US3714023A

US3714023A - High octane gasoline production

Info

Publication number: US3714023A
Application number: US00885859A
Authority: US
Inventors: L Stine
Original assignee: Universal Oil Products Co
Current assignee: Honeywell UOP LLC; Universal Oil Products Co
Priority date: 1969-12-17
Filing date: 1969-12-17
Publication date: 1973-01-30
Anticipated expiration: 1990-01-30
Also published as: FR2070902A1; YU35270B; PL81513B1; ZA708450B; EG10506A; NL7018328A; CA943484A; DK137765B; FR2070902B1; CS153570B2; DE2061945A1; AR212954A1; IL35865A0; IL35865A; DE2061945B2; GB1338612A; YU306070A; TR17194A; ES386517A1; DK137765C

Abstract

AN INTEGRATED REFINERY PROCESS FOR THE PRODUCTION OF A HIGH OCTANE GASOLINE POOL. THE INVENTION ESSENTIALLY COMPRISES A COMBINATION LOW SEVERITY REFORMING ZONE AND A SATURATE CRACKING ZONE. THE LOW SEVERITY REFORMING ZONE EFFECTS THE PRODUCTION OF HIGH OCTANE AROMATIC COMPONENTS WITHOUT AN ACCOMPANYING LOSS IN LIQUID YIELD FROM EXCES-

SIVE DEHYDROCYCLIZATION AND CRACKING REACTIONS WHILE THE SATURATE CRACKING ZONE CRACKS THE UNREACTED SATURATES PASSING THROUGH THE REFORMING ZONE TO EFFECT PRODUCTION OF HIGH OCTANE PRECUSORS SUCH AS LOW MOLECULAR WEIGHT OLEFINS.

Description

Jln- 30, 1973 1 .o. snNE HIGH QCTANE GASOLINE PRODUCTION Filed Deo. 17, 1969 i .www

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"United States Patent 3,714,023 HlGH OCTNE GASOLINE PRODUCTION Laurence O. Stine, Western Springs, Ill., assignor to Universal Oil Products Company, Des Plaines, Ill. Filed Dec. 17, 1969, Ser. No. 885,859 Int. Cl. Cg 37/10 U5. Cl. 208-62 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The field of art to which this invention pertains is catalytic conversion of hydrocarbons. More specifically, this invention pertains to a combination of integrated reiinery processes including low severity reforming and cracking of hydrocarbons to provide a resulting high octane gasoline pool, requiring, in most cases, no lead addition for present-day gasoline octane requirements for internal combustion engines.

Description of the prior art Typical of the problems encountered in refinery processes when producing high octane motor fuels is the loss of liquid yield when producing high octane gasoline via reforming operations. In reforming operations the primary octane improving reactions are naphthene dehydrogenation, napthhene dehydroisomerization and paraflin dehydrocyclization. The naphthene dehydrogenation reaction is quite rapid and is the primary octane improving reaction in catalytic reforming. When five memlbered alkyl naphthenes are present in a naphtha feed it is necessary to isomerize the alkyl cyclopentanes into six membered ring naphthenes following by the dehydrogenation to aromatics. Aromatization of paraflins is achieved by the dehydroeyclization of straight chain p araflins having at least siX carbon atoms per molecule. Dehydrocyclization is limited in the once-through reforming operations because as the aromatic concentrations increase through the reforming zone the rate of additional dehydrocyclization of paraffins is greatly reduced. This leaves unreacted parafns present in the reformate effluent which greatly reduces the octane ratin-g of the reformate. In the reforming zone, the parains which at low reforming severity would pass through unreacted, are cracked, at high reforming severity, to yield partly gasoline material but largely light hydrocarbons. Because of the hydrogen present during the cracking step the light hydrocarbons are saturated forming primarily normal and non-normal para'fns in the C1 to C4 carbon number range.

The unreacted saturates which pass through the reforming zone typically are of low octane rating and in some cases require further processing to upgrade the gasoline pool. Further processing in order to improve the octane rating of the saturates leaving the reforming zone can be eliminated by in effect overwhelming the low octane components of the reformate by increasing the reformed severity of operations to produce an increased quantity of aromatic components. This type of operation has a twofold effect in increasing a reformate octane rating; first, additional high octane aromatic components are produced; and, secondly, the lower octane components are partially eliminated by being converted into aromatic components or into light products outside the gasoline boiling range.

