US2324165A - Dehydroaromatization - Google Patents

Description

July 13, 1943. E. T. LAYNG Erm. 2,324,165

DEHYDRO-AROMATI ZATION Filed sept. 13, 1959 2 sheets-sheet 1l ATTORNEY' July 13, 1943. E- T- LAYNG ETA'- 2,324,165

DEHYDRO -AROMATI ZAT ION Heilig/EIMS ATTORNEY hydrocarbons to aromatics.

Patented July 13, 1943 2,324,165 DEHYDROARCMATIZATION Edwin T. Layne', Jersey City, N. J., and Robert F. Marschner, Chicago, Ill., assignors of one-half to Standard Oil Company, a corporation of Indiana, and one-half to The M. W. Kellogg Company, a corporation of Delaware Application September 13, 1939, Serial No. 294,782

17 Claims. (Cl. ISG-50) an improved dehydro-aromatization process wherein the reforming is effected by means of a catalyst in the presence of hydrogen, although the hydrogen itself is not consumed in the reaction. An object of our invention is to provide a system for obtaining maximum yields of high quality gasoline from petroleum naphtha and to produce motor fuels of higher octane number than can possibly be produced by cracking and by thermal conversion processes. A further ob- -ject is to provide a system for obtaining maximum yields o4E motor fuel per unit of catalyst employed, or in other words, to utilize the catalyst more effectively and for a. much longer period of time than has heretofore been possible.

A further object is to provide a system wherein various naphtha fractions may be most effectively and efficiently converted into motor fuels of high octane number, and wherein the partially spent catalyst from the treating of one fraction may be eiectively employed for the treating of another fraction. A further object is to provide a new combination of catalyst conversion systems with means forsegregating relatively pure hydrogen produced in one of said systems and for using that hydrogen in all of said systems.

Another object is to provide a method and means for preventing degradation of heavy naphtha fractions by subjecting them to the severe conditions required for the processing of light naphtha fractions and to avoid dilution of light naphtha fractions by non-aromatizable very light naphtha constituents such as pentanes. Other objects will be apparent as the detailed description of our invention proceeds.

It is now known that under certain operating conditions dehydrogenation catalysts such as molybdenum oxide on alumina., chromium oxide on alumina, etc. have the remarkable and unexpected property of causing ring closure, i. e., the conversion of straight chain and branched chain Naphthenes are also converted to aromatics. In order to prolong catalystlife forcommercially feasible periods of time the reaction is effected in the presence of hydrogen. Our invention is a further improvement in the above process and is based 'on our discovery that some naphtha fractionsirequire different conversion conditions than other naphtha fractions. More specically, we have found that the light naphtha fractions, particularly Cs ating conditions than heavynaphtha fractions, for instance, those containing predominantly Ca to C12 hydrocarbons. If naphtha is treated in a single conversion zone either the light components will be insufficiently reformed or the heavy components suffer thermal degradation.

In accordance with our invention the predominantly Ce and Cv fraction is treated with relatively fresh catalyst of maximum activity and the catalyst which has served its purpose for the conversion of this fraction is thereafter employed for converting the predominantly Cs to C12 fraction. This method of operation offers the distinct advantage that operating conditions in both catalyst systems may be substantially the same, namely, about 30 to 450, preferably about 250, pounds per sqare inch pressure, at 875 to 1075,

^ preferably about 950 F. average bed temperature,

space velocity of about 0.04` to l0 or preferably 0.2 to 2.0 volumes of liquid naphtha per volume of catalyst space per hour, and a hydrogen ratio of about 0.4 to 8, preferably about 3 mols per mol of naphtha. It should be understood that severity can be obtained by either increasing temperature or decreasing space velocity and that for a given severity of treatment the higher the temperature, the higher the space velocity. Thus operating at 1000 F. with a space velocity of 1 may be about equivalent in severity to operating at 950 F. with a space velocity of 0.5.

