US3190828A - Catalytic process for cracking oils containing metallic contaminants - Google Patents

Description

June22, 1965 h E. H. DANIEL ETAL CATALYTIC- PR 3,190,828 ocEss FOR cRAcxING oILs GONTAINING METALLIC CONTAMINANTS Filed 001'.. 8, 1962 2 Sheets-Sheet 1 E. H. DANIEL ETAL CATALYTIC PROCESS FOR CRACKING OILS June 22, 1965 CONTAINING METALLIC CONTAMINANTS 2 Sheets-Sheet 2 Filed Oct. 8, 1962 INVENTRS EH. DAN|EL C.C. AKERS BY N.W. MITCHELL S.E. FORSYTH ym? "1 TTRN 5 United States Patent O 3,190,828 CATALYTEC PROCESS FR `CRACKING OILS CUN- TAINING METALLIC CONTAMINANTS Elbert H. Daniel, Carol C. Alters, and Norris W. Mitchell,

Phillips, Tex., and Sam E. Forsyth, Bartlesville, Qkla.,

assignors to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 8, 1962, Ser. No. 223,392 9 Ciaims. (Ci. 20S- 78) ing coke and hydrogen production in a catalytic cracking Y operation wherein the feed stream is contaminated with compounds of nickel, va-nadium or iron.

It is known to crack hydrocarbon fluids catalytically to increase the quantity and quality of the gasoline or motor fuel product. In such operations a renery bottoms product is produced in the distillation step following the cracking step for which there is little demand and therefore this b-ottoms product is usually returned to the cracking operation. It is also known to solvent extract this heavy bottoms product a-nd also the heavy recycle -oil so as to remove aromatic hydrocarbons therefrom, which aromatic hydrocarbons are carbon for-mers and gas formers. The raffinate from the solvent extraction step is then recycled to the cracking operation. It isalso known .to employ two or more cracking zones wherein feed stocks containing differing concentrations of contaminating metals are separately cracked. An improved .process for operating a plurality of cracking zones in the V'hydrocarbon conversion process has recently been proposed wherein :a relatively Irefractory, highly parafiinic, low metal-content hydrocarbon feed stock is supplied to a first catalytic cracking Zone operating at high conversion level; a less refractory, high metal-content hydrocarbon feed stock is supplied -to ya second catalytic cracking Zone operated at low conversion; and the heavy cycle oil and the decant oil from the two cracking zones 'are solvent extracted to provide a raffinate stream which is passed `as a portion of the feed stock to the first catalytic cracking zone. The aromatic oil from the solvent extraction step is valuable as a carbon bla-ck process feed stock. This new method of operation has greatly increased the catalyst life in the clean oil cracking step which is operated at high conversion levels; however, theclean oil charged to the clean oil unit did not provide a sufficient coke laydfown on the -catalystto provide the required amount of heat in the regeneration step to operate the catalytic cracking unit. It has been found that the heat requirements in the regeneration step of the clean oil unit can be met by passing a portion-of the highest boiling fraction of the low level conversion catalytic cracking unit to the clean oil unit so as to provide a coke laydown on the clean catalyst which will be suicient yto supply the necessary heat to operate the clean oil unit satisfactorily.

We have now found that an improved operation occurs when at least a portion of the highly parafiinic raffinate ordinarily charged to the clean oil unit is admixed wit-h the feed to `the dirty oil unit (low level conversion catalytic cracking unit). Top-pcd crude oil, which comprises the bottom 20 to 25 liquid volue percent of the total ice crude oil, is `a hydrogen-poor stream `and is contaminatedwith metallic materials such as compounds 'of nickel, vanadium and iron. Gas oils will usually contain from about 1 to 20 pounds of metallic contaminants per 1000 barrels whereas topped crude or residuum may contain as much as 200 pounds of metal per 1000 barrels as show-n in U.S. Patent 2,971,905, issued to Herman Bieber et al. February 14, 1961. U.S. Patent 3,004,911, issued to l. W. Slover October 17, 1961, shows a topped crude (dirtier oil) containing 200 ppm, of contaminating metal. Thus a gas oil or distillate will usually contain not more than about 20 pounds of metallic contaminants per 1000 barrels which is equivalent to `about 65 to 75 ppm. of metallic contaminants and a topped crude or residuum will `otten contain 200 or more p.p.m. of metallic contaminants. Some of these contaminants act as catalysts in effecting la high production of coke and hydrogen gas upon catalytically cracking this high carbon content topped crude using conventional fluidized cracking catalysts, for example, those of the silicaalumina type. tion of the highly p'arafiinic rafiinate from the solvent extraction step is admixed with the topped crude-containing liquid oil charge prior to contacting the Oil charge with the hot regenerated catalyst. The practice of the invention results in a surprising an-d unexpected improveent in product distribution, for example, lower coke laydown, higher gasoline yields and high recovery of other valuable products.

