US2968609A

US2968609A - Process for fractionating and blending a reformate to obtain a high octane gasoline

Info

Publication number: US2968609A
Application number: US556498A
Authority: US
Inventors: Irvin H Lutz
Original assignee: American Oil Co
Current assignee: American Oil Co
Priority date: 1955-12-30
Filing date: 1955-12-30
Publication date: 1961-01-17
Anticipated expiration: 1978-01-17

Description

Jan. 17, 1961 H. LUTz 2 968,609

PROCESS FOR FRACTIONATING AND BLENDING A REFORMA@ TO OBTAIN A HIGH OCTANE GASOLINE Filed Dec. 30, 1955 vm TR INVENTOR. Irvin h'. Luiz W/wQ/w ATTORNEY SINNH'.

United States Patent O PROCESS FOR FRACTIONATING AND BLENDING p A REFORMATE TO OBTAIN A HIGH OCTANE GASOLINE Irvin H. Lutz, Texas City, Tex., assignor to The american Oil Company, Texas City, Tex., a corporation of Texas Filed Dec. 30, 1955, Ser. No. 556,498

5 Claims. (Cl. 208-100) My invention relates to the production of high octane gasoline from low octane naphthas by catalytic reforming. More particularly, it relates to the production of a high octane premium gasoline, e.g. at least 98 and more especially 100 F-l (CFR-R) octane number or higher, 'and a second gasoline of lower octane number from gasoline forming and gasoline blending components in a common refinery gasoline pool by an integrated process including selective reforming, fractionation, and blending steps. Y

Conventional practice has been to produce premium gasoline from catalytic gasoline, i.e. the gasoline produced iby catalytic cracking of gas oil. Catalytic gasoline as produced may average 93 to 95 F-l octane number clear. Thus, it can be increased in octane, up to lthe 96 to 97 F-l level, simply and economically by the addition of tetraethyl lead in amounts up to the legal limit. There has been virtually no incentive to date therefore, except in special situations, to use catalytic reforming for the production of base stock for premium Igrade leaded gasoline. Although catalytic reforming has been described in numerous patents 'and publications as -producing very high octane gasolines, actually the installation and operating costs for the production of reformate of the necessary octane quality in the necessary Volume, except for feedstocks of unusual quality, cannot lbe justified for premium gasoline, compared tothe use of catalytic gasoline and the cost of tetraethyl lead. Hence, catalytic reforming has been used by most refiners to upgrade as necessary the octane value of lower quality gasolines such as virgin naphthas, -thermally cracked gasolines, coke-still naphthas and the like in the refinery pool, for 'the production of a second structure gasoline, variously 4referred to as regular, house-brand, etc. This has contributed indirectly howvever to the production of premium gasoline by upgrading the over-all octane level of the refinery gasoline pool and by permitting the segregation of high quality naphthas necessary to meet premium octane goals.

In the production of unleaded premium gasoline of higher octane number than about 95 F-l, of course it has not been possible to use catalytic gasoline as the major base stock component. Moreover, at 98 F-1 and higher, even with tetraethyl lead, it is uneconomic or impossible within legal lead limits to rely on catalytic gasoline as a major base stock for premium gasoline. Consequently, as premium octanes reach the 98 to 100 F-l level, it has become necessary to consider catalytic reforming on a major scale for the production of premium grade base stocks. The severi-ty of reforming required, however, imposes severe economic penalties. As the octane level.of the C5+ reformate produced is increased above the 90'to 95 level, depending upon the quality of the charge stock, yield lossA tends to become excessive. Catalyst life y 2,968,609 Patented Jan. 17, 19.61

lice,

converting low octane naphthas to high octane premium gasoline components by means of a process which conserves feed and catalyst requirements and yet produces more octane-barrels of refoimate than produced by conventional reforming. The process has special value in the production of 100 F-l octane number unleaded premium gasoline. The naphtha charge stock is prefractionated, either as an incident to crude distillation or in special facilities, to obtain a C,{ heavy naphtha fraction, more advantageously a C8+ heavy naphtha fraction. The linal boiling point should not exceed 400 F. to any substantial extent because the product then will contain an undesirable volume of components boiling above the gasoline range. The heavy naphtha charge is subjected to reforming in the presence of a reforming catalyst and hydrogen to a severity producing a C54- reformate of at least 93 F-l octane number. Advantageously, the reforming severity exceeds that producing a C5+ re,.-

