US 3071535 A
Description (OCR text may contain errors)
PROCESS FOR MAKING A LOW SENSITIVITY PREMIUM GASOLIEE Filed July 6, 1959 Patented Jan. l, 1963 3,071,535 .PROCESS FR MAKNG A LW SENSTFVETY PREMlUM GASOLINE .lohn A. Condrasky, Penn Hills, Pa., and Edwin M. Glazier, Fox Chapel Borough, Pa., assiguors to Gulf Research fr Development Company, Pittsburgh, Pa., a corporation of Delaware Fiied .iuly 6, i959, Ser. No. 825,@75 l Claim. (Cl. 208-55) This invention relates to a process for producing a premium gasoline of low sensitivity and more particularly to such a process employing a combination of catalytic cracking and alkylation.
Our process combines the use of catalytic cracking and alkylation with other rening procedures to produce a premium gasoline of low sensitivity. By sensitivity is meant the difference between the research method and motor method octane numbers of the gasoline. We use the shorter terms research method and motor method to refer to the 'standard ASTM knock test methods, namely, the Test for Knock Characteristics of Motor Fuels by the Motor Method (ASTM D357) and the Test for Knock Characteristics of Motor Fueis by the Research Method (ASTM D908). High research octane number is desirable for city driving at low engine speeds and with frequent acceleration and high motor octane number is desirable vfor highway driving at high engine speeds. Premium gasolines now being marketed frequently have high research octane number but unsatisfactorily low motor octane number. The octane rating sensitivity, or in other words, the diiference between motor and research octane number is too high. Typical premium gasolines now in use have a sensitivity of or higher. The process of the present invention makes possible the production of premium gasolines, ie., gasolines having a research octane number (-}-,3 cc. TEL) of 97 or higher, that have a sensitivity of 7.5 or less. This means that for a given research octane number the gasoline has a high motor octane rating. The process of the invention produces high octane gasoline of low sensitivity by a novel cornbination of procedures for rening various refinery fractions and accomplishes this result at a cost competitive with conventional rening procedures that are unable to produce premium gasoline of low sensitivity.
In processing crude oil for the production of premium gasoline it is known to employ in combination duid catalytic cracking and alkylation. The catalytic cracking charge normally comprises a straight run gas oil fraction of the crude oil. Conventionally, the aim of the catalytic cracking operation is to produce from the straight run middle distillate or gas oil a maximum yield of gasoline range hydrocarbons. The catalytic cracker is run at a space velocity and temperature providing a cracking severity such that the amount of butenes produced do not exceed the amount that can be alkylated with isobutane recoverable from the crude oil and available for alkylation, a portion of the n-butane recoverable from the crude being required for blending with the final gasoline product to raise its vapor pressure to the required level. In other Words, in conventional practice, the severity of the catalytic cracking operation and the consequent yield of light olens is limited by the yield of butanes from the particular crude oil being processed.
We have now discovered that premium gasoline of unusually low sensitivity can be produced economically by maximizing the alkylation phase of crude oil processing. We can accomplish this result by employing, in combination, high severity fluid catalytic cracking, alkylation, coking of reduced crude and by employing in the alkylation stage butanes obtained from an outside source.
In accordance with our procedure, after fractionating the crude oil to obtain straight run gas oil cracking charge and other straight run products, the crude oil residuum is subjected to coking to obtain additional gas oil cracking charge. The catalytic cracking unit is then operated, not at conventional conditions for maximum production of gasoline range hydrocarbons, but at severe conditions to obtain a high yield of C5 and lighter olens :as alkylation charge stock. In our procedure all of the butenes and at least a portion of the pentenes obtained by catalytic cracking are subjected to alkylation. We employ cracking conditions of severity such that the yield of these olefins exceeds the yield that can be alkylated with the isobutane available directly or indirectly from the crude oil. Accordingly, we use isobutane derived from an outside source for alkylation and thus markedly increase the production of alkylate. The alkylate being a mixture of branched chain paraflins of high motor octane rating contributes greatly as a blending component to our ultimate production of premium gasoline of low sensitivity.`
ln the preferred embodiment of our process we employ additional processes that yield gasoline range hydrocarbons, some of which yield products rich in branched chain paraftns and, therefore, contribute to production of a high octane premium gasoline of low sensitivity. These additional processes include catalytic isomerization of C5 and C6 parafns, catalytic reforming of straight run naphtha and catalytic polymerization of propylene.
