IL35865A - High octane gasoline production - Google Patents

Description

High Octane Gasoline Producti UNIVERSAL OIL PRODUCTS COMPANT C: 34026 The field of art to which this invention pertains is catalytic conversion of hydrocarbons. More specifically, this invention pertains to a combination of integrated refinery 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.

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 naphthcne dehydrogen seion, naphthcne dohydroisomcr« ization and paraffin dehydrocyclisa on . The naphthcne dehydro-genation reaction is quite rapid and is the primary octane improving reaction in catalytic reforming. VJhen five membered a ky naphthcnee arc present in a naphtha feed it is necessary to isomerizc the alkyl cyclopcntanes into six membe ed ring naphthenes followed by the dehydrogenation to aromatics.

Arornatization of paraffins is achieved by the dehyd ocyclization of straight chain paraffins having at least six carbon atoms per molecule. Dehydrocyc!ination ie limited in the once-through reforming operations because as the aromatic concentrations increase throu.gh the reforming zone the rate of additional dehydrocyclization of paraffins is greatly reduced. This leaves unreacted paraffins present in the refornu^e effluent which greatly reduces the octane rating of the reformate. In the reforming zone, the paraffins which, at lev; reforming severit 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 paraffins in the to 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 c" . bo eliminated by in effect "overwhelming" the low octane componen s of the reformate by increasing 35865/2 t-.b: efo me severity of o er tions to produce an increased quantity of aromatic com o ents' T is typo of operation haa a twofold effect in increasing a reformate octane rating; first, additional high octane aromatic components are produced; and, secondly, the lower octane couponentr; arc partially eliminated by being converted ' into aromatic components or into light products outside tho gasoline boiling range. — Tho improvement in octane accompanied by tho increased severity of the reforming -aone, therefore, results in lower liquid yields of gasoline partly due to the "shrinkage" of the molecular s ze of tho paraffins and naphthoncs vhcn thoy are converted to aromatic type hydrocarbons and partly duo to production of tho aforesaid light products. It has now been found that instead of "overwhelming" the lower octane components of reformat© gasoline with high octane aromatic components, that the cracking of the low octane reforma o components (paraffins and naphthenea) iito lower molecular weight olefins and paraffins allows cub-sequent processing to convert these materials into improved . high octane components which improve the overall refinery gasoline pool octane while substantially eliminating tho volumetric yield loos which accompanies high severity reforming conditions.

Hardin et al disclose' in US Patent Specification No. 3,060,116 a combination p rocess for manufacturing from a gasoline feed stock a high-octane fuel and ethylene, wherein a saturated-hydrocarbon - 3a -teachings of Hardin et al, however, do not disclose the low-severity reforming of this invention wi.ch ia characterized by greater than 80 conversion of naphthenes to aromatics and less than 40 conversion of alkanes to aromatics. Another distinguishing feature between this invention and the Hardin et al disclosure is that the cracking conditions employed in this invention are such that the unsaturated light hydrocarbons produced consist almost entirely of propylene and bu enes which can be easily converted to a high-octane gasoline component. The novel combination of low-severity reforming and selective cracking of this invention results in the improvement of the overall refinery gasoline pool octane without the usua loss in volumetric yield.

It is an object of this invention to provide an integrated refinery process wherei the gasoline produced from said process is of high octane quality and in most instances <¾es not require addition of lead to increase its octane rating 35865/2 to meet the requirements of most present day internal combustion engines.

Accordingly, the present invention provides 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 which produce 80 to 100 moles of aromatics per 100 moles of naphthenes charged and less than 40 moles of aromatics per 100 moles of alkanes charged, to produce a gasoline reformate containing aromatic and saturated hydrocarbons; (b) passing at least a portion of said gasoline reformate which contains a portion of saturates 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.

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-". The , light hydrocarbons having one and two carbon atoms per moleai le are generally referred to as dry gases and are generally used as refinery fuel gas while the and portions' of the light hydrocarbons are valuable; the C3 and C4 olefins can be used in the process of this invention for alkylate or polymer or isopropyl alcohol production. The C3 and normal paraffin portions of the light hydrocarbons are generally referred to as liquid petroleum gases and can be used as such.

