US2504415A - Catalytic cracking and reforming process - Google Patents

Description

April 18, 1950 H, J, HEPP 2,504,415

CATALYTIC CRACKING AND REFORMING PROCESS Filed Jan. 2s, 194e ATTORNEYS Patented Apr. 18, 1950 CATALYTIC CRACKING AND REFORMIN G PROCESS Harold J. Hepp, Bartlesville, Okla., assgnor to Phillips Petroleum Delaware Company, a corporation of Application January 23, 1948, Serial No. 4,045

The present invention relates to the art of hydrocarbon conversion. In a particular modification the present invention relates to the conversion of a relatively heavier hydrocarbon and the reforming of a refractory stock for an improved yield of gasoline. In one specific aspect the present invention relates to catalytic reforming ofnaphtha in the presence of refractory heavier hydrocarbon stock and to the concomitant catalytic conversion of gas oil and further improvement of the reformed naphtha in the production of an improved gasoline.

Many cracking methods are known and a wide range of cracking conditions has been disclosed. It has been desirable to improve the quality of gasoline produced and it has been found that relatively specific conditions are usually best suited to different and particular feed stocks, that is, a particular feed stock of relatively narrow range responds most effectively to a particular set of conditions of temperature and pressure of fairly narrow range with certain particular catalytic agents. It has also been found that two or more of the particular feed stocks may be combined in conversion processes such as cracking, and slightly different conditions of processing applied thereto to prepare satisfactory gasoline. It has also been proposed to convert hydrocarbon stocks of various boiling ranges with subsequent separation and further treatment of individual fractions thereof. Thus, in at least o ne `instance it has been proposed to treat a relatively light hydrocarbon stock free of heavier materials and subsequently to add a heavier hy drocarbon stock to a resulting eliluent with further `treatment of the mixture under more drastic conversion conditions in the production of motor fuels.

I have now found that an improved gasoline may be prepared in increased yields by a processv which comprises treating a mixture of relatively light and relatively heavy refractory hydrocarbon stocks under conditions suitable for reform- `ing the light hydrocarbons, adding relatively 2 claims. (cl. 19e-49) these two operations are suitably carried out naphtha and a refractory heavy hydrocarbon stock, such as recycle catalytic gas oil, under fairly drastic conditions of conversion and without separation of the resulting reformed effluent, adding virgin gas oil and treating the latter mixture under conditions suitable for cracking the gas oil while the reformed naphtha and heavier stock are further improved and transformed concomitantly with the conversion of the gas oil.

It is, therefore, the object of the present invention to provide a process of preparing increased yields of improved octane number gasoline. A further object is to provide a process of increasing the yield of an improved gasoline from a mixture Yof gas oil and reformed naphtha. Another object is to provide a novel process of reforming a mixture of naphtha and heavier hydrocarbons and of concomitantly cracking a gas oil and a reformed naphtha to produce increased yields of improved gasoline. A further object is to provide a novel process of preparing improved gasoline byrreforming and cracking a mixture of naphtha and refractory oil and sub-` sequently upgrading and cracking the reformed naphtha and a mutable heavier oil. lOther objects will be apparent to those skilled in the art from the accompanying discussion and drawing. The accompanying figure is a diagrammatic Vview in elevation illustrating one modification 30;;

of the present invention.

By the process of this invention a virgin cracking stock such as gas oil, a relatively refractory recycle hydrocarbon stock and a naphtha may be cracked and reformed. Thus, a relatively heavy refractory hydrocarbon stock may be cracked during the reforming o f a naphtha and an upgrading of the products economically effected during a subsequent cracking of an intermediately heavy stock such as a virgin gas oil. The process is performed in a single, integrated unit with substantial savings in equipment and operational cost. More specifically, a recycle catalytic stock may be cracked and a naphthal stock reformed concurrently in a rst catalyst chamber under relatively severe conditions since under substantially the same conditions with the same catalyst. Further improvement of the reformed naphtha and the gasoline obtained from cracking the recycle stock is realized by Subsccracking stock and simultaneously processed in a second catalyst chamber under the milder processing conditions which will upgrade the products from the first catalyst chamber and promote cracking of the virgin stock for the production of a further quantity of gasoline.

In addition :to :the realization vof :conversions and transformations occurring the various hydrocarbon stock characterized by particular properties and boiling ranges is the very important feature of having a lighter hydrocarbon present during the conversion of a heavier hydrocarbon. It is found that much more complete conversion of any particular heavier stock vt :products :inthe gasoline range is possible with 'less ormation :of undesirable carbonaceous deposits and gases when relatively lighter hydrocarbons .are present during the c-onversion. These lighter compounds which comprise especially the normally -liquid hydrocarbons of loW end point are reformed and converted into valuable product themselveswhile providing favorable diluent and other benecial conditions during the conversion -of the heavier compounds.