Our process in general comprises charging a total crude oil to fractional distillation to obtain straight run fractions including a gaseous fraction, a C4 fraction, a gasoline fraction, a gas oil fraction and a residual fraction. The residual straight run fraction is subjected to coking to recover coking products including a fuel gas, propylene, C4-C5 olens, a naphtha fraction, a gas oil fraction and coke. The straight run gas oil fraction and the coker gas oil fraction are subject to uid catalytic cracking at severe conditions including a temperature of at least 975 F. to achieve conversion of at least 70 volume percent of the fresh cracking charge and thereby to produce C4 olefins in aI molar yield greater than the molar yield of butanes recovered from the straight run distillation of the crude oil and from conversion products of the straight run fractions of the crude oil less the amount of n-butane required for vapor pressure adjustment of the final gasoline products. All of the C4 olens and at least a portion of the C5 olefins produced by fluid catalytic cracking and coking are subjected to alkylation with all of the butanes obtained directly and indirectly from the crude oil and with butanes obtained from another source. In preferred embodiments of the process, straight run gasoline is subjected to catalytic reforming, propylene fractions from catalytic cracking and coking are coking are subjected to catalytic polymerization and a straight run paratlin fraction of the C5-C6 range is subjected to catalytic isomerization. A high octane premium gasoline of low sensitivity is produced by blending at least portions of the alkylate, the reforming product and the catalytic isomerization product.
We will describe our process in more detail by reference to the drawing which is a schematic flow diagram of an embodiment of our process.
Total crude oil is fractionated in a conventional atmospheric-vacuum crude distillation unit tu. This equipment comprises an atmospheric fractionating column for topping the crude oil and a vacuum tower for fractionating the topped crude oil to obtain gas oil for catalytic cracking charge stock and vacuum reduced crude for coking charge stock. The products of the atornsphericvacuum distillation include fuel gas; a C., stream of n-butane and isobutane; a C5 to 190 F. fraction containing n-pentane, sopentane, n-hexane and the branched chain hexanes; a
amnesia 3 190 to 375 F. straight run gasoline fraction; a 370 to 620 F. straight run furnace oil fraction; a 620 to 1050 F. heavy gas oil fraction and vacuum reduced crude.
The straight run C4 fraction is charged by line li to the alkylation unit 12. The C5 to 190 F. fraction is charged by line 14 to the hydroisornerization unit The 190 to 375 F. straight run gasoline fraction is charged by line i6 to the catalytic reforming unit i3. The 375 to 620 F. fraction is charged by line 19 to hydrogen treating unit 20 where it is upgraded for light fuel oil blending. The heavy gas oil fraction is charged by line 2l to the fluid catalytic cracking unit 22. Vacuum reduced crude is charged by line 2.3 to the delayed coking unit 24.
The coker Z4- is operated according to the technique of delayed coking principally to produce gas oil cracking charge from the vacuum reduced crude. in this type of process the reduced crude is heated to a high temperature, e.g., 920 F., and is passed into a coking drum Where it is `maintained at high temperature for a sufficient length of time to thermally crack or decompose the reduced crude and produce lighter hydrocarbons and coke. Coke forms on the Walls of the drum. After one drum is lled with coke the operation is switched to another drum and the coke is removed mechanically or hydraulically from the rst drum.
The hydrocarbon stream from lthe coking drum is fractionated and, as shown in the drawing, several fractions are recovered. A light gas fraction is withdrawn by line 25 as fuel gas. A C3 fraction rich in propylene is charged by line 25 to the catalytic polymerization unit 28. A C4 fraction containing n-butane, isobutane, n-butene and isobutylene is charged by line 29 to the alkylation unit 12. A coker C5 fraction consisting mainly of pentanes and pentenes is charged to gasoline blending by line 30. Preferably, the coker C5 fraction and a Cfr-400 F. gasoline fraction from catalytic cracker 22 are sweetened before gasoline blending is a conventional gasoline sweetening unit 45 wherein objectionable forms of sulfur, eg., mercaptans, are converted to less objectionable form. A coker naphtha fraction of C5 to about 400 F. range is charged by line 31 to the hydrogen treating unit 20. The heaviest liquid product of the coking reaction, the coker gas oil which consists of all of the liquid product higher boiling than about 400 F., is charged by line 32 to the fluid catalytic cracking unit 22.
