US2944001A - Naphtha reforming process - Google Patents

Description

ly 9 c. N. KIMBERLIN, JR.. ETAL 2,944,001

NAPHTHA REFORMING PROCESS Filed May 29. 1956 1 f I N-PARAFFIN-FREE N-PARAFFIN FREE HEAVY NAPHT HA NAPHTHA FEED HEAVY NAPHTHA Charles Newfon Kimberlin, Jr. a William Judson Maffox 'Mmors By 2 .59 Afforney United ta e P t n NAPHTHA REFORMING PRocEss Charles Newton Kimberlin, Jr., and William Judson Mattox, both of BatonRonge, La. assignors to Esso Research and Engineering Company, a corporation of Delaware.

Filed M 1 56, Sen. Ne- 5 1,99 2 Claims. ((11. 208-80) The present invention relates to the; hydroforming, of hydrocarbons and particul rly to an improved combination ofprocess steps for converting low grade, light or full boiling range naphthas into high octane number motor fuels in high yields.

Hydroforming is a well-known and widely used process for upgrading hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range to increase. their octane numbers and to improve their burning .or' engine cleanliness characteristics. In hydroforming, the hydrocarbon fraction or naphtha is contacted at elevated temperatures and pressures and in the. presence of hydrogen or hydrogen-rich process gas with solid catalytic materials under conditions such that there is no net' con-. sumpt-ion of hydrogen and ordinarily there, is a net production of hydrogen in the process. A variety of reac tions occur during hydroforming including dehydrogenation of naphthenes to the corresponding aromatics, hydrocracking of paraffins, isomerization of straight chain parafiins to, form branch chain paraffins, dehydrocyclization of parafiins, and isomerization of compounds such as ethylcyclopentane to form methylcyclohexane which is readily converted to toluene. In addition to these reactions, some hydrogenation of olefins and. polyolefins occurs when such compounds are present, and sulfur or sulfur compounds are eliminated by conversion to, hydrogen sulfide or to metal sulfides on the catalyst making the. hydroformate burn cleaner or form less engine deposits when used as the fuel in an internal combustion engine.

Hydroforming is usually applied to a rather wide boiling range naphtha, i.e., one having a boiling range of from about 125 F. to about 400 to 430 F. It hasbeen known that the lower boiling naphthas are not substantially improved by hydroforming processes as ordinarily conducted. The extensive report entitled An Appraisal of Catalytic Reforming? in Petroleum Processing, for August 1955; for example, states on page 1174 Optimum reformer utilization is. obtained by not using feed stool; constituents boiling much below 200 F. which do not contribute greatly to the increased octane during reforming as these merely take up. reformer capacity better; used for. high boiling-materials more susceptible to octane upgrading. In view of the continuing demand for more and higher octane number gasolines, however, it is becoming increasingly, important to upgradev these lower boiling fractions.

Itis the object of this invention to provide theart with an improved method for reforming. or upgrading naphthas.

It is also an object of this invention to provide the art with an improved process for reforming or upgrading a low octane, wide boiling range naphtha into high octane number motor fuels.

It is a further object of this inventionto provide the art with an integrated process'for'upgrading low octane;

wide boiling range naphthaswhich will efiectivelyup' 2,944,001 Patented July 5, 1960 7 "ice 21 grade the lower boiling as well as the higher boilingconstituents of the naphtha.

It is also a further object of this invention to provide an integrated process for producing high yields of high octane number motor fuels.

These and other objects willv appear more clearly fiom the detailed specification and claims which follow.

