US2397329A - Selective catalytic cracking - Google Patents

Description

March 26, 1946.'. R. F. IRuTl-IRUFF SELECTIVE cATAmf'frIo".CRAGKIMII Filed Dec. 1, V 1341 aix MENNENNQNMJ NNSWNN NOM' Patented Mar. 26, 1946 UNITED STATES PATENT* OFFICE;

sELncrIvE CATALYTIC, Casciano.

Robert F. Ruthruff, Chicago, Ill. Annotation December 1, 1941, serialV No. 421,143

6 Claims.

This invention relates to the-selective. catalytic cracking of hydrocabon oils.. More particularly, this invention relates to the separation of hydrocarbon oils into a relatively refractory component and a relatively non-refractory component and Separately subjecting the two components to catalytic cracking under conditions selected primarily on the basis of the refractoriness of said com ponents.

A primaryl object of my invention is to provide an improved selective catalytic cracking process for treating hydrocarbon oils whereby a maximum yield of motor fuel of superior antiknock quality is obtained.

Another object of my invention is to Provide an improved selective catalytic cracking process for treating hydrocarbon oils wherein. said hydrocarbon oils are separated into a plurality of components of differing refractoriness which` are subjected to separate catalytic conversion, processes whereby a maximum yield of motor fuel of superior antiknock quality is obtained.

A further object of my invention is to provide an improved selective catalytic cracking process for treating hydrocarbon oils wherein said hydrocarbon oils are subjected to.y solvent extraction to form a plurality of components of differing refractoriness which are subjected to separate catalytic conversion. processes. whereby a maximum yield of motor fuel of superior antiknock quality is obtained.

An additional object. of my invention is to provide an improved selective catalytic cracking process for treating hydrocarbon oils wherein said hydrocarbon oils Aare separated into a plurality of components of diifering refractoriness which are subjected to separate catalytic conversion processes wherein byproducts from certain of said separate catalytic conversion Processes are introduced into other of Said separate catalytic conversion processes whereby a maximum yield of motor fuel of superior antiknock quality is obtained.

Another object of my invention is to provide an improved selective` catalytic crackingprocess for treating hydrocarbon oils wherein, said hydrocarbon oils are subjected to solvent extraction to form a plurality of components of` differing refractoriness which are subjected to separate catalytic conversion processes wherein byproducts fromcertain of said separate catalytic conversion processes are introduced into other of said sep.- arate catalytic conversion processes whereby a maximum yield of motor fuel of superior antiknock quality is obtained.

Further. objects and' advantages. of my invention will become evident as the description thereof proceeds. f

Various selective thermal' conversin processes for separately transformingl a plurality of hydrocarbon fractions into motor fuel are well known inthe art. For example, it is known to fraotonate crude oiIY into light, naphtha, heavy naphtha,` gas oil and reduced' crude following which the heavy naphtha is thermally reformed, the Igas oil is thermally cracked while the reduced crude is thermally viscosity broken. Reactiony products from the thermal cracking zone and the thermal viscosity breakingzone are combined and fractionated to give gasoline plus, gas, light cycle gas oil, heavy cycle gas oil and tar. The light cycle gas oil is recycled to the thermal cracking zone while the heavy cycle gas oil is recycled to the thermal, viscosity ltireakinefy zione. Reaction products from the thermal reforming zone are fractionated to give reformed gasoline. The` virgin light naphtha, reformed.v gasoline and cracked gasolinel from the thermal cracking and thermal viscosity breaking zones are blended to give the desired ultimate product of the process. In this, and similar schemes, a plurality ofcomponents produced by fractionation are subjected to separate thermal conversion processes wherein byproducts from certain of said separate thermal conversion processes are introduced into other of saidl separate thermal conversion processes whereby a high yield of motor fuel is obtained.

Also, in my copending application, Serial No. 334,741,l filed May 13, 1,940, now U. S. Patent 2,312,445, issued ,March 2,l 1943, a selective catalytic conversion process is described for separately transforming` a plurality of hydrocarbon fractions, wherein byproducts from certain of the separate catalytic conversion processes are introduced into other of' said separate catalytic conversion processes whereby a high yield of motor fuel oi" high antiknock value is obtained.

The selectiveconversion processes of the prior art are primarily' concerned with the efficient treatment of" changing stocks of wide boiling range. To accomplish this, the charging stock selected is fractionated into' a plurality of cuts ofjnarrower boiling range which are each separately processed under conditions best suited for each particular fraction. Obviously, the operating'conditions are selected for each individual conversion zone primarily on the basis of'V the boiling range of the particular fraction charged to said zone.l In contradlstinction to this, in the instant invention, the charging stock, which is Y fraction charged to said zone.

preferably of comparatively narrow boiling range, for example, one of the fractions employed in prior art selective conversion processes, is separated into a plurality of components of the same or approximately the same boiling range as that of the original charge but of diifering refracto-riness and these are separately processed under catalytic conversion conditions best suited'for each particular component. Here the operating conditions are selected'for each individual catalytic conversion zone primarily on the basis of the chemical characteristics ofthe particular The boiling range of the several'components being identical or ap-V proximately so, this factor need not be considered in xing operating conditions.