ormate of 95 F-l octane number clear and, in the prof duction of super fuels, may approximate 100 F-l clear. The reformate obtained is split by fractional distillation ata cut point in the range between about. 225 and 300". F. to obtain a heavy fraction and a light fraction. AIt has been found that by correlating in a simple manner the cut point with the reforming severity for 'the boiling range of any particular charge stock that a heavy fraction can be produced by simple fractional distillation comprising 40 volume percent or more of the total reformate which comprises percent or more aromatics. Heavy frac tions so produced have been Ifound to have octane numbers of 100+ F-l clear and may be blended with light fractions of suitably high blending octane values to produce a full boiling range premium gasoline of 98to 100 F-l octane number or higher. The light fraction split from the reformate is significantly lower in octane num.-` ber than the heavy fraction. It is advantageous therefore, according to the invention, to reprocess this fraction as by recycling to the reforming zone but preferably by selective processing in a second conversion stage favoring para'in cyclization and/or isomerization. When the cut point in the splitting operation is such as to include C7s in the light fraction, it may be advantageous, partie,-- illarly at .the higher severity levels, to segregate the toluene cut for separate blending, or for toluene recovery.

The invention thus provides processing means for upgrading the renery gasoline pool to an optimum extent Iby producing premium grade blending stocks from low octane number naphthas through reforming combined with segregation of the super octane heavy components of reformate with suitably high octane light components from extraneous sources, e.g. light catalytic gasoline, lightl alkylate, reprocessed light reformate, etc. The reforming severity burden is significantly reduced compared to conf ventionalV processing requirements. The refinery pool may lbe upgraded further by selective reprocessing and( or segregation of the low boiling, low octane components of the reformate.I In processing to maximum octane levels, this provides a substantial yield advantage overboth once-through and recycle reforming. For example, thejyield of 100 F- gasoline base stock from ya blend of the heavy reformate cut from a F-l reformatewith selectively reprocessed lighter components rups 5 9.10

'to' 100 F-'l orby' extracting'aroma'tics and"recycling' the overhead 'by line '13. "Heavier' than '400 'F.-naphtha is 'removed asebottoms lthr'o'ugh line 14.

The CH- `naphthais preheated in a 'lir'ed heater '15, and 'in adm'ixture "with recycle gas 'comprising mainly 'hydrogen from'line`1164,`is charged by line 17 to catalytic reforming 'z'one 18. The inlet ltemperature `to 'the 'r'eforming'zofne is'in'the rang'eof'about'875f 'to l000 F., an'dthe'recycle'gas'ratio comprises'about 2000 to`10,000 cubic" fe'etgper "bai-rel'v of charge. 'The charge mixture is contacted in the'r'eform'ing zone with'a reforming catalyst underapressure'in 'therange of'about 100 -t0500 p.s.i.g., preferablyin thera'n'g'e "of 'about'lSO to 400 p.s.i.g., and at'ta space'velocity in'the range of about 0.1to 5.0,' usually about' 0.5 .to' 115,- weight ratio feed per hour to weight ofcatalyst inthe reforming zone. Thereformin'g conditions area adjusted' so a'sto provide a severity `producing areforrned product 'having'anunleadedF-l roctane number, vafter"stabilition,"of "at least 9.3, Jand'preferably -blit v95 sto "98.

'Th'ecatalyst yused in 'thereforniing zone '18 'most advantageously "comprises 'a 'platinum-alumina reforming catalyst. The catalyst is 'usually in 'the form of pellets ortblets arranged as a plurality of'lixed beds disposed in lafseries"of'separate reactors. `Interheating'facilities are rprovided V'between "the reactors to compensate for endothermic temperature Vdrop through the reforming z'one. Other 'platinum-containing reforming catalysts 'may' be tused, for example, platinum on sintered silicaalumina 'or platinum onhalide 'promoted alumina. Also, a @molybdenum oxide-alumina or a chromia-alumina catalyst "can be used although 'with less advantage in terms of activity a'nds'electivity. These catalysts are readily handled "i'ntnely divided -form 'in a iluidized state, 'thus facilitating regeneration.