Liglt naphtha streams generally refer to hydrocarbon streams containing hydrocarbons in the C5 and carbon range.

The light naphthas generally arc recovered directly, as virgin light naphthas, from a crude distillation unit. The end boiling point of most light naphthas is generally from about 79 to 93°C (175 to 200°F). The heavy naphthas are generally referred to as those hydrocarbons boiling ithin the range of from about 82°C (180°F) to about 204°C (400°F) which includes those hydrocarbons having carbon numbers of about 7 or greater.

The light cycle oils generally boil within the range of 204 to 316 °C (400 to 600°F) while atmospheric and vacuum gas oils are generally higher coiling materials having boiling ranges of about 316°C (600°F) to about 649°C (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.

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.

In the reforming zone a suitable hydrocarbon feed stock io contacted with a reforming catalyst to effect conversion of the reformer feed stock to a higher octane reformat© product. Hydrocarbon eed stocks which c be useel in the reforming zone include' hydrocarbon fractions containing lvsphthenes and paraffins. The preferred stocks are tho.se consi ting essentially of naph-thenes and paraff ns although, in soma 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 cafca.lytiec.lly cracked gasolines or higher boiling fractions thereof to t e conversion process of the reforming zone. The reformer charge stock may be a full boiling range gasoline char-go stock having' an initial boiling point of from about 10 to 380C (50 to 100°Fj and an end boiling point within the range of from about 163 to 218°-C (325 to 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 aluraim and the crystalline aluminor-silicates. Metallic components which are generally recognised 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-13 metal, la s 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 fluorine, chlorine, bromine, iodine or mixtures thereof.

Effective reforming operating conditions include temperat res? within the range of about 427 to 593°C (800 toJL100°F) and preferably between about 454 to 566°C (850 to 1050°F). A liquid hourly space velocity or LHSV (volume per hour of liquid . feed per volume of catalyst) in the range of from about 0.5 to about 15 and preferably from about 1 to about 5 is 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 ½:1 to about 20:1 moles of hydrogen per mole of hydrocarbon feed, and preferably from about 4:1 to about 12:1 moles of hydrogen per mole of hydrocarbon feed. The catalyst in the reforming zone may be a fluidized or moving bed-type process, but the well-known fixed bed system is preferred. The reforming zone reactor effluent, 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 are within the range of from about 1.7 to 103 atm (10 to 1500 psig).

The reforming zone used in this combination process with is operated at low severity. To those familiar -to- the reforming art, the term relatively high severity generally indicates high temperature or low space velocity or both high temperature and low space velocity operating conditions. High severity operations increase the reformate octane 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 substa2itially 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 tr high octane aromatic compounds with the qualification that the dehydrocyclization of feed paraffins 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 80 moles of aromatics produced per 100 moles of naphthenes charged to the reforming zone to about 100 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 κοηο. In determining the degree of conversion of nophthenos to aromatics (dohydrogcnation) and alkanes to aromatics (dchydrocyclization) , it is generally assumed that a relatively small amount of naphthenes are cracked or converted to hydrocarbons other than aromaticr. and that a major portion of the alkanes which disappear through the reforming zone ere converted to aromatic hydrocarbons v:ith come 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.