It has now been found that high yields of high octane numberv motor fuels may be prepared in an integrated process. if the virgin naphtha feed having, for example, aboiling range of about to about 400 F. is first fractionated to separate a light naphtha fraction comprising the initial to 200 F. end point fraction and a. heavy naphtha comprising the 200-400 F. end point fraction. These two fractions are then separately hydroformed under the optimum conditions for upgrading each. Both hydroformates are then subjected to treatment with molecular sieves having pore diameters of about 5 A.

units which adsorb the normal parafins while passing the.

treatment in order that the branch chain compounds formed by this treatment may be recovered and added to the other non-normal paraflin constituents. The heavy normal paraflins recovered from the molecular sieve treatment of the heavy hydroformate are not particularly suited as a feed to an isomerization treatment. These heavy normal paraifins, however, do form a satisfactory feed, for an aromatization treatment or, if desired, they may be recycled to the heavy naphtha hydroformer vessel. In accordance with a further embodiment of the present invention, propylene and/or n-butylene, or a cracked refinery gas stream which contains these olefins is utilized to desorb the normal paraflins from the molecular sieves. In accordance with this invention the olefins utilized for desorption are separated from the normal paraflins and passed to a polymerization unit and the resultant polymer may thereafter be subjected. to a hydrogenation treatment utilizing make-gas from the hydroformer operation in order to hydrogenate the polymer and render it suitable for blending with the other motor fuel constituents produced in accordance with this invention.

Reference is made to the accompanying drawing which illustrates diagrammatically a suitable flow plan for carrying out the process in accordance with the present invention.

Referring to the drawing, a wide boiling range naphtha feed is supplied to the system through inlet line 10 into fractionator 11 where the feed is separated into an overhead light naphtha fraction boiling up to about 200 F. and a heavy naphtha fraction boiling in the. range of about 200 to 400 F. The light naphtha fraction is withdrawn through line 12 and supplied to low pressure platinum hydroformer 13. Catalysts that may be used for hydroforming the light naphtha fraction in-reactor 13" are those containing 0.01 to 1.0 wt. percent platinum or num amylate and having a surface area of about 150 to 220 square meters per gram. 7

The pressure in the hydroforming reaction zone 13 should be in the range of to 12 p.s.i.g. andis preferably about 50 p.s.i.g. It has been found that in the pressure range of about atmospheric pressure to 125 p.s.i.g. it is possible with the platinum-containing catalysts described above 'to upgrade light virgin naphthas having a mean average boiling point offl69 F. and a Research Clear oc-. 'tane number of 66 into a hydroformate having a Retaining catalysts producesa hydroformate of only 85 Research O.N.'a-t 75 vol. percent yield. Moreover, it was found impossible to increase the octane number much above 85 by'hydroforming this light naphtha with platimum-containing" catalysts at 200 p.s.i.g.

' The temperature of the, catalyst bed in reactor 13 should be in the range of from 800975 F preferably from 875 to 950? F. The naphtha feed is preheated to temperatures in the. range of from 900l.050 F., preferably about 975 to. 1000" F., preparatory to charging to the hydroforming reaction zone 13.. Hydrogen or hydrogen-rich process or recycle gas is supplied to the hydroformer 13 by line '14 and is preheated to 900 1300 F., preferably about 1200 F., preparatory to charging to the hydroforming reaction zone. If desired, the naphtha and hydrogen-rich gas may be heated together in which event the preferred preheat temperature is in the range of from 9001000 F.

a The hydrogen-rich or recycle gas normally contains about .6590 mol. percent hydrogen with the remainder being light hydrocarbon gases. The exact composition of the recycle gas depends upon the hydroforming reaction conditions and upon the pressure and temperature at which the recycle gas is separated from thehydroformate. The amount of recycle gas employed, may. vary from 500-5000 and is preferably aboutl000-3000 stand ard cubic feet per barrel of naphtha feed.

In addition to preheating the naphtha feed. and recycle gas, the. additional heat load may be supplied to the hydroforming reaction Zone 13 by the sensible heat of the regenerated catalyst in the event that a fluidized solids operation is employed or by circulating reactor catalyst through a heating zone or by arranging heating coils in the catalyst bed or jacketing the reactor-and circulating hot flue gases, mercury, Dowtherm, or the like there through. a

the agglomeration of the platinum metal into relatively large or massive crystals having diameters in excess of about A. units. Treatment of the catalyst with a halogen compound such as hydrogen chloride or the like is eifective in restoring the halogen content of the catalyst to the desired level and to this extent it is effective in restoring the activity of deactivated or partially deactivated catalyst. On the other hand, treatment of the catalyst with an elementary halogen, such as'chlorine or the like, not only restores the catalyst halogen content to the desired level but also acomplishes the redispersion of the platinum metal by breaking up the large platinum crystalites. p