:Because-'of the highreforming'severitis required in the process of the invention, 'regeneration'facilities for maintaining "thefactivity of `the 'catalyst in reforming zone 18 by tp'erio'dic'burn-off of 'carbon 'and oxygen' treatment are desirable. The regeneration process is'not a part of the present invention Vbut will be described briefly. It'may be `conducted periodically or continuously. For examv ple, one or-more of the reactors ,can'be taken off-stream,

or the-'unit can'be shutdown, after the catalyst activity has 'dropped 'tto a levelre'quiring the use of excessive temperatureslto'obtain the desired octane quality reformate. 'By providing 'a swing reactor,the unit can be 'operated continuously without shut-down While 'the extra reactor is being regenerated.

The regeneration cycle normally requires "an vinert `gas purging :operation vfollowed by carbon burn-olf with :a dilute oxygen containing gas,e.g. about Zpercent oxygen, to'prevent .undue temperature rise -at a-relatively'moderate temperature in thezrange of about 700 to 900 F. Following the carbon burn-off, vthe catalyst is advantageously rejuvenated by treatment with oxygen or enihed air 'ata partial pressure of oxygen exceeding 0.4 atmosphere 'andat a temperature in the range of about V950 to 1150 F., Zfor 'a period of time suflicien't to res't'ore'the c'atalyst'to the'virgin 'activity ','level or higher.

"When the catalystis handled in fluidized form, as is preferred :ijn 'the case 'of molybdenum oxide-alumina 'cataflowing a stream of spent catalyst from the reactor to ithe' regenerator for'carbon'burn-oif' with air4 at 900"t`o From catalytic reforming zone 18, the charge mixture is passed via line 19 to high pressure separator 20. Recycle gas is separated through line 21 for recycle via compressor 22, line 23, heater 24 and line 16. Excess gas can be vented through line 21a. The liquid stream separated in separator 20 is removed through line 25 to stabilizer 26. The stabilizer.zisequipped with reboiler 27. Cgs and lighter `hydrocarbons are removed overhead through '-line 28, `and in "lsom'e" 'cases fit V"may -be desirable to include isopentane inthe stabilizer overhead.A The stabilized reformate is passed by line 29 to splitter tower 30. Splitterf30lisequipped 'with 'a-rebo'iler31. 'The tower is'operatedrso asito-take overhead throughy line' 32 a light reformate fraction which contains the Cei hydrocarbons and lighter "and,r"d epending upon the=severity of operation, part or.V all Vof lthe C7 fraction and part of the C8 fraction. y'Theheavy reformate is removed as bottoms through line 33, and advantageously is rerun in tower 34 to remove as bottoms via connection 35 hydrocarbons boiling'higher than the [gasoline endpoint, i.e. 400 lto 415 'The heavy reformate productistream is'recovere'd asoverhea'dv through line'50 and ispumped to'storage or blending facilities via connectionSl. Ultimately, 'as indicated by line 52,the heavy-reformate is blended'to'-specication octane and volatility properties with at least 'one"hi`gh"'octane numberlight stock, which may comprise reprocesse'd light material as irldicatedby li'n'es^ 53 and' 54 (see below).

The light reformate `produced according toftheprocess of the invention vmay 'be @passed 'to .storage 'or Ablending via line 32a butadvantageously is passed by lines "36 and 37'to a repro'eessingzone 38'for'further upgrading by selectivetreating. V'Forvexample, the light fractionncan be rer'unin a second pass'catalyticreforming'zone. The same'or a 'different catalyst asthat used in 'catalyticreforming 'zone 18 may be'used,'but advantageouslythe conditions of reforming'are'favorable to paraflin'isomerization anddehydrocyclization so Vas'to obtain optimum octane improvement Without 'excessive stock loss. For example, W'ith a severity in zone 18 lproducinga 9'8"0 1`00'F1 octane 'number reformate clear at 300 p.s.i.g., a'severity 'producing a'reformate inthe range'of 92 may be employed in zone 38'at 200300 p.s.i.g.- d