Many variations are possible in the practice of Yasevgssae the bottom of tower 3 and the heavier phase, usually the solvent, is introduced near the top of tower 3. Tower 3 is preferably provided with means to facilitate liquid-liquid contact, for ex ample, perforated plates fi, but other suitable means, such as bubble trays, Raschig rings, Berl saddles or the like may be employed. The rey .spective liquids flow countercurrently, contactsubjected to catalytic cracking under relatively mild conditions in the presence of an active catalyst, the products being separated into gas, gasoline and cycle stock. The cycle stock is added to the relatively refractory portion of the charge and the resulting mixture is subjected to catalytic cracking under relatively severe conditions in the presence of an active catalyst, the reaction prod- ;ucts being again separated into gas, gasoline and V`cycle stock. Y,This second cycle stock may be dis- .carded while the two gasoline streams are blended to formY the desired ultimate product of the combination.V

For the better understanding of this invention,

` referencemaybe had to the accompanying gure,

forming a part of this speoiiication and wherein said figure isa diagrammatic representation in elevational view of one formof apparatus suitable for accomplishing the objects of this invention.

Turning now to a more detailed consideration of the iigure, a suitable hydrocarbon charge, for

example, straight run gasoline, heavy naphtha,

light gas oil,` heavy gas oil,`reduoed crude or the like enters the system through line I and is moved 1 by pump 2 to the solvent extraction tower 3. It

is well known in the art to treat petroleum fractions with various solvents in order to separate said fractions, at least partially, into their respective components. For example,it is well known to treat petroleum fractions with solvents, solvent mixtures or modiiied solvents selected from the .class of solvents having a preferential selectivity Yfor the relatively hydrogen poor components 4(aromatics, naphthenes, olenes) as compared `with the relatively hydrogen rich com ponentsV (paraflins) of the petroleum fractions. Solvents of this class include, for example, phenol, phenol plus water, benzene plus acetone, furfural, sulfur dioxide, aniline, Vdichloro diethyl ether and the like. The petroleum fraction and the selected .solvent may be contacted in any suitable manner, as for example in a single ormulti-stage batch Y operation. The petroleum fraction and the se-V lected Vsolvent however, are Vusually contacted in Y, `a countercurrent treatingV tower such as is indi-V cated by theV reference numeral V3.

:lighter phase, usually the oil, is introduced near Here the.V

and the chemical nature of the particular hydrocarbon oil being extracted. Generally, a selective solvent is used having a boiling point or boiling range. below, preferably appreciably below, the initial boiling point of the particular hydrocarbon charge being extracted although it is ob'- vious that this is largely a matter of convenience rather' than an absolute requirement, especially in the case of lower boiling hydrocarbon oils, but it might be a matter of some dihiculty to'iind a satisfactory selective solvent boiling above the range of heavy gas oil or reduced crude. Liquid sulfur dioxide is frequently employed in the solvent extraction of gasoline, heavy naphtha, kero-V serie and similar fractions or". relatively low boiling range while one of the higher boiling solvents previously mentioned orother suitable materials of similar nature may be employed while extrach ing light gas oil, heavy gas oil, reduced crude and similar fractions of relatively elevated boiling range.

Yemployed. if the Yextraction zone is operated under pressure. The other solvents mentioned as well as other selective solvents also have preferred op erating temperatures. Furfural, for example, is generally what may be considered. a high temperature solvent, being used frequently in the neighborhood of 290 F., more or less. v

The solvent extraction step per se forms no par of the instant invention except in the combination shown and since such processes are familiar to those skilled in the art, further discussion is unnecessary.

The raffinate phase, which is poor in solvent and rich in hydrocarbon components of high hydrogen content, is sent to fractionating tower 5. This tower is provided with means to facili- .tate liquid-Vapor Contact, yfor example, bubble trays l, bottom heating means, for example, coil 8 and top cooling means,` for example, coil S.

4Vaporized solvent passes overheadV through line ing than the oil. If the opposite obtains the re- Y quired changes will be obviousY to those skilled inY the art.

In some casesV it is possible toremove solvent from the raiiinate'phaseby vwater washing or by a similar extraction process with a suitable second solvent. AFractionation of the ralnate phase can then be dispensed with. Obviously in :such cases, the extract phase may be worked up similarly if desired and also it is not necessary to select la primary solvent that boils either above or below the boiling range of .the hydrocarbon oil being processed. Also, with a very few solvents, the ramate phase is solvent free or practically so. Under such circumstances tower 6 may be dispensed with and raina'te sent di- "rectly from valved line 4A to line Ill Via valved line I5.

The extract phase, which is rich in solvent and in hydrogen-poor hydrocarbon components, is sent to fractionating tower I5 which is similar to tower 5. Solvent Avapors pass overhead through line I'I, are condensed in cooler Il and sent to reservoir I2. Solvent in reservoir l2 is moved by pump IB to manifold I9, line 2li and valve .2| to extraction tower 3. A part of the solvent may be sent through line 22 and valve '2-3 to the top of tower 6 to provide open reflux therein while part may be sent through valve 25 to tower IB for the same purpose. Extract oil is removed vfrom tower 16 by line 25 to be processed as subsequently described.

