US2616836A - Products from catalytic cracking - Google Patents

Description

NOV. 4, 1952 w. J. SCHMIDT, JR., Er Al.

PRODUCTS FROM CATALYTIC CRCKING Filed Dec. 29, 1949 Patented Nov. 4, 1952 APRo'DU-otls FROM CATALYTIC `CRACKING Walter J. schmidt, Jr., lana Forrest H, Blending,

Cranford, N. J., assignors'ito StandardlOil Del vclopment Company, a corporation of Delaware o I Applioation December 29, 1949, serial'No.-1a5,s54

4 Claims. (Cl. 1116-52) y' This invention relates to the catalytic conversionv of hydrocarbon oils and pertains more particularlyv to a method of increasing the' yield of 'heating or domestic furnace oil.

Economical oilreflning processes dictate that a proper balance be maintainedbetween theY production of gasolineon the one hand and domestic furnace oil on the other. Both of these products are obtained from the same general relning operations, such as by crude distillation and cracking.' In the past, the relatively large demand for gasoline, as compared with domestic heatingfoil, hasmade it possible to maintain the proper balance without diiliculty since any excess production of furnace oil could-readily be converted into gasoline by conventional cracking treatment.

In recent years. however, the demand fonfurnace oil has increased at a greater pace than the demand for gasoline so that at times there is -a shortage of furnace oil produced when the cracking operations are geared to meet gasoline requirements. It is, therefore, important to be ableto increase the ratio of furnace oil to gasoline produced during the cracking process.

The present invention provides a simple and effective method of increasing the proportion'A offurnace oil relative to the amount of gasoline formed during the cracking process.

It *has been found vthat in the catalytic cracking process, the yield of heating 'oil is increased appreciably without loss of` gasoline yieldby cracking the oil under relatively mild conditions,` separating the cycle gas oil into a heat-.- ing oil fraction and a heavy gas oil fraction, removing the aromatics from the heavy gas oil fraction by a suitable solvent extraction and returning the parainic raiiinate from the extraction step to the cracking operation.

When carrying out ordinary recycle operations `wherein heavy cycle gas oil produced in the process is` returned to cracking without solvent extraction, the gasoline yield and heating oil yield Vare generally increased as the conversion per pass is reduced. Even when Vwithdrawing aiixed amount of heavy cycle gas oil as product, operation at low conversion with recycling will produce a considerably higher yield of gasoline and a slightlyhigher yield of heat.-

ing oilv than will once-through operation at high lBy extraction of the heavy cycle gasoil to remove the aromatics and utilizing thearomatic extract as fuel oil, returning the parainic raffinate to the cracking operation, theyield of gasoline from a given amount of feedstock will be higher than in a once-throughsingle pass cracking operation without recycling but the gasoline yield will nctbe substantiallyaffected as the conversion per pass or severityV of cracking isvreduced. On the other hand, the yield of heating oil from a given amount of feed willbe appreciably higher than in the case of a once-through single pass cracking operation and the amount of heating oil will be increased as the conversion per pass is reduced. This is illustrated in the following table, wherein a heavy West Texas gas oil was catalytically cracked employing the fluid type cracking process at a temperature of 975 F. and a conventional type The rst column in the above table givesthe volume of gasoline and heating oil produced in a once-through single pass cracking operation with no recycling of heavy gas oil. Columns 2 and 3 give the results produced when recycling different amounts of heavy gas oil without solvent extraction. In column 2 the amount of recycle oil as indicated by the recycle ratio is 1 part of fresh feed to .12 part of recycle gas oil;

and in column 3 the recycle ratio gas oil is 1 part of fresh feed to .33 part of heavy cycle gas oil. Columns 4 and 5 show the relative volumes lof gasoline and heating oil produced in accordance with the present invention in which the heavy cycle gas oil is extracted to remove the aromatics and the rainate is recycle. Comparing columns 4 and 2 it will be noted that the amounts of material recycle (raflinate or heavy i cycle gas oil) are the same and also that the amount of heavy oil withdrawn (extract or heavy cycle gas oil) are the same. Similarly, columns 5 and 3 are based upon equal recycle and withdrawal. In all of the operations illustrated in the table, the gasoline yield is substantially the same. However. by recycling the ralnate as tions such Vas gasoline and heating oil.

shown in columns 4 and 5, the amount of heating oil is materially increased without sacrificing the yield of gasoline. For example, by using the present invention and by recycling rahinate in the amounts shown in column 5, it is possible to increase the amount of heating oil by about 6% as compared to that which can be produced either in a once-through cracking operation Aor in a recycling operation wherein 1a portion ofthe total heavy gas oil is recycle.

For a better understanding of the invention, reference is made to the accompanying drawing which is a diagrammatic illustration of apparatus capable of carrying the invention into effect. The drawing illustrates laxfluid'typeprocess for cracking of the oil, although it will .be understood that other types of catalytic cracking operation may be used, -if desired.