It is an object of this invention to provide a method for improving 4the quality and quantity of products ob- Itained in a catalytic cracking yoper-ation employing a plurai-lty of cracking steps. It is also lan object of thisinvention to provide a method for oper-ating a cracking operation employing a plurality of cracking steps so as `to decrease the amount of coke and hydrogen produced. Still another object of the invention is to provide Ia method for operating a catalytic cracking process employing a plurality of cracking steps so as to improve the color stability of the cycle oil produced in the cracking step wherein the charge stock contains metal oantarninants. y

It is still another object ofthe invention to provide a means for passing a portion of a highly parafiinic raffinate from a solvent extraction step to the charge stock having a highmetal content which is utilized as feed to a catalytic cracking operation. Other q objects and advantages will be apparent to one ski-lied in the art upon study of this disclosure, including rthe detailed descrip- ,tion of the invention and the appended drawing wherein:

FIGURE l is a diagrammatic ow plan of one embodiment of the invention; and

FIGURE 2 is a diagrammatic flow plan of a specific, preferred embodiment of the invention.

Referring now to FIGURE l of the drawing, a hydrocarbon feed stream is fed to a catalytic cracking zone 10 via conduit 11. This feed stream introduced Via conduit l2 is made up of gas oil and other distillates so that the metal content of the feed stream is quite small. Recycle streams which can be introduced via conduits 13, 14, 15 and- 35a make up the total feed to the catalytic cracking zone 10. A heater 16 heats the fresh feed and recycle cycle oil to a temperature slightly under that at which thermal cracking might occur prior to admission to the cracking zone 1t). Hot, regenerated catalyst is added to the catalytic cracking zone 10 via conduit 17 and used catalyst is removed via conduit 18 and passed to a regeneration zone (not shown) and is then returned to the catalytic cracking zone 10 at a temperaturev higher than catalytic cracking temperature sol that the mixture of heated oil and regenerated catalyst achieves the desired cracking temperature in the cracking zone. The catalyst can be any desired type of cracking catalyst and According to the present invention a por? in the embodiment of the present invention being described the catalyst is a silica-alumina cracking catalyst. Also in the embodiment f the invention presently described the catalytic cracking reactors are ofthe ffuidized flow type employing a finely divided catalyst. A regen- `erator also employing the fluid-solids fiow technique along with fractionating facilities and other facilities make up the system known in the art as an FCC unit. The hydrocarbon effluent from the catalytic cracking zone is passed through the conduit 19 to the product fractionator 20 wherein the effluent products are separated into fractions having different boiling ranges from whence C4 and lighter materials are removed via conduit 21, a gasoline cut is removed via conduit 22 and light cycle oil is removed via conduit 23 to form these various products of the process. Heavy cycle oil, removed via conduit 24, and decant oil, removed via conduit 25, are passed to a solvent extraction plant 27. Catalyst which is entrained in the cracking zone effluent in conduit 19 is accumulated in settling zone 28 which is shown as an external settler communicating with product fractionator 20 by means of conduit 29. The accumulated catalyst fines are removed from settler 28 as a slurry in oil and this slurry is returned to the catalytic cracking zone 10 via conduit 15.

A second hydrocarbon feed stream comprising topped crude, pitch, and other hydrocarbon fluids containing relatively large amounts of metal contaminants or coke and gas forming components is fed to a second catalytic cracking zone 30 via conduits 31 and 32. Heat is provided to this feed stream by means of heater 33. Recycle streams can be added via conduits 34 and 35. Highly parafinic raffinate is added to the feed stream via conduit 14a prior to entry of the feed to the catalytic cracking zone 10. Used catalyst which is employed as make-up catalyst for catalytic cracking zone 30 is introduced via conduit 36 and catalyst is removed and passed through a regeneration zone (not shown) via conduit 37 or is discarded via conduit 38. Hydrocarbon effluent from catalytic cracking zone 30 is passed via conduit 39 to a second product fractionation zone 40. C4 and lighter hydrocarbons removed via conduit 41, a gasoline fraction removed via conduit 42 and a light cycle oil removed via conduit 43 are recovered as products of the process. Heavy cycle Voil removed via conduit 44 land decant oil removed via conduit 45 are passed via conduit 46 to the solvent extraction zone 27 along with the oil in conduit 26. The aromatic hydrocarbon product which comprises the extract from solvent extraction zone 27 is recovered via conduit 47 for use as feed to a carbon black producing plant (not shown) or for other desired use. A portion of the slurry of catalyst and oil removed from the product fractionator 40 can be passed via conduits 35 and 35a to catalytic cracker 10. The rafiinate removed from solvent extraction zone 27 is passed via conduit 14 as feed to the catalytic cracking zone 10 and via conduit 14a as feed to the catalytic cracking zone 30.

