US2921026A - Fractionation process - Google Patents

Description

Jan. 12, 1960 R. N. FLEcK ETAL 2,921,025

FRACTIONATION PROCESS Filed July 13, 1956 l 3 Sheets-Sheet 2 Jan. 12, 1960 R. N. FLECK ET AL 2,921,026

FRACTIONATION PRocEss 3 Sheets-Sheet 3 Filed July l5, 1956 til/514414151419# 'United vStates Patenti() FRAcnoNA'rroN rRocEss Application July 13, 1956, Serial No. 597,742 7 claims.y (ci. 20s- 310) This invention relates to the fractionation of Huid mixtures, either gaseous or liquid, such as mixtures of hydrocarbons. 'Ihe invention relates particularly to an improved process for the fractionation of complex hydrocarbon mixtures in lthe gasoline boiling range to produce a high antiknock rating gasoline through the selective removal of low antiknock rating components.

Gasoline improvement to raise the antiknock rating is required to provide an adequate fuel for modern high compression internal combustion reciprocatingpiston engines. Gasoline in general comprises many individual components, including hydrocarbons having between about 4 and about 12 carbon atoms per molecule. In this range are found many straight and branched chain parain hydrocarbons, straight and branched chain olefin hydrocarbons in cracked gasolines, as well as many naphthene and aromatic hydrocarbons. The complexity of gasoline stocks is appreciated by the fact that there are some 660 possible parain isomers and over 3800 olefin hydrocarbon isomers in this range of from 4 to 12 carbon atoms per molecule. In addition there are a great many naphthene and aromatic hydrocarbons. Each component has its own tendency to knock in internal combustion engines and its molecular character strongly governs this tendency. In general the straight chain or normal para'lin hydrocarbons have the greatest tendency to knock and therefore have the lowest antiknock rating. The naphthene hydrocarbons having slightly higher antiknock rating, followed by the normal oleins, the iso-olefins, the iso-parains, and the aromatic hydrocarbons have the highest antiknock rating. p

The gasoline is a mixture therefore that has an antiknock rating which is a function of its composition. Straight-run gasoline generally has a low rating due to its relatively high normal parain content and relatively low iso-paraflin and aromatic content. Cracked gasolines on the other hand have higher antiknock ratings due to the presence of normal and iso-olefin hydrocarbons. Distillation alone is not especially effective in removing only the low antiknock rating components since the rating is essentially determined by molecular structure rather than boiling point.

'In the past, elective antiknock rating increase has been accomplished by the addition of materials to the gasoline such as antiknock agents like tetraethyl lead and hydrocarbon components of very high knock ratings such as high branched chain hydrocarbons like the alkylate of iso-butane and iso-butylene, or aromatic hydrocarbons, and the like. Antiknock rating increase is also obtainable by high temperature treatment such as thermal or catalytic cracking, dehydroaromatization or reforming, and the like. Such treatment effectively converts some of the low antiknock rating components into components having higher knock ratings.4

The addition of antiknock agents or of hydrocarbons of unusually 'high antiknock rating is expensive sincev usually they must be purchased or synthesized for`such use. Even the high temperature treatments to raise the knock rating is only partly elective since the product from these processes still contains appreciable quantities of low antiknock rating materials. For example, a desulfurized naphtha having a knock rating of 51 (F-l clear) is reformed to effect dehydrogenation of normal parains and cyclization to form aromatics over a platinum catalyst to produce a product having a knock rating of 96 (F-l clear). Although this knock rating is satisfactory in some cases, the product still contains about 13% by volume of normal parains whose antiknock rat ings were of the order of 20 or less. y v

The present invention is therefore directed to an improved process for increasing the antiknock rating of straight-run or cracked gasolines without high temperature treatment, and which is also applicable to the improvement of fairly high antiknock rating gasolines such as those producedin high temperature thermal or catalytic treatments. Specifically the process comprises the separation of low antiknock components from these materials so as to leave only the high antiknock rating materials. The process involves the selective adsorption of normal parathns or normal olelns from the mixture of hydrocarbons on the basis of their straight chain molecular shape. The process however does not require the usual high temperature desorption of the rich adsorbent which is conventionally used in all other adsorptive fractionation processes. Thus the adsorbent saturated with low antiknock rating components need not be heated, or stripped with a stripping gas, or both, to render it reusable in the process. Rather, theadsorbent is subjected to a novel and simple treatment in'which an active exchange or displacement of the low antiknock rate materials is effected by means of a selected recycle stream of adsorbable hydrocarbons.` The processthus produces an unadsorbed or raiiinate stream of gasoline containing the recycle component which can be separated from the nonadsorbed material by ordinary distillation, and a desorbed or extract'gasoline stream including adsorbed low antiknock rating materials together with the recycle component, which is also readily separable therefrom by distillation.

dt is therefore a'primary object of this invention to provide an improved fractionation process using a specific adsorbent which is active in adsorbing materials on the basis of their molecular size or shape.

It is a further object of `this invention to provide an improved selective adsorption and distillation process for the fractionation of complex mixtures and which is characterized by the absence of the usual high temperature adsorbent-desorption treatment. p

It is a specific object of this invention to provide a fractionation process for the separation of complex mixtures using aV specific adsorbent, which selectively adsorbs components having linearor straight chain molecules, and including a desorption step which involves an exchange displacement with a recycle stream containing a substantial proportion of components having linear or straight chain molecules and which are readily separable, by virtue ofa substantially different boiling point or range, from the straight chain materials adsorbed from the complex mixture.

It is a more specific object of this invention to provide an improved continuous process for gasoline fractionation to remove low antiknock rating components there' from by alternately contacting a substantially compact bedof solid granular adsorbent with the gasoline fraction to adsorb straight chain oleiins and parains therefrom,`

then contacting the adsorbent with a recycle stream of hydrocarbons readily separable by distillation from the feed stream and consisting of other straight chain olens or paraftins-so as to displace .the components adsorbed: from the gasoline fraction and pre-saturate the adsorbent with straight chain components from the recycle stream,

and nallydistilling both the unadsorbed raffinate fraction and the desorbed or displaced extract fraction from vthe `adsorbent so as to lseparate the straight chain recycle materials therefrom leaving an unadsorbed gasoline fraction of high antiknocky rating and an adsorbed gasoline fraction of very low antiknock rating.

Other objects of the present invention will become apparent to those skilled in the art as the description and illustration thereof proceed.