It .is .to vbe appreciated that vcracking .and :reforming are affected .by -both contact time and temperature and that the milder conditions referred to in the second catalyst chamber fwill be interpreted as Ameaning a lcombinationrof variousspecic conditions to give a milder treatment to .the .materials in the second chamber. Thus, milder conditions in the second chamber may be understood to lrneanthose conditions ,of :contact time, temperature, andpressure Awhich would produce less conversion of a -given charge 4stock than is produced under-conditions prevailing in the .first catalyst chamber. Hence, the milder conditions of .the second chamber may tbe due :to a, .lower temperature or a lower conta-ct time, or to both. Although it is possible that .the temperature of the second chamber could be higher 4than :the temperature of 'the first Ychamber and ther-contact time of the vcharge :shortened sufficiently Athat the results :would :be a milder conversion, it is preferred that the temperature in the second chamber beat least somewhat lower than the temperature `in the first chamber. Thus, a preferred v,condition in the first naphtha is reformed and the recycle and/ or heavy stock is cracked into substantial yields of gasoline. An inert diluent such as steam may be introduced through a line 20, heated to a desirable temperature in a heater 2l and introduced into the catalyst chamber with the hydrocarbonsthroughaline 22. Additional steam may be .addedat various points .throughout rthe catalyst chamber through a line 26 and manifold laines 23, 2li and 25 as required to supply addi- .tional heat to the .conversion at various points .and `to serve as a diluent in the conversion zone.

catalyst chamber maybe Aa ytemperature between about 900 and 1100 F. and a superatmospheric pressure :between .about atmospheric and V300 pounds .per square inch and a time Ysufficient to reform the naphtha and 'to convert `the .heavier hydrocarbons to substantial amounts of gasoline. Conditions inthe secondcatalyst chamber after the .addition of ,gas -oil lto the products ffrom-fthe rst catalyst chamber 4will preferably ibe milder than `those in the -first chamber, but suitable =to crack and yconvert :the gas nil to desirable vproducts in the gasoline range and :to upgrade the products :from the first conversion zone.

Referring to the-drawing, a hydrocarbon such as naphtha boiling between about 200 and about 400 F. is introduced :by..a .line I0 into -a yheating zone H and thence .through :line t2 'into a'rst catalyst chamber 13. Relatively heavy `.hydrocarbons `are introduced through fa yrecycle lline Llili and/-or through -a lline fl 5 -into a'dmixture 'with the napthacharged. Where desirable, :lighter ihydrocarbons mayalsobe addedto thenaphthazcharge through -a .line ,IJ .and .may consist in part :or entirely .of .recycle C3 .and 1C; .hydrocarbons :from a `subsequent v.separation rstep, Areturned -through a line i8. The Vheated hydrocarbon :mixture passes through catalyst chamber :t3 `Where fthe 'The product eiuent from chamber I3 is with- A:tirait/.n .and conducted through a line 21 into a second .catalyst'chamber 28. A virgin cracking stock, such as a-gas oil, is introduced through a .1ine.3.0 .heated to a temperature between about 800 and 10.50 F. in heater 3| and added to the productfetiiuent entering chamber 28. As desired, steam may be added to the gas oil through a line 3,3 before the :heaterbr through aLlineM immediately ybefore the 'second catalytic ;reactor, .-or at both places.. .Gaseous hydrocarbons :may also Pbe mixed with gas =0il through `a .line 35 as .-required. The heated gas oil vand .products from .the 4Iirst catalyst chamber ,are mixed .as .described :and

introduced into the second catalyst chamber 23 where the gas oil is cracked and the products .of the iii-st catalyst chamber are upgraded .at a temperature between ,about :800 and "1050o and a Vpressure lbetween about .atmospheric and 250 pounds per square Ainch. 'The cracked 'and upgraded products :from :the secondcatalyst chamber :are Withdrawn through .a heat lexchanger '31 in a lline .33 into Ya ractionating zone 130 which may represent several individual tractionators necessary to make the -separationldesired "Heat may vbe supplied thereto by steam icoils, rboilers or other customary means (not shown). @From the system, C2 .and fliglrter gases fare removed through ,a 'line M. Normally gaseous products suchas the Ca vand C4 -hydrocarbonsare removed by ia `line .A2 or may be recycled tothe catalyst zones Vby Ava line |12 as described above, and a gasoline fraction .is recovered by a line 43 and taken to vstorage or further treatment (not shown). A heavy residue is removed from the fractionating zone "by a line 44, and Ian intermediate hydrocarbon f'fractionheavi'er than-gasoline v-is recovered through yaline 545 land -may "be recycled to the first catalystchamber 'I3 'through line lli vas l.then-relatively Lrefractory hydrocarbon to 4the rstconversion zone asfdescribed. Various valves, ipumps, .and Vother Iequipment necessary to `practice the process will "be obvious to one skilled in the .art and have been omitted *from the rdiscussiomand.drawingforthe sake ofclarity.