' Regeneration of the catalyst is effected as required by burning carbonaceous materials therefrom with oxygencontaining gas at temperatures of 900-l200 F., preferably at 1.000-1100 F. The pressure in the regeneration operation may be the same as during hydroforming or it may, if desired, be lowered to near atmospheric pressure. In burning off the carbonaceous deposits, a certain amount of water is formed by combustion of hydrogen in said deposits. This water is stripped from the catalyst and passes overhead with the flue gases and is removed from the system. Excess air is used for. the regeneration to insure the complete removal of carbon or coke from the catalyst and to eifect reactivation in admixture with chlorine. The regenerated or carbon-free catalyst can advantageously be treated with air at temperatures of 8501l00 F. for from about 1-4 hours. The regenerated catalyst is then contacted with chlorine gas or a mixture of chlorine gas and air in order to reactivate the catalyst, restore its chlorine content, and redisperse or break up the large platinum crystalites that formed during the use of the catalyst. I

V The chlorine partial pressure during reactivation may be in the range of from 0.00lto 2 atmospheres, preferably, 0.01 to 1 atmosphere. The quantity ofchlorine supplied may be in the range of 0.1 to 2.0 wt. percent, preferably, about 0.5 wt. percent based on the catalyst. The chlorine treatment may be carried out'for periods of from about 15 seconds to 1 hour, preferably, about 1-15 minutes;

While the chlorinetreated catalyst may be subjected to air-stripping to remove excess chlorine, it is usually preferred to avoid stripping chlorine from the reactivated catalyst since the chlorine content governs the hydrocracking activity of the catalyst which in turn controls the volatility of the hydroformate. The amount of chlorine which is desirableto have remaining on the stripped cata- Under the reactor conditions maintained in hydro- V former 13, there is a tendency for carbon to form on lyst is related to the platinum content of the catalyst.

With high platinum content catalysts a relatively high chlorine content is desirable and a correspondingly lower chlorine content is desirable for lower platinum contents.

A In general, the total amount of chlorine (i.e., both chemi-' Reaction products are taken overhead from hydro 'fo rmer 13 by line 15 and are cooled to condensation perature of regeneration and it is preferred to contact the from the accumulation of poisons the deactivation of hydroforming catalysts proceds by two mechanisms: (1)

is the preferred treating agent for reactivation. Aside the loss of chlorine or other halogen which is normally present as part of the catalyst composition and that con tributes substantially to the catalyst activity and (2) temperatures and passed into gas-liquid separator 16. Hydrogen-rich recycle gas is withdrawn from the separator by line 17 and is returned to the hydroformer by line 14. Liquid hydroformate is withdrawn from the bottom of the separator by line 18 and it is supplied to molecular sieve separation vessel 20, preferably, after preheat ing 'to 200'-300 F. or sufiiciently high to completely vaporize the hydroformate.

V V The scientific and patent literature contain numerous references to the sorbing action of natural and synthetic zeolites. Among the natural zeolites having thissieving property may be mentioned chabazites. A synthetic zeolite with molecular sieve properties is. described in US. Patent No. 2,442,191. Zeolites vary somewhat in composition but generally contain the elements silicon, aluminum. and oxygen as well as an alkali metal and/or an alkaline earth metal element, e.g., sodium and/ or calcium. The naturally occurring zeolite,analcite, for instance, has the empirical formula NaAlSi O H O. Barrer in U.S. Patent No. 2,306,610 teaches that all or 'part of the sodium is replaceable by calcium to yield on dehydration a molecular sieve having the formula (CaN'q z) Al- Si O Black, U.S. Patent No. 2,522,426 describes a synthetic molecular sieve zeolite having, the formula A large number of other naturally occurring zeolites havingmolecular' sieve activity, i.e., the ability to adsorb a straight chain hydrocarbon and exclude or reject the branch chain isomers and aromatics because of differences in molecular size, are described in an article entitled Molecular Sieve Action of Solids appearing in Quarterly Reviews, vol. Ill, pages 293-320 (1949 published by the Chemical Society (London).