Briefly the present invention comprises an improved fractionation process involving a combination of selective adsorption on a granular solid adsorbent anddistillation of the fluids being treated so as to effect an improved separation of complex mixtures of components on the basis of their molecular species. The present invention will be described in connection with fractionation of a mixture or" a complex mixture of hydrocarbons of the gasoline boiling range. Such `mixtures contain many different hydrocarbon components having from about 4 to about 12 carbon atoms per molecule and which components are of diiferent molecular species.. The feed mixture, herein considered to be gasoline for purposes of example, is first passed through contact with a compact bed of solid granular adsorbent to adsorb more readily adsorbable constituents leaving the less readily adsorbable constituents as an unadsorbed raffinate phase. Instead of heating the resultant rich adsorbent and contacting it with a stripping fluid as in conventional adsorptive fractionation processes, in the present invention this rich adsorbent containing the more readily adsorbable constituents of the feed is contacted with a recycle stream ofA hydrocarbons containing adsorbable components and selected to have a boiling point or boiling range sufficiently different from that of both the adsorbed and unadsorbed phases of the feed gasoline that it may readily be distilled from the unadsorbed as well as from the adsorbed fractions of the feed. An active exchange displacement occurs in which the adsorbable recycle stream is adsorbed in exchange with and displacing the feed components previously adsorbed. This removal of the more readily adsorbable constituents in the adsorbed phase from the adsorbent by'contacting the rich adsorbent with a recycled exchange Vdisplacement stream produces an extract stream comprising a mixture of the desorbed more readily adsorbable constituents of the feedstock plus the constituents of the recycle stream andk the adsorbent is left saturated with recycle stream components. The extract stream is then distilled to recover the desorbed fraction from the recycle components. The adsorbent is then contacted with further quantities of the feedstock in which the more readily adsorbable components exchange with and displace the recycle components present on theadsorbent and produce a raflinate stream containing the unadsorbed components of the feed gasoline plus the desorbed recycle components. This eluent rainate stream is also distilled Vto separate the unadsorbed fraction from the recycle components.

The recycle stream employed in the process of this invention for exchange displacement of the adsorbed feedstock materials from the adsorbent may be a mixture of adsorbable components, or a single pure adsorbable component,V naturally occurring in the feedstock. TheV recirculavted material however must have a different boiling point or boiling range from the boiling point or boiling range of the feedstock so that it is readily and economically separable from both the adsorbed phase components and the unadsorbed phase components of the feedstock. In the process the raffinate stream of unadsorbedy materials from the adsorption zone as well as the extract stream of displaced'adsorbed materials, both con tain the recycledidisplacementexchange materials. Each of these streams is separately distilled, the recycle cornponents are recirculated in the process to effect exchange displacement from the. rich adsorbent, and theunad:

sorbed gasoline hydrocarbons and the adsorbed gasoline hydrocarbons are produced as separate products of the process. The character and antiknock rating of the hydrocarbons in these two product streams are governed by the nature of the selective adsorbent used in the process. With the adsorbent more particularly described below, only normal or straight chain paraflins, and normal olens if present, are adsorbable. Therefore the extract phase displaced from the adsorbent contains the relatively low anti-knock rating materials. The unadsorbed rafnate phase contains the branched chain and naphthene and aromatic hydrocarbons whose molecular size renders them unadsorbable.

The adsorbent employed in the process of this invention is a solid granular material having a mesh size range between about 2 and 100 mesh and preferably between about 4 and about 30 mesh. It is used in the form of a dense compact bed of material through which the feed and displacement and exchange recycle streams pass, either in the vapor phase or in the liquid phase. The process may employ the adsorbent in the form of a single static bed of material in which case the process is only semicontinuous. Preferably a plurality of two or more static beds of adsorbent are employed with appropriate remotely operable valving so that the feed stream is passed through one or more of the adsorbers in a set while the exchange displacement stream passes through one or more of the other adsorbers in the set. In this case the feed and product flows are continuous, in either the vapor or liquid phase, and either upor down through the adsorbent. When the granular adsorbent is suinciently rugged physically then the moving solids bed modification may be employed in which flow of feed is maintained continuously through an adsorption zone, the low of displacement exchange fluid is maintained continuously through a desorption zone, and the granular adsorbent is recirculated successively through these two zones. With the smaller sized mesh ranges of adsorbent, the material may be iluidized in and by the iluid streams contacting it, although the compact bed modifications are preferred since a greater number of theoretical and actual contact stages are more readily obtained in smaller and simpler equipment.y

The adsorbents employed in practicing the present invention are the natural or synthetic zeolitic crystalline partially dehydrated metallo alumino silicates. The composition of one typical synthetic zeolite having a pore size of about 4 A. is [Na2O'Al2O3- (Si02) 2]. It may be prepared by heating stoichiometric quantities of alumina and silica and,v excess caustic under pressure. The excess is washedk out and the desired metal ion may then be introduced by ion exchange. Part of the sodium in this material can be ion exchanged with` concentrated salt solutions at superatmospheric pressure and temperatures of 300 C. to introduce other-metal-ions-such as calcium to produce having a pore sizeof about 5 A. Certain naturally occurring minerals, such as chabazite, analcite, gmelinite, and the like, can be heated to dehydrate the molecule and obtain an activatedY zeolitic adsorbent similar in adsorption properties to the manufactured materials. These naturaland synthetic materials are all zeolites and their sodium and calcium derivatives areA very stable adsorbents which apparently have pores available for adsorption which are quite uniform in size.k Other derivatives have different sized pores The molecules which are the more readilyadsorbable and for which the adsorbent exertsV preferential adsorptive forces are those having straight chainemolecules whose minimum dimensions are equal to or slightly less than these pore dimensions. Thus the normal parains and normal olenswith cross chain dimensions of under 5 A..are.ver,y strongly and very readily adsorbedby thesematerials. However the branched chain parafiins or olefins, and the naphthene and aromatic hydrocarbons, all having molecular dimensions in the shortest direction in excess of 5 A. are substantially nonadsorbable. These adsorbents are thus selective for normal paraliins, and normal olefins if presentyand will not adsorb any appreciable quantity of other hydrocarbons. Other derivatives of these particular inorganic adsorbent materials'have uniformly sized pores as high as from 12 to 13 A. and these will adsorb molecules having a dimension less than about 12 A. and will exclude a material Whose minimum molecular dimension is above l2 A.

The synthetic crystalline partially dehydrated metallo alumino silicate Zeolitic adsorbents are presently available items of commerce marketed by Linde Air Products Company, 30 E42nd Street, New York 17, New York, under the name lof Molecular Sieves 4A, 5A, 13X, etc.

The present metallo alumino silicates adsorb polar molecules to a certainement. In gasoline treating this interferes with the fractionation of gasoline hydrocarbons as a function of molecular shape. Accordingly it is contemplated in this invention to contact the feed stream first with a material which exhibits very strong adsorptive forces for these polar materials and remove them from the stream to be treated. This pre-adsorption or pre-treating of the feed may be accomplished by contacting the feed stream with an inorganic halide such as copper chloride, calcium chloride, magnesium chloride, and the like. In this way large and highly polar materials such as ethers, thioethers, water, alcohols, mercaptans, and amines are readily removed from the feed. Also removable in thisy way are the highly polar nitrogen and sulfur compounds which commonly occur in small amounts in gasolines. These specifically include such materials as thiophene and the alkylated thiophenes, pyridine and alkylated pyridines. Thus this pre-treatment removes these polar materials and prevents them from interfering with the subsequent fractionation in which the feed is separated into streams containing components of a specific molecular size or structure. Y

Although the pre-adsorption step prevents rapid deactivation of the main adsorbent beds, some deactivation may' eventually occur. It is within the contemplation of this invention to regenerate the adsorbent by high temperature stripping with steam etc. to desorb impurities, with hot ue gas, to burn off the impurities as in catalyst regeneration, or both.