The fresh charge to the fluid catalytic cracking unit 22 thus consists of heavy straight run gas oil charged by line 21 and the coker gas oil, 400 F. pius, charged by line 32, The catalytic cracking unit is a conventional fluid catalytic cracker wherein a suspended bed of powdered silica-alumina catalyst 'is contacted at high temperature with an upflowing stream of vaporized hydrocarbon charge stock. An essential feature of our process is that the catalytic cracking is carried out at a higher than conventional temperature of at least 975 F. and preferably in the range 975 to 1050 F. The space velocity of the total hydrocarbon charge stock is selected in accordance with the cracking temperature to provide cracking conditions of suiiicient severity to achieve conversion of at least 70 volume percent of the fresh cracking charge and thereby to make a high yield of C5 and lighter olefns.
More specifically, the cracking conditions are of such severity that for a given amount of crude oil charged to the primary distillation unit, the number of mols of butenes produced by catalytic cracking is greater than the number of mols of available butanes obtained from the same amount of crude oil either directly in the straight run C4 fraction of the crude oil or indirectly by recovery from conversion products of fractions of the crude oil such as the C4 fraction of the coking products and the C4 fraction of the reformate. By available butanes We mean the aomunt of isobutane, or of n-butane which can be isomerized to isobutane as needed for alkylation, in excess of the amount required in the form of n-butane for blending with final gasoline products to obtain the required vapor pressure. Consequently, in accordance with our process, to supply the total amount of isobutane required for alkylating all of the C4 oleiins produced by catalytic cracking of gas oil fractions derived from the crude oil, butane from another source is supplied to the alkylation unit. Such butane is referred to herein as outside butane and can be supplied either as isobutane or as n-butane which is isomerized to isobutane as needed.
The butenes produced by catalytic cracking exceed the amount that can be alkylated by the available butanes. Eutenes for alkylation are also produced to some extent in the coking unit. Furthermore, at least a portion of theV pentenes produced by catalytic cracking are aikyated, Accordingly, a considerable amount of outside butane is required to supplement the available butane for alkylating both sources of butenes and at least a portion of the pentenes from the catalytic cracker. The production of pentenes as alkylation charge is not a deliberate obiect of our process. However, by operating the catalytic cracking unit at high severity to obtain a high yield of butenes as alkylation charge we also make more pentenes than can be accommodated as blending components of the nal gasoline. Accordingly, in our process we subject to alkylation at least a portion of the pentenes produced in catalytic cracking so that the remainder of the C5 olens can be accommodated in the gasoline products without exceeding the amounts permitted within the Volatility specifications of the gasoline.
As shown in the drawing, the charge to the alkylation unit l2 consists of the straight run C4 fraction charged by line li, the C4 fraction of the catalytic reforming product charged by line 34, the C4 fraction from the delayed coking unit charged by line 29, the product of isomerization of outside n-butane introduced by line 36 and the C4-C5 fraction of the fluid catalytic cracking product introduced by line 37.
The alkylation unit 12 can operate according to any of the known alkylation procedures in which isobutane reacts in equi-molecular proportions with C4 olens, and in our process with C5 olens, to produce branched chain paraiiins having 8 or 9 carbon atoms in the molecule. The schematic drawing omits details of the alkylation process but these are'well-known and any of the known procedures and equipment can be used. The feed containing olens and isobutane, as Well as n-butane which is mixed with the isobutane and which passes through the alkylation reactor without being converted, is contacted in the liquid phase with an alkylation catalyst such as a concentrated sulfuric acid catalyst at a temperature of 35 to 45 F. or with a hydrofluoric acid catalyst at a temperature of 45 to 100 F. In order to prevent polymerization and control the alkylation reaction the feed will contain a high ratio of isobutane to olelins, for example, a mol ratio in the range of 3:1 to 6:1. The alkylate stream is deisobutanized and debutanized. The isobutane or a portion thereof can be recycled to the aikylation unit and the n-butane or a portion thereof can be passed by line 33 to the butane isomerization unit 39 to produce isobutane for the alkylation reaction. Alternatively, the n-butane or a portion thereof can be blended with the iinal gasoline product to control its vapor pressure.
The butane isomerization unit 39 can operate according to any of the known catalytic isomer-ization procedures. rthe process can be a low temperature (e.g., to 500 F.) liquid phase isomerization process employing a Freidel-Crafts type of catalyst such as aluminum chloride or it can be one of the more recently developed procedures which empolys a solid reformingtype catalyst such as halogen-promoted platinum-onalumina. in this type of process the butane charge stock is contacted with the catalyst in the vapor phase at high or moderate temperature, e.g., 7002900" in the pres;-
ence of hydrogen. The charge stock for the butane isomerization unit will include outside n-butane, that is to say, butane obtained from a source other than the crude oil charged to the atmospheric-vacuum crude distillation unit 10. The outside butane, which is introduced to the isomerization unit by line 52, can be obtained directly or indirectly from other crude oil sources or from natural gas or natural gasoline. The charge to the unit can also comprise recycled n-butane from the alkylation unit and n-butane from various product streams of the process, as shown in the drawing.