The improvement in octane accompanied by the increased severity of the reforming zone, therefore, results 1n lower liquid yields of gasoline partly due to the shrinkage of the molecular size of the paraffins and naphthenes when they are converted to aromatic type hydrocarbons and partly due to production of the aforesaid light products. I have found that instead of over- Whelming the lower octane components of reformate gasoline with high octane aromatic components, that the cracking of the low octane reformate components (paraflins and naphthenes) into lower molecular weight olefins and parafns allows subsequent processing to convert these materials into improved high octane componets which improve the overall refinery gasoline pool octane while substantially eliminating the volumetric yield loss which accompanies high severity reforming conditions.

SUMMARY Objects of the present invention include the following:

It is an object of this 'invention to provide an integrated refinery process wherein the gasoline produced from said process is of high octane quality and in most instances does not require addition of lead to increase its octane rating to meet the requirements of most present day internal combustion engines.

It is another object of this invention to operate an integrated refinery process Wherein a reforming zone is operated at relatively low severity to effect the production of aromatic hydrocarbons While reducing hydrocracking and dehydrocyclization reactions in said reforming zone and thereafter passing the saturate portion of the reforming zone reformate through a saturate cracking zone wherein olenic and paratnic light hydrocarbons and a cracked gasoline are produced.

Because throughout this specification numerous terms will be used to characterize various hydrocarbon charge stocks and fractions thereof, various conversion products, and various characteristics of the aforesaid stocks, fractions and products, such terms will first be defined in order to facilitate an understanding of the subsequent description of the invention.

The term light hydrocarbons generally refers to those hydrocarbons which have from one to four carbon atoms per molecule and is generally expressed in the art as C4-f The light hydrocarbons having one and two carbon atoms per molecule are generally referred to as dry gases and are generally used as refinery fuel gas while the C3 and C4 portions of the light hydrocarbons are valuable; the C3 and C., oleiins can be used in the process of this invention for alkylate or polymer or isopropyl alcohol production. The C3 and normal C4 parain portions of the light hydrocarbons are generally referred to as liquid petroleum gases and can be used as such.

Light naphtha streams generally refer to hydrocarbon streams containing hydrocarbons in the C5 and Cs carbon range. The light naphthas generally are recovered directly, as virgin light naphthas, from a crude distillation unit. The end boiling point of most light naphthas is generally from about 175 F. to about 200 F. The heavy naphthas are generally referred to as those hydrocarbons streams having boiling points from about F. to about 400 F. which includes those hydrocarbons having carbon numbers of about 7 or greater and which boil below about 400 F.

The light cycle oils generally boil immediately above the heavy naphtha boiling range generally around 400 to 600 F. while atmospheric and vacuum gas oils are generally higher boiling materials having boiling ranges of about 600 to about 1200 F. with the atmospheric gas oils generally boiling at the lower end of the given temperature range. The vacuum gas oils are generally distilled from the crude oil in a vacuum tower to prevent thermal cracking because of the relatively high boiling range of that material.

As with most definitions of hydrocarbons based on boiling points, there is a certain amount of overlap of the boiling range of the individual hydrocarbons of adjacent carbon numbers when referring to hydrocarbon boiling ranges in this specification. The hydrocarbon stream identified by a boiling range shall be assumed to have about 10% of its volume boiling below the lower temperature and about 95% of its volume boiling below the upper temperature of its given boiling range.

In order to fully understand the process of this invention, a brief explanation of the various reaction zones which are used as part of the process of this invention are described in greater detail below.

REFORMING ZONE In the reforming zone a suitable hydrocarbon feed stock is contacted with a reforming catalyst to effect conversion of the reformer feed stock to a higher octane reformate product. Hydrocarbon feed stocks which can be used in the reforming zone include hydrocarbon fractions containing naphthenes and parains. The preferred stocks are those consisting essentially of naphthenes and paraffins although in some cases aromatics or olefins or both aromatics and olefins may be present. Preferred reformer feeds include straight-run gasoline, natural gasolines, and the like. It is frequently advantageous to charge thermally or catalytically cracked gasolines or higher boiling fractions thereof to the conversion process of the reforming zone. The reformer charge stock may be a full boiling range gasoline charge stock having an initial boiling point of from about 50 F. to about 100 F. and an end boiling point within the range of from about 325 F. to about 425 F., or may be a selected fraction thereof.

The catalysts which can be used in the reforming zone include refractory inorganic oxide carriers containing a reactive metallic component thereon. Inorganic refractory oxides which can be used as carriers for reforming catalysts include alumina, the crystalline aluminosilicates such as the faujasites or mordenite, or combinations of alumina and the crystalline aluminosilicates. Metallic components which are generally recognized in the art as being favorable catalytic components for reforming operations generally include the Group VIII metals. The Group VIII metals include iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Rhenium, a Group VII-B metal, has also been shown to be a favorable metallic component which can be used in reforming catalysts. Reforming catalysts may also contain combined halogen as one of the catalytic components. The halogens which can be used include uorine, chlorine, bromine, iodine or mixtures thereof.