The molecular sieve separation vessel 20 is charged with a natural or synthetic zeolite of the class described above having a pore size of approximately 5 A. which will readily adsorb the normal parafiins" contained in the hydroformate but will not adsorb the isoparaffins or aromatics contained therein. if desired, the hydroforrnate can be passed through a guard zone containing a molecular sieve material having pore diameters of 4 A. or smaller which will serve to remove any water or hydrogen sulfide or the like contained in the hydroformate. This is highly desirable since both water and certain sulfur compounds are more strongly adsorbed than most hydrocarbons and it is difiicultto desorb them. Since these contaminants frequently occur in hydroformates in small amounts, continued use' of the 5 A. sieveswould require periodic interruptions to desorb the. contaminants and restore adsorbent capacity. By using a guard bed of" molecular sieves having pore openings of 4 A. or less, the contaminants are removed, but the hydrocarbons are not adsorbed. Since the capacity of the, 4 A. and

smaller sieves for water is high, the total volume or amount of this sieve as compared to the total volume or amount of the 5 A. molecular sieve is small. Ordinarily, it is preferred to arrange the adsorbent units in pairs so that one unit may undergo desorption or regeneration while the other unitis on stream. Water may be desorbed from the guard'bedfbyfpassing hot gases such as dry air therethrough. It'should be understood, however, that if the'hydr'oformate is dry and /or substantially free of sulfur compounds, ii -5. HOtnecessary to provide a guard bed;

The hydroformate feed is passed in vapor phase, preferably, at temperatures of about 200-300 R, into' 'the molecular sieve separation zone or tower 20. The adsol-bent or molecular sieve material is arranged in any desired manner in the adsorption zone or tower. It may, for example, be arranged on trays or packed. therein with orf without supports. Conditions maintained, for the molecular sieve treatment in the adsorption zone or 'tower are flow rates of 0.1 to 5 v./-v./hr., temperatures of about 175-350 F., and pressures from atmospheric pressure to several hundred pounds per square inch.

The light naphtha hydroformate substantially free from straight chain parafi'ins is withdrawn from the adsorption zone or tower by line 21 and is sent to storage or used for blending or for direct employment as a high octane number motor fuel.

When the molecular sieves in the adsorption zone or tower 20 become saturated with normal paraflins as may be determined by conventional means, such as refractive index, gravity, or spectrographic analysis of the effluent, the flow of hydroformate is stopped and the desorption or regeneration of the sieves begins. Desorption is offected by passing an olefin-containing gas, preferably, one containing a substantial proportion of propylene, preheatedto 200250 F. through the bed of molecular sieves via. line 22. The stripping gas may be passed through a guard bed similarly'to the hydroformate 1f necessary to remove the contaminants that might bee come absorbed on the molecular sieve. Cracked refinery gases containing propylene and/or n-butylene are pre: ferred as thestripping gas, not only because of their availability and efficacy in stripping off the adsorbed nor.- mal parafiins but also because of the value of these olefins after separation from the absorbate as a feed to a poly: merization unit. Without changing the temperature of the adsorption zone or tower the stripping or desorbing gas replaces the adsorbed parafins with the propylene and/or other olefins. The desorbed normal paratfins and the non-olefinic constituents of the stripping gas and any iso-butylene are withdrawn from the tower 20' via line 23, cooled or condensed and passed into gas-liquid sepae rator 24. The unadsorbed stripping gases are removed through line 54. If sufiicient iso-butyle'ne is present, this gas stream may be passed "to polymerization zone 57 for ctr-polymerization with propylene and/or n-butylene ree covered from gas-liquid separators 38 and/or. 39. However, for desorbing G and C normal paraffins, propylene will usually be preferred. For higher boiling normal paraflins, such as C C paraflins, either propylene or n butylene may be used, preferably, n-butylene. In some instances, the molecular sieve may have sufiicient catalytic activity to polymerize iso-butylene. In such instances, it may be preferred to use iso-butylene-free gas or to remove this isomer by selective conversion in the poly: merization zone before use as a desorbing gas in the. molecular sieve towers. The light, normal paraflms are withdrawn from gas-liquid separator 24 via line 25 and supplied to hydroisornerization reactor. 26. Isomerization ofthe light normal paraffins is preferably carried out. as hydroisomerization or by. means ofF-riedel-Crafts catalyst, such as. A101 in whichcase a substantial partial pressure of hydrogen will advantageously be employed to promotev selectivity and prolong catalyst life. Although a number of catalytic materials may be employed to pros. mote hydroisomerization, nickel deposited on silica-v alumina or. platinum deposited on silica-alumina, are, particularly useful for this purpose. For example, 5'. percentnickel on silica-alumina may be employed at a pressure of about 350 |p.s.'i.g. and at a temperature of about 700 F. to isomerize a wide range of normal parafiins fallingwithin the gasoline range. Hydrogen, partial pressure in the hydroisomerizatio-n reaction zone may be provided by withdrawing excess or gas from line 17 by line 27. It is usually desirable, to employ a sulfur removal or guard zone 28 in the hydrogen feed line so as to avoid deactivation of the catalyst in the reactor vessel 26. The hydroisomerizate is Withdrawn. from reactor vessel 26 by line 28 and is cooled and; condensed and discharged into gas-liquid separator 29. The liquid hydroisomerizate is withdrawn from separator 29 by line 30 and recycled to molecular sieve separation zone 20 for recovery of isoparaffins along with nonnorm'al hydrocarbons and the aromatics formed in the hydrofo-rming zone.