In addition to the principal units which have been discussed, eg., the atmospheric-vacuum distillation unit, the alkylation unit, the fluid catalytic cracking unit and the coking unit, certain other upgrading procedures are employed in the preferred form of our process and these contribute to the production of a high octane, low sensitivity premium gasoline. Thus, the process can employ a catalytic isomerization unit to which is charged, erg., a straight run C5-l90 F. fraction withdrawn from the distillation unit by line 14. The isomerization unit 15 preferably includes a prefractionator, not shown in the drawing, for separating isoheptanes and heavier from C5-C5 parafns of the C5-l90 F. fraction, the isoheptane and heavier being passed, if desired, to hydrogen treating unit 50 for desulfurization and the C5-C6 fraction being charged to the isomerizaton reactor or reactors of unit 15. Preferably, the C5-C5 fraction is fractionally distilled to obtain a highly concentrated n-pentane fraction and a fraction highly concentrated in n-hexane and methylpentanes. Then these fractions are separately isomerized, preferably over a halogen-promoted, platinum-alumina catalyst in the presence of hydrogen.
The efuent from the isomerization reactors can be fractionated to recover unconverted n-pentane, n-hexanes and methylpentanes which are recycled to the isomerization reactors. The branched chain parain products are blended with the final gasoline product and, being branched chain paraflins of high research and motor octane ratings, they contribute to the low sensitivity of the high octane premium gasoline product of our process.
As We have indicated, the charge to the catalytic reforming unit 13 comprises the straight run 190 to 375 naphtha fraction withdrawn from the atm0spheric-vacnum distillation unit by line 16. Another suitable reforming charge stock is the fraction of similar boiling range obtained by hydrogen treating a C6 to 400 F. fraction of 4the coking product. This fraction is subjected to mild hydrogen treatment in the hydrogen treating unit by contact with a hydrogenation catalyst such as cobalt molybdate on alumina in the presence of hydrogen at a temperature of 600 to 800 F. Specific conditions suitable for this hydrogen treatment include `a temperature of 675 F., a pressure of 600 pounds per square inch gauge, a liquid hourly space velocity of 8 volumes per volume per hour and a hydrogen circulation rate of 4,000 standard cubic feet per barrel with a hydrogen consumption of 200 standard cubic feet per barrel. The hydrogen treatment saturates `and desulfurizes the coker naphtha but reduces its octaine rating. The hydrogenated coker naphtha requires octane improvement before it can be lsatisfactorily employed as a premium gasoline component. Accordingly, the hydrogen treated fraction is charged by line 40 to the catalytic reformer 18.
The `catalytic reformer can be any of the conventional units employed for upgrading naphtha fractions wherein such reactions as aromatization, dehydrogenation, isomerization and hydrccracking occur. The naphtha charge stock is contacted with -a reforming catalyst such as platinum-alumina or molybdena-alumina in the presence of hydrogen lat elevated pressure and temperature, e.g., 400 to 600 pounds per square inch gauge and 850 to 950 F. The reformate is fractionated to separate a hydrogen-rich gas which is recycled to the reforming unit and a C4 fraction which can be passed by line 34 to the' alkylation unit 12. The reformate withdrawn by line 41 is of high octane rating and is charged. to the inal gasoline product blending unit.
Another unit employed in the preferred form of our process is the catalytic polymerization unit 28. In this unit the various olefinic C3 streams produced in the process are contacted with a polymerization catalyst such as phosphoric acid to polymerize the propylene and produce an olenic polymer gasoline which, because of its rather high octane sensitivity, is used as a blending component for the regular grade gasoline rather than for the premium grade gasoline.
An important stage of our process is the blending of the gasoline components. Products available for gasoline blending include `alkylate from alkylation unit 12; reformate from reforming unit 18; sweetened gasoline, including the sweetened coker C5 fraction and the sweetened FCC C5-400" F. fraction from sweetening unit 45; isopentane and branched chain hexanes from C5C6 isomerization unit 15; and polymer vgasoline from catalytic polymerization unit 28. To adjust vapor pressure to the required level, eg., to Ia Reid vapor pressure of 10 pounds per square inch, n-butane is added to the gasoline blend. This can be n-butane recovered from the Ialkylation unit 12 and/ or outside n-butane.