'I'he catalyst may be on stream from 2 to 20 or more hours with light naphtha and from 5 to 20 hours with heavy naphtha, after which it is regenerated and reconditioned for repetition of this cycle. Pentanes and butanes are removed from the light lnaphtha fraction and by-passed around the conversion zone to. avoid dilution in the light naphtha conversion chamber. This bypassing of C4 and C5 hydrocarbons increases the paraiiinicity and decreases the acid heat of the finished motor fuel which is an important consideration in aviation fuels. The by-passing of C4-C5 fractions also prolongs catalyst life.

As above stated, we first treat one close-cut naphtha fraction until the catalyst becomes appreciably less active with regardto that fraction and then we process a fraction of different molecular weight with the same catalyst. Ordinarily the fresh catalyst is employed with the most dilcultly aromatizable stock but it should be understood that the fresh catalyst maybe employed with the more easily aromatizable stock under mild operating conditions, particularly unand C7 hydrocarbons,Y require more drastic oper- 55 lder low temperatures of about 875 to 925 F.,

after which the more difdcultly aromatizable stock may be converted over the partially spent catalyst at high temperatures which may range from 950 to 1075" F. Many other modifications of the invention will be apparent to those skilled in the art as the detailed description of our invention proceeds.

In the accompanying drawings, which form a part of this specification and in which similar parts are designated by like reference characters through the several views:

Figure 1 is a flow diagram of our improved reforming system;

Figure 2 is a iiow diagram showing one portion of the system in further detail, namely the rotation system for employing fixed bed catalysts; and

Figure 3 is a flow diagram of another modification of the system employing moving bed catalyst chambers.

The invention is not limited to any particular naphtha. The naphtha may be either straightrun or cracked or it may be produced by the hydrogenation of carbonaceous materials, by the catalytic conversion of carbon monoxide and hydrogen or by any other known method. In the preferred embodiment of the invention we will describe the conversion of straight-run naphtha obtained from East Texas crude. Preferably the original naphtha is straight-run or parafilnic hydrocarbon which initially has a relatively low octane number.

The catalyst employed for the reforming or conversion step is preferably an oxide of a 6th group metal mounted on active alumina (a form of alumina obtained as a scale in aluminum ore purification). About 2 to 10% of molybdenum oxide on alumina or about 8 to 40% of chromium oxide on alumina have been found to give excellent results. It should be understood, however, that the present invention is not limited to any particular catalyst but is applicable to the use of any dehydro-aromatization catalyst known to the art. The minor ingredient of the catalyst is preferably an oxide or sulfide of molybdenum, chromium, tungsten or uranium or any mixture thereof mounted on bauxite, precipitated alumina, activated alumina or any other suitable catalyst support. Magnesium, aluminum or zinc chromites, molybdenites, etc. may be employed since it has been found that the 6th group metal is particularly active when it is in the anion. Vanadium and cerium oxides have been found to be effective for this conversion. Oxides of copper, nickel, manganese, etc. may be included to facilitate regeneration or to supplement or promote catalyst activity.

The catalyst may be made by impregnating activated alumina or other support with molybdic acid, ammonium molybdate or any other catalyst compound decomposable by heat. Also the aluminum and molybdenum oxides may be co-precipitated as a gel or the separate oxides may be mixed together as a paste, dried, extruded under pressureor pelleted and heated to a temperature of about 900 to 1200 F. Since the-preparation of the catalyst forms no part of the present invention it will not be described in further detail.

The catalyst may be employed in -fixed beds, in movable beds or as a powder suspended in a gaseous stream, the conversion in all cases being inthe vapor phase. The xed bed catalysts may be positioned in tubes mounted for instance in the convection section of a furnace or they may be positioned in a single bed or plurality Of beds perature and pressure, the regeneration beingl effected outside of the conversion zone. The powdered catalyst may be fed into a rapidly moving stream of vaporized naphtha and hydrogen, separated therefrom after reaction is completed and separately regenerated by oxygen while suspended in iiue gas. Any of these specific catalyst reactors or their equivalents may be used in practicing the invention, but they will not be described in further detail. In the case of powdered catalyst the expression space velocity is not applicable-the equivalent effect is obtained by using about 1 to l5 volumes of catalyst per volume of oil and using a contact time of about 5 to 200 seconds.