The heavy naphtha or the 200 400 P. fraction, is withdrawn from fractionator 11 by line 31 and passed to high pressure hydroformer 32.

The heavy naphtha fraction is hydroformed in reactor 32 under essentially conventional or well known conditions. For example, the heavy naphtha may be hydroformed incontact with 10 wt. percent molybdic oxide on activated alumina catalyst. at temperatures of about; 850-l 000 F., preferably, about 925 F. at pressuresup to about 750 p.s.i.g., preferably, about 200 p.s.i.g., and in the presence of from about 2000-8000 cu. ft. ofhydrogen-rich gas per barrel of feed. Alternatively, the heavy naphtha may be hydroformed-in contact with a catalyst-v consisting essentially of about .5 wt. percent platinumi' '7 heavy naphtha hydroformate is taken overhead from the hydroformer 32 by line 33 and passed through coolers or condensers and thence into gas-liquid separator 34. Hydrogen rich or recycle gas is removed irom separator 34 by line 35'- for recycling to the hydroformer 32. Excess hydrogen-rich gas is removed from the system by discharge line 36. The heavy naphtha hydroformate is withdrawn from separator 34 by line 37 and passed to molecular sieve separation Zone or tower 40. Tower 40 is similar to tower 20 and is charged with the same type of zeolite or molecular sieve and is operated in essentially the same way as tower 20, i.e., at a temperature sufficiently high to maintain the hydro-formate in vaporous form.

Heavy naphtha hydroformate essentially free of norrnal paraflins is withdrawn from the molecular sieve separation tower 40 by line 41, through gas-liquid separator 38, and is then passed to storage or blending or is used directly as a high octane number motor fuel. When the molecular sieves in the adsorption zone 40 become saturated with normal paraflins, they are regenerated by supplying an olefin-containing gas via line 42 as described above for the regeneration of the molecular sieve material in tower 20f The desorbed heavy normal paraflins and the unadsorbed components of the desorbing gas are withdrawn from tower 40 via line 43 and cooled prior to discharge to gas-liquid separator 44. The unadsorbed gases are removed through lines 55 and may be vented or passed to polymerization zone 57 for conversion of iso-butylene, if desired. The heavy, normal parafi'lns are withdrawn from separator 44 via line 45 and are passed or. recycled via line 46 to the high pressure hydroformer 32 or are passed .via line 47 ,to aromatizer 48 where they may be subjected to known aromatization catalysts and reaction conditions to convert the heavy paraffins to aromatics. For example, the heavy normal paraffins may be aromatized in contact with such catalysts as chromia-alumina, chromia-magnesia-alumina, platinum-alumina, molybdena-alumina, etc. at temperatures of about 8501050 F., at pressuresbelow about 500 p.s.i.g., preferably, below about 200 p.s.i.g., and in the presence of about 2000-8000 cu. ft of hydrogen-rich gas per. barrel of feed The 'aromatizate iswithdrawn irom reactor 48 via line 49, condensed and passed to gas-liquid separator 50. The liquid aromatizate is withdrawn from separator 50 .via line 51 and-either passed to blending or storage via outlet line 52 or is recycled via line 53 to molecular sieve separation zone .40.