The process of this invention and the modifications thereof, as well as several forms of apparatus employed to carry out the process, will be more readily understood by reference to the accompanying drawings, each of which is described in connection with its application to the fractionation of gasoline as a specific example and in which:

Figure 1 shows a schematic flow diagram of a simple modification of the process of this invention adapted to contact continuously a feed gasoline stream with two fixed beds of adsorbent and utilizes either a liquid or vapor phase feed contact with a relatively low boiling displacement exchange recycle stream,

Figure 2 shows a modification of the process of Figure l adapted to the use of a recirculatng or moving adsorbent stream, 1

Figure 3 shows a third modification of the present process in which the recirculated displacement exchange stream is of any intermediate boiling range or boiling .point With respect to the unadsorbed stream and which is therefore heart cut from the unadsorbed or rainate portion of the feed,

Figure -4 shows another modification of this invention in which the displacement exchange stream is of an intermediate boiling point or boiling range with respect to both the adsorbed and unadsorbed streams and is thus heart cut from both of these streams for recycle,

Figure 5 shows still another modification of this invention which is applied to the successive contact ofthe feedstock in two or more adsorbent stages, for example to adsorb normal olefins from the feed in the first stage to recover them for blending into a high knock rating gaso.

line and adsorbs normal paraffins in the second stage to reject them as a low antiknock rating product stream, and Figure 6 shows an alternate control valve connection which causes the feed and the exchange-displacement streams to ow in opposite directions through the adsorbent beds.

Example I Referring now more particularly to Figure l, the simplest modification of the present invention is shown in the form of a schematic flow diagram. Two adsorbers 10 and 12 packed with a compact mass of granular metallo alumino silicates having pore openings approximating 5 A. are shown. Adsorbers 10 and 12 are used in alternation with each other and the appropriate flow changes are effected by means of four-way control valves 14 and 16 actuated by cycle timer 18. In the position shown adsorber 10 is being desorbed while adsorber 12 is contacting fresh feed. Vessel 20 is provided as a pre-adsorber or guard chamber to remove highly polar materials from the feedstock.

A depentanized gasoline is passed in the vapor phase through line 22 at a rate controlled by valve 24 through pre-adsorber 20 wherein polar materials are removed from the feed. This pre-treated feed continues through line 26 through the interconnected ports in valve 14 and then through line 28 through adsorber 12. Herein an active displacement exchange` takes place between the normal parafiins in the gasoline stream and normal butane which is employed in this modification for the recycle stream and which saturates the adsorbent prior to contact with the feed.l The normal butane recycle stream in this invention is substantially lower in boiling point than any component of the feed. The normal butane pre-saturating the adsorbent is exchanged with the normal parafiins of the feed stream so that the adsorbent in adsorber 12 finally becomes substantially saturated with these heavier normal parafiins. The effluent or raffinate stream from adsorber 12, containing the non-adsorbable gasoline components together with the exchanged normal butane, passes on through line 30 through the interconnected ports in valve 16 and through line 32 into raffinate fractionator 34. This distillation column is provided with an overhead condenser 36 and reboiler 38. The raffinate is distilled separating the normal butane from the normal paraffin-free gasoline. The normal butane recovered from the gasoline is passedin the vapor phase through line 40 at a rate controlled by valve 42 into displacement exchange recycle line 44. The treated gasoline is removed from the bottom of the column and is passed to further processing or storage facilities not shown through line 46 at a rate controlled by valve 48, Because of the elimination of normal parafiins from this gasoline stream, the antiknock rating is readily increased by 7 to l0 points.

The normal butane exchange displacement recycle stream ows on through line 44, through the interconnected ports of four-way control valve 14, and then through line 50l to adsorber 10 which is now in the desorption part of the cycle. The normal butane passes in the vapor phase through the adsorbent saturated with normal parains from the previous feed contacting step. A reverse displacement exchange takes place whereby the normal parains from the gasoline are displaced from the adsorbent and it adsorbs normal butane instead. Flowing from the top of adsorber 10 through line 52 is a desorbed extract stream comprising a rich mixture of normal paratiins desorbed from the adsorbent and normal butane used in their desorption. This stream passes through the interconnected ports of valve 16 on through line 54 into extract distillation column 56, provided with overhead condenser 58 and reboiler 60. The normal butane present in the extract stream is distilled from the normal paraflins removed from the gasoline feed. The

normal butane ows through line 60 in the vapor phase at a rate controlled by valve 62 and is returned to and through displacement exchange recycle manifold 44. The very low antiknock extract, comprising a concentrated mixture of normal paraflins, is removed from the system through line 64 at a rate controlled by valve 66. Thus the high antiknock fraction is produced from the process through line 46 containing substantially no normal para'ins, while the low antiknock gasoline fraction is produced through line 64 containing substantially all of the normal parans of the feed.

In the event that the feed stream contains normal butane, the net product of normal butane from the system over and above that required from the displacement exchange recycle may be removed through column 34 via line 68 at a rate controlled by valve 70, or it may be re moved through column 56 through line 72 at a rate controlled by valve 7 4.

In the foregoing example it should be noted that the displacement exchange recycle stream consisted of normal butane vapor which is lighter or has a lower boiling point than any of the components present in the feed stream. It should also be noted that both the adsorption and desorption steps of the process are conducted in the vapor phase.

Example Il In the present invention it has been found that olen hydrocarbons of the straight chain type are more strongly adsorbed than are normal paraffins having the same number of carbon atoms as the olefin. It has been determined that the metallo alumino silicate adsorbents appear to have about an equal preference for a straight chain olefin and for a straight chain parain having three more carbon atoms per molecule than the olefin. This discovery is utilized according to the present invention by modication of the process described in connection with Figure 1 so as to employ low molecular weight olefin as the exchange displacement recycle and which has about three carbon atoms per molecule less than the mol average of the more readily adsorbable parafins. In this case gaseous ethylene is used as the olefin and is found to displace very effectively from they adsorbent the normal paraflins adsorbed from the gasoline. In Figure 1 the feed stream llows as before through adsorber 12 into fractionator 34. In adsorber 12 the gasoline normal paraflins are adsorbed on the adsorbent displacing ethylene therefrom, and in column 34 the gaseous ethylene is stripped from the Vnonadsorbed rainate gasoline and recireulated through line 44. The gaseous ethylene flows from line 44 through adsorber 10 into extract still 56. The gaseous ethylene in adsorber 10 exchanges with the gasoline normal paraffins on the adsorbent and extract still 56 strips the gaseous ethylene for recirculation from these gasoline normal paraflins. It is found that the olenfin in this case is somewhat more effective in displacing gasoline normal parafns from the adsorbent than was the normal butene.