Referring specifically to Figure 1, a crude East Texas petroleum is passed from a still (not shown) through line IIJ to fractionator II from which a butane-pentane' fraction is Withdrawn overhead through line I2, a hexane-heptane fraction is withdrawn through line I3, an octanenonane-decane fraction is withdrawn through line I4 and heavy ends, gas oils, lubricating oils, etc. are withdrawn through line I5.

The hexane-heptane fraction which is commonly referred to as light naphtha may be supplemented by light naphtha from outside sources introduced through line I6. Generally speaking, the boiling range of this fraction will be in the general range of from about to 225 F. and it will contain predominantly normal and isohexanes and heptanes. If cracked naphtha is used, oleflns will also be present. This light naphtha fraction is passed by pump I1 through coils I8 of furnace I9 and thence through transfer line 20 to catalyst chamber 2I.

Hydrogen from line 22 is heated in coils 23 and introduced by line 24 either into transfer line 20 `or into the top of catalyst chamber 2|, preferably so that the hydrogen contacts and conditions the catalyst before the catalyst meets the heated naphtha stream. Catalyst may be introduced into chamber 2l by means of a suitable valve of hydrogen to 1 mol of naphtha, preferably about 3 mols.

Reaction products and vapors leave reaction chamber 2I through line 26 and are cooled in condenser 21 and introduced into hydrogen separator 28 which is preferably maintained at substantially reaction pressure but at a temperature of about 35 to 105 F; 'I'he separated hydrogen is withdrawn to line 29 and either discarded through line 30 or4 passed by line 3| and pump 32 to line 22 for reuse in the system. Generally speaking, the fresh catalyst tends to produce a hydrogen of sufficient purity for reuse in the system but if necessary or desirable hydrogen discarded through line 30 may be suitably puried and returned to line 3|. I

Liquids from separator 28 l are withdrawn through line 33 to line 34 for nal fractionation and/ or stabilization and/or finishing treatments.

After reaction chamber 2| has been on stream for about 2 to 20 hours, for instance about 4 or 5 hours, the catalyst from chamber 2| is withdrawn through line 35 to catalyst chamber 36 and new catalyst is introduced into chamber 2|.

If continuous or intermittent catalyst flow is A employed the rate of ilowis such that the catalyst in each chamber is entirely replaced about every 2 to 20 hours, although it should be understood that this is dependent on the nature of the catalyst employed and that for` some catalysts the replacement should be as rapid as every hour, while with others it may be as slow as every 20 or 30 hours.

The heavy naphtha from line 4 may be supplemented by heavy naphtha from other sources introduced' through line 31. This fraction has a boiling range in the general neighborhood of about 225 to 425 F. or higher, and it contains normal and iso-octanes, nonanes, decanes`, etc. If desired a part or all of the octanes may be included with the light naphtha fractions. The cut point temperature between light and heavy naphtha may be anywhere between about 200 and about 300 F.

The heavy naphtha is passed by pump 38 through coil 39 in furnace 40, thence through transfer line 4I to catalyst chamber 35. Hydrogen from line 42 is heated in line 43 and introduced by line V44 into this catalyst chamber.

The conditions in catalyst chamber 36 are substantially the same as those in catalyst chamber 2| except that slightly higher temperatures may be used.