Effective reforming operating conditions include temperatures within the range of about 800 F. to about 1100" F. and preferably between about 850 F. and about 1050 F., liquid hourly space velocities in the range of from about 0.5 to about 15.0 and preferably in the range of from about 1 to about 5 are normally used. The quantity of hydrogen-rich recycle gas which is charged along with the hydrocarbon feed stock to the reforming zone. generally is present in amounts of from about 1/2 to about 20 moles of hydrogen per mole of hydrocarbon feed, and preferably from about 4 to about 12 moles of hydrogen per mole of hydrcserbon feed.: The @farming 20H@ may be effected in any suitable process system familiar to those skilled in the art such as uidized type processes, moving bed-type process, etc. Particularly suitable processes comprise the well-known fixed bed system in which the catalyst is disposed in the reaction zone, and the hydrocarbons to be converted are passed therethrough in either upward or downward flow. The reforming zone reactor efuent, or reformate, is generally passed through a separation zone where it can be fractionated to remove lighter weight components from heavier weight liquid components of the reformate and where the recycle gas, which is reused in the reforming zone can be easily separated. Since normal reforming operations produce excess amounts of gaseous hydrogen, a certain amount of the recycled gas is generally removed from the reforming system to maintain a given operating pressure. Reforming zone pressures generally used in normal reforming operations are generally within the range of from about l0 to about 1500 pounds per square inch.

The reforming zone used in this combination process is operated at low severity. To those familiar to the re' forming art, the term relatively high severity generally indicates high temperature or low space velocity or both high temperature and low space velocity operating conditions. The direct results of high severity operations are generally noticed in the reformate octane being increased substantially. While the reforming zone used in this operation does not necessarily upgrade the octane of the reformer feed to that of the pool gasoline, the reforming zone feed stock is substantially improved in octane rating.

Low severity reforming operations as used in the specification and attached claims shall generally define a reforming process in which a large percentage of the naphthenes in the reformer feed are dehydrogenated to high octane aromatic compounds with the qualification that the dehydrocyclization of feed parains to aromatics is substantially reduced. A more detailed definition of the term low severity reforming operations can include conversion of feed naphthenes to aromatics within the range of from about moles of aromatics produced per 100 moles of naphthenes charged to the reforming zone to about moles of aromatics produced per 100 moles of naphthenes charged to the reforming zone and less than about 40 moles of aromatics produced per 100 moles of alkanes charged to the reforming zone. In determining the degree of conversion of naphthenes to aromatics (dehydrogenation) and alkanes to aromatics (dehydrocyclization), it is generally assumed that a relatively small amount of naphthenes are cracked or converted to hydrocarbons other than aromatics and that a major portion of the alkanes which disappear through the reforming zone are converted to aromatic hydrocarbons with some naphthenes and higher molecular weight alkanes being converted to low value light gas alkanes. The individual naphthenes and alkanes are also assumed to be aromatic precursors having the same number of carbon atoms per molecule as the aromatic hydrocarbons they form.

SATURATE CRACKING ZONE The function of the saturate cracking zone is to crack the saturated hydrocarbons fed to it by either thermal or catalytic means or both. The feed stock to the staturate cracking zone can be the entire low severity reformer gasoline effluent or just the saturated portion thereof depending on whether there is an intermediate separation zone between the reforming zone and the saturate cracking zone,

Where there is present between the reforming zone and saturate cracking zone, a separation zone which can separate aromatic and saturate hydrocarbons from each other, the saturated cracking zone will primarily receive saturated feed stock comprising parains and cyclic paraffins. However, in instances where the reforming zone liquid eluent is passed directly into the saturate cracking zone, aromatic hydrocarbons will also necessarily be present in the saturate cracking zone feed stock. In either case, the saturate cracking zone must be able to selectively crack that zones feed stock saturates to lower` molecular weight hydrocarbons in a manner so as to minimize the production of dry gases such as methane, ethane, ethylene or acetylene, while maximizing the production of C3 and C4 saturates or unsaturates and cracked gasoline materials. The saturate cracking zone produces cracked gasoline and valuable light hydrocarbons from most of the aromatic precursors which are not converted to aromatics in the reforming zone because of the requirement that the zone be operated at low severity conditions to gain an overall advantage in liquid yield of a high octane gasoline pool.