Example III The process shown in Figure l is also readily applicable to the treatment of relatively narrow boiling range feed streams using as a displacement exchange recycle stream a component which has an intermediate separation factor between the two fractions which it is desired to separate from the feed. For example, in the process shown in Figure l a C6 cut of cracked (olenic) gasoline is passed in the vapor phase through adsorber 12 in contact with the adsorbent which is already saturated with normal octane as the displacement exchange component. The normal octane is of an intermediate adsorbability between the normal hexene for which the adsorbent exerts strong adsorptive forces, and normal hexane for which the adsorbent exhibits weaker adsorptive forces. The rainate from adsorber 12 consists of the normal octane recycle components and the nonadsorbed raiinate cempauents, :in this .case comprising normal hexane. In raffinate still 34 the normal hexane is produced from the top of the still through line 68 at a rate controlled by valve 70 while the recycle component normal octane accumulates at the bottom of column 34 and is recirculated in the vapor phase through line 76 controlled by valve 78 wherefrom it passes through line 80 into recycle manifold 44. The normal octane flows through adsorber 10 which is in the desorption part of the cycle and here it exchanges with the normal hexene to produce an extract stream through line 52 comprising normal octane and normal hexene. This extract ows t0 fractionator 56 in which the normal hexene is produced as an overhead product through line 72. It has a. relatively high knock rating and may, if desired, be combined with other high antiknock rating components to produce a quality gasoline. The normal octane recycle component is removed from the bottom of still 56 through line 79 and is controlled by valve 82 and passes through line 84 back into recycle manifold 44 for recirculation in the system.

In this modification it is noted that the displacement exchange component is of intermediate adsorbability between normal hexene and normal hexane but it is of a higher boiling point so that it is produced for recycle as a bottoms product in both the extract and ratiinate stills.

Example IV The process shown in Figure l was also applied to the vapor phase removal of normal paraflins from a depentanized light gasoline which had been reformed over a platinum catalyst. Normal pentane was employed as the displacement exchange recycle stream. The feed had a knock rating (motor method, clear) of 66.8. Using a bed of metallo alumino silicate adsorbent having 5 A. pores the raffinate or unadsorbed treated gasoline had a knock rating of 78.4 while the adsorbed normal paraffin or extract stream had a knock rating 17.2. The leaded knock rating of the treated gasoline raffinate (research method-H ml. TEL) was 97.9. The normal parain recycle adequately displaced and exchanged with the gasoline normal parains from the adsorbent so that continued treatment of the feed gasoline was permitted.

Example V The treating of reformed depentanized gasoline, discussed immediately above, was continued through 30 cycles, contacting the feed gasoline to adsorb normal paraflins in alternation with a displacement exchange step with normal pentane vapors to regenerate. Over this period no decrease in the quantity adsorbed or the ability of the adsorbent to remove normal paraflins from the feedstock was noted. In one run an F-2 clear octane rating of the adsorbed material of as low as 9.8 was noted and simultaneously the raffinate knock rating (F-l clear) was 83.7. The leaded knock ratings of the unadsorbed phase in each of the 30 cycles all fell between 97.5 and 98.3. Example VI The process shown in Figure l was applied to the treating of light alkylate having a clear research octane rating of 96.4. This material contains highly branched hydrocarbons and substantially no straight chain hydrocarbons. The volume of the feed which was adsorbed on the adsorbent was substantially zero at 280 F. and the unadsorbed raffinate product had the same knock rating of 96.4. n

Example VII The process of Figure l was applied to the removal of normal parains from a catalytically hydrocracked gasoline boiling between F. and 402 F. The feed had a research octane rating with 3 ml. TEL of 94.9. At an adsorption temperature of 403 F., approximately 6 volume percent of the feed was adsorbed and the unadsorbed rali'inate gasoline had a research octane rating witl13 ml. TEL of 97.3..

` adsorbed gasoline raffinate had a research octane rating-l-3 ml. TEL of 88.3 average. The knock rating of the feedstock was 76.0.

Example IX In a pair of identical 30 cycle 4tests on platinumreformed light gasoline, the process of Figure 1 was first employed using normal pentane as the exchange displacement recycle stream. In the first case a depentanized platinum reformed gasoline having a research octane rating of 3 ml. TEL of 89.8 was treated to produce an unadsorbed gasoline rainate having an average knock rating of 96.2. This is an average increase of 6.4 octane numbers.

In the second case, ya dehexanized platinum reformed light gasoline, having a research octane rating of 91.0 (with 3 ml. TEL), was treated under identical conditions to produce an unadsorbed gasoline raffinate product having an average knock rating of 97.9 for an average increase of 6.9 octane numbers.

Example X In the process of this invention employing the metallo alumino silicates as adsorbents, it is found that in the liquid phase the adsorbent has a tendency to adsorb the lower molecular weight normal parains in preference to the higher molecular weight normal parains.- This is just the reverse of the tendency for adsorption in the vapor phase. Applying this inthe process of Figure 1, a C5 to C10 gasoline was treated using normal butane in the liquid phase as the desorption exchange recycle. In this case the feed passes through line 22 into and through adsorber 12 wherein the normal paraflns in the C5 to C range are adsorbed and exchanged for normal butane in the vapor phase. The nonadsorbed high knock rating gasoline is fractionated in raflinate still 34 .producing a bottoms product of high antiknock rating gasoline and the normal butane is produced as an overhead product. In this modification the normal butane is produced in the liquid phase through line 86 controlled by valve 88 and passed into and through recycle manifold `44 Ato adsorber 10 which is in the desorption part of the cycle. Adsorber 10 is contacted with liquid normal butane and it displaces and exchanges with the adsorbed C6 to C10 normal parafiins adsorbed from the gasoline during the previous cycle. The extract stream ows through lines 52 and 54 into extract still 56. Here the displaced low antiknock rating normal parains are produced from the bottom of the column, the recycled normal butane in the liquid phase is removed from the top of the column through line 90 controlled by valve 92, and is returned through manifold 44 to contact further quantities of rich adsorbent.

In the foregoing example, because of the change in phase between adsorption and desorption and because of the reversal of the preference of adsorption, both the adsorption and desorption steps are substantially 100% efiicient.

Referring now more particularly to Figure2 a modification of the process shown in Figure 1 is described in which a recirculating stream of adsorbent is employed. The inlet and outlet cycle valves have been eliminated. In this fgure'the essential elements of the present invention include adsorption zone 100, desorption zone 102', solids conveyor 104, raffinate still 106, and extract still 108. Feed gasoline is passed through line 110 at Aa rate controlled by valve 112 through adsorption zone 100 in which the normal paraflins and other straight chain hydrocarbons are adsorbed thereby displacing and'cxchanging with the recycle components saturating the adsorbent. The raffinate passes through line. 114 to rafnate still 106. Reboiler 116 and overhead condenser 118 are provided. The unadsorbed raffinate gasoline having a high `antiknock rating is produced through line 120 controlled by valve 1 22 as a product of the process'. The exchange displacement recycle stream separated from the raffinate passes in the vapor phase through line 124 into recycle manifold 126 and is introduced into desorption zone 102. Herein the recycle stream exchanges with and displaces the adsorbed normal parafins from the feed producing an extract which flows through line 128 into extract still 108. Reboiler 130 and overhead condenser 132 are provided. Herein the extract is separated into a low antiknock rating gasoline, consisting essentially of normal paraflins, which is produced as a product through line 134 controlled by valve 136. The displacement exchange components separated from the extract pass through line 138 controlled by valve 140 into recycle manifold 126. Any components occurring in the feed which are the same as those used for the exchange displacement cycle can be accumulated as an excess in the system and can be produced therefrom as products from eitheror both of raffinate still 106 or extract still 108 through lines 142 and 144 respectively.