Referring to the drawing, the fresh feed to be cracked is introduced into the system through line I0. This fresh feedJnay be any suitable .oil which is desired to vcrack into lower boiling frac- The .Oil passing through `line l "Intermixes with a stream of ne'lydivided cracked catalyst such Vas synthetic silica-*alumina .gel catalyst discharging Y through standpipe H at fa controlled rate through "valve 12. .The catalyst introduced into the oil is at substantially `regeneration temperature,isuch as'ateniperature of from 1050-115.O F. `and ltheoilgprior to. contacting/with .the catalyst, maybe preheated to such temperature that :the resulting mixture forms arsuspension of oil vapors and "catalyst :at asuitable cracking temperature such :as from `850 to 1000 F.

The resulting suspension is 'transferredthrough the transfer line l3 which terminates in. an inverted cone distributor 'Id -located within the reactor 15. The cone distributor. Hi is provided with a perforated grid at 'its upper end for dispersing the suspension over a substantial horizontal portion of the reactor. Upon entering the reactor, the velocity of the oil vapors is reduced to such .point that the catalyst is allowed to settle into a relatively dense phase in the bottom portion thereof, which is maintained in a highly turbulent lstate by the vapors passing upwardly therethrough.

The oil vapors, after contacting with thecatalyst at cracking temperature for a sufficient period to obtain the desired conversion, are removed frorn the top vof the reactor through line Iafter passing through a suitable cyclone or other separating device 'l'l for removing entrained catalyst particles from the gas. :The catalyst 'separated iny the separator I1 is returned tothe dense turbulent bed of catalyst in the reactor. The crackedvapo-rs continue through line I8 and enter 'the bottom of a Yconventional fractionating tower I3 wherein they vare subjected to fractional condensation.

The initial condensate formed in the bottom section I9 of the tower t3 .may contain -a smal-l amount of catalyst carried over from the reactor. The condensate containing the catalyst is withdrawn from Ythe bottom of the fractionator l-8 through linek 28 'and may be recycled by means of pump 2l for further cracking treatment along withithe fresh feed.

The tower I8 is provided with a lower'trap-out tray 2.2 for collecting heavy cycle gas oil boiling above the boiling point of vdomestic heating oil, such as boiling above 60G-'650 F. To this end, the temperature in the intermediate section vof the fractionating tower 8 is .controlled to con- .fraction is liquefied.

dense constituents boiling above the furnace oil boiling range.

A second trap-out tray 23 is positioned in the upper portion of the fractionating tower I8 and is adapted to collect a furnace oil fraction which forms one of the nal products of the process. The furnace oil fraction is withdrawn from trap- .out tray 23 through line Hand-may be subjected to `further stabilization, or distillation, or any further treatment required to produce a marketable product. Vapors remaining uncondensed yafter passing through the fractionating tower I8 are removed voverhead through line 25 which leads to a condenser 26 wherein the gasoline The products from the -condenser 26 pass -to a receiver 21 wherein the liquid condensate is allowed to separate from uncondensed lgases vand vapors. The uncondensed vapors and gas are removed from the receiver 21 through line 28 and may be passed to any suitable equipment .for recovery of. the desired components therefrom. The `gasoline. formed .in the process is .withdrawn ythrough .line y29 and may be vstabilized or .subjected -to .any .further treatment desired.

Returning 'to .the Afra'ctiona'ting tower IS, the heavy' gas oil collected-inthe flower. trap-out .tray 22 is withdrawn through linell Vand subjected to solvent extraction to separate the paraiinic `constituents .from the aromatic constituents. To this end, vthefraction may be passed 'to a solvent extractor .3j into which is charged .a suitable solvent through .'line '32'. This .solventsmay comprise any suitable 'material capable of .selec.tively extracting aromatic constituents from the parafnnic constituents. Such solvents .may ,include, for example, such materials -as liquid .sulfurv dioxide, phenol, vdichlordiethyl .ether Vf.ur.`fural, chlorinated hydrocarbons such as carbon .tetrachloride 'and the like.

vAny Asuitable .means may be .used .for .effecting intimate contact 'between the heavy .cycle .gas oil and the solvent.. As vi1lustrated,.the solvent is introducedLnear'the 'top ofthe extractor. .and .passes downwardly in countercurren't contact to `the oil. The solvent containing the aromatics .is withdrawn from the bottom of the extractor through line '33r and may be passed to a distill'ing column 34 'wherein the Iextract 'is heatedlto vaporize the solvent. .The extract is withdrawn from .the distillingl zone '34 through ,l'i-ne .35 :and the vaporized solventis drawn 4overhead .through '.line 1316 which leads to a cooler 31, which serves to .-liquefy the solvent prior :to the return to .the extractor through line 32. The extracted rafnate Yis withdrawn from the top yof the .solvent extractor throughline 38 which leads 'to a distillingcolumn 39 lwherein the raflina'te may be heated to vaporize the solvent absorbed therein. In such case, the vaporized solvent. isV removed from the distilling column 39"throug'h line 40 and is combined with 'the vaporized solvent from the distilling column 34 passing tothe cooler 3.1.. Following the removal of the solvent from the rainatathe latter is vpassed through line '4I `and pump 42 and combined with fresh feed passing to the cracking Zone. It is notnecessary, in all cases, to subject .the raninate to distilling vtreatment to remove solvent therefrom. In such cases, the raiinate from the extractor '3| may be recycled without being subjected 'to distilling for removal of solvent` vapor.

vIn vsome casesytheinitial condensate formed in the bottom of the fractionating Vtower I8 maybe passed to the solvent. .extractor 3l through line cracking zone.