The materials produced in the saturate cracking zone generally comprise a relatively high octane cracked gasoline plus C3 through C5 light hydrocarbons comprising propane, propylene, normal and iso-butane, normal and isobutene, and pentanes and pentenes. The products are eX- cellent feed stocks for other processes which form valuable gasoline components such as amines, esters, ethers, ketones, branched chain parafiins or alcohols. The olefinic portion of the aforesaid light hydrocarbons is especially suited for conversion to the previously mentioned gasoline components while in general the parainic portion of the saturate cracking zone effluent which contains a relatively large amount of branched chain molecules is suited for production of alkylate gasoline.

A general but not all inclusive listing of individual valuable gasoline components which can be produced from the saturate cracking zone light hydrocarbons includes methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, tertiary butyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, isopropylamine, n-butylamine, diethylamine, tirethylamine, methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate, propylene oxide, n-propyl ether, isopropyl ether, m-butyl ether, isoamyl ether, acetone, methyl ethyl ketone, methyl n-propyl ketone, diethyl ketone, C3 alkylate or C4 alkylate.

In order to catalytically crack the saturates fed to the saturate cracking zone, high activity catalysts and high temperature operatingconditions are required. It is preferred to use reaction temperatures within the range of from about 850 F. to about 1200 F. and preferably temperatures within the range of from about 850 F. to about 1l501 F. Probably the most important operating parameter for the selective production of olefinic light hydrocarbons (propylene and butene) is the contact time between the parainic cracking zone feed and the catalyst contained therein. In fixed bed type cracking incorporating once-through operations, the weight ratio of olens over saturates is almost directly related to the space velocity being used in the reaction zone. Increasing the space velocity of the saturate feed passing through the reaction zone increases the amount of olefinic hydrocarbons produced.

In uidized catalystic cracking operations, space velocity is generally measured in terms of weight hourly space velocity (WHSV) which is defined as the weight of charge oil per hour over the weight of the catalyst in the reaction zone. The WHSV based on raw charge oil is most frequently used. Weight hourly space velocities greater than about are preferred when effecting saturate cracking in the saturate cracking zone.

In some instances where the conversion of saturate cracking zone feed is relatively low, a portion of the eflluent material from this zone may be recycled back to the cracking zone to effect a further conversion to more valuable components.

The catalytic cracking zone requires a catalyst that specifically can produce the valuable saturated and unsaturated light hydrocarbons which can contribute to the process efficiency after further conversion to gasoline components. Additionally, the saturate cracking zone catalyst effects the production of a cracked gasoline product which contributes to the overall high octane gasoline pool which the combination process of this invention provides. The catalyst used in this zone can be selected from a number of known materials including amorphous silica-alumina and zeolitic type aluminosilicates, both of which may contain composited thereon various catalytic components selected from the Periodic Table metals of combined or elemental character.

Cracking catalysts which may be used in the saturate cracking zone including certain types of silica-alumina, silica-magnesia, silica-zirconia and more preferably crystalline aluminosilicates characterized as having relatively high cracking activities.

The preferred crystalline aluminosilicate cracking catalysts can be mixed with less active amorphous type cracking catalysts or can be present in substantially pure form depending on the severities required of the process. The crystalline aluminosilicate may be naturally occurring or synthetically prepared. In the latter case the crystalline aluminosilicate may be selected from the group of synthetically prepared zeolites A, Y, L, D, R, S, T, Z, E, F, U, Q, B, X, ZK-4, ZK-S, etc. The naturally-occurring materials include faujasite, mordenite, montmorillonite, etc.

Whether the catalyst comprisesa crystalline aluminosilicate, or amorphous material, selected metals may be composited thereon by ion-exchange or impregnation methods. The metals composited on the catalyst may include the rare earth metals, alkali metals, alkaline earth metals, Group VIII metals, etc., and various combinations thereof. Hydrogen may also be present within the catalyst to effect increased catalyst activity.

In instances where the saturate cracking zone is a thermal type cracking zone, there is no need for a catalyst and the feed stock passed into the saturate cracking zone then generally produces a larger amount of lighter hydrocarbons than a catalytic cracking zone would yield. Thermal cracking conditions can vary from pressures ranging from about atmospheric to about 500 p.s.i.g. and a temperature of from about 900 F. to about l500 F.

BRIEF` DESCRIPTION OF THE PROCESS FLOW The process of this invention, while essentially residing in a combination low severity reforming zone and a saturate cracking zone, is more fully understood when it is placed in a proper relation to other conventional refinery operations. The attached drawing illustrates theV relationship of the claimed invention when employed in conjunction with other segments of an integrated refinery to provide a process capable of producing high octane gasoline.