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 saturate cracking zone can be the entire lov; 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 paraffins and cyclic paraffins. However, in instances where the reforming zone liquid effluent is passed directly into the saturate cracking zona, aromatic hydrocarbons will also bo present in the a u ate cr cking zone food stock. In either case, the r.ati ate cracking aono must be able to oe!cc-tively crack that acne's feed stock saturates to lower molecular weight hydrocarbons in a n. nner GO s to minimise the production of dry gases ouch as meth.no, ethane, ethylene or acetylene, while maximising the product on of C and C saturates or uns turates and cracked gasoline ma e Is, The saturate cracking gone produces cracked gasol ne and valuable light hydroca.rbons from most of the aromatic precursors which a e not converted to aromatics in the reforming ;.',ons 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 sa ""ci e cracking zone generally comprise a relatively high oatane cracked gasoline plus C3 through light hydrocarbons comprising propane, propylene, normal and iso- i>.tane, normal and iso-butene, and pentancs and pantencs. The products are excellent feed stocks for other processes which form valuable gasoline components such as amines, esters, ethers, ketones, branched chain paraffins 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 paraffinic portion of the saturate cracking zone effluent which contains n relatively large amount of branched chain molecules is suited for production of alkylate gasoline. Λ general but not all inclusive listing of individual saturate cracking zone light hydrocarbons includes methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, tertiary butyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, isopro lamine, n-butylamine, diethylamine, triethylamine, methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate, propylene oxide, n-propyl ether, isopropyl ether, o 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 operating conditions are required. It is preferred to use reaction temperatures within the range of from about 454 to 649°C (850 to 1200°F) and preferably within the range of from about 454 to 62l°C (850 to 1150°F). Probably the most important operating parameter for the selective production of olefinic light hydrocarbons (propylene and butene) is the contact time between the paraffinic cracking zone feed and the catalyst contained therein. In fixed bed type cracking incorporating once-through operations, the weight ratio of olefins 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 fluid iaccl catalytic cracking operations, space velocity is generally measured in terms of weight hourly space velocity (WJISV) which s defined as the weight of charge oil per hour over the weight of the catalyst in the reaction zone. The V2JISV based on raw charge oil ir. most frequently used .

Weight hourly space velocities greater than about 15 are preferred when effecting saturate cracking in the saturate cracking zone.

In some instances where the conversion of saturate crackincj zone feed is relatively low, a portion of the effluent material from this sone may be recycled back to the cracking zo , 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. he 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 froai a number of known materials including amorphous silica-alumina and zcolitic type aluminos 1 ca es , both of which may contain composited thereon various catalytic components selected from the Periodic Table mev.als of combined or elemental character. sil ica-m gnesia, silica-zireonia and more preferably crystalline aluinino ilicates characterized as having relatively high cracking activities.

The preferred crystalline aluminos.ilicate 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 ma be selected from the group of synthetically prepared zeolites such as A, Yf L, Ώ, Rf Sf Tr Zf E, Q, B, X, ZK-4 and ZK-5. The naturally-occurring materials include faujasite, mordenite and montmorillonite Whether the catalyst comprises a 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, and Group VIII metals, 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 include pressures ranging from about atmospheric to about 35 atm (500 psig) and a temperature of from about 482 to 816°C (900 to 1500°F).

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 the 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.

FIGURE 1 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.

FIGURE 2 represents an embodiment where 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 FIGURE 1, a heavy naphtha feed from a source including a crude unit or other refinery processing equipment flows through line 5 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 coditions employed in reforming zone 1 are more specif cally low severity conditions which are more specifically defined previously herein. The effluent from the reforming zone 1 passes through line 7 to separation zone 2 wherein the gasoline portion of the reforming zone is separated from the lighter portions of the reforming zone effluent: . 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 Cj_ through molecular weight hydrocarbons is withdrawn from separat zone 2 via line 9 while a gasoline stream is withdrawn via line 10. The material withdrawn via line 10 may alternately be fed directly to the saturate cracking zone in admixture with the major gasoline portion of the reforming zone effluent which passes via line 11 to the saturate cracking zone 3. Recycle material from the effluent 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 31 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 FIGURE 2 the reforming zone 15 fresh feed flows through line 20 and contacts a hydrogen rich gas stream flowing through line 21. The resulting mixture continues through HU into the low severity reforming zone. The reacted and' unreacte nm or nl en paasen into separation szo e 16 where the reforming zone effluent is ccpar ed into a hydrogen-rich ga.'j stream which flows through line 23, a light hydrocarbon stream comprising through C hydrocarbons which flows through line 24, a C5/C6 gasoline stream which flows through line 25 and a C6+ gasoline stream v/hich flows through line 26 to extraction zone 17. The C5/C6 gasoline stream may instead be diverted so as to flow together with the gasoline which flows through line 26. In extraction zone 17, the aromatic portion of the feed passing into that zone via line 26 is separated from the saturated portion of the feed. The enriched aromatic stream is collected via line 28 while the saturate rich stream is passed via line 27 to the saturate cracking zone 18 which effects selective cracking of saturate feed streams to gasoline and light hydrocarbons. The effluent from the saturate cracking zone passes via line 29 to separation zone 19 wherein the cracked gasoline product and light hydrocarbons are withdrawn via line 31 and 30 respectively. Λ portion of the cracked gasoline may be recycled back to the cracking zone 18, and where this is desired, recycle material passes through line 33 into feed line 27 to the cracking zone.