Besides the above main gasoline components other products for gasoline blending include a small amount of pentanes recovered from the butane isomerization product of unit 39 and the hydrogen-treated gasoline fraction from hydrogen treating unit 50. In the latter unit a light gas oil from catalytic cracking and a Cq-I- fraction from the isomerization unit 15 prefractionator `are desulfurized by contact with hydrogen and a hydrogenaton catalyst, eg., `cobalt molybdate on alumina, at, for example, 700 F., 600 p.s.i.g., space velocity of 4 vol./ VOL/hr. and hydrogen rate of 4,000 sci/bbl.
The other principal liquid product of our process is No. 2 fuel oil. This product is formed by blending the hydrogen-treated light FCC gas oil from hydrogen treating unit 50; the hydrogentreated coker naphtha, 370 to 400 F. and straight run furnace oil from hydrogen treating unit 20. Other products of our process include fuel gas which is recovered from the diferent units as indicated and petroleum coke obtained from delayed coking unit 24. Another product is heavy gas oil recovered from catalytic cracking unit 22. If desired, this product can be fractionated to obtain a light fraction suitable as No. 5 fuel oil and a heavy fraction which is employed as refinery liquid fuel. p
From the above description it can be seen that butanes are employed for two ultimate purposes in our process. They are used to provide isobutane for alkylation with the C4 and C5 olens in the alkylation unit 12 and to provide n-butane for blending with the iinal gasoline product to raise the vapor pressure thereof to the required level. We have shown that the sources of the butanes include a straight run C4 fraction obtained directly from the crude oil and other streams obtained indirectly from the crude oil such as a C4 stream from the delayed coking unit 24, a C4 stream from the fluid cracking unit 22, an isobutane stream from the butane isomerization unit 39 and a C4 stream from the reforming unit 18.
The other source of butane is the outside butane stream 52 which can be obtained, for example, from another crude oil or from natural gas or natural gasoline. We refer throughoutl this specication to the fact that the catalytic cracking unit is operated under conditions of such severity as to yield a greater amount of C4 oleiins than can be alkylated with the available isobutane obtained directly and indirectly from the crude oil. By this we mean that the amount of butanes obtained from the particular crude oil is insuiiicient to supply :isobutane for alkylating all of the C4 olefins produced in the catalytic cracking stage and to provide butanes as required for blending With the nal gasoline products. Consequently, an outside butane stream is introduced into the process. It should be understood that the outside butane can be used either for gasoline blending or can be isomerized and used for alkylation. If the outside butane stream is employed for gasoline blending, it may very Well be that the butanes obtained directly and indirectly from the crude oil will be suicient for alkylation but, the amount will be inadequate to supply the over-all requirement. Therefore, it should be understood that when we refer to the 10 fact that the fluid catalytic cracking stage is carried out at such severity as to yield a greater amount of C4 oleus than can be alkylated with the isobutane obtained from vthe crude oil, we are defining the relative yields of butanes and of C4 oletins, Whether the butanes obtained from 15 the crude oil are employed for alkylation or for ual product blending is immaterial. The important fact is that outside butanes must be added to the butanes obtained from the crude oii to meet the over-all requirement for alkylation and gasoline blendin. 20
The following example illustrates results obtainable with our process.
3 EXAMPLE In this example, 100,000 barrels per calendar day (hereinafter abbreviated as b./c.d.) of Kuwait crude oil of 31.5 API gravity is processed by our new procedure to produce regular and premium lgrade gasolines in a volume ratio of 40 to 60. In this operation the fluid catalytic cracking unit operates at a temperature of 975 F. and achieves 71.5 percent conversion of the fresh cracking charge which consists of straight run and coker gas oil fractions. An outside butane stream is introduced into the system at a rate of 3,406 b./c.d. The yield of premium gasoline having a research octane rating (TEL content: 2.7 cc./ gal.) of 102.7 and a sensitivity of 7.5 is 22,892 b./c.d. The yield of regular gasoline having a research octane rating (TEL content: 2.7 cc./ga1.) of 95.7 and a sensitivity of 11.2 is 34,337 b./c.d. Details as to the charge and product streams for each of the process units are given in Tables I through IV below. In the tables the yields of gaseous Vproducts such as fuel gas are reported as barrels per day of fuel oil equivalent, the latter being abbreviated in the tables as FOB Table I Final products Atmosphericwacuum distillation:
barge: Kuwait: crude Products:
Fuel gas, FOE SR C4 fraction SR gaso., C5490" F SR naphtha, 190-375 F- SR furnace oil, 375-620 F SR hvy. gas oil, 620-1,050 F. Vacuum bottoms, 1,050o F.-l- Delayed coking:
Charge: Vacuum bottoms Products:
Fuel gas, FOE Coker C3 fra Miou B,/c.d. 100, 000
115 Fuel gas, 115 b./c.d.
884 Fuel gas, 884 b./c.d.
FCC hvy. gas oil.