FIG. l of the drawing represents the basic flow pattern of the invention where the saturate cracking zone contains a catalyst which selectively cracks the saturated portion of the reforming zone reformate while maintaining relative inertness towards the aromatic portions of the reformate. A more detailed description of FIG. l follows. In FIG. l, a heavy naphtha feed from a source including a crude unit or other refinery processing equipment flows through line S together with recycle hydrogen from line 6 into reforming zone 1 wherein a portion of the feed stock is changed in structure to primarily aromatic structured molecules. As has been stated before, the reforming zone is operated at specific conditions to allow a maximum production of aromatic hydrocarbons with a minimum loss of liquid yield of gasoline. The reaction conditions employed in reforming zone 1 are more specifically low severity conditions which are more specifically defined previously herein. The efiiuent from the reforming zone 1 passes through line 7 to separation zone 2 wherein the gasoline portion of the reforming zone eiuent is separated from the lighter portions of the reforming zone efiiuent. Off gas comprising primarily hydrogen is withdrawn from separation zone 2 via line 8. A portion of this gas stream may be recycled via line 6 to the reforming zone. A light hydrocarbon stream primarily comprising the C1 through C4 molecular weight hydrocarbons is withdrawn from separation zone 2 via line 9 while a C5/CG gasoline stream is withdrawn via line 10. The material withdrawn via line may alternately be fed directly to the saturate cracking zone in admixture with the major gasoline portion of the reforming zone eluent which passes via line 11 to the saturate cracking zone 3. Recycle material from the eiuent from the saturate cracking zone when used passes through line 32 in admixture with the feed to the saturate cracking zone. The material fed to the saturate cracking zone is cracked to lower molecular weight light hydrocarbons which are removed via line 13 from separation zone 4 and to gasoline boiling range material which is removed via line 14 and collected for direct use as a valuable component of the overall refinery gasoline pool.

In FIG. 2 there is located between the reforming zone 15 and the saturate cracking zone 18, extraction zone 17 which separates the aromatic constituents of the reforming zone gasoline from the saturated constituents present in the gasoline. The saturated portion of the reforming zone reformate is passed into the saturate cracking zone in a relatively pure form. In FIG. 2 the reforming zone 15 fresh feed flows through line and contacts a hydrogen rich gas stream flowing through line 21. The resulting mixture continues through line 20 into the low severity reforming zone. The reacted and unreacted material then passes into separation zone 16 where the reforming zone effluent is separated into a hydrogen-rich gas stream which Hows through line 23, a light hydrocarbon stream comprising C1 through C4 hydrocarbons which flows through line 24, a C5/C6 gasoline stream which ows through line and a CS-igasoline stream which ows through line 26 to extraction zone 17. The C5/C6 gasoline stream may instead be diverted so as to ilow together with the C-lgasoline which flows through line 26. In extraction zone The following examples more specically illustrate the operation of the process of this invention and are not intended to be limitations thereon.

EXAMPLE I TABLE I.-UNIFINED NAPHTHA PROPERTIES API 55. 0 Clear research octane. 40. 0 Specific gravity... 0.7587 Clear motor octane 35.0 RVP 1.2 Aromatics, vol. percent... 13. 5

Distillation, F.:

10 vel. pcrcent 238 vol. percent.. 278 J0 vol. percent 331 The reforming zone contained a typical platinum metal on an alumina base and was operated at conditions to produce a C5-tplatformate of about 85.0 Research Clear Octane Number (RON). The eluent from the low severity reforming zone was separated into a hydrogen rich stream, a CTC.; light hydrocarbon stream, a C/CS gasoline stream and a Cq-lgasoline stream, the Cq-treformate stream was passed into a solvent extraction zone which separated the Cq-I- reformate into an aromatic rich stream and a saturate rich stream with the saturate stream being passed into the saturate cracking zone for conversion to cracked gasoline and lower molecular weight light hydrocarbons. A material balance for the process flow according to FIG. 2. is shown in Table II and the various stream compositions are indicated in Table III both following.

