US2702782A

US2702782A - Hydrocarbon conversion

Info

Publication number: US2702782A
Application number: US131078A
Authority: US
Inventors: Donald M Little
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1949-12-05
Filing date: 1949-12-05
Publication date: 1955-02-22
Anticipated expiration: 1972-02-22

Description

Feb. 22, 1955 D. M. LITTLE 2 285B? TOPPED. I 4 VACUUM CRUDE H CRACKING DISTILLATION ZONE ZONE REFORMING ZONE 24] CRACKING h fzfg- ,[6

ACTION ZONE ZONE B N l8 CARBON 20 BLACK BLACK L FURNACE RECOVERY INVENTOR. D M. LITTLE BY 2 g M g ATTORNEYS United States Patent HYDROCARBON CONVERSION Donald M. Little, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 5, 1949, Serial No. 131,078

4 Claims. (Cl. 196-49) This invention relates to the conversion of hydrocarbon oils. In a specific aspect this invention relates to a novel process 'for the conversion of heavy carbonaceous residues. In one specific embodiment this invention relates to a novel combination of processing steps for the conversion of a topped crude oil.

It is an object of this invention to provide a novel process for the conversion of hydrocarbons.

It is another object of this invention to provide a novel grocess for the conversion of heavy carbonaceous resiues.

It is a further object of this invention to provide a novel combination of steps for the cracking of a topped crude oil that causes a decrease in the yield of fuel oil and an increalse in the yield of gasoline and low aniline number gas 0 Further objects and advantages of my invention will be readily apparent from the disclosure hereinbelow and the accompanying drawing.

In a novel combination of processing steps I have found that I can crack a heavy carbonaceous residue or a topped crude oil in such a manner that the yield of fuel oil is reduced and the yields of gasoline and gas oil are increased when compared with prior art methods of cracking topped crude oils. In one method of operation my process can be employed to obtain only slightly increased yields of gasoline and, consequently, greater increases in the yield of gas oil. Since the gasoline produced from these operations is of lower quality than that generally desired for present day motor fuels, this latter method of operation is regarded as the preferred one.

The accompanying drawing is a schematic diagram showing an arrangement of processing steps that may be employed in practicing my invention. Many connecting lines, recycle lines, valves, compressors, pressure and temperature measuring and controlling apparatus, and the like, have not been shown on this drawing in order to facilitate the understanding of my invention. However, the inclusion of such equipment and apparatus is within the scope of my process. The materials of construction of the various pieces of equipment may be selected from those commercially available as required by the specific process steps taking place in each unit.

Throughout my disclosure I will refer frequently to the aniline number or aniline point of a gas oil. This is an indication of the aromaticity of the gas oil, and it is determined by a g a quantity of aniline with the oil to be tested and then determining the minimum equilibrium solution temperature. That temperature is called the aniline number or aniline point, and throughout this disclosure and claims the aniline points are in F.

Referring now to the accompanying drawing, a topped crude oil from a crude oil topping or'reducing operation (not shown) enters the system via line 1 and passes to cracking zone 2 where the topped crude oil undergoes a thermal cracking treatment. In normal topped crude cracking operations, the residue or fuel oil yield depends to a large extent upon the severity of the cracking. However, as the severity of the cracking is increased, more coke is formed, and, thus, frequent shutdowns of the cracking unit for clean-outs are required. In order that the severity of the cracking in zone 2 can be increased without increased coke formation, I introduce a highly refractory gas oil to zone 2 to act as a diluent. Volumetric ratios of topped crude oil to diluent within the range of 1:0.5 to 1:1.5 are employed, and at these conditions thermal cracking temperatures about 15 F. higher 2,702,782 Patented Feb. 22, 1955 than the temperatures employed without a diluent are feasible without increased coke formation. Thermal cracking temperatures within the range of 875 to 890 F. have been employed for the thermal cracking of topped crude oils, but in my process temperatures above 890 F. but not above 905 F., other conditions remaining fixed, may be employed. This temperature range may be used when thermally cracking a topped Texas Panhandle crude oil, but, depending upon the feed stock, higher and lower temperatures may be used efliciently. The actual temperature employed also depends to a large extent upon the actual design of the cracking'unit. The diluent that I employ is a highly refractory gas oil having an aniline number within the range of 20 to 50, preferably not above 20, and more preferably within the range of l0 to 0, and it is introduced to zone 2 along with the topped crude oil via line l.