In the conversion of hydrocarbons by the present method, a suitable charge 1to the first catalyst chamber may be a hydrocarbon 'mixture comprising '5G-170 Avolume Ivper -cent lo'f a `naphtha boiling between 4about 200 and400 `F., 5-'15 volumeiper .cent Us and l C4 gases, 4and jthe remaining 15-@45 `volume 'per cent substantially heavier hydrocarbons. The catalyst may be cracking .and reforming catalysts of high, or relatively high, catalytic factiv'ityoperating at fa temperature between abouti300-1100o F. at a `pressure Abetweenabout ratmospheric Yand 300 -pounds per square inch. 'Generally *the space velocity Awill '-be tbetween 1 "co5 liquid volumescf charge yper volume of .catalyst per -hour `based on fthe lftotal hydrocarbon charge and, lif desired, 'steam imay be added :at `v1"0 to '80 pounds per barrel -of liquid charge. 'Conditions .fin 'the second r catalystcham.

ber are controlled such that a milder conversion is effected as described. In this latter chamber catalyst of lower activity may be used and a lower temperature between about BOO-1025 F. and pressure between atmospheric and 250 pounds per square inch employed. Preheated gas oil is added at the rate of about 0.5-5 liquid volumes of the gas oil per volume of catalyst is delivered per hour. Similarly, additional steam may be added in this conversion zone, if desirable. The specific set of conditions in each conversion zone will, of course, depend upon the particular charge stock being treated and the catalyst employed in each zone. 'Ihe conditions stated merely set out an optimum range, and the most satisfactory combination is readily determinable for any particular charge.

The contact catalysts suitable for the present process are those having activity in promoting the cracking of gas oil and the reforming of naphtha and are particularly those rugged minerals or natural and synthetic mixtures thereof and similar materials comprising bauxite, brucite, various clay-type minerals and active aluminum silicates. These natural catalysts may be used after activation by various means such as acid treating and/or may be promoted with minor amounts of active metals or metal salts or oxides. Also useful are natural materials comprising zirconia, titania, and synthetic preparations comprising zirconia, titania, magnesia, alumina, and various silica-alumina combinations. These latter materials may be promoted with minor quantities of metal oxides, particularly those of chromium, nickel and Zinc.

After periods of service in our process, these catalysts are gradually deactivated through accumulation of tarry deposits and carbonaceous residues. When their activity has declined to a degree which renders the conversion unsatisfactory, they are quickly and completely restored to substantially their original activity by reactivation at controlled temperatures in an oxidizing atmosphere. For this reactivation, it is usually preferred to pass oxygen-containing gases, such as mixtures of air With steam, nitrogen, carbondioxide or inert combustion gas, through the catalyst to burn off the materials responsible for deactivation without thereby producing combustion temperatures harmful to the catalyst. By providing a plurality of catalyst chambers, it is possible to operate continuously, with one or more chambers on stream while spent catalyst in other chambers is being reactivated.

In a typical example of the present invention a 35 A. P. I. catalytic gas oil distilling between about 480 and 680 F. is admixed with an equal volume of 33 octane number naphtha of 440 F. end-point. The mixture is vaporized and charged, together with 60 pounds of steam per barrel of liquid charge, at a pressure of 85 pounds per square inch gage and 1025 F. to a catalyst chamber containing bauxite at a rate of 1.5 barrels of liquid hydrocarbon per hour per barrel of bauxite. Under these conditions, the naphtha is reformed to yield about 80 per cent of a 55 octane number gasoline and the gas oil is cracked to yield about 27 per cent of 77 octane number gasoline. To the efiiuent from this first chamber is added preheated virgin gas oil and steam, and the combined stream is passed through a second catalyst chamber at a temperature of 1000 F. and a space velocity of 1.5 barrels of hydrocarbon per hour per barrel of bauxite. In the second chamber the virgin gas oil is cracked to yield about 35 per cent of '17 octane number gasoline.