In this modification the adsorbent passes downwardly by gravity as a substantially compact moving bed through adsorber 100 exchanging its adsorbed recycle components for the adsorbable straight chain components of the feed. The rich adsorbent is then conveyed through conveyor 104 and introduced into desorption zone 102. Here it passes downwardly as a moving bed in contact with the displacement exchange recycle stream. In contact therewith it gives up its adsorbed straight chain gasoline hydrocarbons and adsorbs components of the recycle stream thus producinga regenerated adsorbent and the extract. The regenerated adsorbent is introduced through line 146 into the top of adsorption zone 100 for repassage therethrough.

In the process of Figure 2 utilizing a movingbed of granular contact material, it is within the contemplation of this invention to employ any or all of the Well known steps and apparatus elements characteristically employed with moving bed processes. Since these are well known they have not been detailed but are well understood by those skilled in the art. It is also contemplated to use the Same feed pre-treating steps described in connection with Figure 1 in the processes described in conjunction with Figures 2 through 6. y

Referring now more particularly to Figure 3, a schematic flow diagram of this invention is shown modified so as to employ a component of the feed stream as the recirculated exchange displacement component for desorbing the adsorbed materials from the feed.

Example XI In Figure 3 the essential elements of the process include adsorbers 150 and 152, control valves 154 and 156,- cycle timer operator 158, extract still 160, and rafiinate heart cutting stills 162 and 164. The adsorbent used is the metallo alumino silicate having pores of approximately 5 A. size. A light fraction of gasoline, reformed on a platinum catalyst, contains in addition to the aromatic hydrocarbons having high antiknock ratings, the iso and normal hexanes, heptanes, octanes, and nonanes with relatively low antiknock ratings. The feed introduced through line 166 controlled by valve 168 through the interconnected ports of valve 154 through first adsorber 152 in which the adsorbent is saturated with normal hexane. 'Ihe raflnate consisting of aromatic hydrocarbons in this boiling range and the branched chain isomers of hexane, heptane, octane, and nonane together with the displaced and normal hexane flows through line 1'69 `through the interconnected ports of control valve 156 through line to the first heart cutting column 1,62. The raffinate heart cutting stills are provided with over- 11 head condensers and bottoms reboilers as in previous examples. The overhead product from still 162 is produced through line 172 controlled by valve 174 and consists of iso-hexane and any lower boiling components. The bottoms product from the iirst still contains the displaced normal hexane together with the unadsorbed branched chain hydrocarbons in the C through C9 range and unadsorbed aromatic hydrocarbons in this same boiling range. rThis material ows through line 176 controlled by Valve 178 into second heart cutting still 164. The lightest material in this stream is the displacement exchange recycle stream of normal hexane. The net product of normal hexane is removed from the top of the column through line 180 controlled by valve 182 and the remainder is removed as an overhead vapor product through line 184 controlled by valve 186 as part of the exchange displacement recycle stream. The bottoms product is removed from still 164 through line 188 at a rate controlled by valve 190 and consists of the unadsorbed aromatic hydrocarbons and branched chain hydrocarbons boiling in the C6 to C9 range. This material together with the iso-hexane produced through line 172 may be combined if desired to produce high antiknock rating fuel substantially freed of normal parains.

still is also provided with an overhead condenser and bottoms reboiler. Herein the normal hexane, Sutlicient to make up the required amount of displacement exchange recycle, is removed in the vapor phase through line 196 controlled by valve 198 and combined with the overhead vapor from second heart cutting still 164 in recycle manifold 192. A net product of normal hexane may be produced, if desired, through line 200 controlled by valve 202 from the top of still 160. The adsorbed normal parains in the C8 through C9 range are removed from the bottom of extract still '160 through line 204 at a rate controlled by valve -6 and sent to further processing or storage facilities not shown. This concentrate consists of a very low antiknock rating gasoline stream.

Referring now particularly to VFigure 4, the schematic ow diagram of another modication of the process of this invention is shown in which the exchange displacement recycle stream is a straight chain component which has a boiling range intermediate both the unadsorbed raffinate components and the adsorbed extract components of a wide range feedstock. The essential elements of the modification of Figure 4 include adsorbers 210 and 212 containing metallo alumino silicate adsorbents having 5 A. pores, four-way control valves 214 and 216 operated by cycle timer 218, the extract heart cutting stills 220 and 222, and the raflinate heart cutting stills 224 and 226.

Example XII In the process of Figure 4 a gasoline fraction containing normal and branched chain hydrocarbons of from 6 to l0 carbon atoms per molecule, and which may contain also naphthene and aromatic hydrocarbons ofrthis boiling range, is introduced through line 228 controlled by valve 230, through control valve 214 and into adsorber 2'12 wherein the straight chain normal. parains are adsorbed and exchanged with normal octane which is the exchange displacement recycle component in this modiiication. The unadsorbed hydrocarbons including the branched chain paraffins and other non-adsorbed hydroarbons together with the displaced normal octane flows through line 232 through valve 216 through line 234 into rst column 224 of the raflinate heart cutting stills. Each of the heart cutting stills is provided with an overhead condenser and a bottoms reboiler as in previous modifications.v The overhead product from first raiiinate heart cutting still 224 is removed through line 236 controlled by valve 238 and consists of the unadsorbed branched chain hydrocarbons in the C6 through C8 range together with traces of the branched chain C9 hydrocarbons. This is a high antiknock rating stream. The bottoms fraction from rst raffinate heart cutting still 224 is introduced through line 240 controlled by valve 242 into second raiiinate vheart cutting still 226. This stream consists of the displaced normal octane together with the remaining unadsorbed branched chain hydrocarbons of the C9 and C10 species. In the second still 226 the overhead vapor is recirculated through line 244 controlled by valve 246 and consists essentially of the exchange displacement stream of normal octane together with a trace of iso-nonanes. The bottoms product from second still 226 is a high antiknock gas stream consisting of branched chain hydrocarbons of 9 and 10 carbon atoms per molecule. This stream may be produced separately or it may be passed through line 248 controlled by valve 258 with the lower boiling branched chain hydrocarbons flowing through line 236. This stream is the rafnate and contains the high antiknock components of the feed.