The highly refractory or aromatic diluent for my process may be introduced to the system when operation is initiated, and, since it remains substantially-unconverted during the cracking process or merely rides through" unchanged, it can be recycled toczone 2 for cracking of additional topped crude oil. However, in the thermal cracking of a topped crude oil ta fraction of the gas oil produced has a relatively low arliline number and is suitable for use as a diluent in my process. Alternatively, then, the thermal cracking step can be operated at the less severe temperatures until suflicient gas oil is produced which is suitable for use as a diluent. The diluent gas oil is then recycled to zone 2 where it permits the 'use of the more severe cracking temperatures. In my process, as described herein, sufiicient diluent is available either from an outside source or from the operation of zone 2 at the lower temperatures to permit the operation of zone 2 at the more severe conditions. It will be understood that, if the diluent gas oil is introduced from an outside source, suflicient gas oil is required only for initiation of the process, and the gas oil diluent is then recycled to zone 2. Thus, if barrels of topped crude oil is introduced to zone 1, 100 barrels of diluent gas oil will also be introduced. This diluent gas oil remains unconverted in the process, and it is recycled to zone 2 for use with the next 100 barrels of topped crude oil.

From zone 2 that fraction of the cracking eflluent boiling not above 400 F. is withdrawn via line 3. This fraction contains gasoline in addition to lower boiling components, and the gasoline can be separated therefrom by any suitable means (not shown). From zone 2 the fraction of the eflluent boiling above 400 F. and containing gas oil and fuel oil is withdrawn via line 4 and passed to zone 5 where gas oil and fuel oil are conveniently separated. The gas oil entering zone 5 contains the gas oil employed in zone 2 as a diluent and the gas oil resulting from the cracking operation in zone 2. Zone 5 is preferably a vacuum distillation zone operated at a temperature of 650 to 825 F. to recover completely the gas oil from the fuel oil. Fuel oil or pitch having a softening point of 200 to 300 F. is withdrawn from the bottom of the still via line 6, and gas oil is taken overhead via line 7 and passed to solvent extraction zone 8. The gas oil passing via line 7 has an aniline number of 90 to and it contains the gas oil employed as a diluent in zone 2 and the gas oil produced in the cracking operation in zone 2.

Solvent extraction zone 8 is employed to separate a high aniline number rafiinate gas oil from a low aniline number extract gas oil. The latter, having an aniline number suitable for use in zone 2, is withdrawn via line 9, and that portion that is required as a diluent in zone 2 is recycled thereto via line 10. In zone 8 any suitable extractive solvent, such as cellosolve, acetonitrile, and nitrobenzene is employed, but furfural is the preferred solvent. The conditions employed in zone 8 depend to a large extent upon the degree of extraction desired and upon the aniline number desired for the extract gas oil. Usually the solvent extraction is etfected at a temperature of 70 to F. and with volumetric ratios of solvent to gas oil within the range of 0.5 to 5.0.

The solvent extraction step is operated in a manner that the aniline number of the extract gas oil withdrawn via line 9 is suitable for use in zone 2 or about 10, and