Spent catalyst from chamber 36 is withdrawn through suitable gas-tight valved means diagrammatically illustrated at line 53. Reaction products from chamber 36 are withdrawn through line 45, cooled in condenser 46 and introduced into hydrogen separator 41 which is maintained under substantially the same conditions as separator 28. The hydrogen in this case is usually a lower grade than obtained in separator 28 and it may be withdrawn through line 48 and discarded through line 49. However, if this hydrogen is of suiiicient purity for reuse in the system without purication it may be passed by line 50 to line 3| or by line 5I directly through line 28 to condenser 21 and separator 28 while branch lines 45a, b, c, and d selectively lead through line 45 to condenser 46 and separator 41.

In this gure the hydrogen from separator 41 A is of suflicient purity to be reused and it is therefore introduced by pump 55 into hydrogen storage tank 56. It should be understood that similar storage tanks may be employed in the system for hydrogen from line 5I.

The hydrogen Afrom storage tank 56 may be heated in coils 51 of furnace 58. and introduced by line 59 into the various catalyst chambers by branch lines59a, b, c and d. It should be under-4 stood, however, that the same furnace may be employed for heating the naphtha as that employed for heating the hydrogen, as illustrated in Figure l-also that the separate heating of hy- V drogen illustrated in Figure 2 may be used in the to une 42. Irwin thus be seen that the hydrogen for reaction chamber 36 may be supplied either from separator 41 by line 5I or from separator 28 by lines 22 and 52. Here again the hydrogen discarded through line 49 may be wholly or partially purified and returned for reuse.

Liquids from separator 41 are withdrawn through line 54 to line 34 where they join the reformed light naphtha from line 33 and the unreacted butane and pentane fraction from line Where ilxed bed catalystchambers are employed and a plurality of such beds are arranged in parallel, the operation will be as illustrated in Figure 2. The light naphtha transfer line 20 serves as a manifold so that the hot vapors may be introduced through any one of branch lines 20a, b, c andd. Similarly, the heavy naphtha may be introduced into any one of the catalyst chambers A, B, C and D through any of the system of Figure 1.

In Figure 2 while catalyst chamber A is being repaired or standing by, catalyst chamber B may be undergoing regeneration while catalyst chamber C is operating on heavy naphtha and catalyst chamber D onlight naphtha. After a period of perhaps 4 to 10 hours, when chamber B is fully regenerated, the light naphtha stream is switched to chamber B, the heavy naphtha to chamber D and chamber C is regenerated. Next the light naphtha will be charged to chamber C, the heavy naphtha to chamber B, while chamber D is regenerated, etc. It will thus be seen that in each chamber the fresh catalyst is used for converting the most difIicultly aromatizablestock and that after it has served its usefulness on such stock it is employed for another period on` a. stock of different character so that in effect each catalyst chamber is used much longer than would` otherwise be possible.

In the above description it is understood that the reaction temperatures for heavy naphtha are approximately the same or slightly lower than the temperatures for light naphtha. We may, however, pass the heavy naphtha through the catalyst yonder markedly higher temperatures.

Under such conditions the purest hydrogen is 6|, the gasoline'through line 62 and fractions` heavier 'than gasoline through lin'e `63. Any conventional fractionating or stabilizirgmeans may be employed for this purpose. The gases may be used for further conversion processes and the heavier-than-gasoline products may be either recycled to the system with the heavy naphtha'or may be thermallyor catalytically converted into motor fuel in some other system. In Figure 2, of

course, it should be understood that a prelimstocks charged through lines I3 and I4.

In Figure 3 we have shown another embodiment of our invention wherein moving catalyst beds are employed and wherein three separate naphtha fractions are treated. In this case the heavy 1 i naphtha will have a boiling range of about 225 to 325 F. and the heavy heavy naphtha will have a boiling range of about 325 to 450 F. Catalyst chambers E, F and G may be operated either concurrently or countercurrently and the catalyst may be regenerated in chamber H and returned to chamber E for reuse. Here again the temperatures may be slightly increased as the catalyst proceeds from stage to stage; pressure, hydrogen concentration, space velocity, etc. may vary, but in general the reaction conditions are the same in each chamber. However, if the heavy heavy naptha is introduced into chamber E and the light naphtha in chamber G, the temperature conditions should be drastically changed because in such case the temperature in E must be maintained below about 925 F., while in chamber G it may be as high as 1025 to 1100 F.