43, particularly where the initial condensate is relatively free of catalyst particles carried overhead from the reaction zone.

Returning to the reactor I5, a stream of catalyst containing carbonaceous deposits formed during the cracking reaction is continuously withdrawn from the reactor I5 through standpipe 44, which may be provided with suitable aeratlng lines to maintain the catalyst in a uid condition. Prior to removal of the catalyst from the reactor I5, it may be subjected to a stripping operation by injection of steam through line 45 to remove vaporizable hydrocarbons therefrom. The stripped hydrocarbons discharge from the base of the standpipe 44 into a stream of air passing through line 46, which carries the catalyst into the regenerator 41. Within the regenerator the catalyst is subjected to oxidation to burn carbonaceous deposits. The regenerated catalyst is withdrawn from the regenerator 41 through the standpipe and intermixed with fresh feed as previously described.

The present invention comprehends a process wherein the initial feed is subjected to catalytic cracking under relatively mild conditions and the heavy cycle gas oil produced in the process is solvent extracted to remove the aromatics and the non-aromatic fraction is recycled back to the The extent of cracking within the reactor I5 may be controlled by regulating the amount of catalyst introduced into the oil charge, by regulating the level of the dense phase of catalyst in the reactor I5, by the feed rate of oil through the reactor and the temperature maintained within the reactor. As previously stated, cracking conditions should be relatively mild so that the extent of conversion of the fresh feed as measured by gas oil disappearance during its initial passage through the cracking zone should be in the range of from 30 to 40 preferably about 35 Having given a detailed description of the invention, it will be understood that it embraces such other` variations and modifications as come within the scope of the following claims.

We claim:

l. A process for the conversion of heavy hydrocarbon oils into lower boiling furnace oil and gasoline, which comprises cracking fresh uncracked oil in the presence of a catalyst under conditions controlled to convert from about 30 to A40% of said fresh oil into gasoline constituregate a gasoline fraction, a light furnace oil fraction and a heavy cycle oil fraction, removing said light furnace oil fraction as a product of the process, treating said heavy cycle oil fraction to remove aromatics therefrom and subjecting said extracted oil to further cracking treatment with said first-named oil.

2. In a process for catalytically cracking heavy hydrocarbon oils to form lower boiling furnace oil boiling between about 450 and 650 F. and to form gasoline, the method of increasing the amount of furnace oil relative to the amount of gasoline formed during said cracking process, which comprises passing the fresh oil to be cracked through a cracking zone maintained at cracking temperature, contacting said oil within said cracking zone with an active cracking catalyst for a period sufficient to convert between 30 and 40% of said oil into gasoline, thereafter fractionating lthe resulting products to segregate a gasoline fraction, a light furnace oil fraction and a heavier cycle oil fraction, removing said light furnace oil fraction as a product of the process, treating said heavy cycle oil fraction with a, solvent capable of selectively extracting aromatic constituents therefrom, separating the solvent containing said aromatic constituents from the remainder of said oil and thereafter returning oil so extracted to the cracking zone for further cracking treatment in the presence of said firstnamed oil.

3. The process defined in claim 2 wherein the oil is cracked in the presence of a synthetic silicaalumina gel catalyst.

4. Process defined in claim 3 wherein cracking is carried out in the presence of nely divided catalyst.

WALTER J. SCHMIDT, JR. FORREST VI-I. BLANDING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,278,228 Watson Mar. 31, 1942 2,342,288 Nysewander et al. Feb. 29, 1944 2,377,613 Conn June 5, 1945 OTHER REFERENCES Conversion of Petroleum Sachanen, 2nd Ed., 1948, Reinhold Publishing Co., New York, page 331.

Claims (1)

1. A PROCESS FOR THE CONVERSION OF HEAVY HYDROCARBON OILS INTO LOWER BOILING FURNACE OIL AND GASOLINE, WHICH COMPRISES CRAKING FRESH UNCRACKED OIL IN THE PRESENCE OF A CATALYST UNDER CONDITIONS CONTROLLED TO CONVERT FROM ABOUT 30 TO 40% OF SAID FRESH OIL INTO GASOLINE CONSTITUENTS, FRACTIONATING THE RESULTING PRODUCTS TO SEGREGATE A GASOLINE FRACTION, A LIGHT FURNACE OIL FRACTION AND A HEAVY CYCLE OIL FRACTION, REMOVING SAID LIGHT FURNACE OIL FRACTION AS A PRODUCT OF THE PROCESS, TREATING SAID HEAVY CYCLE OIL FRACTION TO REMOVE AROMATICS THEREFROM AND SUBJECTING SAID EXTRACTED OIL TO FURTHER CRACKING TREATMENT WITH SAID FIRST-NAMED OIL.

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