a-rafinate gas oil having an aniline number of 180 is withdrawn from extraction zone 8 via line 11 into cracking zone 12. The rafiinate gas oil may be withdrawn from the system or it may be treated'further in any suitable manner. Since its content of aromatic hydrocarbons is low, this gas oil is quite suitable for use as a feed for either a catalytic or thermal cracking operation, both of which are processes well known to those skilled in the art. Catalytic cracking operations employ synthetic or natural clay catalysts, silica-alumina, or bauxite catalyst in either a stationary or mobile bed, and the reaction conditions are dependent upon the particular catalyst that is used and the depth of cracking desired. The temperature is within the range of 850 to ll50 F. and the pressure is less than 100 pounds per square inch gauge. Gas oil space velocities of 0.5 to 5.0 volumes of oil per volume of catalyst per hour are used, and, if desired, steam or other diluent may be introduced to the cracking zone. Thermal cracking of gas oil is effected at a temperature of 900 to 1150 F. and at a pressure of 500 to 2000 pounds per square inch gauge. Both cracking operations produce an eflluent fraction boiling not above 400 F. and containing gasoline. This fraction is with drawn from zone 12 via line 13 and gasoline is subsequently recovered therefrom. ln zone 12 a gas oil having an aniline number lower than that of the raflinate gas oil from extraction zone 8 is produced. The aniline number of this gas oil is about 150, and it is recycled to solvent extraction zone 8 via lines 14 and 7.

The highly aromatic extract gas oil that is removed from extraction zone 8 via line 9 contains the low aniline number diluent that was employed in zone 2 and gas oil of equally low aniline number produced during the cracking operation in zone 2. The portion of the gas oil passing via line 9 that is required in zone 2 is recycled thereto via line 10. The remaining portion passing via line 9 is withdrawn vialine 15, and it may be treated further in any suitable manner. I prefer to use this remaining portion for the production of carbon black, but for this process a gas oil feed having an aniline number within the range of 25 to 65 is preferred. If the aniline number of the gas oil passing via line 15 is lower than that required for carbon black production, gas oil passing via line 7 is passed to line 15 via line 16 in a quantity sufficient to obtain a gas oil in line 15 suitable for carbon black production. A detailed disclosure of a process for producing a feed suitable for producing carbon black is in the application of E. V. Mathy, Serial No. 134,403, filed December 22, 1949. Alternatively, instead of withdrawing gas oil from line 7 for this purpose, a portion or, if needed, all of the gas oil passing via line 14 may be admixed with the gas oil in line 15 to produce a gas oil having the desired aniline number.

The gas oil suitable for carbon black production passes through a preheater (not shown) where it is vaporized, and then it is continuously introduced to carbon black furnace 17 at about the center of the inlet end wall. The vaporized gas oil passes through furnace 17 in a direction parallel to the longitudinal axis of the furnace at a rate in the order of 50 (D) gallons per hour, where D is the diameter of the chamber in feet. Air or an air-gas mixture is introduced into the furnace near its inlet end wall through a tangential port in the side wall, said port being directed tangentially with respect to the longitudinal axis of the furnace. The air or air-gas mixture is introduced at a rate of about 400 cubic feet per gallon of oil and at a velocity in the tangential port preferably in excess of 50 feet per second. The combustible mixture is burned to maintain the temperature in the furnace at 2100 to 2400' F. and to decompose the unburned oil to carbon black, said furnace being of at least sufficient length to produce carbon black substantially free of tarry materials. The eflluent from the furnace is quickly quenched to about 1250 F. with a water spray, and it is then cooled further to about 450 F. (by means not shown), by passing in heat exchange relation with the topped crude oil entering the system via line 1. The second cooling step may also be effected bypassing furnace eflluent, after cooling with a water spray, in heat exchange relation with the extract gas oil passing via line 9. The furnace efiluent thence passes via line 18 to carbon black recovery unit 19 which may be any suitable means for recovering the carbon black, such as an electrical precipitator. In unit 19 combustion gases from furnace 17 are separated from the carbon black, and. if desired, they may be withdrawn via line 26 and used as a diluent in cracking zone 12 when a catalytic cracking operation is effected therein. Carbon blackzois subsequently withdrawn from the system via In an alternative method of operation and instead of passing the entire eflluent boiling above 400 F. from zone 2 to zone 5, a naphtha fraction boiling between 400 and 500 F. is withdrawn from zone 2 via line 21 and thence passed to reforming zone 22. The reforming operation in zone 22 is effected at a temperature within the range of 950 to 1000 F. and at a pressure of 1500 to 2500 pounds per square inch gauge. From zone 22 a gasoline fraction is withdrawn via line 23, and this fraction may be combined with the gasoline withdrawn via lines 3 and 13 to form the gasoline product of the process. A gas oil fraction is withdrawn via line 24, and it is admixed in line 7 with the gas oil passing into extraction zone 8. A fuel oil fraction is withdrawn via line 25, and it is passed-via the thermal cracking of a topped crude oil, 16 barrels of pitch having a'softening point of 200 to 300 F., 55 barrels of gasoline, l1 barrels of gas oil having an aniline number of 180, and 5 barrels of gas oil having an aniline number of 10 are produced from each barrels of topped crude oil. In my process wherein 100 barrels of 10 aniline number gas oil are employed with each 100 barrels of topped crude oil, 10 barrels of pitch having a softening point of 200 to 300 F., 56 barrels of gasoline, 13 barrels of gas oil having an aniline number of 180, and 6 barrels of gas oil having an aniline number of -10 are produced from each 100 barrels of topped crude oil. The data that I have cited for my process represent those volumes of topped crude oil cracking products passing via lines 6. 3, 11 and 15, respectively. Even greater yields of gasoline and the gas oils can be obtained by incorporating in the process reforming zone 22 and cracking zone 12, as discussed in detail hereinabove.