Alternatively, the light -fraction, lpreferably after dehexan'ization, 'can'betreated in the presence'of a dehydrocyclization catalyst such as allialized chromia-alumina or in thepresence'of 'an isomeri'zation catalyst nsuch as aluminum chloride. Furthermore, vthe light fraction 4can be further fractionated, as bysol'vent'extraction or adsorpti'on-toseparate'paraiins 'and aromatics,'prior to 'reprocessingthe'parains for octane upgrading. `If the'Q, fraction is vvsegregated, it can be processed for benzene recovery. Where this'islundes'irable, it-may'be advantageous to '-segreg'ateatoluene cut (200 F. to the reformate vcut-point) for .toluene extraction and-dehydrogenate'the C5- (200 F.-) "fraction to produce a light oleinic gasoline blending stock. The dehydrogenation can "be Ysuitably Vandeconomically accomplished by rerunning in -a catalytic 'cra`ckin`g'unit, v particularly where facilities Vareiprovidedv for 'splitting 'catalytic gasoline into light and heavy fractions. .'If desired "the light .fraction can 'be 'thermally'refor'med Also, lthe light fraction, or apportionthereofjrray 'befrecycled'via connection. to reformingz'o'n'e .18. "'Lig'ht components of virginanaphtha which 'are 'not suitable'for'cl'larging to reforming Zone 18 c'anjbe "combined 'a's by'line d40 withlthe'light reformate for processing under 'conditions more selective for upgrading 'liglt hydrocarbons. vides "a highly'ilexible process for .upgrading the gasoline pool while providing anreconomical source ofheavy high octane `Qmm'p'mients for premium gasoline of 100+ oc-. tan'e'qulity.

Thus, the yinvention .pro-` Operation according to the invention will be more specifcally illustrated by means of the following example in which the feed stock comprises a 200 to 436 F. heavy naphtha of 51.4 API gravity and 0.024 weight percent sulfur content. Typically it contains 14 percent aromatics, 52 percent naphthenes and 34 percent paraflins (all by volume), and has an octane number of 46.7 F1. The stock is treated in a fixed bed reforming system in the presence of a catalyst containing 0.6 weight percent platinum on an alumina base and in theA presence of hydrogen recycle gas supplied at a rate of 5000 s.c.f./bbl. The reactor inlet temperature is 930 F. and the average pressure is 340 p.s.i.g. The space velocity is about 1.5 weight of feed per hour per weight of catalyst.

The separation conditions in high pressure separator Z are 105 F. and 235 p.s.i.g. Stabilizer 26 is operated with a reflux ratio of 3.5 (hot), with an overhead temperature of 142 F., and a pressure of 140 p.s.i.g. The reboiler temperature is 405 F. at 150 p.s.i.g. The C5 to 400 F. reformate charged to splitter tower 30 as an F-l number of 98.2. A comparison of the `distillation data on the feed to the reforming zone and the C54- reformate charged to the splitter tower is shown in Table I.

TABLE I ASTM Distillation, F., Vol. Percent Distilled Reformate (Topped to 400 F.)

The splitter tower contains about 40 theoretical trays and is operated at 45 p.s.i.g. (tower top) and a reflux ratio of 0.85` r./d. (hot). The operating conditions in rerun tower 34 are 355 F. overhead (atmospheric pressure) and 495 F. bottoms.

With the reformate of 98 F-l octane, the toluene fraction advantageously is included in the heavy reformate fraction separated in the splitter tower. Under these conditions, the overhead temperature is about 260 F. and the bottoms temperature is about 425 F. The yield of heavy reformate is vapproximately 70 volume percent. By increasing the overhead temperature to about 285 to 290 `F., and with a bottoms temperature 445 F., most of the toluene fraction is taken overhead. A comparison of typical yield and octane data for the two operations follows:

The-octanes were 76.6 and 82.8 F-l, and the ASTM distillation ranges were 104 to 220 F. and 105 to 247 F., respectively for the light fractions.

` Hence, high yields of very high octane number reformate, above 100 F-l clear, can be obtained by the process of the invention without requiring excessive severity in the reforming zone. The light components rejected are replaced with components of higher octane number from the refinery pool, c g. light catalytic gasoline, polymer gasoline or light alkylate. The rejected light components may be blended to regular gasoline, or may be reprocessed selectively to higher octane level. Savings with tion of 100 octane gasoline by operating at about the.

93 octane level rather than at the 100 level. Also, there is a marked fall-olf in yield as reforming severity is increased. For example, in reforming the naphtha described in the above example, the loss in C54- yield in going from the F-1 level to the 90 F-l level is only` about 5%, but the yield loss is doubled in going from to 100 octane.