In addition further cracking of the catalytic gas oil and additional reforming of the naphtha occur. Also light olens formed in the first step are partly converted to gasoline in this second chamber. Gasoline is recovered in a larger yield and has a higher octane number than the gasoline which is recovered from separately treating the individual stocks and combining the gasoline produced during the separate treatments.

Various changes and modifications may be made without departing from the spirit of the invention and will be apparent to those familiar with the art. The example is illustrative only and is not to be interpreted as limiting the scope of the disclosure and claims which are intended to cover all aspects of the invention inherent with the disclosure.

I claim:

1. An improved process for the manufacture of motor fuels which comprises treating an admixture of hydrocarbons comprising 50 to 70 volume per cent of naphtha, 5 to 15 volume per cent of added C3 and C4 gases and 15 to 45 per cent of refractory gas oil in a rst catalytic zone at a temperature between about 900 and 1100 F. and at a pressure between about atmospheric and 300 pounds per square inch and at a space velocity between 1 to 5 volumes of total hydrocarbon charge per volume of catalyst per hour to substantially reform the said naphtha and crack the said refractorir gas oil, withdrawing a resulting reformed effluent, admixing suilicient virgin gas oil with all of said reformed eliluent to permit a space velocity between about 0.5 to 5 liquid volumes of said virgin gas oil per volume of catalyst per hour in a second catalytic zone, contacting the thus resulting mixture with a cracking catalyst in said second catalytic zone at a temperature between about 800 and 1050 F. and at a pressure between about atmospheric and 250 pounds per square inch and separately recovering a gasoline fraction and an intermediate hydrocarbon fraction from the resulting product eiiiuent from said second catalytic zone.

2. An improved process for the manufacture of motor fuels which comprises treating an admixture of hydrocarbons comprising substantially equal volumes of a refractory gas oil and a naphtha in a first catalytic zone at a temperature of about 1025" F. and at a pressure of about pounds per square inch thereby substantially reforming the said naphtha and cracking the said refractory gas oil to yield substantial quantities of a low octane gasoline; withdrawing a resulting reformed eiiiuent, admixing a substantial quantity of virgin gas oil with said reformed effluent; contacting the thus resulting mixture with a cracking catalyst in a second catalytic zone at a temperature of about 1000 F. to substantially crack said virgin gas oil and to improve the octane number of the said low octane gasoline produced in said first catalytic zone; and separately recovering a gasoline fraction and an intermediate hydrocarbon fraction from the resulting product eiiiuent from said second catalytic zone.

HAROLD J. HEPP.

REFERENCES CITED UNITED STATES PATENTS Name Date Egloff Mar, 7, 1944 Number

Claims (1)

1. AN IMPROVED PROCESS FOR THE MANUFACTURE OF MOTOR FUELS WHICH COMPRISES TREATING AN ADMIXTURE OF HYDROCARBONS COMPRISING 50 TO 70 VOLUME PER CENT OF NAPHTHA, 5 TO 15 VOLUME PER CENT OF ADDED C3 AND C4 GASES AND 15 TO 45 PER CENT OF REFRACTORY GAS OIL IN A FIRST CATALYTIC ZONE AT A TEMPERATURE BETWEEN ABOUT 900* AND 1100* F. AND AT A PRESSURE BETWEEN ABOUT ATMOSPHERIC AND 300 POUNDS PER SQUARE INCH AND AT A SPACE VELOCITY BETWEEN 1 TO 5 VOLUMES OF TOTAL HYDROCARBON CHARGE PER VOLUME OF CATALYST PER HOUR TO SUBSTANTIALLY REFORM THE SAID NAPHTHA AND CRACK THE SAID REFRACTORY GAS OIL, WITHDRAWING A RESULTING REFORMED EFFLUENT, ADMIXING SUFFICIENT VIRGIN GAS OIL WITH ALL OF SAID REFORMED EFFLUENT TO PERMIT A SPACE VELOCITY BETWEEN ABOUT 0.5 TO 5 LIQUID VOLUMES OF SAID VIRGIN GAS OIL PER VOLUME OF CATALYST PER HOUR IN A SECOND CATALYTIC ZONE, CONTACTING THE THUS RESULTING MIXTURE WITH A CRACKING CATALYST IN SAID SECOND CATALYTIC ZONE AT A TEMPERATURE BETWEEN ABOUT 800* AND 1050*F. AND AT A PRESSURE BETWEEN ABOUT ATMOSPHERIC AND 250 POUNDS PER SQUARE INCH AND SEPARATEL RECOVERING A GASOLINE FRACTION AND AN INTERMEDIATE HYDROCARBON FRACTION FROM THE RESULTING PRODUCT EFFLUENT FROM SAID SECOND CATALYTIC ZONE.

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