A conventional solvent-extraction process is employed utilizing liquid sulfur dioxide as the solvent to extract aromatic compounds from the oil so as to produce a paraflinic raffinate to be returned to the cracking zones 10 and 30. Any suitable solvent can be utilized to extract the aromatics from the oil.

A mild cracking step, i.e., a catalytic cracking step conducted at low conversion level and low temperature, is herein defined as a catalytic cracking step operated at a temperature in the range of about 870 to 900 F. and at a conversion level of about 30 to 40 percent conversion. A severe cracking step, i.e., a catalytic cracking step conducted at high temperature and high conversion level, is herein defined as a catalytic cracking step operated at a temperature of about 905 to 930 F. and a conversion level of about 50 to 70 percent conversion.

FIGURE 2 illustrates a specific example of the operation of the invention and demonstrates the advantages obtained by operating the system according to the invention. Referring now to FIGURE 2, operation according to the invention is indicated by the numerals in parentheses which appear as legends on the various streams. It will be noted that operating conditions generally are unchanged in that the temperature and pressure conditions are substantially the same in the reactor and the regenerators when operating according to the prior art and when operating according to the invention. In the prior art 800 barrels per hour of topped crude are charged to the catalytic cracker 30 and according to the present invention this feed stream is increased by the addition of barrels per hour of paraffinic raffinate. When operating according to the invention it will be noted that the products obtained from the fractionator 40 are substantially increased.

Among the improvements realized by the practice of our invention in charging the parafinic raffinate to the catalytic cracker 30 are the following:

(l) Increased yields of gasoline;

(2) Increased yields of olens which can be alkylated to high octane gasoline;

(3) Improved stability of light cycle oil so that heating distillates and Diesel fuels made therefrom meet the color requirements and do not deteriorate in color in storage;

(4) Improved heat balance in the converter section of the dirty oil catalytic cracker;

(5) Decreased production of hydrogen per barrel of hydrocarbon converted; and

(6) Decreased coke yield per barrel of topped crude.

The above advantages are illustrated in the following table wherein data obtained from prior art operation are compared with data obtained from operation according to the lnvention.

Table I Run I- Run II- Data Prior Invention Operation Topped Crude Charge, LV, percent 100 89 Ranate Charge, LV, percent 0 11 Coke on Catalyst, Wt. Percent of Fresh Feed.. 13. 4 11.4 Coke, #/bbl. of Topped Crude y 44.8 42.0 H2, set/bbl. of Conversion 1, 000 820 Conversion, LV, Percent of Fresh Fee 44. 43. 7 Gasoline, LV, Percent Conv G9. 5 71.7 H2, Wt. Percent of Fresh Feed 0.71 0.68 C3, C4 Olens, LV, Percent Conversion 12. 4 12.6

The catalyst used in Run No. I had a metals content as NiO and V205 of 3,680 p.p.m. and the metals content of the catalyst of Run No. II was 4400 p.p.m. Thus it can be seen that with even a higher metals-containing catalyst as used in Run No. II with recycle of a portion of raffinate, improved results are realized.

The quantity of rafnate passed via conduit 14a can be controlled by a rate of flow controller which, in turn, can be reset by a ratio controller connected to a rate of flow indicator or rate of flow controller in the topped crude feed stream to the reactor. A rate of flow controller can also be employed to regulate the stream passing through conduit 35a according, for example, to the temperature in the catalyst regeneration zone of catalytic cracking Zone I0.

It should be noted that the amount of coke produced in the dirty oil unit was decreased by an amount greater than would be accomplished by a mere dilution effect of the parafinic raffinate. Thus, if the raffinate had contributed no coke at all, the amount of coke would be expected to be more than that actually obtained, i.e., about 12.0 weight percent. Also, the amount of coke produced per barrel of topped crude and the amount of hydrogen produced per barrel of conversion was, in each case, less than would be expected.