Rafnate oil in line I4 is moved by pump 2'.' through coil 28 in furnace setting 28 wherein the charge is brought to the desired catalytic cracking temperature. Since the charge is of a relatively non-refractory nature, the desired catalytic cracking temperature is relatively low, being generally in the range 500 F'. to 900 F., more or less. the exact temperature depending upon the boiling range of the stock and other operating conditions as will be more specically set forth herein-under. The thus heated charge, preferably in the vaporized state, is sent to reactor 30 which contains -a suitable cracking cata lyst of high activity. Among suitable contact agents for the purpose may be mentioned cer tain natural clays, especially activated clays of the bentonite, montmorillonite or sepiolite types; synthetic silica-alumina complexes or synthetic silica-magnesia complexes. The clay type catalysts are preferably activated by being treated for several hours with acid or with aqueous solutions of salts of magnesium, aluminum, manganese or the like, then washed and iinally converted to any desired physical form. The synthetic silica-alumina complexes are preferaably made by first precipitating silica gel from water glass solution with acid. The gel is washed and, if desired, dried or partially dried and then activated by hydrolytic adsorption of f alumina thereon. Or the gel is washed and, if desired, partially or completely dried and then impregnated with an aluminum nitrate solution, then dried and heated to 850-l050 F. to decompose the aluminum salt. Alternatively, the washed and, if desired, dried or partially dried silica gel may be mechanically homogenized with aluminum hydroxide. Or, the silica gel may be simultaneously precipitated with aluminum hydroxide by mixing a, water glass solution with a solution of an aluminum salt. Numerous other methods of catalyst preparations may be employed but they will not be described in further detail since the particular catalyst used forms no feature per se of the instant invention. Synthetic silicamagnesia catalysts may be made as described above, substituting magnesium compounds for aluminum compounds. Silica gel may be activated by other .materials in addition to or in place of magnesio. or alumina, .for example, zirconia or boron oxide. Also, various activated carbons and carbon blacks may 'be used as catalysts. Carbons that have been activated by heating to above 400 C., for example, 95.0 C., or even higher in an inert or oxidizing atmosphere may be used,

Reaction products from reactor 30 pass by line 31 .to fractionating tower 32 which is provided with means to .facilitate liquid-Vapor contact, for example, -bubble trays 33, lower disposed heating mean-s, for example, coil 34 and upper disposed cooling means, for example, coil 35. Overhead from tower 32., `consisting of gasoline and gas, passes Athrough line 36 is condensed in 3'! and separated in `33. Gas passes overhead from the .separator through line 39 while gasoline may be moved by pump 40 to storage through valved line V4I.` Part .of the gasoline may be recycled through the valved line 02 to tower 32 to provide open redux therein.

Cycle :stock is removed from tower 32 by line d3.. 4This material'is considerably more refrac tory than the raffinate o'il from which it was ob tained and accordingly it is moved by pump M through line l45 and valve 46 to line 2E; where it is admixed with relatively refractory extract oil. The blend is moved by pump M through heating coil 48 in ,furnace setting 49. During passage through coil 48 the charge is brought to .a relatively high catalytic cracking temperature, for example, a temperature in the approximate range'85`0 F. to l050 F., more or less. The thus heated charge passes to reactor Eil which contains la suitable cracking catalyst of a nature previously described. Reaction products from reactor 50 pass byline 5I., valve 52 and line 53 to tower 54 which is similar to tower 32. Cycle stock from tower 54 is moved by pump 55 and since it is usually very refractory it may be discharged through'valve 56 for disposal. If desired however, part or all of this cycle stock may be :sent through valved line 51 to solvent extraction tower 3.

Many variations of the above described single embodiment are possible. Among these may be mentioned the following:

(l) Cycle stock from tower 32, instead of being combined with the extract oil, is instead sent through valved line 58 to extraction tower valve 46 being closed. In this way, only the relatively refractory portions of this stock are processed in reactor 50, the relatively non-refractory portions 'being recycled, after extraction, to reactor 30. Cycle stock from tower 54 is then either discharged through valved line 5S or is sent in part or entirely to the solvent extractor 3.

(2) If desired, reaction products from reactor 50 .may be sent to ractionating tower 32 by closing valve '52 and opening valve 59. Inthis scheme of operation, tower 5l may be dispensed with, including its auxiliary equipment. If desired, material from reactm l5l! may be slightly cooled in vSi) prior to entering tower`32. When operating in accordance with this scheme, cycle stock from tower 32 is preferably eliminated from the system through vaived line r6| .but part or all of it may be sent to the solvent extraction zone and/or to the second catalytic cracking zone by paths previously outlined.

`(3) If desired', the liquid hydrocarbons of lower boiling point thanthat of the charge which are produced in reactor '39 and/or reactor 5B may also be extracted in extractor 3. .For example, liquid reaction products of lower boiling range than that of the charge'which are products of reactor 30 may be passed through valve 96 and line ,91 to the lowerpart of the extraction tower 3. yIn such a case, fractionating tower 6 isprovided with means for removing a side stream, e, g., valved line 92. Tower 6 then produces (a) solvent as overhead through line I0, (b) the ra'inate portion of liquid hydrocarbons ofV lower boiling point than that of the charge produced in reactor 3|] as an intermediate cut through valved line 92 and (c) the rafnate oil portions of the hydrocarbon charge as bottoms through line I4. When operatingV in .this way it isobvious that a selective solvent of low boiling point, e. g., sulfur dioxide is used but if a high boiling solvent is employed it may be eliminated as bottoms by obvious modications as has already been mentioned. Similarly, when operating in the manner described, tower i6 produces (a) solvent as overhead through line il, (b) the extract portions of liquid hydrocarbons of lower boiling point than' that 'of the charge which are produced in reactor 33 asian intermediate cut through valved line 95 and (c) the extract oil portions of the hydrocarbon charge Y as bottoms through line 26.