TABLE II.-MATERIAL BALANCE OF PROCESS FLOW 17, the aromatic portion of the feed passing into that zone stream description (refer t0 FIG' 2) Bp-d- Lbs-ml via line 26 is separated from the saturated portion of the Reiermingseetion: t d

i Line 20, reiorming zone ee 25 890.7 286,710 feed. rIjhe enriched aioniatic stream' is coliected via line um ggyhydmgewchSeparator gas 14,593 28 while the saturated rich stream is passed via line 27 40 Line 24,oi-Ciiigiithydroearbons 4,043 to the saturate cracking zone 18 which effects selective MM5, cs cgasom "-2,57% 28,648 cracking of saturated feed streams to gasoline and light Li1w26,c1+gasoiiiic 20,384.4 239,306 hydrocarbons. The eiuent freni the saturate cracking zone Tom, gasoline from reformer 23,211. 7 268 038 passes via line 29 to separation zone 19 wherein the ww- Extraction Section: clocked sasolmo product and llsht hydrocarbons are with- 4o me 215mm? righ Stream 8 5? 8 899,23 drawn via lines 31 and 30 respectively. A portion of the C time 2s, romatic rich stream 11,816 6 i50,7

C l' SOC I cracked gasoline may be recycled back to the cracking mmglm, ffxclight hydrocarbons Mm.; 5,6 19'2 zone 18, and where this is desired, recycle material passes Totlggsgtggsolm@ 1?/ ggg through line 33 into feed line 27 to the cracking zone.

TABLE IIL-STREAM ANALYSIS FIG. 2. iin@ number 20 23 24 25 26 27 28 30 3i Stream properties:

API et F 52. 6 Specific gravity at 60 F 0. 7686 nvr 6.7 Distillation, F.:

10 vol. percent 137 50 vol. percent. c227 vol. percent. `587 Clear octane number: 0 Motor 84.0 Aromatics, vol. percent 20 Wt. Wt. Wt. Wt. Wt. V01. Wt. Wt. Wt. percent percent percent percent percent percent percent percent percent Component:

HL., C1 Ci C3 oletins C3 paraffins Ci olctins i O4 paratlins n Ci parans.. Rcforniate gasoline (l5/C6 gasoline Cracked gasoline.

Aromatic rich stream saturate rich stream:

Saturatcs Aromatics.

It should be noted that in this example, an extraction zone was employed to effect separation of saturated material from aromatic material present in the C74- reformatc stream fed to the extraction zone. This is not a requirement of the process to effect cracking of the saturate material where the saturate cracking zone is adapted to selectively convert saturates when large quantities of aromatic hydrocarbons are also contacting the saturate cracking zone catalyst. It is anticipated that the yields from the saturate cracking zone will not be substantially altered when large quantities of aromatics are fed to the saturate cracking zone.

EXAMPLE II In this example, a higher severity reforming zone was employed without subsequent cracking of the reformate saturate materials. The catalyst used was the same as the reforming catalyst used in Example I. The severity was such that the C5 434 F. EP. gasoline produced in the reforming zone was maintained at 92.0 RON. The higher octane reformate produced by these operations was much higher in aromatic content than the C54- reformate having an 85.0 RON of Example I. In fact, the 92.0 Octane reformate contained 69 vol. percent aromatics While the 85.0 Octane reformate contained only about 45 vol. percent aromatics. The higher octane reformate consequently was also lower in saturate content because of the higher quantity of saturates converted to aromatics via dehydrogenation of cycloparains and dehydrocyclization and/or cracking of parains.

The reforming zone effluent was separated into a hydrogen-rich gas stream, a C1C4 light hydrocarbon stream and a C5 434 F. E.P. gasoline material. Analysis of the products and material balance are shown in Table 1V.

TABLE IV.PRODUCT ANALYSIS AND MATERIAL BAL- ANCE OF 92.0 RESEARCH CLEAR REFORMING ZONE OPERATION B.p.d. Lbs/hr.

Stream:

Feed stock to reformer. 25, 899. 7 280, 710 Hydrogen rich separator gas 16, 285 (l1-C4 light hydrocarbons 18, 981 05+' retormate gasoline 21, 828 0 251,445 Properties of 05+ reformate gaso API at 60F 47.7 Specific gravity at 60 F.. 7896 R P 2. 9 Distillation, F.

10 vol. percent 188 257 340 End point 434 Clear octane number Research 92. Motor 82. Aromatics, vol. percent 69. 0 Hydrogen rich gas and CreC.; light hydrocarbon stream analysis:

Component, wt. percent: H2 rich gas Ci-C4 hydrocarbons 26. 7 25. 0 3. 0 2l. 4 13. 17. 9 34. 5. 4 22. 3. 6 25.

A comparison of the overall results from the two above examples indicates that improved gasoline production occurs when low severity reforming operations are employed in conjunction with a saturate cracking operation.

