic cracking step.

The limitations of ordinary non-catalytic cracking in the production of high yields of antiknock gasoline are fairly well recognized. The increasingly severe conditions of temperature and pressure employed in increasing the antiknock particularly such fractions as may be distilled at atmospheric pressure without substantial decomposition, such as gas oils, kerosene. land the like.

During the catalytic cracking Aof petroleum fractions, carbonaceous deposits develop. on ,the catalytic surfaces, necessitating frequent reactivation by means of oxygen-containing gas.

When.'heav'ler fractions, such as topped crude oils, are cracked catalytically, the amount of such deposits becomes disproportionately large, and as `a. result reactivation becomes ldiiilcult, and in some cases,is deiinitely harmful .to the catalytic and anti-knock value by the combination of catalytic and non-catalytic cracking operations.

In one specific embodiment the present invention comprises a process for converting crude hydrocarbonoil into substantial yields of high oc-V tane number gasoline, which comprises charging said hydrocarbon oil to a primary fractionator,

life because of the amount of carbon which must be consumed and the consequent development of subjecting the heavy unvaporized portion oi' the oil `to cracking treatment in a. non-catalytic cracking step comprising a primary tubular heating coil communicating with a reaction chamber operated under conditions adequate to effect substantial conversion to. gas and gasoline, passing the reaction products to a vaporization stepat reducedpressure, separating a residue unsuitable for further conversion, passing the vaporized products to the primary fractionator, separating therefrom the gas, gasoline, and an intermediate boiling fraction and a-relatively heavy fraction, returning said relatively heavy fraction to the non-catalytic cracking step, contacting said intermediate-boiling fraction in vaporous form with a cracking catalyst in a catalytic cracking step under conditions adequate to effect substantial cracking thereof, passing the reaction products from said catalytic cracking step to a secondary fractionation step, recovering the gas, gasoline and insuiiiciently converted oil, passing a portion of said insuiliclently converted oil to a secondary tubular heating coil operated at temperatures and pressures substantially higher than the primary tubular heating coil, said secondary coil communicating with said reaction chamber, and returning a second portion of said insufilciently converted oil to said catalytic crack- 1118 step.

The various cooperative features ofthe present invention may be further understood from 'a description of a process flow, and for this purposeV the accompanying drawing has been provided which shows by the aid of conventional figures a diagrammatic outline of interconnected units in which the. process may be conducted. 'I'he appa,- ratus has not been drawn to scale nor has any attempt been made to proportionate the various units thereof. Furthermore, heat exchangers, condensers, stabilizers, and various other parts of equipment conventionally 'used inthe operation of cracking units have been omitted in the interests of simplifying the' drawing. The invention shouldnot be construed as limited to the 'exact apparatus or conditions given therein.`

Referring to the drawing, the raw 'oi1`charge enters the system through line l, valve 2, pump l. valve I, line 5 and enters the lower section of gasoline occurs.

fractionator 6. If gas or gasoline is present it is removed through line 1 and valve 8 through suitable stabilizers heat exchangers, condensers, etc., not shown. The high-boiling unvaporizedl fraction of the crude oil is withdrawn through line 9, valve Ill, pump II and valve I2 to primary or heavy-oil heating coil I3I which is disposed in furnace I4. 'I'he pressure and temperature are increased to a suitable point and the oil is passed through line I 5 and valve I6 into reaction chamber I1 where substantial conversion to gas and The reaction products are removed through line I8 and valve I9 and Ipassed into ash chamber 20 wherein the pressure is 'reduced and substantial vaporization of theoil occurs. A residue unsuitable for further conversion is withdrawn through line 2I and valve 22. The vaporized portion passes overhead through line 23 and valve 24 into fractionator 6. The gas and gasoline are removed overhead through line 'I and valve 8. An intermediate-boiling fraction including that present in the raw oil charge as well as that produced during the non-catalytic cracking step is removed through line 25, valve 25, pump 21 and valve 28 to coil 29 which is disposed in furnace 30. The pressure at this point may be atmospheric or only sufficiently superatmospheric to insure the passage of the oil vapors through the various parts of the apparatus. The

oil vapors are passed'through line 3| and valve 32 to catalytic converter 33 which may comprise any suitable type of catalytic reactor such as reaction chambers containing the catalytic mass or tubes disposed Within a heated Zone, the catalyst being placed in said tubes. The reaction products pass through line 34 and valve 35 to secondary fractionator 36. The gas and gasoline are removed through line 31 and valve 38 from which they pass to suitable condensers, etc., not shown. From this point a number of alternative flows are possible.