Olefinic displacement gas is withdrawn from separator 39 via line 56 and from separator 38 via line 65 and these streams are combined and passed through line 66 into polymerization zone 57 where the gaseous olefins, preferably, the C s and C s, used to displace the normal paraflins from the sieve adsorbent, are polymerized to yield additional quantities of high octane fuel components. Isobutylene may be obtained through lines 54 and 55 as already indicated. Usually it will be desirable to hydrogenate the polymer if the gaseous olefin feed is predominantly normal and isobutene; In this case the polymer is withdrawn from zone 57 via line 58 and passed to hydrogenation tower 6!). Hydrogen from the hydroformer zone 13 may be supplied to the hydrogenationzone 60 by connecting lines 61, 27 and 17. Additional hydrogen may be supplied via lines 36 and 67. The hydrogenated polymer is discharged from hydrogenation'zone '60 through line 62 into gas-liquid separator 63 and is withdrawn as liquid product through line 64 for transfer to storage or for use as a blending agent in the preparation of high octane number motor parafiins, the poorest octane components, so thafthy may be further processed to improve their octane numbers and increase their'valu e for blending into the motor gasoline pool and which utilizes to the full excess hydrogen produced in the hydroforming processes as well as the olefinic gases used for regenerating the molecular sieves.

Example I A light virgin naphtha from West Texas crude, boiling (5% to 95%) in the range of 162 to 191 F. and having an 'API gravity of 679 and a Research clear octane number of 66.1, is hydroformed by contacting with a catalyst comprising 0.6 wt. percent platinum deposited on al: coholate alumina at a' temperature of 900 F.,'a pressure of 50 pounds per square inch, a feed rate of l.2.weights of naphtha f eed per hour per Weight of catalyst, and in the presence of 2000 cu. ft. of recycle hydrogen per barrel of feed for a processing period of 8 hours. There is obtained a yield of 73.0 vol. percent of C product having a Research O.N. clear of 93.0. V

. The C hydroformed naphtha is. combined with stabilized isomerizate, vaporized, and passed at 240 F. through a bed of molecular sieves having pore openings of about 5 A. until the sieves are about saturated with normal paraflins. The adsorbed normal parafiins are then desorbed with propylene at the same bed temperature and are passed to a hydroisomerization zone consisting of a fixed-bed of 4.5% nickel on silica-alumina catalyst at 675 F., 400 pounds per square inch pressure, 0.8 weight of n-paraflins per hour per weight of catalyst, and with 8000 cu. ft. of hydrogen per barrel of hydrocarbon. The isomerizate is stabilized to remove small amounts of C and lighter hydrocarbons and is com Example II i A 53.1 Research O.N., virgin naphtha is fractionated to obtain,28 vol. percent of a light naphtha (157254 F.) and 72% of heavy naphtha (228330 F.). The 66.1 octane number light naphtha is hydroformed, the

0 hydroformate treated with molecular sieves to re-' move normal parafiins, and the normal paraflins desorbed from the sieves by propylene displacement and hydroisomerized as in Example I. V

The 48.0 octane number heavy naphtha is hydroformed by contacting with a 10%. molybdena-on-alumina catalyst at 900 F., 200 pounds per square inch pressure, 0.4 weight of naphtha feed per hour per weight of catalyst, and in the presence of 2000 cu. ft. of recycle hydrogen per barrel of feed for a processing period of 4 hours. The C hydroformate obtained has an octane number of 96.0 and is combined with aromatized, heavy n-paraffins, vaporized, and passed at 350 F. through a bed of molecular sieves having pore openings of about 5 A. until the sieves are about 90% saturated with normal paraffins. The adsorbed normal parafiins are then desorbed at the same bed temperature with n-butylene contained in a refinery gas stream at 22% concentration. The normal parafiins (11 vol. percent on C hydroformate) are aromatized at 1000 F. and 10 pounds per square inch pressure over 10% MoO -on-ZnA1 O and combined with the heavy hydroformate for molecular sieve treating as indicated. i