233 No. 5 fuel oil, 233 b./c.d.
Hvy. gas oiH-decan ed 01., 2, 154 Rcfin. fuel, 2,154 b./c.d. Catalytic polymerization:
Coker C3 fraction 621 FCC C3 fraction 4,230
C3 fuel gas, FOE Polymer gasoline 1, 552 Fuel gas, 1,552 b./c.d.
Charge: B./c.d. B./c.d. SR C4 frac 2, 241 i-Butane 5, 811 Coker C4 frac. 488 n-Butane 4, 050 FCC C4-C5fra 7, 547 Butenes" 4, 556 Isom. unit i- 4. 3, 248 Pentanes.. 387 Platformer Cis 2, O07 Pentenes 727 Total 15, 531 Total 15,531 B./c.d. Products:
n-But'me 4, 050 Alkylate 9, 368 Fontane-hexane hydroisomerization:
SR gaso., (E5-190 F 7, 549 Platormer oft-gas (360,000 s.c.f./c.d.). Products:
Fuel gas, FOE 156 Fuel Gas, 15G b./c.d. i-Pentane 2, 873 i-Tll'e 'aries 2, 792 i-Heptaues. 1, 796 Butaue isomerization (l ase, A1013 c Charge: u-Butane (from etal of 3,400 b./C.d. outside 3, 352
butane and 4,050 b./C.d. n-butane from alkylation unit).
Table I-Continued Final products Hydrogen treating (A):
FCC lt. gas oil 10,555 i-Heptanes l, 796 Platormer oigas (4,230,000 s.c,f./c.d.). Products:
Fuel gas, FOE 334 Fuel gas, 334 b./c.d. Hydro-treated gasoline 1, 825 Hydrotroated FOC light gas oil 550 Hydrogen treating (B):
SR furnace oil, 375-620 F 20, 900 Coker naptlia, C-400 F Platforrnor ott-gas (5,200,000 s.c.f./c.d.). Products:
Fuel gas, FOE 529 Fuel gas, 529 b./c,d. Hydro-treated eoker naphtha Cri-370 F 3, 747 370-400 F 72s Hydro-treated SR furnace oil 20, 750 Platforming:
SR naphtha, 190-375 F 15,700 Hydro-treated coker naphtlia, Ca370 F 3, 747 Products:
Fuel gas, FOE 1, 598 Fuel gas, 1,598 b./c.d. H2 separator gas (9,700,000 s.c.i./c.d.). C4 fraction 2, 007 Reformate 14, 916 Gasoline sweetenng:
Coker C, fr'ir-iinn 177 FCC C5 fraction 4,393 FCC gaso., Cri-400 F.- 15,052 Products: sweetened gasoline 19, 622 Gasoline blending:
Pentane from butancisoinerization 84 sweetened gasoline (coller C5, FCO C5-400 F.) 19,622 Polymer gasoline 1, 645 Alk ate.. 9,368 i-Pcntane from C5-Ce isomerization. 2, 873 i-Hexanes from (l5-C5 isonierization 2, 792 Hydro-treated gasoline 1, 825 Refornmte 14, 916 Butaries (from total of 3,400 b./o.d. outside lontane 4,104
and 4,050 b./c.d. n-butane from alkylation unit). Products:
Premium gasoline 22, 892 Premium gasoline, 22,892 b./c.d. Regular gasoline, 34. 337 Regular gasoline, 34,3 7 b./c,d. No. 2 fuel oil blending;
Hydro-treated light gas oil 10, 20, 750 Products: N o. 2 fuel oil 32, 037 No. 2 fuel oil, 32,037 b./o.d.
the component to 10 pounds per square inch absolute. Table Il Since butanes are included with various gasoline compo- SUMMARY 0F CHARGE AND PRODUCTS nents the butanes are not listed as a separate component as in the blending stage of Table I. Vol. B./c.d. T./c.d. percent Table III PREMIUM GASOLINE Cha-e: t d O0 o 0 Components: B./c.d.