The preferred alternative consists in returning a portion ofthe insufiicienctly converted oil to the catalytic cracking step by way of a light-oil coil operating at a temperature and pressure substantially above those employed in heating the heavy fraction of the raw oil charge prior to passage to the reaction chamber. The intermediate fraction may be withdrawn through line 39, Valve 40, pump 4I, valve 42 to secondary or light-oil heating coil 43 which is disposed in furnace 44 wherein it is heatedto a suitable cracking temperature. The hot oil passes through Y being returned to fractionator 6 a portion of this intermediate fraction may be passed through line 84 and valve 65 and returned together with the high-boiling fraction from lines 41 and 49 to either the light-oil coil by means of line 55, valve 56, line 39 and valve 42 or may be passed through line 53 and valve 54 to the flash chamber.

It is possible from the drawing that only one intermediate-boiling fraction need be withdrawn from fractionator 36, said fraction being withdrawn through either line 39 or line 51 and processed as previously described.

'Ifhe thermal cracking step may-be operated at pressures of 10G-500 pounds per square inch or higher and temperatures within the range of approximately 850-1000 F. The catalytic cracking step may be operated at substantially atmospheric or slightly superatmospheric pressures of the order of 50-100 pounds per square inch and temperatures of 800-l200 F. 'I

Numerous types of cracking catalysts may be used, among which are fullers earth or other clays, including montmorillonite, bentonite, etc., which have been treated with acids or other chemicals to increase their activity and which may have added metal oxides disposed thereon to serve as promoters of catalytic cracking.

Another type of catalyst which has been particularly useful comprises a composite of a major portion of precipitated silica having added thereto minor portions of precipitated alumina and/or zirconia, said catalytic masses being substantially free o f alkali-metal compounds. 'I'hese catalytic masses are prepared by mixing the precipitated and washed hydrogels or coprecipitating the masses under conditions whereby alkalimetal compounds are substantially eliminated. The masses are then formed into suitable shapes by compression or extrusion methods, dried, and calcned at temperatures in excess of 800 F. prior to their use in the process. ,The ratio of the added compound to silica may vary over a considerable range and is normally within the f limits of approximately 5-30% by weight.

The charging stocks used in this process may comprise distillate fractions of crude petroleum, crude petroleum oils or other fractions such as topped crude oils or similar hydrocarbon oils from other sources.

The following example is given for purposes of illustration and should not be interpreted as limiting the process to the exact conditions given line 45 and valve 46 to reaction chamber I1.

Simultaneously a high-boiling fraction of the insufliciently converted oil .from the catalytic cracking step may be withdrawn through line 41 and valve 48 to storage.

\ Another portion may be withdrawn through line 49 and valve 50 by pump 5I and valve 52,

line 53 and valve 54 to flash chamber 20. A part or all of the heavy oil is withdrawn through valve 48 and may be passed through line 55 and valve 56 which joins with line 39 and passes thence to the light-oil coil. A further intermediate-boiling fraction somewhat heavier than that withdrawn therein.

A 26 A. P. I. gravity Midcontinent topped crude oil was charged to fractionating column 6 and the unvaporized portion was passed through coil I3 and reaction chamber I1 where it was cracked at a .temperature of 950 F. and

'a' pressure of 400 pounds per square inch. The

reaction products4 were passed to flash chamber 20 from which residual fuel oil having a furol viscosity of 500 seconds at 122 F. -was Withdrawn. The vaporized products passed to fractionator 6 where the'gas and gas- 1y atmospheric'pressure and a temperature of 975 F. The vapors were contacted with a precipitated silica-alumina-zirconia mass. The reaction products were passed to fractionator` 36 from which gas and gasoline were removed.