The investment and operating costs for installing the invention are moderate, and in some cases can be reduced to very low values by integration with existing or conventionally employed fractionating facilities such as prefractionators or wet gas absorption towers and the like. Nevertheless, I have found that there is a breakpoint in the advantages obtainable with the invention as the se- Verity in the reforming step exceeds that producing about 93 to 95 reformates as for the production of 100 octane clear reformate. As reforming severity increases, elimination of non-aromatic components is eifected, increas ing octane. In relation to yield, or barreloctanes, however, the resulting benefit is increasingly counterbalanced by non-selective production of light components, particularly Css and Ces, representing only marginal gain as straight-through severities are increased above about 9,3..

This seems to correlate satisfactorily, in the contemplation of the invention, with the decline in catalyst life, so that as octanes spiral higher and demand higher overall severity, the advantages alforded by the invention increase.

The actual severity limit for feasibility in any particular case is related to the nature of the feed stock as well as the cut-point in the splitting operation. The more highly paraiiinic naphthas such as certain Middle East naphthas may require more severe conditions to reach the 90 to 93 level than are required `with more naphthenic naphthas such as Mid-Continent naphtha. Lighter boiling naphthas suifer greater yield losses for the same octane improvement over the 90 to 93 level than heavier naphthas, i.e. CB-lnaphthas.

As reforming severity is increased to obtain higher than 95 F-l reformates, there appears to be selective conversion of high boiling low octane materials to high octane aromatics boiling in the heavy range. The increase in octane of the heavy fraction is almost equal to the increase in the octane of the total reformate, provided the cutpoint for the splitting is properly correlated. Thus, as the octane of the total reformate is increased from the 96 level to the 100 F-l level, the C7+ fraction increases in octane number from about 100 to 103, and the Cs-I- fraction increases to about F-l octane. This is obtained at a level Where octane improvement is most diflicult. Moreover, there is a substantial increase in the volume of C8 aromatics relative to other aromatics as the octane of the total reformate is increased from the 93 to 100 F-l level. On the contrary, the octane of the C5 to 220 F. fraction changes very little with total reformate octane. For example, octanel is increased from 73.6 to only 76.6 F-l when the octane of the total reformate is increased from 93 F-l to 100 F-l. There is comparatively greater improvement in C5 to 270 F. octane, from 75.1 to 83.1, because of increased production of toluene, but the level is still low.

Test data comparing the effect of severity on a typical naphtha charge boiling in the range of 222 to 424 P. and having an F-l octaneof 45 follow: t

TABLE II Properties of reformates TBP-IBI IBP 140 190 205 225v 239 254 302 398+ des TBP-FE1' 140 190 `205 225 239 254 302 39s octane severity 92.0 F-1 V01.Per`centofout s 8.9 4.2 4.0 9.4 3.0 25.1 30.5 5.2 1.7 Percent Aromatics 13.9 2.1 20.8 01.7 9.5 62.6 78.0 93.9

Octane Severity 96.6 F-l Vo1.1 ercentef0uts4 8.0 3.0 2.8 10.9 10 24.7 27.0 5.8 8.4 Percent Aromatics 20.4 2.7 13.8 74.8 20 3 74.9 87.8 93.1

' octane seeerity 99.3 F-1 Vo1.PercentofCut 9.3 11.0 42.13 2.1 9.6 0.8 25.8 27.0 5.2 6.4 Percent Aromatics 22.4 9.2 22.9 78.7 38.9 84.4 95.2 96.3

The cutpoint also depends upon the boiling range of the feed. The cost of obtaining octane appreciation by Vreforming C7 to C8 components to 100 F-l octane is very high compared to the cost of obtaining octanes by reforming to 92 F-l and separating the Cq-lfraction. The increased severity appears to increase hydrocracking to an extent thatthe octane gain is obtained at the expense of excessive loss of hydrocarbons to the lighter than gasoline range. By comparison, reforming heavy naphthasv to 100 F-l ishmuch moreattractive. Consequently, it is advantageous to prefractionate the charge naphtharto eliminate the C7 fraction from the feed, and for maximum advantage, split the reformate correspondingly. However, at the higher severity. levels, the increase in toluene concentration justifies its inclusion in the heavy reformate.

The composition of the feed, as noted above, also may beV a factor in determiningthe severity level at which reformate splitting becomes attractive. Thus, in running a highly paraiiinic naphtha such as a'Kuwait naphtha, the yield fall-off with increasing reformate octane is such as to impose a limit of about 92 to 93 F-l clear. With stocks containing higher percentages of naphthenes such as Mid-Continent naphthas, the operation is most attractive as reformate octane exceeds 95 F-l. Also, with mixed feeds such as blends containing thermally cracked or catalytically cracked heavy naphthas, it may be desirable to limit the severity to about the 92 to 95 F-l range.