Although I have discussed in considerable detail the novel arrangement of steps that I have employed to obtain improved results, modifications within the scope of my process will be apparent to those skilled in the art.

I claim:

1. The process for the conversion of a topped crude oil which comprises heating and cracking said topped crude oil in a cracking zone at a temperature in excess of 890 F. in the presence of a gas oil having an aniline number within the range of 20 to 50 in a volumetric ratio of topped crude oil to gas oil diluent within the range of 1:05 to 1:1.5, to severely thermally crack the same, recovering a fraction from said severe thermal cracking step containing gasoline, vacuum distilling a second fraction from said thermal cracking step containing gas oil and fuel oil and boiling above the firstnamed fraction, recovering from said vacuum distillation as overhead a stream containing said gas oil having said aniline number by conducting said vacuum distillation so as to obtain as bottoms product thereof pitch having a softening point within the range of 200 to 300 F., solvent extracting the overhead from said vacuum distillation to produce an aromatic-lean raflinate phase and an aromatic-rich extract phase, separating solvent from said extract phase to produce an aromatic-rich extract oil, and recycling aromatic-rich extract oil to said thermal cracking of topped crude oil in a quantity suflicient to act as a diluent therein.

2. A process according to claim 1 wherein furfural is employed as solvent in the solvent extraction step at a temperature of 70 to F. and at a volumetric ratio of solvent to vacuum distillation overhead within the range of 0.5 to 5.0. r

3. The process for the conversion of a topped crude oil which comprises heating and cracking said topped crude oil in a cracking zone at a temperature in excess of 890 F. but not above 905 F. in the presence of a gas oil having an aniline number not above 20 in a volumetric ratio of topped crude oil to gas oil diluent within the range of 120.5 to 121.5, to severely thermally crack the same, recovering a fraction from said thermal an aromatic-rich extract phase, separating from said rafiinate phase any solvent contained therein to produce an aromatic-lean raffinate oil, cracking said rafiinate oil in the presence of a bauxite catalyst at a temperature within the range of 850 to 1150' F., recovering from the efiiuent of said catalytic cracking step a fraction boiling below 400 F., returning to said solvent extraction a portion of the catalytic cracking emuent having a boiling point of at least 400 F., separating solvent from the extract phase from said solvent extraction step to produce an aromatic-rich extract oil, and recycling aromatic-rich extract oil to-said thermal cracking of topped crude oil in a volumetric ratio of topped crude oil to aromaticrich extract within the range of 1:0.5 to 1:1.5