The reforming zone which was operated at 92.0 RON severity level yielded 21,828 barrels per day (BPD) of C5 to 434 F. E.P. gasoline on a feed stock of about 25,900 (Barrels per Day) BPD feed rate as seen from Table IV. The only other valuable gasoline component recovered from the light hydrocarbons produced by this reforming zone was about 523.5 BPD of isobutane which is an excellent feed material for an alkylation zone to produce a C3 or C4 gasoline alkylate having RON ratings of 92.0 and 98.0 respectively. In comparison, about 17,483 BPD of gasoline was produced directly from the combination reforming-extraction-saturate cracking process of this invention, as shown in Example I, Table II. The gasoline pool comprised cracked gasoline from the saturate cracking zone, C5/C5 gasoline derived directly from the reforming zone and an aromatic concentrate which was also obtained from the reforming zone after the C74- gasoline therefrom was solvent extracted to remove its aromatic hydrocarbons prior to the cracking operation. The C5/C6 gasoline was found to possess a RON of 71.0, the cracked gasoline possessed a RON of 95.0 and the aromatic rich gasoline from the solvent extraction zone was 115.0 RON quality. Together the C54- gasoline pool from the combination process of this invention totaled 17,483 BPD and had an overall pool RON of 104.7 which is substantially higher than the pool octane of 92.0 obtained from the high severity reforming zone by itself.

In order, however, to fully appreciate the advantages which accompany the combination process of this invention, it is necessary to look to the quantity of the high octane percursors represented by the C3 and C4 oletins and the i-C4 parafns which are produced in large quantities from the saturate cracking zone by the catalytic cracking of the parans and naphthenes which are allowed to pass through the reforming zone without molecular structural change vit reformation. These high octane precursors can be readily alkylated in a suitable alkylation zone to yield alkylate gasoline components possessing RONs of 92.0 and higher depending on whether a C3 or a C4 alkylate gasoline is produced. The advantage of employing the combination process of this invention resides in the production of light hydrocarbons consisting of C3 and C4 molecular size which, when further reacted by alkylation, polymerization, hydrolysis or other octane improving processes, yield a gasoline component which improves the overall gasoline pool in octane number and in addition provides additional volumetric yield on the fresh feed.

The quantity of high octane precursor light hydrocarbons produced by the combination process as indicated in Tables II and III amounted to about 8,248 lb./hr. of

isobutane, of which 865 1b./hr. was derived from the reforming zone, 15,139 1b./hr. of propylene and 22,441 lb./hr. of butene which was derived from the saturate cracking zone. In order to take advantage of the high octane potential of the light hydrocarbons, they were passed into an alkylation zone to produce C3 and C4 alkylate gasoline. Because of the large amounts of propylene and butylene produced, it was required that a certain amount of outside isobutane be used to fully react all of the C3 and C4 olens. A total of about 36,822 lb./hr. or 4,490 BPD of isobutane was consumed in producing the alkylate gasoline; of the 4,490 BPD of isobutane consumed, 3,477 BPD was required from outside sources. The total gasoline pool composition including alkylate gasolines from the light hydrocarbons produced in the saturate cracking zone is illustrated in Table V below:

TABLE V Gasoline pool BPD C3/C3 gasoline from 85 RON reforming zone 2,827.3

Aromatic extract from extraction zone 11,876.6

Cracked gasoline from saturate cracking zone 2,779.4 C3 alkylate gasoline 3,630.0 C4 alkylate gasoline 4,460.0

Total 25,573.3

The overall octane rating of the gasoline pool of Table V was 101.8 RON. The outside isobutane required to alkylate the butene and propylene, because it Was additional feedstock, did allow the low severity reforming zone and saturate cracking zone to produce a larger absolute quantity of pool gasoline from the same amount of feed material passed into the reforming zone.

The liquid yied of C-lgasoline produced, including the C3 and C4 alkylate gasoline based on the reforming zone feed plus the outside isobutane required, was found to be 25,573.3 BPD of C45-{- gasoline (25,899.7 BPD of reforming zone feed -l- 3477 BPD of outside isobutane) 87.0 liquid volume percent or 87.0 barrels of 101.8 RON gasoline produced per 100 total barrels of feed to the combination process.

The high severity reforming zone gasoline yield was calculated taking account of the isobutane produced by that reformer as being converted to a C4 alkylate gasoline. The 92.0 RON reforming zone produced only isobutane light hydrocarbons which were potentially alkylateable and consequently to take advantage of this high octane precursor outside butene was used in such quantity to convert all of the isobutane from this reforming zone to C4 alkylate gasoline. The outside butylene was chosen to allow production of the high octane C4 alkylate. Table VI shows the total gasoline pool produced by the high severity reforming zone.