In order to obtain the benefits of this invention the raflinate to topped crude, or other metal contaminantcontaining feed stock, ratio should be at least about 1:16 and not more than about 1:4. Thus in a system as described in FIGURE. 2 the amount of raffinate should be in the range of about 50 to 200 barrels per hour when the topped crude charge is 800 barrels per hour. It has been shown that the step of mixing the rafiinate with the topped crude prior to passing the charge to the low conversion-level cracking unit reduces the formation of coke. The step of passing a portion of the catalyst-oil slurry from the low conversion-level cracking unit distillation column to the high conversion-level cracking unit further reduces the amount of coke in the regeneration unit of the low conversion-level cracking unit and thus the amount of heat which must be dissipated in making steam, for example, is greatly reduced.

Reasonable variations and modifications are possible within the scope of the disclosure of the invention Without departing from the spirit and scope of the invention.

That which is claimed is:

ll. In a process for treating hydrocarbon fluids wherein a hydrocarbon stream having a low metal contaminant content of not more than about 65 to 75 ppm. is catalytically cracked at a high conversion level of about 50 to 70 percent conversion in a first catalytic cracking zone at a temperature in the range of about 905 to 930 F., and a hydrocarbon stream having a high metal contaminant content of at least about 200 p.p.m. is catalytically cracked at a low conversion level of about 30 to 40 percent conversion in a second catalytic cracking zone at a temperature in the range of about 870 to 900 F., the improvement comprising solvent extracting the heavy cycle oil and decant oil from said first and second cracking zones; passing a portion of raffinate from the solvent extraction step to the feed to the second cracking zone in an amount sufiicient to provide a ratio of about one volurne of raffinate per 4 to 16 volumes of fresh feed; and passing the remaining raffinate to the first catalytic cracking Zone.

2. In a process for treating hydrocarbon fluids wherein a hydrocarbon stream having a low metal contaminant content of not more than about 65 to 75 p.p.m. is catalytically cracked in a severe first catalytic cracking Zone at a temperature in the range of about 905 to 930 F. and a conversion level of about 50 to 70 percent conversion and a hydrocarbon stream having a high metal contaminant content of at least about 200 p.p.m. is catalytically cracked in a mild second catalytic cracking zone at a temperature in the range of about 870 to 900 F. and a conversion level of about 30 to 40 percent conversion, the improvement comprising recovering the light cycle oil and lighter hydrocarbons from said first and second cracking zones as products of the process; passing a minor portion of decant oil obtained from said second cracking zone to the feed stream to said first cracking zone; solvent extracting the heavy cycle oil and remaining decant oil recovered from said first and second cracking zones; passing a major portion of the raffinate from said solvent extraction step as feed to said first cracking zone; passing a minor portion of the raffinate from said solvent extraction step as feed to said second cracking zone; adding new catalyst to said first cracking zone; passing used catalyst from said first cracking zone to said second cracking Zone; and recovering thev aromatic extract from said solvent extraction step as an additional product of the process.

3. In a process for treating hydrocarbon fluids wherein a hydrocarbon stream having a low metal contaminant content of not more than about 65 to 75 p.p.m. is catalytically cracked in a first catalytic cracking zone at a conversion level of about 50 to 70 percent conversionand at a temperature in the range of about 905 to 930 F. and a hydrocarbon stream having a high metal contaminant content of at least about 200 ppm. is catalytically cracket in a second cracking zone at low conversion level of about 30 to 40 percent conversion, the improvement comprising recovering the light cycle oil and lighter hydrocarbons from said first and secondcracking zones as products of the process; passing highest boiling fraction obtained from said second cracking zone to the feed to the first cracking zone in an amount suilicient to maintain crackingtemperature in said first cracking Zone; solvent extracting the remaining highest boiling fraction and heavy cycle oil recovered from said first and second cracking zones; passing a first portion of raffinate from said solvent extraction step as feed to said first cracking zone; and passing a second portion of raffinate from said solvent extraction step to the feed to the second cracking zone in a ratio of about one volume of raffinate to 4 to 16 volumes of fresh feed.