`It will benoted that when operating as described immediately above, if the bottoms from tower32 are to be recycled to the solvent extraction towers by pump 44, line 45 and valve 58, there is no need for tower 32 and its auxiliary equipment. Reaction products from reactor 3|! are cooled and separated, the liquid portions then being sent to the solvent extraction tower 3. Fractionation of the reaction products is then accomplished, after solvent extraction, in frac- V tionatingtowers 6 and I6.

' By operating Yas described under (3) liquid reaction products of low olene content and high Y octane number are obtained via valved line 92.

These are eminently suitable for aviation use. On the other hand, less suitable products for aviation use but which are eminently suited for automotive use are obtained as an intermediate fraction from tower l via valved line 95.

Liquid hydrocarbon conversion products of lower boiling range than the charge and produced in reactor 50 may similarly be solvent extracted in part or entirely.A This is accomplished by sending the liquid conversion products obtained as an overhead from tower 54 to extractor 3 through valve 98 and line 99. Again, if all the cycle stock eliminated as bottoms from tower 54 is to be sent to solvent extraction tower 3 along with the liquid conversion products made in reactor 5D, then tower 5d may be dispensed with, the reaction products from reactor 50 being cooled and separated, the liquidV portions thereof being sent to extractionrtower 3, the reaction products made in reactor 50Abeing fractionated in towers 6 and I6. Y

YThe above described variation is useful when it is desired to produce a high octane number light Vnaphtha of low olene content from a heavy naphtha charge or a high octane number' gasosecond catalyticv cracking'zone') most simply, gas may be taken overhead from separator 38 through lines 39, 62 and valve 63 and disposed of as de-` therefrom by stabilization, both conventional and well known processes. For example, valve 63 may be closed and the gas sent from separator 38 through lines 39, 64 and valve 65 to a conven- Y tional absorber represented by reference numeral 65. Dry gas may be removed via line 61 and valve 68 for disposal as desired while absorption gasoline is discharged through valved line 69.`

Also, liquid from separator Y38 may be sent through valved line 10 to a conventional stabilizer represented by reference numeral 7|, valve 4| being closed. f Dry gas may be removed via line 12 and valve i3 for disposal as desired while stabilized gasoline may be discharged through valved f line l.

line of -lowolene content from a gas oil charge.

' Vli'or'reasons to be given subsequently, this schemeV Considering in detail the overhead system follow-` ing the first catalytick cracking zone (which is identical with the overhead system following the r desired, valves 68 and/or I3 may be closed and the gas from absorber 66 and/or stabilizer 1| may be passed through valved lines 'l5 and/or I6 to manifold Tl and thence to fractionator 18,

Fractionator 78 is conventional, being provided with means to facilitate liquid-vapor contact, for example, bubble trays 19,'1owerdisposed'heating means, for example, coil 80 and upper disposed be eliminated through valved line 82 for disposal as desired. As has been mentioned previously, the overhead system following the second catalytic reactor 50 may be operated similarly.

It will be noted that at the choice of the oper- Vator one or moreY g-as streams -of practically any desired characteristics become available. In general, the characteristics of the several gas streams are approximately as follows:

From lines containing valves 63 and84: Approximately total gas somewhat decient however in heavier gaseous components and containing some normally liquid hydrocarbons.

From lines containingvalves 68 and S5: Simllar to above but lacking normally liquid components.

From lines containing valves land 85: Gas rich in heavier gaseous components.

From lines containing valves and 8l; Gas rich in lighter gaseous components.

From lines containing valves 82 and 88: Gas rich in heavier gaseous components. Y

Obviously, the nature of the gas eliminated from the top and bottom ofYY fractional-tors 'I8 *andY fractionators are operated on this charge. The

charge may be relatively heavy gas, relatively light gas or total gas. The fractionators separate their respective charges into a relatively heaw and a relatively light fraction.

If desiredthe various gas streams, or portions thereof, may be vented from the system gas from separator 38 through'valve |193, gas from absorber sthrough valve ylill, gas from-stabilizer 1| through valve |52, overhead gas from fractionator i8 through valve |63 and bottoms gasy from iractionator 18 through valve |04. In the overhead system following reactor 50 the corre spending valves are designated |05, |06, |01, |08 and |09.

It should be emphasized that the gas produced in reactor 30 is relatively poor in olenes while that produced in reactor 50 is relatively rich in olenes.

It is possible to send, if desired, a portion or all of a selected gas stream or streams from the overhead system following reactor 30 to the second catalytic cracking zone by manifold 90 and compressor 94 and likewise it is po-ssible to send, if desired, a portion or all of a selected stream or streams from the overhead system following reactor 50 to the rst catalytic cracking zone by manifold 9| and compressor 93.

.An especially valuable embodiment may be employed when the liquid conversion products have.

been solvent extracted as previously described. When operating in this manner part or all of the liquid. hydrocarbon conversion products boiling lower than the original charge are separated into a rainate portion of low olefine content and high octane number and an extract portion of high oleiine content and-high octane number. Highly olenic gas .from the second catalytic cracking zone, E0, may be used to alkylate by known methods the raiiinate portion ofthe conversion products to produce a high yield of saturated alkylate of high octane number and/or gas of low olene content from the first catalytic cracking zone, 30, may be alkylated by known methods by the extract portion of the conversion products to produce a high yield of saturated alkylate of high octane number.