uwai cru e 1 0 10 ,000 Banane 3.4i ,406 Aikyla o 10302 Proiaucts: 1 22 89 9 2 Light reformate (I.B.P.-269 F.) 544 remiuin gaso ine Q 89 o Hema, gasoline 34. 34 34, 337 Heavy reformat@ (269 EP) 6,150 02?? 3g. 32, Light FCCl (LBR-200 F.) 3,600 0.5 ue o yemleum 1 p Isopentane 2,296 Refinery fuel (liquid) FOE 2.15 2, 154 Reneryfuei (gas) Fon 0.30 9,301 Total l Total 100.95 100, 054 Octane rating:
Research, +2.7 cc. TEL/gal 102.7 In Table I We have shown all of the gasoline compo- .MOOY +27 CC- TEL/gal 952 nents as being charged to ,the gasoline blending stage for Sensltlvlty 7-5 premium and regular gasoline products. In actual prac- REGULAR GASOLINE tice the components or their proportions will be diiferent Components: B./c.d.
l 0 for the premium and regular grade products. Table III Llght FCC (LBR-200 F) 5,030
v l n C below illustrates amounts of the various gasoline compo- Heavy FCC (200 FEP) 12,693 nents of Table I that can be employed in forming premium PG13/mel' 1,870
n l 0 gasoline and regular gasoline in our process when proc- Llght reformat@ (LBR-269 FJ 7,722 essing 100,000 b./c.d. of Kuwait crude. Table III also Heavy reformate (269 F.-EP) 2,227 lists the octane numbers of these products. All data in Hydro-treated gasoline 1,991 this table are reported on the basis of 10 pounds Reid Isghexanes 2,804 vapor pressure. In other Words, the amount of each gaso- Total w34 337 line component reported in Table III includes butanes in 1 I 1 d l C y y an amount suicient to raise the Reid vapor pressure of less cfshtlms 'and C5 s from humm somematon i 1 Table ILL-Continued REGULAR GAsoLrNn-oontinued Octane rating: B./c.d. Research, +2.7 cc. TEL/gal 95.7 Motor, +2.7 cc. TEL/gal 84.5
Table III illustrates one suitable blending combination for the different gasoline components produced in our process. In this particular blending scheme all of the high yield of 10,302 b./c.d. of alkylate is used in the premium gasoline product. Since our process produces other fractions rich in branched chain parains, e.g., branched chain C and C5 parain fractions and light reformate, and since the branched chain paraffins have good research and motor octane ratings, it is possible to vary the combination considerably and still produce a high yield of premium gasoline of very high research octane rating and low sensitivity.
We have indicated that our process produces high octane gasoline of low sensitivity at a cost competitive with conventional rening procedures that are unable to produce premium gasoline of low sensitivity. Furthermore, our process achieves this result at lower cost per gallon than other procedures aimed at producing high octane gasoline of low sensitivity. This can be demonstrated by comparison of the embodiment of our process as described in the foregoing example and in Tables I, II and III, with the results of other procedures which are intended for producing high octane premium gasoline and which employ certain process elements in common with our process. One such process, which we will refer to as process A, employs atmospheric-vacuum distillation, delayed coking of vacuum bottoms, uid catalytic cracking of straight run and coker gas oils, catalytic polymerization of propylene, alkylation of butylenes with isobutane, catalytic reforming of straight run naphtha and hydro-treated coker naphtha, as well as such additional elements as hydro-treating and gasoline sweetening of fractions similar to those that are subjected to such treatments in our process. An essential difference between process A and our process in the embodiment described in the example and tables is that in process A the liuid catalytic cracking unit is operated under conventional conditions to achieve 65 percent conversion whereas in our process the liuid catalytic cracking is carried out at 975 F. to achieve 71.5 percent conversion. As a result, in process A outside butanes are not required for alkylating the C4 and C5 oleins produced by fluid catalytic cracking. The butanes obtained from the crude oil are adquate for the alkylation stageand for vapor pressure adjustment of the gasoline products. Other differences are that the preferred form of our process employs hydroisomerization for upgrading low octane rating C5 and C5 parains and employs butane isomerization for isomerizing either outside n-butane or n-butane obtained from the crude oil whereas process A does not.