The high-boiling fraction of the insuillciently were y converted bottoms was removed through lines l1, 49, Il and to light-oil coil 43 and mixed witha low-boiling intermediate fraction from line 39. I'he light-oil coil was ,operated at 500 pounds pressure and 950 F. J'I'he heated 7'oil passed then to reaction-chamber I1. A higherboiling intermediate fraction was removed from fractionator 3B through line 51 and returned through lines 60 and 25 to the catalytic cracking step. A total yield of approximately 61% of gasoline including that formed by polymerizing the Ca and C4 oleilns from both cracking steps was obtained. The catalytically crackedv fraction had an octane number of 8l and the thermally cracked portion had an octane number of 72. The blend was 76. octane number 400 F. end-point motor` fuel. Thel yield of cracked gasoline obtainable from this stock by non-catalytic cracking 'alone was approximate- 1y 51%. y

I claim as my invention:

l. A process for converting a hydrocarbon oil into substantial yields of relatively high antiknock gasoline which comprises charging said oil to\a primary fractionation step, separating a heavy non-vaporous fraction of the oil, subjecting said fraction to non-catalytic cracking in a primary cracking step by passage through aheating coiland communicating reaction chamberV at a temperature and pressure adequate to eifect substantial cracking thereof, passing the reaction products into a vaporizing zone et a reduced pressure, separating and recovering therefrom a heavy fraction yunsuitable for further conversion, passin the vaporous portion of said reaction products to said primary fractionation step, removing the gas and gasoline, separately removing from said fractionating step, an intermediate-boiling fraction, comprising components of the charging oil not previously subjected to cracking conditions in the process, and contacting the same with a catalyst in a secondry cracking step under conditions adequate to eilect substantial cracking thereof, separating gas and gasoline from the products of the secondary cracking step in a secondary fracthe same in vaporous form with a catalyst in a secondary cracking step under conditions adequate to effect substantial cracking thereof, sep- -arating resulting gas and gasoline in a secondary fractionation step and recovering the same,

separating resulting insuiiiciently converted oil v into a low-boiling fraction, an Iintermediateboiling fraction, and a residual fraction returning the intermediate-boiling fraction of said insufficiently converted oil to said secondaryA cracking step, mixing the low-boiling fraction and the residual fraction of said insufllciently converted oil and passing the mixture to `a seoondary heating coil communicating with the aforesaid reaction chamber of said primary cracking step and subjecting the same in said secondary coil to independently controlled -cracking conditions of temperature and presreduced pressure, separating .and recovering therefrom a heavy fraction unsuitable for further conversion, passing the vaporous portion of said reaction products to said primary fractionatin step, removing the gas and gasoline, separately removing from said fractionating step an intermediate-boiling fraction and contacting tionation step and recovering the same, re-

turning an intermediate-boiling fraction of insufficiently converted oil separated from the last named products to said secondary cracking step, and supplying a higher-boiling fraction of said insufficiently converted oil to a secondary heating coil communicating Awith said reaction chamber of said primary cracking step and subjecting the same in said secondary coil to inde pendently controlled cracking conditions oi' temperature and pressure.