The following Examples more specifically illustrate the operation of the process of this invention and are not intended to be limitations thereon.

In this example, a combination low severity reforming zone and a saturate cracking zone combination, as shown in attached FIGURE 2 was employed.

The feed stock used in this example and other examples was a Unifined (i.e. hydrotreated) naphtha which generally described in Table 1.

TABLE I Unifined Naphtha Properties API°@60°F 55.0 *Reid Vapor Pressure (RVP) 1.2psi (0.08 Sp.Gr.@15.6°C 0.7587 **Clear Research Octane 40.0 Distillation.' ***Clear Motor Octane 35.0 Aromatics 13.5 vol% vol% 115°C(238°F) 50 vol% 137°C(278°F) 90 vol% 167°C (331°F) The reforming zsie contained a platinum metal on alumina base catalyst and was operated at conditions to produce a reformate of about 85.0 Research clear Octane Number (RON). The effluent from the low severity reforming zone was separated into a hydrogen rich stream, a C1-C light hydrocarbon stream, a C5/C5 gasoline stream and a C7+ gasoline stream, the C7+ reformate stream was passed into a solvent extraction zone which separated the C7+ 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 gasdine and lower molecular weight light hydrocarbons. A material balance for the process flow according to FIGURE 2 is shown in Table II and the various stream compositions are indicated in Table III both following.

*As determined by the method of the American Society for Testing and Materials, ASTM Designation D 323-58 **ASTM Designation D 908 ***ASTM Designation D 357 TABLE II Material Balance of Process Flow Stream Description (refer to FIGURE 2) M3/HR BPD LBS/HR kg/H REFORMING SECTION Line 20, Reforming Zone Feed 171.4 25,899.7 286, 710 Line 23, Hydrogen-Rich Separator Gas 14, 593 6J630 Line 24, C^-C^ Light Hydrocarbons 4,043 1840 Line 25, Cg-Cg Gasoline 18.7 2, 827.3 28,648 Line 26, C + Gasoline 134.8 20, 384.4 239, 390 Total Gasoline from Reformer 153.5 23, 211.7 268,038 EXTRACTION SECTION Line 27, Saturate Rich Stream 56.3 8,512.8 89,053 Line 28, Aromatic Rich Stream 78.6 11,876.6 150,337 CRACKING SECTION Line 30, C^-C/ Light Hydrocarbons 44.4 6,718.4 56,192 Line 31, CracRed Gasoline 18.4 2,779.4 31,169 Total Gasoline Produced 115.6 17,483.3 210,154 Stream Analysis FIGURE 2, LINE NO. 20 23 24 25 26 27 Stream Properties: API at 60°F 55 72.0 44.3 Sp RV Di 50 90 Clear Octane No., Research 40.0 77.0 86.1 Motor 35.0 Aromatics, vol% 13.5 Component : wt.% wt.% wt.% wt.% wt%vbl% 41.2 ccl2 11.8 C2 15.7 7.2 C3 olefins Cj paraffins 17.6 28.6 C4 olefins i C4 paraffins 5.9 21.4 n C4 paraffins 7.8 42.8 Reformate gasoline 100.0- C5/Cg gasoline 100.0 Cracked gasoline Aromatic rich stream Saturate rich stream Saturates 95.0 95.7 Aromatics 5.0 4.3 It should be noted that in thla E:cample, an extraction zone was employed to effect Reparation of saturated material from aromatic material present in the cyi- reformato 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 in adapted to selectively convert saturates when large quantities of aromatic hydrocarbons are also contacting the saturate cracking one catalyst. It is anticipated that the yields from the saturate cracking zone will not be substantially altered heiu large quantities of arornatics are fed to the saturate e e eking zone.