The normal octane exchange displacement recycle is returned through line 252 through valve 214 into and through adsorber 210 which is in the desorption part of the cycle. Herein it exchanges with and displaces the adsorbed straight chain paraflins previously adsorbed from the feed and producing extract consisting of the desorbed C6 through C10 normal paraiiins and part of the recirculated normal octane. This extract flows through line 254 and valve 216 through iirst extract heart .cutting still 220. The overhead product from the still consists of normal hexane and normal heptane and is removed through line 256 controlled by valve 258. The bottoms product consisting of normal octane, nonane, and decane passes through line 260 controlled by valve 262 into second extract heart cutting still 222. Hereinthe recirculated normal octane displacement exchange stream is removed as an overhead product through line 264 controlled by valve 266 and combined with the overhead product from the second eiuent heart cutting still 226 for recirculation to the adsorbent being desorbed. The bottoms fraction of still 222, owing through line 268 controlled by valve 270 contains the normal straight chain paraiins having 9 and l0 carbon atoms per molecule and which may be combined with the lighter normal parafns produced overhead from still 220 to produce a low antiknock rating gasoline through line 272. lt should be noted in the present case that the normal octane recycle employed iny this modication is in the liquid phase while the feed to the adsorbers is passed in the vapor phase. Because of the intermediate adsorption preference for the normal octane, it is recovered from the extract and from the raffinate by a double heart cutting distillation.

Referring now Vto Figure 5, a still further modification of the process of this invention is shown which is especially adapted to the treatment of cracked gasoline streams containing both normal and branched chain parafn and olefin hydrocarbons. The esential elements of this modication include olefin adsorbers 280 and 282, with associated four- way control valves 284 and 286, paraffin adsorbers 288 and 290 with associated control valves 292 and 294, olefin extract still 296, paraffin extract stills 298 and 300, and rafiinate still 302. All of these stills are provided as before with overhead condensers and bottoms reboilers. The adsorbers contain metallo alumino silicate adsorbent having approximately 5 A. pores. It is found that because of the polar nature of normal oleiin hydrocarbons theyfare considerably more strongly adsorbed than normal parafiins having the same number of carbon atoms. Therefore in this modificationthe feed stream is contacted twice in succession lwith the adsorbent, first to adsorb normal olefins from the feed and second to adsorb normal paraffins from lthe first adsorber raffinate to produce a product raffinate of a high antiknock rating. This modification also permits the separate recovery and reuse of the normal olefins which have relative high antiknock rating and rejection of normal paraffins which do not. Example X III A`cracked gasoline feedstock and containing normal and branched chain paraffins and'olefins having from 6 to 9 carbon atoms per molecule boiling below about 425 F. is passed in the vapor phase through line 304 controlled by valve 306 through control valve 284 to olefin adsorber 282 previously ksaturated with a first displacement exchange recycle stream consisting of normal parafiins in the C10 and C11 range, i.e. those which boil in or above the upper gasoline boiling range. The normal olefins are adsorbed herein and produce a first raffinate consisting of the unadsorbed branched chain parafiins as well as the unadsorbed branched chain and normal olefins together with the displaced higher normal paraffins of the first displacement exchange recycle stream. vThis first raffinate fiows through line 306 and control valves 286 and 292 into paraffin adsorber 290. Here the higher normal paraffins of the first displacement exchange' recycle stream together with the normal paraffins of the feedstock are adsorbed and displace a relatively low molecular weight olefin hydrocarbon, in this case normal pentene, or other olefin boiling near the lower end of the gasoline boiling range, e.g. onvthe order of 50-100 F. The second raffinate produced from adsorber 290 consists of the unadsorbed branched chain paraffins and olefins of the feedstock together with the normal pentene which is the second exchange ydisplacement component. This material flows through line 308 and valve 294 and through line 310 into rafiinate still 302. The overhead product from raffinate still 302 consists of substantially pure normal pentene, which is the second exchange displacement recycle stream. This material is recirculated through line 312 controlled by valve 314 and is recirculated together with the normal pentene overhead vapor from paraffin extract still 298, hereinafter described. The bottoms product from raffinate still 302 is produced through line 316 controlled byv valve 318 and consists of the unadsorbed iso-olefins and iso-paraffins of the feedstock having between 6 and 9 carbon atoms per molecule. This is aY high antiknock rating gasoline stream.

The first recycle stream employed to exchange with and displace the Vadsorbed normal olefins is a relatively heavy normal parafiin mixture of C10 and C11 hydrocarbons. This material is recirculated through line 320 through valve 284 and through olefin adsorber 280 which is in the desorption part of the cycle. Here the first recycle stream paraffins are adsorbed and displace the adsorbed normal olefins from the adsorbent. The olefin extract consisting of normal olefins in the C6 through C9 range together with the first recycle C10 and C11 normal paraffins flows from adsorber 280 through line 322, valve 286, line 324 into olefin extract still 396. The adsorbednormal olefins are produced therefrom as an overhead prod uct through line 326 controlled by valve 328 and may be blended with the high antiknock rating unadsorbed components of the feed flowing through line 316 from the bottom of raffinate still 302. The normal olefin-free first recycle stream is removed from the bottom of olefin extract still 296 through line 330 controlled by valve 332 and is recirculated through line 320 to displace additional normal olefins from the adsorbent.

14 stream passes through line 334, valve 292, into and through paraffin adsorber 288 which is being desorbed1 The parafiin extract is produced therefrom through line t 336'and'consists of normal pentene of the second recycle stream together with desorbed normal paraffins in the C6 through C9 range. This parafiin extract flows through valve 294 and line 338 into paraffin extract still 298. The second recycle stream being of lower boiling point is produced as an overhead vproduct through line 340 com trolled by valve 342. This normal pentene is combined with that separated from the rafiinate in rafiinate still 302 and the combined stream is recirculated as the second re cycle stream in the process.

The desorbed normal paraffins in the C6 through C@ range together with traces of the C10 and Cn heavy par afiin of the first recycle stream are produced as a bottoms product from parafn extract still 298 through line 344 controlled by valve 346 and are introduced to second paraffin extract still 300.' The overhead product from this still consists of the desorbed normal parafiins originating in the feed stream, namely the C6 through C9 paraliin hydrocarbons, and they are produced as a low antiknock rating gasoline product through line 348 controlled by valve 350. Because the parain extract was derived in adsorber 288 from an adsorbent previously contacted with the olefin raliinate from adsorber 280, which in turn had been previously desorbed by the first recycle stream consisting of heavy parafiins, the desorbed normal paraffins of the feed are contaminated with small amounts of the C10 and C11 normal paraliins of the first recycle stream. These materials are separated as a bottoms product from still 300, are recirculated through line 352 controlled by valve 354 and pass through line 356 into admixture with the heavy paraffins of the first recycle stream produced as a bottoms product from olefin extract still 296. This heavy paraffin mixture provides the first recycle stream employed to exchange with and displace the adsorbed normal olefins.

In the modification of the process one or more normal paraffins having a boilingpoint above the end point of the feedstock is employed as the first recycle stream to exchange with and displace the normal olefins first adsorbed from the feedstock and from which such heavy paraffins are readily separable by distillation. The second recycle stream in the modification comprises a normal olefin having a normal boiling point below that of the lightest component of thelfeed stream and which, bec ause of its greater adsorbability,.can successfully be desorbed and displace higher molecular weight normal parafiins. It is also readily separable by distillation from the desorbed normal paraliins of thefeedstock.