2. A process for converting a hydrocarbon oil into substantial yields of relatively high antiknock gasoline which comprises charging said oil to a primary fractionation step, separating a heavy non-vaporous fraction 'of the oil. subjecting said fraction to non-catalytic cracking in a primary cracking step by passage throughaheating coil and communicating reaction chamber at a temperature and pressure adequate to effect substantial cracking thereof, passing the reaction products into a vaporizing zone at a reduced pressure, separating and therefrom a heavy fraction unsuitable for further conversion, passing the vaporous portion of said reaction products to said primary fractionrecovering ation step, removing the'gas and gasoline, sepathe same in vaporous form with a catalyst in a secondary cracking step under conditions adequate to effect substantial cracking thereof, separating resulting gas-and gasoline in a secondary fractionation step and recovering the same. separating resulting insufficiently converted oil into a low-boiling fraction,v an intennediateboiling fraction, and a residual fraction, passing said low-'boiling fraction to a secondary heating coil communicating with the aforesaid reaction chamber-of the. non-catalytic cracking step and subjecting the same in said secondary coilvto independently controlled cracking conditions of temperature and pressure, returning -the intermediate-boiling fraction of said insumciently converted oil to said secondary cracking step, and passing said residual fraction to the aforesaid vaporizing zone of said primary cracking step.

4. A process for convex-ting a hydrocarbon oil Y `mary fractionation step, removing the gas and gasoline, separately removing from said fractionating step an intermediate-boiling fraction and contacting the same in vaporous form with a catalyst in a secondary cracking step under conditions adequate to' effect substantial cracking thereof, separating resulting gas and gasoline in a secondaryfractionation step and recovering the same, separating a relatively loW- boiling fraction and a higher-boiling fraction of the resulting insuiiiciently converted oil, passing said relatively low-boiling fraction to a secondary heating coil\ communicating with said reaction chamber of said primary cracking step and subjecting the same in said secondary coil to independently controlled cracking conditions of temperature and pressure, and returning the higher-boiling fraction of insuiiiciently converted oil tothe secondary cracking step.

5. A process for converting a hydrocarbon oil into substantial yields of relatively high antiknock gasoline which comprises charging said oil to a primary fractionation step, separating a heavy non-vaporous fraction of the oil, subjecting said fraction to non-catalytic cracking in a primary cracking step by passage through a heating oil and communicating reaction chamber at a temperature and pressure adequate 'to effect substantial cracking thereof, passing the reaction products into a vaporizing zone at a reduced pressure, separating and recovering therefrom a heavy fraction unsuitable for further conversion, passing the vaporous portion of said reaction products t said primary fractionation step, removing the gas and gasoline, separately removing from said fractionating step an intermediate-boiling fraction, comprising components of the charging-oil not previously subjected to cracking conditions in the process, and contacting the same with a catalyst in a secondary cracking step under conditions adequate to effect substantial cracking thereof, separating resulting ga-s and gasoline in a secondary fractionation step and recovering the same, separating a relatively low-boiling fraction and a higher-boiling fraction of the resulting insuciently converted oil, and passing the higherboiling fraction of the nsumciently converted oil to a secondary heating coil communicating with the reaction chamber of said primary cracking step and subjecting the same in said secondary coil to independently controlled cracking conditions of temperature and pressure.

6. A process for converting a hydrocarbon oil' into substantial yields of relatively high antiknock gasoline which comprises charging said oil to a primary fractionation step, separating a heavy non-vaporous fraction of the oil, subjecting said fraction to non-catalytic cracking in a primary cracking step by passage through a heating coil and communicating reaction chamber -at a temperature and pressure adequate to effect substantial cracking thereof, passing the reaction productsinto a vaporizing zone at a reduced pressure, separating and recovering therefrom a heavy fraction unsuitable for further conversion, passing the vaporous portion of said reaction products to said primary fractionation step, removing the gas and gasoline, separately removing from said fractionating step an intermediate-boiling fraction and contactirg the same in vaporous form with a catalyst in a secondary cracking step under conditions adequate to effect substantial cracking thereof, separating resulting gas and gasoline in a secondary fractionation step and recovering. the same, separating a relatively 10W- boiling fraction and a higher-boiling fraction of the resulting insuiiiciently converted oil, passing the relatively low-boiling fraction of insufciently converted oil to a secondary heating coil communicating with the reaction chamber of said primary cracking step and subjecting the same in said secondary coil to independent- -ly controlled cracking conditions of temperature and pressure, and returning the higherboilingvfraction of said insufiiciently converted oil to said secondary cracking step. y.

CHARLES L. THOMAS.

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