4. The process for the conversion of a topped crude oil which comprises heating and cracking said topped crude oil in a cracking zone to thermal cracking at a temperature above 890' F. but not above 905 F. in the presence of a gas oil having an aniline number within the range of -10 to 0 in a volumetric ratio of topped crude oil to gas oil diluent within the range of 1:0.5 to 1:15, to severely thermally crack the same, recovering a fraction from said thermal cracking step boiling below 400 F., vacuum distilling a second fraction from said thermal cracking step containing gas oil and fuel oil and boiling above the first-named fraction, recovering from said vacuum distillation as overhead a stream containing said gas oil having' said aniline number by conducting said vacuum distillation so as to obtain as bottoms product thereof pitch having a softening point within the range of 200 to 300 F., solvent extracting the overhead from said vacuum distillation to produce an aromatic-lean ratfinate phase and an aromatic-rich extract phase, separating from said ratfinate phase any solvent contained therein to produce an aromatic-lean rafi'inate oil, cracking said rafiinate oil in the presence of a bauxite catalyst at a temperature within the range of 850 to 1150 F., recovering from the efliuent of said catalytic cracking step a fraction boiling below 400 F., returning to said solvent extraction a portion of the catalytic cracking effiuent having a boiling point of at least 400 F., separating solvent from the extract phase from said solvent extraction step to produce an aromatic-rich extract oil, recycling aromatic-rich extract oil to said thermal cracking of topped crude oil in a volumetric ratio of topped crude oil to aromatic-rich extract within the range of 1:05 to 121.5, admixing with the remaining extract oil overhead from said vacuum distillation step to produce an oil having an aniline number within the range of 25 to 65, subjecting the thusproduced oil to carbon black producing conditions in a ereactor furnace at a temperature of 2100 to 2400 F., recovering carbon black from the resulting effluent, and passing gaseous effluent from said carbon black producing sttlep to said catalytic cracking step to act as a diluent t erein.

References Cited in the file of this patent UNITED STATES PATENTS 2,160,814 Arveson June 6, 1939 2,197,460 Adams Apr. 16, 1940 2,228,510 Dearborn et al. Jan. 14, 1941 2,247,535 Voorhees July 1, 1941 2,352,025 Seguy June 20, 1944 2,375,796 Krejci May 15, 1945 2,436,257 Hansford Feb. 17, 1948 2,516,134 Molique July 25, 1950 2,529,790 Waddill Nov. 14, 1950

Claims

1. THE PROCESS FOR THE CONVERSION OF A TROPPED CRUDE OIL WHICH COMPRISES HEATING AND CRACKING SAID TOPPED CRUDE IL IN A CRACKING ZONE AT A TEMPERATURE IN EXCESS OF 890* F. IN THE PRESENCE OF A GAS OIL HAVING AN ANILINE NUMBER WITHIN THE RANGE OF -20 TO 50 IN A VOLUMETRIC RATIO OF TOPPED CRUDE OIL TO GAS OIL DILUENT WITH THE RANGE OF 1:0.5 TO 1:1.5, TO SEVERELY THERMALLY CRACK THE SAME, RECOVERING A FRACTION FROM SAID SEVERE THERMAL CRACKING STEP CONTAINING GASOLINE, VACUUM DISTILLING A SECOND FRACTION FROM SAID THERMAL CRACKING STEP CONTAINING GAS OIL AND FUEL OIL AND BOILING ABOVE THE FIRSTNAMED FRACTION, RECOVERING FROM SAID VACUUM DISTILLATION AS OVERHEAD A STREAM CONTAINING SAID GAS IN HAVING SAID ANILINE NUMBER BY CONDUCTING SAID VACUUM DISTILLATION SO AS TO OBTAIN AS BOTTOMS PRODUCT THEREOF PITCH HAVING A SOFTENING POINT WITHIN THE RANGE OF 200 TO 300* F., SOLVENT EXTRACTING THE OVERHEAD FROM SAID VACUUM DISTILLATION TO PRODUCE AN AROMATIC-LEAN RAFFINATE PHASE AND AN AROMATIC-RICH EXTRACT PHASE, SEPARATING SOLVENT FROM SAID EXTRACT PHASE TO PRODUCE AN AROMATIC-RICH EXTRACT OIL, AND RECYCLING AROMATIC-RICH EXTRACT OIL TO SAID THERMAL CRACKING OF TOPPED CRUDE OIL IN A QUANTITY SUFFICIENT TO ACT AS A DILUENT THEREIN.