The cutpoint in splitting'also should b e correlated with the properties of light stocks available for premium gasoline blending. Thus, to obtain the` maximum benefit of theinvention, it is advantageous to cut at -as low a tem perature, providingl about 80% aromatics or more in theheavy reformate, as will permit replacement of the light components separated with higher octane light components from thegasoline pool. A suitable example of the -latter is a light fraction separated from catalytic gasoline which'l includes all of the amylenes and enough ofthe Cs and Cqs to provide afull range gasoline, after blendingwith Athe heavy reformate and added butanes to octane specification, without exceeding the maximum seasonal Reid vapor pressure. The light catalytic gasoline willhave an F-l octane rating approximately 3 to 5 numbers higher than the total catalytic gasoline since the amylenerfraction, usually comprising upto about volume percent of the total catalytic gasoline, has an Fl octane exceeding 100. Thus, for example, a 25% by volume cut on total catalytic gasoline of 93.3 F-l octane has an octane of 97.6 F-l. Other high .octane light components of suitable volatility for blending withr the heavy reformate include light alkylate, particularly technical ethylene alkylate produced by alkylation of aluminumchloride isomerization of C5-C parafns, light olen fractions such as di-isobutylene, and the like. Several illustrative gasoline blends followc.

The invention thus provides aY feasible and relatively economical means for producing Vpremium Vgasolines of 100 F-l clear octane and higher. These ratings, of course, can be `improved by the addition of tetraethyl leadto an extent determined by the response of the particular blend to octane appreciation by this means. In blending, advantages in yield of high octane gasoline can. be obtained at the higher reforming severities in conjunction with splitting as indicated by Athe following data indicat.v

ing the yield in barrels of 100 F-l octane gasoline per 100 barrels of feed obtained by blending heavy reformate with 93.3 F-l catalytic gasoline.

' Heavy Reformatc Yield, Total Reformate F-l bbls./100

' bbls. feed Percent F-l 99.7; 50.5 102.5` es 101.5 l47 Y104.9A 81 Expressed somewhat differently, the availability of high octane blending stock from reformate for super octane fuels decreases rapidly as the reforming severity is re-V duced below the 95 to 100 F-l level The yield of 9.8-

octane clear blending stock from 95-0ctane reformate is 80%, but if the totalreformate splitis only 90-octane, the availability of 98octane blending stock drops t0. 57%. The advantage in selectivity of platinum containking reforming catalysts isrindicated by comparison of these data with the yield of 98-,octane blending stock from 90-octane reformate from fluid molybdenum oxide-pV alumina reforming which is only 50%. lFrom 85V-octa'ne platinumA reformate, the yield ise37 from corresponding moly. reformate, the yield is almost zero.. If 98-octane blending stock is produced by straight reforming molybethylene with isobutanein the presence of. aluminum chlo.

dena type catalyst to 9S-octane, the yield is 65% on the.

feed. If the 98-octane stock is produced by fractionating -octane. reformate, the yield is 55% on feed while a distillate `fraction of kabout 20% on feed, rating about' .182 to 84 octane number clear, is produced in addition for blending to regular gasoline or for selective processing. Since the light reformate characteristically shows good lead response, its use in upgrading regular leaded gasoline is valuable or it can be blended to 91-96 aviation gasoline. In effect, therefore, the yield of liquid product has been increased by a minimum of 10% through an advantageous exchange of the lower octane light components of the reformate with higher octane light hydrocarbons available in the pool. At the same time, reforming severity has been reduced with resulting catalyst savings. If a 100+, rather than 98, octane stock is produced the resultant advantages are increased significantly.

In the operation of the invention, high yields of high octane stocks are produced at maximum throughput in contrast to conventional reforming or proposed methods of recycle reforming. Compared to the latter, conversion of both high and low boiling components is more p selective, for the severity of recycle treatment on unconverted paraflins results predominantly in hydrocracking with resulting losses from the gasoline range and in an undesirable production of light gasoline components which inherently degrade the octane level of the high octane pool so as to limit the volume of 100+ gasoline which can be produced. Selective handling of the light fractions to produce benzene, toluene and light aromatics, or isoparaflins by isomerization, is facilitated. Thus, the over-all octane of the refinery pool can be raised to the optimum extent (or chemicals production increased) while maximizing the production of super octane premium fuel.