In this example, a higher severity reforming isone was employed wi hout subsequent cracking of the ref ma © saturate materials. The catalyst used was the same as the reforming catalvst used in Example I. The severity was such that the to 223°C (434°F) gasoline produced i the reforming zona was maintained at 92.0 RON. The higher octane reformato produced by these operations was. much higher in aromatic content than the reforma e having an 8Γ>.0 ROW of Example I. In fact, the 92.0 Octane reforma e contained 69 vol.% arornatics while the 05.0 Octane reformato contained only about 45 vol.% arornatics. The higher octane reformato consequently was also lower in saturate content because of the higher quantity of saturates converted to arornatics via dehydrogenation of cyelo-paraffins and dehydrocyclization and/or cracking of paraffins.

The reforming zone effluent was separated into a hydrogen-rich gar, stream, a C - li ht h <h:ocarlxn stream and Cr to 223°C (434°F) gasoline material. Analysis of the product and ma erial b lance are shown in Table IV.

TABLE IV ^^ c-__An ly_sis and Material Balance St eam : M3/HR BPD LBS/HR Feed Stock to Reformer 171.4 25,899.7 286,710 Hydrogen Rich Separator Gas 16,285 7,420 C1-C4" Light . Hydrocarbons 18,981 8,630 C5+ Reformate Gasoline 144.3 21,828.0 251,445 Properties of Reformate Gasoline: API at 60° F 47.7 Sp.Gr. at 15.6°C .7896 RVP atm (psi ) 0.29 (2.9) Distillation, 0c/?F vol% 87/188 50 vol% 125/257 90 vol% 171/340 End Point 223/434 C7 ea Octane No . , Research 92.0 Motor 82.5 Aromatics, vol 69,0 Hydrogen Rich Gas and C-^-C^ Light Hydrocarbon Stream Analysis: Component, wt H2 Rich Gas C1~C4 Hydrocarbons H2 26.7 Ci 25.0 3.0 C2 21.4 13.6 C3 17.9 34.9 i-C4 5.4 22.7 n-C4 3.6 25.8 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 144.3 cubic meters per hour (CMPH) (21,828 barrels per day ( BPD)) of C5 to 223°C (434°F) E.P. gasoline on a feed stock of about 171.4 CMPH (25,900 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 3.5 CMPH (523.5 BPD) of iso-butane which is an excellent feed material for an alkylation zone to produce a C^ or C^ gasoline alkylate having RON ratings of 92.0 and 98.0 respectively. In comparison, about 115.6 CMPH (17,483 BPD) of gasoline was produced directly from tlie 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, C^/ ^ gasoline derived directly from the reforming zone and an aromatic concentrate which was also obtained from the reforming zone after the C-7+ gasoline therefrom was solvent extracted to remove its aromatic hydrocarbons prior to the cracking operation. The C5/C& 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 C5+ gasoline pool from the combination process of this invention totaled 115.6 CMPH (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 precur- which ore produced in large quantities from the saturate cracking zone by the catalytic cracking of the paraffins and naphthenes which are allowed to pass through the reforming zone without molecular structural change via reformation. These high octane precursors can be readily alkylated in a suitable alkylation zone to yield alkylate gasoline components possessing RON's of 92.0 and higher depending on whether a 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 and a 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 3., 750 kg/hr (8,248 Ib/hr) of isobutane, of which 394 kg/hr (865 lb/hr) was derived from the reforming zone, 6,880 kg/hr (15,139 lb/hr) of propylene and 10,200 kg/hr (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 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 olefins. A total of about 16,720 kg/hr ( 36, 882 lb/hr ) or 29.7 CMPH (4,490 BP ) of isobutane was consumed in producing the alkylate gasoline; of the isobutane consumed, 23.0 CMPH (3477 RPD)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 GASOLI E POOL BPD CMPH Cracked gasoline from saturate cracking zone 2779.4 18.4 C, alkylate gasoline 3630.0 24.0 C4 alkylate gasoline 4460.0 29.5 TOTAL 25573.3 169.2 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 feed stock, did allow the lo 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 yield of C^+ gasoline produced, including the C3 and C4 alkylate gasoline, based on the reforming zone feed plus the outside isobutane required, was found to be 169.2 CMPH (25,573.3 BPD) of gasoline yield from 171.4 CMPH (25,899.7 BPD) of reforming zone feed + 23.0 CMPH (3477 BPD) of outside isobutane or 87.0 liquid volume %.