In Figure 6, the schematic flow .diagram of Figure l has been modified so that valves 14' and 16 route the feed up through the adsorbent beds in adsorbers 10 and 12' and the exchange-,displacement recycle down through it. The reverse type of opposed flow canof course be used if desired by appropriate reconnection of the valves. Such opposed ow of feed and recycle streams can be used in ,any of the processes described and illustrated above, and has beenrfound to be a highly eflicient contacting method. y Y

The foregoing description of several modifications of the present invention will serve to explain to those skilled in the art the principles of the present invention and the application thereof to various complex mixtures. Although the examples herein given have been directed to the fractionation of complex mitxures of hydrocarbons, this is not to be understood as a limitation of the process of this invention since the same principles may readily be applied to other mixtures of materials. Furthermore, the adsorbent materials specified in the foregoing examples have been specified as the metallo alumino silicate presently available. This also is not intended to be a limitation since other adsorbents can be substituted de pendingonthe nature of the feed stream and the`adsorp.

tion characteristics on the materials to be adsorbed therefrom.V These particular inorganic adsorbents with vtheir uniform poresizes have been specified here since they are preferred in the illustrative applications of the process of this invention to the removal of straight chain paraflins and olelins from gasoline streams. These hydrocarbons are usually present in a minor proportion, particularly with reformed gasolines, so that the unadsorbed materials consist of aromatic and branched chain paraffin hydrocarbons of high antiknock rating.

The process of this invention thus consists of an improved fractionation process for complex mixtures employing the principles of solid adsorption and distillation in such a way so as to remove specific materials from the feed stream by means of the adsorbent and whereby the ordinary heating and gas stripping or liquid washing of the rich adsorbent have been completely eliminated. The process of this invention may be operated under pressure or under vacuum, and the actual operating pressures are actually determined by the pressure at which the feed stream is available and its boiling range, and whether the material being contacted is desirably in the vapor phase or the liquid phase. The proper operating pressure can be determined by those skilled in the art from known physical characteristics of the materials to be separated; namely the bubble point and dew point of complex hydrocarbon mixtures and the known way in which these change with pressure. The adsorption temperatures employed in the process of this Ainvention are also determined by the physical characteristics of the feed stream and the operating pressure and also whether a vapor phase or a liquid phase Contact is desired. In the complex gasoline streams the operating temperature is largely determined by the dew point and the bubble point of the stream at a given operating pressure. For example, adsorption temperatures above the dew point will obviously be in the `vapor phase while operating temperatures below the bubble point will be in the liquid phase. It is within the contemplation of the present invention to adsorb to feed stream at a temperature between its bubble point and its dew point so that a mixed phase adsorption or displacement exchange desorption will be maintained for some special streams and obviously the feed contact may be in the vapor phase followed by recycle stream Contactin the liquid phase, or vise versa, if desired.

A particular embodiment of the present invention has been hereinabove described in considerable detail by way of illustration. It should be understood that various other modifications and adaptations thereof may be made by those skilled in this particular art without departing from the spirit and scope of this invention as set forth in the appended claims.

We claim:

1. The process for treating a petroleum hydrocarbon feed mixture boiling over a relatively wide range within the gasoline boiling range and comprising straight chain and non-straight chain hydrocarbons, which process comprises: (1) contacting said mixture with a lean solid granular adsorbent essentially comprising a partially dehydrated zeolitic metallo alumino silicate having substantially uniform pores of about A. in diameter and having adsorbed lthereon a displacement exchange fluid of relatively narrow boiling range consisting substantially only of'straight chain hydrocarbon components of said feed mixture, whereby there is obtained a rainate product comprising non-adsorbed non-straight chain hydrocarbon components of the feed mixture in admixture with desorbed displacement exchange fiuid, and a rich adsorbent comprising saidgranularV silicate having adsorbed thereon straight chain components of the feed mixture; (2) separating said raffinate product from said rich adsorbent; (3) contacting said rich adsorbent with said displacement exchange fluid whereby the adsorbent is returned to its lean state and there is obtained an extract 16 product comprising desorbed straight chain hydrocarbon components of the feed mixture in admixture with said displacement exchange tiuid; (4) separating said extract product from the lean adsorbent; (5) returning the said lean adsorbent obtained in step (4) to step (1); (6) treating the raffinate product obtained in step (2) to separate said non-adsorbed non-straight chain hydrocarbon components of the feed mixture from said displacement exchange fiuid; (7) treating the extract product obtained in step (4) to separate therefrom a fraction of relatively narrow boiling range; and (8) returning at least a part of said fraction of relatively narrow boiling range to step (3) as said displacement exchange fluid.

2. A process as defined by claim l wherein, in step (l), said feed mixture is maintained in the vapor state and, in step (3), said displacement exchange fluid is maintained in the vapor state.

3. A process as defined by claim l wherein at least part of the displacement exchange fluid which separated from the raffinate product in step (6) is returned to step (3).

4. A process as defined by claim 1 wherein the said displacement exchange fiuid is a relatively narrow boiling range heart-cut of the said extract product.

5. The process for treating a petroleum hydrocarbon feed mixture comprising straight chain and non-straight chain hydrocarbons containing from 6 to about 9 carbon atoms, including isohexane and n-hexane, which process comprises (1) contacting said mixture with a lean solid granular adsorbent comprising a partially dehydrated zeolitic metallo alumino silicate having substantially uniform pores of about 5 A. in diameter having n-hexane adsorbed thereon, whereby there is obtained a raffinate product comprising non-adsorbed non-straight chain hydrocarbon components of the feed mixture, including isohexane, in admixture with desorbed n-hexane, and a rich adsorbent comprising said granular silicate having adsorbed thereon straight chain components of the feed mixture; (2) separating said raffinate product from said rich adsorbent; (3) contacting said rich adsorbent with n-hexane, whereby the adsorbent is returned to its lean state and there is obtained an extract product comprising desorbed straight chain hydrocarbon components of the feed mixture, including n-hexane', (4) separating said extract product from the adsorbent; (5) returning the said lean adsorbent obtained in step (4) to step (1); (6) distilling the rainate product obtained in step (2) to obtain a raffinate overhead fraction consisting essentially of isohexane and a raffinate bottom product comprising n-hexane and non-straight chain hydrocarbon components of the feed; (7) distilling said raffinate bottoms product to separate n-hexane therefrom; (8) distilling the extract product obtained in step (4) to separate n-hexane therefrom; and (9) returning separated n-hexane to step (3).