I claim:

1. In the production of high octane premium gasoline and a second gasoline of lower octane number from gasoline forming and gasoline blending components of a common refinery gasoline pool, a process for producing 100 octane and higher octane full boiling range premium gasoline from low octane naphthas, which process comprises charging a heavy naphtha charge boiling within the range of C7 hydrocarbons to about a 400 F. end point to a catalytic reforming zone containing a platinumalumina reforming catalyst, subjecting said charge in said reforming zone to a combination of conditions, including a temperature in the range of about 875 to 1000 F., a pressure in the range of about 100 to 500 p.s.i.g., a hydrogen recycle gas ratio in the range of about 2000 to 10,000 cubic feet of gas per barrel of charge and a space velocity in the range of about 0.1 to 5.0 weight ratio charge per hour to weight of catalyst in said reforming zone, providing thereby a severity suicient to produce a reformate having a C+ octane number of at least about 93 F-l (clear), charging said reformate to a fractionating zone, splitting said reformate in said fractionating zone at a cut point within the range of between a maximum of about 300 F. and a minimum of about 225 F. according to the relationship wherein said cut point is near said maximum of 300 F. when the C5+ octane number of said reformate is about 93 F-l (clear) and said cut point is decreased within said range, thereby increasing the yield of the hereinafter designated heavy fraction above a minimum of at least about 40 volume percent of the total C5+ reformate, towards said minimum cut point of about 225 F. as the severity ot reforming is increased to provide a reformate having a C5+ octane number of at least about 100 F-l (clear), whereby two fractions are recovered constituting a light fraction boiling below said cut point and a heavy fraction boiling in the range of said cut point to the end point of said reformate, and whereby said heavy fraction comprises at least about 40 volume percent of the total C5+ reformate and contains at least about volume percent aromatics and has an octane number of at least about 100 F-1 (clear), and thereafter blending said heavy fraction with an extraneous light fraction of high blending octane number in proportions suiiicient to produce a full boiling range premium gasoline of at least about 100 F-l octane number.

2. In the production of high octane premium gasoline and a second gasoline of lower octane number from gasoline forming and gasoline blending components of a common refinery gasoline pool, a process for producing from low octane naphthas a full boiling range premium gasoline having an octane number of at least about 100 F-1, which process comprises charging a heavy naphtha charge boiling in the range of C7 hydrocarbons to about a 400 F. end point to a catalytic reforming zone containing a platinum-alumina reforming catalyst, subjecting said charge in said reforming zone to a combination of conditions, including a temperature in the range of about 875 to 1000 F., a pressure in the range of about 100 to 500 p.s.i.g., a hydrogen recycle gas ratio in the range of about 2000 to 10,000 cubic feet of gas per barrel of charge and a space velocity in the range of about 0.1 to 5.0 weight ratio charge per hour to weight of catalyst in said reforming Zone, providing thereby a severity sufficient to produce a reformate having a C5+ octane number of at least about 93 F-l (clear), charging said reformate to a'fractionating Zone, splitting said reformate in said fractionating zone at a cut point within the range of between a minimum of about 225 F. and a maximum of about 300 F., wherein two fractions are recovered constituting a light fraction boiling below said cut point and a heavy fraction boiling in the range of said cut point to the end point of said reformate, and whereby said heavy fraction comprises at least about 40 volume percent of the total C5+ reformate and contains at least about 80 volume percent aromatics and has an octane number of at least about 100 F-l (clear), selecting said cut point depending upon the severity of reforming said charge as evidence by the 05+ octane number of said reformate, wherein said cut point is selected in the upper portion of said temperature range when the C5+ octane number of said reformate is about 93 F-1 (clear) and said cut point is decreased within said temperature range, thereby increasing the yield of said heavy fraction above said minimum of at least about 40 volume percent of the total C5+ reformate, to said minimum cut point of about 225 F. as the C5+ octane number of said reformate is increased above about 93 F-l (clear) towards at least about 100 F-l (clear), and thereafter blending said heavy fraction with an extraneous light fraction of high blending octane number in proportions sufficient to produce a full boiling range premium gasoline having an octane number of at least about 100 F-l.

3. The process of claim 1 wherein said heavy napththa charge boils within the range of C8 hydrocarbons to about a 400 F. end point.