TABLE VI Gasoline pool BPD C5-lreformate 21,828 C4 alkylate gasoline 827.5

Total 22,655.5

Reforming zone feed 25,899.7 Outside butene required to alkylate i-C4 476.5

Total 26,376.2

The overall pool gasoline octane rating of the above gasoline which included the C4 alkylate produced from the isobutane was 92.3 RON. The increase in octane was due to the addition of the 98 RON C4 alkylate gasoline component to the pool gasoline. The liquid volume yield of gasoline based on the reforming zone feed -ithe outside butene need to alkylate the isobutane was 22,655.5 BPD of C5| gasoline (25,899.7 BPD of reforming zone feed -i- 476.5 BPD of outside butene)=89.4% or 89.4 barrels of 92.3 RON gasoline per 100 barrels of total feed used.

While the yield on total feed (reformer feed -loutside butene or isobutane) for the 92.0 RON reformer was 89.4 liquid volume (LV.) percent as compared to the yield of 87.0 L.V. percent for the low severity reformersaturate cracking zone combination, the combination process of this invention produced a substantially higher gasoline octane pool than the 92.0 reforming zone (101.8 versus 92.3).

EXAMPLE III In this example, a reforming catalyst similar to the catalyst used in the previous examples was employed. The reforming zone was operated at conventional conditions to effect production of a C5-|- reformate having a 102.0 RON from a reformer feed stock identical to the feed stock used previously. The charge rate of material to the reforming zone was identical to the charge rate used in Examples I and II. The isobutane recovered from the C1-C4 light hydrocarbon was alkylated with outside butene to produce C4 alkylate gasoline. Table VII below indicates the results of this experiment.

The overall RON of the above gasoline pool which comprised both C54- reformate and C4 alkylate gasoline was about 101.6. The overall yield on the basis of the total fresh feed including reformate feed-i-butene required to alkylate the isobutane recovered from the reforming zone in the C4-C4 light hydrocarbon stream was about 77.3 L.V. percent versus 87.0 for the combination of this invention. It can be seen that in attempting to produce the higher octane reformate gasolines that reforming alone inherently creates volumetric losses greater than those of the combination of this invention.

PREFERRED EMBODIMENTS In a broad embodiment there is presented a process for the production of a high octane gasoline which process comprises the steps of: (a) converting at least a portion of a heavy naphtha in a reforming zone, at relatively low severity reforming conditions, to produce a gasoline reformate containing aromatic and saturated hydrocarbons; (b) passing at least a portion of said saturated hydrocarbons to a saturate cracking zone and cracking said saturated hydrocarbons at conditions to effect the production of saturated and unsaturated light hydrocarbons and gasoline; and, (c) converting a portion of said saturated and unsaturated light hydrocarbons to a gasoline component.

I claim as my invention:

1. A process for the production of an aromatic gasoline, and saturated and unsaturated light hydrocarbons having from 3 to 4 carbon atoms per molecule, which process comprises the steps of (a) converting at least a portion of a heavy naptha containing alkanes and naphthenes in a reforming zone, at low severity reforming conditions including greater than about mol percent conversion of said naphthenes to aromatics and less than about 40 mol percent conversion of said alkanes to aromatics, to produce a reformate containing aromatic and saturated hydrocarbons;

(b) passing at least a portion of said reformate into an extraction zone at conditions to effect the separation of said reformate into aromatic gasoline and saturated hydrocarbon streams;

(c) passing at least a portion of said saturated hydrocarbons into a saturate cracking zone at catalytic cracking conditions in the absence of added hydrogen to effect the production of said saturated and unsaturated light hydrocarbons and cracked gasoline; and

(d) passing at least a portion of said saturated and unsaturated light hydrocarbons to an alkylation zone to effect the conversion of said hydrocarbons to alkylate product.

(References on following page) 13 14 References Cited 2,780,661 2/ 1957 Hemminger et al. 208-66 2,908,629 10/1959 Themas 208-66 UNITED STATES PATENTS 3,124,523 3/1964 ,seen 20s-62 1513i? ultbe ggg-gg 3,050,456 :3/1962 Melchior 20:3*67 @Paf S0 3,556,987 1/1971 zm t 1 20s-66 5/1968 `Kelley et a1 20s-79 5 merma a 10/1941 Atwell 208-66 HERBERT LEVINE, Primary Examiner 10/ 1956 Haensel et al. 208-66 10/1959 schneider et a1 20:3 66 U.s. C1. XR.

9/1961 Grete 208-66 10 20s- 66, 96