For simplicity, in the figure, the catalytic reactors 30 and 50 are each represented by single vessels. As is well known to those skilled in the art, cracking catalysts decline in activity more or less rapidly while on stream dueto the deposition of carbon or carbonaceous residues thereon. To restore catalytic activity, it is necessary to remove said carbon or carbo-naceous residues periodically at rather frequent intervals. This is usually accomplished by burning said `materials from the catalytic surfaces with air or dilute air. For continuous operation, it is obvious Vthat provision must be made for catalytic material of adequate activity to be available at all times. Many methods are known for' accomplishing this, several being described in some detail in my copending applications, Serial Number 313,898,11ed J anuary 15, 1940, now U. S. Patent 2,323,728, issued July 6, 1943, and Serial Number 334,741, led May 13, 1940, now U. S. Patent 2,312,445, issued March 2, 1943, Viz:

1. Plural reactors containing a stationary bed of catalyst.

2'. Reactors designed for use with moving catalysts.

3. Reactors designed for use with suspended catalysts.

For reasons of simplicity none of the above schemes are shown in the figure but it is to be understood that for continuous operation one such method or its equivalent is employed.

Having now described in general terms one form of apparatus suitable for accomplishing the objects of my invention, more specific illustrative but non-limiting details with respect to the treatment of certain selected charging stocks in accordance thereto will now be' given. The process of this invention is particularly adapted to the `treatment of hydrocarbon 'oils of relatively narrow boiling range as exemplified by gasoline,

heavy naphtha, light gas oil, heavy gas oil, reduced crude and the like but is not necessarily limited thereto.

Any gasoline (which term includes hydrocarbon oils boiling within the approximate range 60 F. to 500 F.) may be employed as charge in the process but virgin gasclines from mixed base crudos, for example, Agasolines from Mid'continent and East Texas c'r'udes are especially suitable. Such gasolines, by solvent extraction, give appreciable amounts `of both a relatively refractory extract oil and a relatively non-refractory railinate oil. The relatively non-refractory raiiinate oil may bevaporized at a comparatively low temperature, .for example, 500 F. to 900 F., more or less and passed over a catalyst of a nature previously described at a rate of from 0.2 to 15 volumes, more or less, of liquid charge per hour per volume of catalyst (hereinafter designated by v./.hr./vi In general, a moderate to low operating pressure is employed, suicient to overcome pressure drop, for example, 50 pounds per square inch or less, -for example, 25 pounds per square inch.y Under certain conditions however, to be outlined in detail subsequently, high superatmospheric pressures are employed. Obviously, such operating variables as temperature, contact time, pressure and catalyst activity are more or less interchangeable. For example, a high operating temperature may be compensated for to` a greater or lesser extent by increasing flow rate (reducing contact time), decreasing the activity of the catalyst employed or by operating at a lower pressure or by any combination of these changes. The corresponding relatively refractory extract oil is pi'focess'ed under more severe conditions than outlined Yalziovel for the rafnateoil.- For example, the extract oil may be vaporized at a relatively high catalytic cracking temperature in theneighborhood =of 850 F. to 1050 F. more or less, and passed atA the flow rates and in the pressure ranges ,previously described over the catalyst seiected.- More specific and obviously non-limiting examples of the' treatment of gasolines will be foundbeloW.

Example 1 East Texas' gasoline `(110 P". to 415 F. A. S. T. M. boiling range) was solvent extracted using sulfur dioxide. The raiiinate oil was vaporized at 850 F. and passed at 50 pounds per square inch pressure and the temperature mentioned over Super Filtrol (a trade name for an acid activated bentonite), the charge rate being 3 v./lir./v`. `The liquid recovery was and the knock' rating of the total liquid product was 10 units vabove Vthat of the charge. This liquid was fractionated and material of 260 F. endpoint and {7'4 octane number (A. S. T. M. designation 13357-39) was reserved. The resulting bottoms were mixed with the extract oil and the blend was passed over' Super Filtrol at 50 pounds per square inchpressur'e, 900 F.' and a flow rate of 2 v./hr./v. The product wasfractionated, giving 83% gasoline of slightly higher octane number than the above mentioned light naphtha from the catalytic cracking of raffinate oil. The two overhead fractions were blended to give a high yield of gasoline of just under 76 octanenumber. Cycle stock from the extract oil conversion step may be sent in part or entirely to the solvent extraction zone or, if clesired, may be thermally reformed.

. Example 2 VSimilar to Example 1,- except that the heavy naphtha obtained from the reaction mixture from with the extract oil, was sent to the solvent extraction zone.

'Erample .Y

The East Texas virgin gasoline was solvent ex-V tracted as previously described and tower 6 was so operated that solvent was taken overhead through line Hl, a light naphtha (260 F. endpoint) was eliminated from the system as a side stream through valved line 92 While the heavy naphtha was removed from tower 6 through line I4 and was processed as described in Example 1. On distilling the catalytically cracked heavy naphtha raiiinate oil, a 260 F. endpoint light naphtha of 80` octane number was obtained. The remaining cycle stock was admixed with extract oil and processed as described in Example 1. The gasoline obtained was above 76 octane number. The virgin light naphtha, light naphtha from processing heavy naphtha railinate oil and gasoline from processing the extract oil-cycle blend were mixed, The cycle `stock from the Yextract Yoil conversion zone may be sent in part or entirely to the solvent extraction zone or it may be thermally reformed.