4. The process of claim 1 in which the severity in the reforming zone is sucient to produce a C5+ reformate of at least 95 F-l octane number clear.

5. The process of claim l in which the severity in the reforming zone is sufficient to produce a C5+ reformate of at least F-l octane number clear.

References Cited in the file of this patent UNlTED STATES PATENTS

Claims

1. IN THE PRODUCTION OF HIGH OCTANE PREMINUM GASOLINE AND A SECOND GASOLINE OF LOWER OCTANE NUMBER FROM GASOLINE FORMING AND GASOLINE BLENDING COMPONENTS OF A COMMON REFINERY GASOLINE POOL, A PROCESS FOR PRODUCING 100 OCTANE AND HIGHER OCTANE FULL BOILING RANGE PREMIUM GASOLINE FROM LOW OCTANE NAPHTHAS, WHICH PROCESS COMPRISES CHARGING A HEAVY NAPHTHA CHARGE BOILING WITHIN THE RANGE OF C7 HYDROCARBONS TO ABOUT A 400*F. END POINT TO A CATALYTIC REFORMING ZONE CONTAINING A PLATINUMALUMINA REFORMING CATALYST, SUBJECTISNG SAID CHARGE IN SAID REFORMING ZONE TO A COMBINATION OF CONDITIONS,S INCLUDING A TEMPERATURE IN THE RANGE OF ABOUT 875* TO 1000* F., A PRESSURE IN THE RANGE OF ABOUT 100 TO 500 P.S.I.G., A HYDROGEN RECYCLE GAS RATIO IN THE RANGE OF ABOUT 2000 TO 10,000 CUBIC FEET OF GAS PER BARREL OF CHARGE AND A SPACE VELOCITYS IN THE RANGE OF ABOUT 0.1 TO 5.0 WEIGHT RATIO CHARGE PER HOUR TO WEIGHT OF CATALYST IN SAID REFORMING ZONE, PROVIDING THEREBY A SEVERITY SUFFICIENT TO PRODUCE A REFORMATE HAVING A C5+ OCTANE NUMBER OF AT LEAST ABUT 93 F-1 (CLEAR), CHARGING SAID REFORMATE TO A FRACTIONATING ZONE, SPLITTING SAID REFORMATE IN SAID FRACTIONATING ZONE AT A CUT POINT WITHIN THE RANGE OF BETWEEN A MAXIMUM OF ABOUT 300*F. AND A MINIMUN OF ABOUT 225*F. ACCORDING TO THE RELATIONSHIP WHEREIN SAID CUT POINT IS NEAR SAID MAXIMUM OF 300*F. WHEN THE C5+ OCTANE NUMBER OF SAID REFORMATE IS ABOUT 95F-1 (CLEAR) AND SAID CUT POINT IS DECREASED WITHIN SAID RANGE, THEREBY INCREASING THE YIELD OF THE HEREINAFTER DESIGNATED HEAVY FRACTION ABOVE A MINIMUM OF AT LEAST ABOUT 40 VOLUME PERCENT OF THE TOTAL C5+ REFORMATE, TOWARDS SAID 3 MINIMUM CUT POINT OF ABOUT 225*F. AS THE SEVERITY OF REFORMING IS INCREASED TO PROVIDE A REFORMATE HAVING A C5+ OCTANE NUMBER OF AT LEAST ABOUT 100F-1 (CLEAR), WHEREBY TWO FRACTIONS ARE RECOVERED CONSTITUTING A LIGHT FRACTION BOILING BELOW SAID CUT POINT AND A HEAVY FRACTION BOILING IN THE RANGE OF SAID CUT POINT TO THE END POINT OF SAID REFORMATE, AND WHEREBY SAID HEAVY FRACTION COMPRISES AT LEAST ABOUT 40 VOLUME PERCENT OF THE TOTAL C5+ REFORMATE AND CONTAINS AT LEAST ABOUT 80 VOLUME PERCENT AROMATICS AND HAS AN OCTANE NUMBER OF AT LEAST ABOUT 100F-1 (CLEAR), AND THEREAFTER BLENDING SASID HEAVY FRACTION WITH AN EXTRANEOUS LIGHT FRACTION OF HIGH BLENDING OCTANE NUMBER IN PROPORTIONS SUFFICIENT TO PRODUCE A FULL BOILING RANGE PREMINUM GASOLINE OF AT LEAST ABOUT 100 F-1 OCTANE NUMBER.