In Figure 3 the hydrogen from storage tank 56 is withdrawn through line 64 and through branch lines 65, 66 and 61 to the inlet of coils I8, 39 and 39". It should be understood, however, that the hydrogen may be heated in separate coils as hereinabove described and/or that the hydrogen in the previous examples may be introduced with the naphtha as shown in Figure 3.

Regeneration in all cases is effected by oxidation with air in the presence of flue gas which may be introduced through line 68, the spent regeneration gases being withdrawn through line I9. Specific methods of regeneration form no part of the present invention and they will not therefore be described in further detail.

In our preferred examples we have illustrated the separate treatment of two or three naphtha fractions but it should be understood that a much larger number of vfractions may thus be separately treated. Cs hydrocarbons are more difilcultly aromatizable than C7, C1 are more diincultly armatizable than Cs. Ca than C9, etc. but the difference in the required severity of treatment gradually diminishes with hydrocarbons of higher and higher molecular weights. Thus our light naphtha may consist essentially of Cs hydrocarbons, a heavier fracti n may consist essentially of C1 hydrocarbons, a sist essentially of Ce hydrocarbons, etc. Alternatively, when the light naphtha consists essentially of Ce hydrocarbons, the next heavier fraction may include C1 to Cn and the next heavier from Cs to Cm, etc.

While the ,ease of aromatization and consequently the mildness of the aromatization conditions gradually increases with the molecular weight of the hydrocarbons, we have found that the tendency toward volatility increase is much greater in the case of heavier hydrocarbons than in the case of light hydrocarbons. When C to C1: hydrocarbons are aromatized there is a pronounced tendency toward increase in volatility. such. a tendency is' appreciable with C1 to Cs hydrocarbons and it is only very slight in the case of Cu and C1 hydrocarbons. `This tendency toward the increase ofvolatility is a further cogent reason for the separate treatment of specific hydrocarbon fractions.

While we have referred to Cs hydrocarbons, Ce-C-r hydrocarbons, etc. and while in our examples we have given certain general boiling ranges, it should be understood that close fractionation is not essential in the practice of our invention. When separately treating a Ce-C'r fraction and a C'f-Ca fraction respectively, it is important that the bulk ofthe lighter hydrocarbons be in the Ce-Cv fractionand that thebulk of the heavier hydrocarbons be in the C'z-C fraction. but some overlapping is of no serious consequence.

eavier fraction may con- The separate treatment of various hydrocarbon fractions serves a very useful purpose in the manufacture of special petroleum products such as aviation gasoline, high solvency naphtha, safety fuel, high knock rating motor fuel, etc. Aromatization of the Ci-Cs fraction, for instance, produces a high solvency naphtha of special quality, the aromatization of heavier naphtha produces an exceptionallyA high grade aviation safety fuel, particularly if the lighter ends of such aromatization products are blended with aromatized Co-C-r hydrocarbons to supply the necessary light and heavy ends for a balanced high antiknock motor fuel. These are only a few examples of the important advantages that are obtainable by the separate aromatization of different naphtha fractions. Of primary importance, of course, is the increased eiliciency of each separate treatment, the increased catalyst life obtainable. the avoidance of stock degradation, the effective means for supplying endothermic heat of reaction, and

v the general flexibility of operation.

While we have described preferred embodiments of our invention it should be understood that we do not limit ourselves to any of such details since various further modifications will be apparent from the above description to those skilled in the art.