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. Trie 92.0 RO N reforming zone produced only isobutane light hydrocarbons which were potentially alky.1 ateable 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 z one .

TABLE VI GASOLI E POOL BPD CMPH 0Γ)+ reformat e 21,828 144.5 C alkylate gasoline 827.5 .5 TOTAL 22,655.5 150.0 Reforming zone feed 25,899.7 171.4 Outside butene required to alkylate i-C4 476.5 3 -_1 TOLCAL 26,376.2 174.5 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 + the outside butene needed to alkylate the isobutane was 150.0 CMPH (22,655.6 BPD) of C5+ gasoline yield from 171.4 CMPH (25,899.7 BPD) of reforming zone feed + 3.1 CMPH (476.5 BPD) of outside butene or 89.4% (89.4 volumes of 92.3 RON gasoline per 100 volumes of total feed used).

While the yield on total feed (reformer feed + out-side butene or isobutane) for the 92.0 RON reformer was 89.4 liquid volume (L.V. ) % as compared to the yield of 87.0 L.V. for the low severity reformer-saturate cracking zone combj!) the combination process of this invention produced a substa t a i 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 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 i to the charge rate used in Examples I and II. The isobutane recovered from the C^-C^ light hydrocarbon was alkylated with outside butene to produce alkylate gasoline. Table VI below indicates the results of' this experiment.

TABLE VII GASOLINE POOL BPD CMPH C5+ refoimate 18,740 124.0 C4 Alkylate gasoline 2, 266 15.0 TOTAL 21,006 139.0 Reforming zone feed 25,899.7 171.4 Outside butene required to alkylate i-C4 1, 312.0 8.7 TOTAL 27,211.7 180.1 The overall RON of the above gasoline pool which com-prised both C5+ reformate and C4 alkylate gasoline was about 101.6. The overall yield on the basis of the total fresh feed 35865/2

Claims (7)

1. A process for the production of a high octane gasoline which comprises the steps of: (a) converting at least a portion of a heavy naphtha in a reforming zone, at relatively low severity reforming conditions which produce 80 to 100 moles of aromatics per 100 moles of naphthenes charged and less than 40 moles of ' aromatics per 100 moles of alkanes charged, to produce a gasoline reformate containing aromatic and saturated hydrocarbons; (b) passing at least a portion of said gasoline reformate which contains a portion of saturates 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.

2. The process of "Claim 1 wherein the gasoline reformate is passed into a separation zone wherein a saturated raffinate stream and an aromat ic extract stream are recovered by solvent extraction means and that said saturated raffinate stream is passed into the saturate cracking zone.

3. The. process of Claim 1 or 2 wherein a portion of the saturated and unsaturated light hydrocarbons of step (c) are converted to a gasoline component selected from the group consisting of amines, esters, ethers, ketones, branched chain paraffins and alcohols.

4. The process of Claim 3 wherein the unsaturated i . 35865/2

5. The process of Claim 3 wherein a portion of the saturated and unsaturated light hydrocarbons are converted to alkylate gasoline in an alkylation reaction zone.

6. The process of any of Claims 1 to 5 wherein the saturate cracking zone is principally a catalytic cracking reaction zone.

7. The process of any of Claims 1 to 5 wherein the saturate cracking zone is principally a thermal cracking zone. 80 Λ process for the production ~>f a high octane gasoline comprising low severity reforming followed by saturate cracking of at least a portion of the saturate reforniate substantially as hereinbefore described. For the Applicants -29-