In still another comparable operation which we designate as process B most of the procedures employed in our process are employed but, instead of linid catalytic cracking, process B employs thermal cracking of straight run and coker gas oils. In process B all of the butanes employed for alkylation and gasoline blending are obtained directly or indirectly from the crude oil.
A comparison of the results obtainable in our process and in processes A and B is given in Table IV below. The table lists yields of various products in processing of 100,000 b./c.d. of Kuwait crude for production of premium and regular gasolines in a 60:40 ratio and shows the comparative costs per gallon of the gasolines produced.
l2 Table 1V Iuven- A B tion Premium gasoline (l0 RVF):
Yield, bb1./100,000 bbl. crude Octane ratings:
Table IV shows that process A makes a premium gasoline at slightly less cost than our process but the sensitivity is 13.0 as compared with 7.5 for our process and the research octane number is only 101.0 as compared with 102.7 for our process. In process B the sensitivity of the gasoline is low but the research octane rating is lower than in our process and the cost is substantially higher. With respect to the regular grade gasoline products, the product of our process has a higher research octane rating than that of either process A or B and the cost per gallon for our product is almost as low as that of process A and is substantially lower than that of process B. From these results it can be seen that our process is markedly superior economically to other methods of making high octane premium gasoline of low sensitivity. A major difference between our process and the other two processes is seen in the alkylate yield as reported in Table IV. For a crude charge of 100,000 barrels the alkylate yield for our process is 10,302 barrels as compared with only 4,766 barrels for process A and 4,195 barrels for process B.
The foregoing example and tables show that We have developed a valuable new combination of refining procedures for producing a high yield of high octane rating premium gasoline of low sensitivity. We accomplish a new result through a new combination of procedures which include Y(1) the use of high lluid catalytic cracking temperature to produce maximum butenes for use as alkylation charge stock, the iluid catalytic cracking unit being operated at 975 F. or higher to achieve conversion of the cracking charge of at least 70 volume percent, (2) alkylating total butene production, plus a portion of the pentenes to the extent required by gasoline volatility restrictions, and (3) isomerizing outside butane to provide adequate isobutane for alkylation.
Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claim.
-A process for making low sensitivity premium gasoline which comprises:
fractionally distilling a total crude oil to obtain a straight run C4 fraction, a straight run C5 to 190 F. light gasoline fraction, a straight run gas oil having an initial boiling point of about 620 F. and a straight run residuum;
`coking said straight run residuum, and recovering converson products including C4 olelins, n-butane, isohutane, a coker gasoline fraction and coker gas oil; subjecting said straight run gas oil and said coker gas oil to iluid catalytic cracking and recovering conversion products including C4 olens, n-butane, isohutane, C5 oletins and a cracked gasoline fraction; said fluid catalytic cracking occurring at severe condi tions, including a temperature of at least 975 F., suiicient to achieve conversion of at least 70 volume 13 iiipercent of said catalytic cracking charge to produce with isobutane from `another source and recovering a molar yield of C4 olefns greater than the numan alkylate therefrom; ber of mo'ls of n-butane and isobutane recovered by and blending said alkylate with said aforementioned straight run fractionation of said crude oil and by gasoline fractions to produce a premium gasoline fractionation of said conversion products minus the 5 having an octane rating sensitivity no greater than mols of butanes required for vapor pressure ad- 7.5.
justment of the nal gasoline products;
subjecting all of said C4 oleins produced by said uid References Cited in the me of this Patent catalytic cracking and coking operations and at UNITED STATES PATENTS least a portion of the C5 olens produced by said 10 2,360,622 Roetheu OGL 17, 1944 uid catalytic cracking to alkylation with all of the 2,415,530 porter F511 11, 1947 isobutane obtained directly and indirectly from frac- 2,644,785 Harding et a1 July 7, 1953 tion of said crude and said conversion products and 2,905,619 Sutherland Sept. 22, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent No. 3,071,535 `Ianuary l, 1963 John A. Condrasky et al.
It s hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 2, line 54, strike out are cokng"; line :37, for
"subjegt" read subjected column 3, line 2, for "620" read 620 line 38, for "is" read in line 7l, for "products" read product same column 3, line 73, for "aomunt" read amount column 4, line l after "with" o insert the column 5, line 44, for "375" read 375 F. Columns 9 and IO, Table I-Continued, first column, line 32 thereof, for "Coker C, fraction" read Coker C5 fraction Signed and sealed this 21st day of January 1964,
ERNEST W SWIDER EDWIN L.; REYNOLDS AC i D Q' Commissioner of Patents Attestng Officer