We claim:

1. The method of converting low knock rating naphtha to highy knock rating motor fuel in a dehydro-aromatization system which comprises fractionating the naphtha into a C4-Cs fraction, a Ca to Ca fraction and a Cn to C12 fraction, romatizing the Cs to Ca fraction under severe conditions" with a dehydro-aromatization catalyst in the presence of hydrogen, separately aromatizing the Cs to Cu fraction under milder/conditions in the presence of the same catalyst,separating the hydrogen from the liquid reaction products of said treating steps, and combining said liquid reaction products with the C4C5 fraction- 2. 'I'he method of claim 1 wherein the Cc to Cl naphtha fraction is contacted with relatively fresh catalyst and wherein the Cs to C1: naphtha fraction is contacted with a relatively spent catalyst under approximately the same temperature conditions.

n 3. The method of prolonging the useful life of a catalyst in a dehydro-aromatization process for converting low knock rating naphtha into high knock rating motor fuel, which comprises fractionating said naphtha into a fraction boiling predominantly below about F., a fraction boiling ypredominantly between about 125 to 225 F.. and a fraction boiling predominantly above about 225 F., respectively, by-passing the catalyst chamber with the fraction boiling below 125 F., contacting catalyst material with one oi' the remaining fractions until the catalyst is partially spent and then contacting said catalyst with the other remaining fraction until the catalyst is substantially spent.

4. 'Ihe method of claim 3 wherein the catalyst is first contacted with the fraction boiling between about 125 and 225 F. at a temperature of about 875 to 1075 F.. and wherein the naphtha fraction boiling above 225 F. is contacted with catalyst which has previously been used for converting the fraction boiling between 125 and 225 5. The method of operating a multi-stage catalytic dehydroaromatization system `which comprises passing a catalyst material through a first stage and then through a second stage, treating a narrow cut naphtha fraction with said catalyst in said flrst stage for converting it into high knock rating motor fuel, and passing a second close-cut naphtha fraction of different boiling range than said first-named fraction into contact with said catalyst in said second stage for a fraction consisting chiefly of butanes and pen-- tanes, a light naphtha fraction, and a heavy naphtha fraction, contacting a dehydro-aromatization catalyst with one of said naphtha fractions under reaction conditions until the catalyst is partially spent with regard to that fraction, then contacting said partially spent catalyst under reaction conditionswith the other fraction to produce aromatization thereof and combining said butane and pentane fraction with at least a part of the aromatization products from both of the aromatization steps to produce a high knock rating motor fuel.

7. The method of operating a multi-stage dehydro-aromatiaation system which comprises treating a close-cutl naphtha fraction having about Cs to Ca carbon atoms per molecule with a dehydro-aromatization catalyst until said catalyst has become partially spent, and subsequently treating'a heavy naphtha substantially free from light naphtha components with said same partially spent catalyst, whereby the catalyst life may be extended materially beyond the life which it would have had the naphtha fractions been mixed andl treated simultaneously.

8. The method of converting naphtha into valuable petroleum products which comprises fractionating said naphtha: into aplurality of fractions of different boilingA ranges, separately supplied by the light ends produced vby the aromatization of heavy naphtha.

1l. The method of aromatizing a plurality of naphtha fractions of different boiling ranges which comprises contacting an aromatization catalyst with a naphtha fraction` under relatively mild conditions. contacting the same catalyst with a lighter hydrocarbon fraction under relatively severe conditions and-blending reaction products from said separate treating stages for lthe production of high quality motor fuel.

l2. The method of obtaining valuable petroleum products from naphtha which comprises fractionating naphtha into a fraction of the class consistingof Cs hydrocarbons, Cv hydrocarbons and a mixture of Ce-Ci hydrocarbons, and another fraction consisting chiefly of hydrocarbons heavier than C'1.hydrocarbons, treating said first fraction with an aromatization catalyst at a temaromatizing each fraction by contacting it with an aromatization catalyst at a temperature of about 875 to 1075 F.with a. space velocity of about 0.04 to 10 volumes of liquid naphtha fraction-per volume of catalyst space per hour under a pressure of Jabout 30 to 450 pounds Der square inch and in the presence of about .4 to 8 mols of hydrogen per mol of naphtha fraction, the severity of the contact conditions. being greater in the case of low boiling fractions than in the case of high boiling fractions, whereby each fraction is aromatized under optimum conditions, removing and fractionating the products of the respective conversion stages to produce high antlknoc'k motor fuel and products heavler'than high antiknock motor fuel.