4. In a process for treating hydrocarbon fluids wherein a gas-oil containing distillate hydrocarbon stream having a low metal contaminant content of not more than about 65 to 75 p.p.m. of metallic contaminants is catalytically cracked at a high conversion level of about 50 to 70 percent conversion and at a temperature in the range of about 905 to 930 F. in a first catalytic cracking Zone and a topped crude-containing hydrocarbon stream having a high metal contaminant content of at least about 200 ppm. of metallic contaminants is catalytically cracked at a low conversion level of about 30 to 40 percent conversion and at a temperature in the range of about 870 to 900 F. in a second catalytic cracking zone, the improvement comprising solvent extracting the'heavy cycle oil and decant oil from said first and second crack* ing zones; passing a portion of raiiinate from the solvent extraction step to the feed to the second cracking zone in an amount sufficient to provide a ratio of about one volume of raffinate per 4 to 16 volumes of fresh feed; and passing the remaining raffinate to the first catalytic cracking zone.

5. The process of claim 4 wherein the ratio of raffinate to fresh feed is about l to 8. Y

6. In apparatus for treating hydrocarbons comprising a first catalytic cracker containing clean catalyst adapted to operate at high conversion level of about 50 to 70 percent conversion and at a temperature in the range of about 905 to 930 F. with a low metal content feed containing not more than about 65 to 75 p.p.m.vof metallic contaminants, a second catalytic cracker containing metal contaminated catalyst adapted to operateat low conversion level of about 30 to 40 percent conversion and ata temperature in the range of about 870 to 900 F. with a high metal content feed containing at least about 200 p.p.m. of metallic contaminants, catalyst regeneration means and product separation means operatively connected to each of said catalytic crackers and a solvent extraction means operatively connected to said separation means, the combination therewith of means to pass a measured quantity of highest boiling fractions from said second cracking Zone to the feed to the first catalytic cracker; and means to pass a measured quantity of raffinate from said solvent extraction means to the feed to the second cracking zone.

7. The apparatus of claim 6 including means to con- `trol the ratio of raffinate to fresh feed to the second cracking zone.

8. In apparatus for treating hydrocarbons comprising a first catalytic cracker containing` clean catalyst adapted to operate at high conversion level of about 50 to 70 percent conversion and at a temperature of about 905 to 930 F. with a low metal content feed containing not more than 65 to'75 ppm. of metallic contaminants, a second catalytic cracker containing metal contaminated catalyst adapted to operate at low conversion level of about 30 to 40 percent conversion and at a temperature of about 870 to 900 F. with a high metal content feed containing at least about 200 p.p.m. of metallic contaminants, catalyst regeneration means and product separation means operatively connected to each of said catalytic crackers and a solvent extraction means operatively connected to said separation means, the combination therewith of means to pass a meaured quantity of ranate from said solvent extraction means to the feed to the second cracking zone.

9. The apparatus of claim 8 including means to control the ratio of raffinate to fresh feed to the second cracking zone.

'8 References Cited by the Examiner UNITED STATES PATENTS 2,941,936 6/60 Harper 208-77 3,004,911 10/61 Slover 208-78 ALPHONSO D. SULLIVAN, Primary Examiner.

Claims (1)

1. IN A PROCESS FOR TREATING HYDROCARBON FLUIDS WHEREIN A HYDROCARBON STREAM HAVING A LOW METAL CONTAMINANT CONTENT OF NOT MORE THAN ABOUT 65 TO 75 P.P.M. IS CATALYTICALLY CRACKED AT A HIGH CONVERSION LEVEL OF ABOUT 50 TO 70 PERCENT CONVERSION IN A FIRST CATALYTIC CRACKING ZONE AT A TEMPERATURE IN THE RANGE OF ABOUT 905 TO 930*F., AND A HYDROCARBON STREAM HAVING A HIGH METAL CONTAMINANT CONTENT OF AT LEAST ABOUT 200 P.P.M. IS CATALYTICALLY CRACKED AT A LOW CONVERSION LEVEL OF ABOUT 30 TO 40 PERCENT CONVERSION IN A SECOND CATALYTIC CRACKING ZONE AT A TEMPERATURE IN THE RANGE OF ABOUT 870 TO 900*F., THE IMPROVEMENT COMPRISING SOLVENT EXTRACTING THE HEAVY CYCLE OIL AND DECANT OIL FROM SAID FIRST AND SECOND CRACKING ZONES; PASSING A PORTION OF RAFFINATE FROM THE SOLVENT EXTRACTION STEP TO THE FEED TO THE SECOND CRACKING ZONE IN AN AMOUNT SUFFICIENT TO PROVIDE A RATIO OF ABOUT ONE VOLUME OF RAFFINATE PER 4 TO 16 VOLUMES OF FRESH FEED; AND PASSING THE REMAINING RAFFINATE TO THE FIRST CATALYTIC CRACKING ZONE.

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