Propylene concentrate obtained from the molecular sieve column used for removal of normal paraflinsfrom the light hydroformate and hydroisomerizate and nbutylene concentrate obtained from the sieve column used for removal of normal parafiins from the heavy hydrofor-mate and heavy, n-paraffin aromatized product are combined and polymerized with a P O -kieselguhr catalyst at 450 F. and 1000 pounds per square inch pressure.

Blending the light hydroformate-isoparaflin fraction and the heavy hdroformate-C -laromatics fraction with the propylene-butylene polymer gives, on the basis of naphtha feed, an 80.1 vol. percent yield of 100.4 Research octane number product. The highest octane number attained in direct, once-through hydroforming at practical plant throughput is 96-98. Under these conditions, the yield is 69 vol. percent.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood, however, that this invention is not limited thereto since numerous variations are possible without departing from the scope of the following claims.

What is claimed is:

1. A method for producing high octane number motor fuels which comprises fraotionating the naphtha to form a 200 F. end point light naphtha fraction and a 200 to 350 or 400 F. end point heavy naphtha fraction, hydroforming the light naphtha fraction in contact with a platinum-alumina catalyst at temperatures of from 800-975 F. and pressures below 125 p.s.i.g. and in the presence of from 500 to 5000 cu. ft. of hydrogen-rich gas per barrel of liquid feed, treating the light naphtha hydroformate with molecular sieves having pores of about 5 A. diameter to separate the normal paraffins contained therein, separating the normal parafims from the sieves by passing olefin-containing gases therethrough, treating the separated normal paraffins under isomerizing conditions to convert normal paraffins to branch chain isomers, passing the isomerizate to the molecular sieves for the recovery of the branch chain isomers along with the non-normal paraflin constituents of the light naphtha hydroformate, subjecting the heavy naphtha fraction to catalytic hydroforming at temperatures of from 850-1000 F. and at pressures above about 200 p.s.i.g. in the presence of from 2000 to 8000 cu. ft. of hydrogen-rich gas per barrel of liquid feed, treating the heavy naphtha hydroformate with molecular sieves having pores of about 5 A. diameter to separate the normal paraifins contained therein, separating the normal parafiins from the molecular sieves by passing olefin-containing gases therethrough, aromatizing the normal paraffins separated from the heavy naphtha hydroformate and recycling the resultant aromatizate to the molecular sieve treatment for the recovery of branch chain paraifins and aromatics therein with the non-normal parafiins in the heavy naphtha hydroformate, separating the olefin-containing desorption gases from the molecular sieves, polymerizing the separated olefins to form additional gasoline boiling range products and passing the resultant polymerizate, the light naphtha products and heavy naphtha products to blending and storage.