9. The method of claim 8`wherein the light components of the products produced by aromatizing a heavy naphtha fraction is removed, whereby a safety aviationv gasoline may be obtained and wherein the light products removed from the aromatized heavy naphtha are blended with the products of aromatized light naphtha for supplying the heavy endsof high antiknock motor fuel.

l0. The method of claim 8 wherein one naphtha'v fraction consists essentially of C1 and C; hydrocarbons which are converted into high solvency naphtha by aromatization and wherein the deficiency in heavy ends for motor fuel produced by aromatization of lighter naphtha is perature of about 875 to 1075 F. under a pressure of about 30 to 450 pounds per square inch, with a space velocity of about 0.04 to l0 volumes of liquid feed per volume of catalyst space per hour in the presence of about 0.4 to 8 mols of hydrogen per mol of naphtha feed, the lower space velocities being associated with lower temperatures and higher space velocities with higher temperatures respectively, separately treating the heavier naphtha fraction under milder conditions than the rst naphtha fraction was treated. and -fractionating products from both conversion steps to obtain high quality motor fuel and products heavier and lighter, respectivethe Cla-C12 fraction under milder conditions in the presence of relatively fresh dehydroaromati'- zation catalyst at a temperaturewithinlthe approximate rangeof 750 to 925 F., separating hydrogen from the liquid reaction products of said treating steps and combining said liquid reaction products-with the C4-C5 fraction.

14. 'I'he method of operating a multi-stage cat- 'l alytic dehydroaromatization system which comprises passing a catalyst material through a first stage and then through a second stage, treating a low boiling close cut naphtha fraction with said catalyst in said first stage at a temperature within the approximate range of 900 to 1000 F. for converting it into high knock rating motor fuel, treating a high boiling clost cut naphtha fraction in said second stage under substantially the same operating conditions as Ithe first'stage for converting said high boiling close cut naphtha fraction into' highquality motor` fuel, regeneratingstage and then through a second stage, treating I anarrow cut high boiling naphtha fraction with said catalyst in said first stage at a temperature witliin the approximate 'range0f875-to 925 F. for converting it into high knock rating motor fuel, treating a close cut light naphtha fraction with said catalyst in said second stage at temperatures within the approximate range of 950 to 1100 F. for converting said light naphtha fraction into high quality motor fuel, regenerating the catalyst from said second stage and returning said regenerated catalyst to said rst stage.

16. The method of converting naphtha into valuable petroleum products which comprises fractionating said naphtha into a plurality of fractions of different boiling ranges, separately aromatizing each fraction by contacting it with an aromatization catalyst, rst contacting said catalyst with one of said fractions and subsequently contacting said catalyst with another of said fractions, each of said contacting steps being within the approximate temperature range of 875 to 1075 F., within the space velocity range of .04 to 10 volumes of liquid naphtha fractionv naphtha fraction, maintaining more severe contact conditions in the case of a low' boiling fraction than in the case of a high boiling fraction and removing and fractionating the separately aromatized products to produce high antlknock motor fuel.

17. The method of obtaining valuable petrolefum products from naphtha which comprises fractionating naphtha into a fraction consistinz essentially of hydrocarbons in the hexane to heptane boiling range and another fraction congen within the approximate range of .4 to 8 mols of hydrogen per mol of naphtha fraction charled. separately treating the second named fraction consisting essentially of hydrocarbons higher boiling than heptane under substantially milder conditions than the ilrst named naphtha fraction is treated, fractionating products from both treating steps to obtain high quality motor fuel and products heavier and lighter respectively than said high quality motor-fuel.

EDWIN T. LAYNG.

ROBERT F.

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