Eample 4 Similar to Example 3 except that the cycle stock from the processing of heavy naphtha ranate oil was sent to the solvent extraction zone.

'Example 5 An East Texas heavy naphtha (250 F. to 400 F. boilingv range) Was solvent extracted With sulfur dioxide. The raffinate oil was Ycatalytically cracked in the presence of Super Filtrol at 50` pounds per square inch pressure, 850 F. and a charge rate of 2.5 v./hr./v. A 35% yield of 78 octane number light naphtha was obtained. The cycle stock was blended with the extract oil and was passedrat 900 F., 50 pounds per square inch` pressure and a now rate of 2 v./hr./v. over Super Filtrol, in a second catalytic cracking zone. The

total liquid obtained was of 76 octane number, the light naphtha Was 80 octane number. `The cycle stock from the extract oil conversion zone may ,be sent in part or entirely to the solvent extrac-` tion zone or it may be thermally reformed.

Y Y `Example 6 f ASimilar to Example 5i except that the cycle stock from rainate oil conversion was returned to the solventextraction zone.

Gasolines prepared in accordance with Examples 1-6 above have an appreciable olene Content andl hence a high acid heat, Such charac- An East Texas heavy naphtha was solvent exrainate oil chargef The cycle stock from` this operation Was'blended vvithY the extract oilf and the mixture was catalytically cracked in a second zone at 675 F., 6000 pounds per square inch pressure and a iiow rate of 0.5 v./hr./v., usingfSuper Filtrol. The 250F. endpoint material from `the reaction ,products had an octane number of 80, an acid heat of 3 F. and the yield was 26%. Cycle stock from the extract oil conversion zone may be sent in part or Yentirely to the solvent extraction zone or it may be thermally reformed.

Example 8 Similar to ExampleV 7 above except ythat the cycle stock from rainate oil processing Was sent to the solvent extraction zone.

It is highly desirable to conduct catalytic cracking operations in the vapor phase. When operating at low-pressures this occurs automatically with light to moderately heavy stocks but at the high superatmospheric pressures previously mentioned a vaporization'aid may be required, especially when the charging'stock is moderately high or high boiling, for example, of the nature of light gas oil, heavy gas oil, reduced crude or the like. With gasolines or heavy naphthas such vaporization aids are usually not essential even at high pressures but may be used if desired. f One of the most convenient vaporization aids is the gas produced by the unit- In Examples 7 and 8,' above, for example, 5% by weight, more or less, of gas (based on liquid charge) may be compressed and added to the raiinate oil charge and/or the eX- tracted with sulfur dioxide and the raffinate oil wasV brought to a pressurerof 6000 pounds per` square inch and heated to 625 F. Under these conditions it was contacted with Super Filtrol at a charge rate of 0.5 v./hr./v. The product formed boiling up to 250 F. had an acid heat'of only 1 F.

` ci. sgr. Meesignanon 13481-39),` was of 79 ocnenumber and theA yield was 22% based on the tract oil charge prior to passage to the proper conversion zones. As mentioned, when operating at high pressures and employing stocks boiling above the usual gasoline boiling range a vaporization aid is almost essential. For example, when charging materials of the boiling range of light gas oil, about 13 cubic feet of total butane free gas per gallon of liquid' charge may be used. Vihen extremely heavystocks are employed evenat moderate toloyv pressures a vaporization aid is highly desirable. For-example, a vaporization aid is almost essential when charging materials of the nature` of reduced crude and highly desirable Vwhen charging gas oil.

y In addition to aiding in vaporizing the charge, components of the added gas react to a greater or lesser extent under the conversion conditions with the liquids present vthereby increasing the yield of desired products. This effect is not very pronounced under the operating conditions outlined in Examples 7 and 8. There are tWo reasons for this. In the rst place, the gas produced under such conditions is practically olene free and hence comparatively unreactive and in thesecond place the operating temperature is low. However, when the raiiinate and extract oils are processed under more normal conditions as regards to temperature, the gases produced contain appreciable oleiines and the reaction temperatures are sufficiently high to bring about alkylation and/or gas reversion if the gas is recycled. Since the operating conditions in the raiiinate oil conversion step are less severe than inthe extract oil conversion step, the relatively 10W olene gas from the rainate oil conversion is less reactive than that from the extract oil conversion. Accordingly, When it is desired Vto take advantage of this alkylation and/or gas rev version eiect itis preferable to sendrelatively non-reactive gas from'railnateY oil conversion to the' 'relatively severe conditions of the' extract materials of the nature of heavy' A iight Midconunent. gas iii cf se A. P. I.

gravity and 430 E'. to 730 F. boiling range was solvent extracted, using furfural. The raiiinate l oil was passed at a flow rate of 1.5 v./hr./V- and a temperature of 850 F. over Super Filtrol, the inlet pressure to the heating coil being 50 pounds per square inch. Exactly 50% by volume of 81 octane number gasoline formed. The cyclev stock (40% by volume) was added to the extract oil and the mixture was brought up to 50 pounds per square inch pressure, heated to 900 F. and passed over Super Filtrol at a rate of 1 v./hr./v. A 55% by volume yield of 8l octane number gasoline was obtained. rIhe cycle stock from this second catalytic cracking operation may be sent in part or entirely to the solvent extraction zone or, if desired, it may be thermally cracked to completion.