6. The process of treating a petroleum hydrocarbon feed mixture comprising straight chain and non-straight chain hydrocarbons containing from 6 to about 9 carbon atoms, including n-octane, which process comprises (l) contacting said mixture with a lean granular adsorbent comprising a partially dehydrated zeolitic metallo alumino silicate having substantially uniform pores of about 5 A. in diameter having n-octane adsorbed thereon, whereby there is obtained a raffinate product comprising non-adsorbed non-straight chain hydrocarbon components of the feed mixture in admixture with desorbed n-octane, and a rich adsorbent comprising said granular silicate having adsorbed thereon straight-chain hydrocarbon components of the feed mixture; (2) separating said raffinate product from said rich adsorbent; (3) contacting the said rich adsorbent with n-octane, whereby the adsorbent is returned to its lean state and there is obtained an extract product comprising desorbed straightchain hydrocarbon components of the feed mixture, including n-octane; (4) separating said extract product from the lean adsorbent; (5) returning the said lean 17 adsorbent to step 1); (6) distilling the raffinate product obtained in step (2) to separate n-octane therefrom; (7) distilling the extract product obtained in step (4) to separate n-octane therefrom; and (8) returning separated n-octane to step 3).

7. A process for treating a petroleum hydrocarbon feed mixture boiling over a relatively wide range within the gasoline boiling range and comprising straight and non-straight chain paratlins and olefines, which process comprises: (1) contacting said feed mixture with a lean first solid granular adsorbent comprising a partially dehydrated zeolitic metallo alumino silicate having substantially uniform pores of about A. in diameter and having ladsorbed thereon a first displacement exchange uid consisting essentially of straight-chain parain hydrocarbon components of said feed mixture boiling between relatively narrow limits at the upper end of the boiling range thereof, whereby there is obtained a first raffinate product comprising non-adsorbed non-straight chain hydrocarbon camponents of the feed mixture and non-adsorbed straight chain hydrocarbon components of the feed mixture in admixture with said first displacement exchange fluid, and a rich first adsorbent comprising said granular silicate having adsorbed thereon normal oleiine hydrocarbon components of the feed mixture; (2) separating said first raffinate product from said rich adsorbent; (3) contacting said rich first adsorbent with said first displacemnet exchange fluid, whereby there is obtained said lean first adsorbent and a first extract product comprising desorbed normal olefines in admixture with said first displacement exchange fluid; (4) separating said first extract product from said lean first adsorbent; (5) treating the separated first extract product to separate said first displacement exchange uid therefrom; (6) contacting the separated first raffinate product with a lean second adsorbent comprising Ia solid granular partially dehydrated zeolitic metallo alumino silicate having substantially uniform pores of about 5 A. in diameter and having adsorbed thereon a second displacement exchange fluid consisting essentially of normal olefine hydrocarbon components of the feed mixture boil- 18 ing between relatively narrow limits at the lower end of the boiling range thereof, whereby there is obtained a second ranate product comprising non-absorbed nonstraight chain hydrocarbon components of the feed mixture in admixture with said second displacement exchange fluid, and a second rich adsorbent comprising said granular silicate having adsorbed thereon straight chain paraflin hydrocarbon components of the feed mixp ture; (7) separating said second rafnate product from said second rich adsorbent; (8) contacting said second rich adsorbent with said second displacement exchange fluid, whereby there is obtained said second lean adsorbent and a second extract product comprising desorbed straight chain paran hydrocarbon components of the feed mixture in admixture with said second displacement exchange tluid; (9) separating said second extract product from said second lean adsorbent; (10) treating the separated second extract product to separate therefrom as separate entities said second displacement exchange fluid and a fraction consisting essentially of straight-chain parain hydrocarbon components of the feed mixture boiling over relatively narrow limits at the upper end of the boiling range thereof; and (l1) treating the separated second raffinate product to separate said second displacement exchange fluid therefrom.

References Cited in the le of this patent UNITED STATES PATENTS 2,306,610 Barrer Dec. 29, 1942 2,459,442 Lipkin Jan. 18, 1949 2,522,426 lBlack Sept. 20, 1950 2,564,717 Olsen Aug. 21, 1951 2,621,149 Scott et al Dec. 9, 1952 2,643,972 Weedman June 30, 1953 2,678,132 Beard May 11, 1954 2,712,008 Kirchner et al .Tune 28, 1955 2,768,221 Findlay Oct. 23, 1956 2,776,250 Capell et al. Jan. 1, 1957 2,818,137 Richmond et al Dec. 31, 1957 2,818,455 Ballard et al. Dec. 31, 1957

Claims (1)

1. THE PROCESS FOR TREATING A PETROLEUM HYDROCARBON FEED MIXTURE BOILING OVER A RELATIVELY WIDE RANGE WITHIN THE GASOLINE BOILING RANGE AND COMPRISING STRAIGHT CHAIN AND NON-STRAIGHT CHAIN HYDROCARBONS, WHICH PROCESS COMPRISES: (1) CONTACTING SAID MIXTURE WITH A LEAN SOLID GRANDULAR ADSORBENT ESSENTIALLY COMPRISING A PARTIALLY DEHYDRATED ZEOLITIC METALLO ALUMINO SILICATE HAVING SUBSTANTIALLY UNIFORM PORES OF ABOUT 5 A. IN DIAMETER AND HAVING ADSORBED THEREON A DISPLACEMENT EXCHANGE FLUID OF RELATIVELY NARROW BOILING RANGE CONSISTING SUBSTANTIALLY ONLY OF STRAIGHT CHAIN HYDROCARBON COMPONENTS OF SAID FEED MIXTURE, WHEREBY THERE IS OBTAINED A RAFFINATE PRODUCT COMPRISING NON-ABSORBED NON-STRAIGHT CHAIN HYDROCARBON COMPONENTS OF THE FEED MIXTURE IN ADMIXTURE WITH DESORBED DISPLACEMENT EXCHANGE FLUID, AND A RICH ADSORBENT COMPRISING SAID GRANDULAR SILICATE HAVING ADSORBED THEREON STRAIGHT CHAIN COMPONENTS OF THE FEED MIXTURE, (2) SEPARATING SAID RAFFINATE PRODUCT FROM SAID RICH ADSORBENT, (3) CONTACTING SAID RICH ADSORBENT WITH SAID DISPLACEMENT EXCHANGE FLUID WHEREBY THE ADSORBENT IS RETURNED TO ITS LEAN STATE AND THERE IS OBTAINED AN EXTRACT PRODUCT COMPRISING DESORBED STRAIGHT CHAIN HYDROCARBON COMPONENTS OF THE FEED MIXTURE IN ADMIXTURE WITH SAID DISPLACEMENT EXCHANGE FLUID, (4) SEPARATING SAID EXTRACT PRODUCT FROM THE LEAN ADSORBENT, (5) RETURNING SAID EXTRACT LEAN ADSORBENT OBTAINED IN STEP (4) TO STEP (1), (6) TREATING THE RAFFINATE PRODUCT OBTAINED IN STEP (2) TO SEPARATE SAID NON-ADSORBED NON-STRAIGHT CHAIN HYDROCARBON COMPONENTS OF THE FEED MIXTURE FROM SAID DISPLACEMENT EXCHANGE FLUID, (7) TREATING THE EXTRACT PRODUCT OBTAINED IN STEP (4) TO SEPARATE THEREFROM A FRACTION OF RELATIVELY NARROW BOILING RANGE, AND (8) RETURNING AT LEAST A PART OF SAID FRACTION OF RELATIVELY NARROW BOILING RANGE TO STEP (3) AS SAID DISPLACEMENT EXCHANGE FLUID.

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