Example Similar to Example 9 above except that the cycle stock from raffinate oil cracking is sent to the solvent extraction zone instead of being mixed With the extract oil.

When a heavy stock, especially a heavy stock of a residual nature is to be processed, for example, reduced crude, it is desirable to deasphalt the stock prior to charging to the solvent extraction zone. In this Way, components having little potential gasoline Value are removed and by so doing deterioration of catalytic activity is retarded since the asphalt and resin-like components, if retained in the charge, deposit on the catalytically active surfaces and bring about an extremely rapid decline in activity. The deasphalting may be accomplished, for example, by dissolving the charge in aliqueed normally gaseous hydrocarbon such as propane or the butanes. On increasing the temperature to about the critical temperature of the normally gaseous hydrocarbons, asphalts and resins are precipitated and may easily be removed. By methods Well known to those skilled in the art, deasphalting and solvent extraction may be accomplished in one step.

Example 11 An East Texas reduced crude was dissolved in 8 volumes of liquid propane and the solution was heated under pressure to 200 F. Precipitated material was separated and the solvent removed. The deasphalted charge was solvent extracted using furfural. The raflinate oil was mixed with gas from the extract oil conversion zone at a rate of 25 cubic feet of gas per gallon of oil and the Whole was brought to a pressure of 50 pounds per square inch, heated to 900 F. and passed over Super Filtrol at a rate of 1 v./hr./v. Gasoline (40% by volume, 78 octane number) was separated together with the gas and the cycle oil was admixed with the extract oil. To this blend, gas from the raffinate oil catalytic cracking zone Was added at arate of cubicaieet-per gallon of oil, the mix wasbrought to 50:l pounds per square -inch pressure, heated to` 975 F; and passed over Super Filtrol at a rate of I v./hr./v. A little over 'of 791 octane number gasoline Was obtained. Cycle stock from theextract oil catalyticv crackingzone may be sent in Whole or in part to the solvent extraction zone or may be thermallyV viscosity broken. i

Y Example 1,2

Like Example l1 above except that cycle from the raiiinate oil catalytic cracking zone is sent to` the solvent extraction zone. instead of being mixed with the extract oil..

In all of the above examples, to facilitate comparisons, Super Filtrol was used as catalyst in both conversion zones. It is to be understood however that other suitable contact agents may be employed in either or both Zones, for example,

alumina hydrolytically adsorbed on silica gel,

synthetic silica-alumina mixtures or complexes, synthetic magnesium silicates and the like. As the activities of the several catalysts vary, obviously operating conditions should be adjusted when changing from one contact agent to another.

While virgin charging stocks are employed in all' of the above examples, the invention is not limited thereto. 'For example, such stocks as coker gas oils and viscosity breaker gas oils may be used'i desired. Also, cracked gasolines or cracked heavyy naph-thas may be processed. When this is done, the extract oil catalytic cracking zone produces ar large amount of valuable gas rich in C4V hydrocarbons, especially isobutane and isobutene. Such gas isy very suitable as a charge to catalytic polymerization or catalytic alkylation units. vWhen available, cracked gasolines of low quali-ty, for example, coker gasolines and viscosity breaker gasolines may be processed in this way to great profit,

While solvent extraction has been exclusively described as the process suitable for separating the selected hydrocarbon charge into a relatively refractorycomponent and-a relatively non-refractory component, other procedures, may be employed for accomplishing the same ends, for example, fractionation. By accurate fractionation the hydrocarbon oil charge may be separated into a plurality of narrow fractions of differing refractorinesa These cuts may be treated separately in accordance with the teachings of this invention or, fractions of like or similar refractoriness may be combined and the resulting blends treated as described. In most cases, separation by fractionation is of limited applicability, being best suited for use in connection with hydrocarbon oils of comparatively low boiling range, for example, gasoline, heavy naphtha, kerosene and the like. With oils of higher boiling range, the mixture of hydrocarbons is usually so complex that-separation by fractionation is practically impossible.

Separation of hydrocarbon oils into relatively refractory and relatively non-refractory components may also be accomplished by fractional crystallization. This method is generally of wider applicability than fractionation, in fact it is particularly suited for removal of relatively non-refractory waxes from oils of comparatively high boiling range.

It is obvious that, if desired, cycle stock from the first catalytic cracking zone obtained through line t3 may be recycled in part or entirely tothe iirst catalytic cracking zone throughV heating coil 23 in furnace setting 29 and/or cycle stock from the second catalytic cracking zone obtainedA as bottoms from tower 54 may berecycled in part or entirely to the second catalytic cracking zone through heating coil 48 Yin furnace setting 49. Means for accomplishing this recycling are so obvious that the necessary lines are not indi cated in the figure.

Be it remembered that while the instant invention has been described by means of several speciiic examples thereofit is to be understood that these examples' are illustrative only and the invention' is not limited to the specificdisclosures therein. Also, it will be obvious that certainv features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and within the scope of the appended claims.

It is further to be understood that various changes may be made `in details within'the scope of the appended claims without departing from the spirit of my invention. It is accordingly'to be understood that my invention is not to be limited to the speciiic details shown and described.

I claim:

1. In the catalytic conversion of a hydrocar` ing thernixture'and iractionating the raffinate lY phase in a second fractionating zone into substantially saturated hydrocarbon conversion products and the previously mentioned raffinate oil. Y Y

2. In the catalytic conversion of a hydrocarbon oil, the steps including 4heating the raiiinate oil obtained from said hydrocarbon oil by solvent the previously mentioned raffinate oil and fractionating the extract phase in a third fractionating zone into highly unsaturated hydrocarbon conversion products and the previously mentioned extract oil. K

3. InV the catalytic conversion of a hydrocarbon oil, the steps including heating the raii'inate oil obtained from said hydrocarbon oil'by solvent extraction as hereinafter described to a relatively lowY catalytic crackingtemperature, contacting said heated rainate oil in a first catalytic cracking zone with a cracking catalyst for a time suilicient to effect substantial conversion of said rainate oil to liquid hydrocarbon conversion products of lower boiling pointthan said raiiinate Y oil, fractionating the resulting reaction products extraction as hereinafter described to a relatively Y low catalytic cracking temperature, contacting said heated rainate oil in a first catalytic cracking zone with a cracking catalyst for a time suffi--v cient to effect substantial conversion of said raiiinate oil to liquid hydrocarbon conversion products of lower Aboiling point than said raiiinate oil,

` heating the extract-oil obtained from s'aid hydrocarbon oil by solvent extraction as Vhereinafter described to a relatively high catalytic cracking tempera-ture, contacting said heatedY extract oil in a second catalytic cracking zone with a crack-V ing catalyst for a time suilicient to effect substantial conversion of said extract oil to liquid hydrocarbon conversion products of lower boiling point than said extract oil, fractionating the resulting reaction products from both catalytic cracking zones in a rst fractionating zone into gas, the y aforementioned liquid hydrocarbon conversion products and cycle stock, admixing said liquid hyin a iirst fractionating zone into gas, the afore- Y mentioned rliquid hydrocarbon conversion products and cycle stock, admixing said liquid hydrocarbon conversion products with the aforementioned hydrocarbon oil, solvent extracting the mixture, fractionating the raffinate phase in a second fractionating zone into substantially saturated hydrocarbon conversion products and the previously mentioned raffinate oil, fractionating the extract phase in a third fractionating Zone into highly unsaturated hydrocarbon conversion products and extract oil, admixing extract oil with the aforementioned cycle stock, heating the mixture of extract oiland cycle stock to a high catalytic cracking temperature and contactingVV said heated mixture of extract oil and cycle stock in a second catalytic cracking zone with a crack-r ing catalyst for a timeV suicient to effect substantial conversion of said last-named mixture to liquid hydrocarbon conversion products of 10W- er boiling point than said last-named mixture.

4. The process of claim 3 furthercharacterized by the fact that the reaction productsV from the conversion of said mixture of extract oil andcycle stock in said second catalytic cracking zone are fractionated in a fourth fractionating zone into gas, the last-named liquid hydrocarbon conversion products and cycle stock and the last-named liquid hydrocarbon conversion products are admixed with the aforementioned hydrocarbon oil.

5. In the catalytic conversion-of a hydrocarbon oil, the steps -including heating the rafnate oil obtained from said hydrocarbon oil4 byY solvent extraction as hereinafter described to a low catalytic `cracking temperature, contacting said heated raiinate oil in a catalytic cracking Zone with a cracking catalyst for a time suicient to eiect substantial conversion of said raffinate oil to liquid hydrocarbon conversion products of lower boiling point than said raffinate oil, cooling the reaction products, separating the reaction products into gas and liquid, admixing said liquid drocarbon conversion products withV the aforeg mentioned hydrocarbon oil, solvent extracting Vthe mixture, fractionating the raiiinate phase in ya second fractionating zone into substantially saturated hydrocarbon conversion `products and with the aforementioned hydrocarbon oil, solvent extracting the mixture and fractionating the rafiinatephase into substantiallyV saturated hydrocarbon conversion products and the previously mentioned raiiinate oil. I Y Y 6.In the catalytic conversion of a hydrocarbon oil, the steps including heating the rainate oil obtained from said hydrocarbon oil by solvent extraction as hereinafter described to alow catalytic cracking temperature,Y contacting said heated raffinate oil in a iirst catalytic cracking zone with a cracking catalyst for a time sufficient to effect substantial conversion of said raflinate oil to liquid hydrocarbon conversion products of lower boiling point than said raiiinate oil, cooling the reaction products, separating4 the reaction products into gas and liquid, admixing said liquid with the aforementioned hydrocarbon oil, solvent extracting the mixture, fractionating the rafnate phase in a first fractionating zone into substantially saturated hydrocarbon conversion products and the aforementioned rainate oil, fractionating the extract phase in a second fractionating zone into highly unsaturated hydrocarbon conversion products and extract oil, heating said extract oil to a high catalytic cracking temperature, contacting said heated extract oil in a second catalytic cracking zone with a cracking catalyst for a time sufficient to eiect substantial conversion of said extract oil to liquid hydrocarbon conversion products of lower boiling point than said extract oil. fractionating the resulting reaction products from said second catalytic cracking zone in a third fractionating zone into gas, said liquid last mentioned hydrocarbon conversion products and cycle stock and admixing said last mentioned liquid hydrocarbon conversion products with the aforementioned hydro- 10 carbon oil.

ROBERT F. RUTHRUF.

Images