2. The method for converting low octane number naphtha feeds into high octane number motor fuels which comprises fractionating the naphtha to form a 200 F. end point light naphtha fraction and a 200 to 350 or 400 F. end point heavy naphtha fraction, hydroforming said light naphtha fraction in contact with a solid catalytic material at elevated temperatures and pressures for a period suflicient to substantially improve the octane number of the light naphtha fraction, separating the hydroformate from the normally gaseous materials, vaporizing the hydroformate, passing the hydrofromate vapors through a bed of molecular sieves having pore diameters of about 5 A. units which selectively adsorbs the normal paraffins from the hydroformate vapors, recovering from said molecular sieve separation hydroformate substantially free from normal parafiins, desorbing the normal paraffins from the molecular sieves by passing olefin-containing gases there through, hydroisomerizing the separated normal paraflins, recycling the hydroisomerizate to the molecular sieve separation step, separately subjecting said heavy naphtha fraction to catalytic hydroforming by contacting said heavy fraction in admixture with hydrogen with a solid catalytic material at elevated temperatures and pressures for a period sufticient to substantially improve the octane number of the heavy naphtha fraction, separating the heavy hydroformate from the normally gaseous materials, vaporizing the heavy hydroformate, passing the heavy hydroformate vapors through a bed of molecular sieves having pore diameters of about 5 A. units which selectively adsorbs the normal parafiins from the heavy hydroformate vapors, recovering from said molecular sieves heavy hydroformate substantially free from normal paraflins, desorbing the heavy normal paraffins removed from the heavy hydroformate vapors from the molecular sieves by passing olefin-containing gases therethrough, aromatizing said heavy normal paraflins separated from the heavy naphtha hydroformate, recycling the resultant aromatiz-ate to the heavy naphtha molecular sieve treatment for the recovery of branch chain parafl'ins and aromatics therein with the non-normal parafiin constituents in the heavy naphtha hydroformate, separating olefin-containing desorption gases from the molecular sieves and polymerizing the separated olefins to form additional gasoline boiling range products.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,695 Laughlin Oct. 22, 1946 2,522,426 Black Sept. 12, 1950 2,653,175 Davis Sept. 22, 1953 2,678,263 Glazier May 11, 1954 2,740,751 Haensel et al Apr. 3, 1956 2,767,124 Myers Oct. 16, 1956 2,818,449 Christensen et a1. Dec. 31, 1957 2,818,455 Ballard et a1 Dec. 31, 1957

Claims (1)

1. A METHOD FOR PRODUCING HIGH OCTANE NUMBER MOTOR FUELS WHICH COMPRISES FRACTIONATING THE NAPHTHA TO FORM A 200*F. END POINT LIGHT NAPHTHA FRACTION AND A 200* TO 350* OR 400*F. END POINTHEAVY NAPHTHA FRACTION, HYDROFORMING THE LIGHT NAPHTHA FRACTION IN CONTACT WITH A PLATIMUM-ALUMINA CATALYST AT TEMPERATURES OF FROM 800*-975* F. AND PRESSURES BELOW 125 P.S.I.G. AND IN THE PRESENCE OF FROM 500 TO 500 CU. FT. OF HYDROGEN-RICH GAS PER BARREL OF LIQUID FEED, TREATING THE LIGHT NAPHTHA HYDROFORMATE WITH MOLECULAR SIEVES HAVING PORES OF ABOUT 5 A. DIAMETER TO SEPERATE THE NORMAL PARAFFINS CONTAINED THEREIN, SEPARATING THE NORMAL PARAFFINS FROM THE SIEVES BY PASSING OLEFIN-CONTAINING GASES THERETHROUGH, TREATING THE SEPERATED NORMAL PARAFFINS UNDER ISOMERIZING CONDITIONS TO CONVERT NORMAL PARAFFINS TO BRANCH CHAIN ISOMERS, PASSING THE ISOMERIZATE TO THE MOLECULAR SIEVES FOR THE RECOVERY OF THE BRANCH CHAIN ISOMERS ALONG WITH THE NON-NORMAL PARAFFIN CONSTITUENTS OF THE LIGHT NAPHTHA HYDROFORMATE, SUBJECTING THE HEAVY NAPHTHA FRACTION TO CATALYTIC HYDROFORMING AT TEMPERATURES OF FROM 850*-1000*F. AND AT PRESSURES ABOVE ABOUT 200 P.S.I.G. IN THE PRESENCE OF FROM 2000 TO 8000 CU. FT. OF HYDROGEN-RICH GAS PER BARREL OF LIQUID FEED, TREATING THE HEAVY NAPHTHA HYDROFORMATE WITH MOLECULAR SIEVES HAVING PORES OF ABOUT 5 A. DIAMETER TO SEPARATE THE NORMAL PARAFFINS CONTAINED THEREIN, SEPARATING THE NORMAL PARAFFINS FROM THE MOLECULAR SIEVES BY PASSING OLEFIN-CONTAINING GASES THERETHROUGH, AROMATIZING THE NORMAL PARAFFINS SEPARATE FROM THE HEAVY NAPHTHA HYDROFORMATE AND RECYCLING THE RESULTANT AROMATIZATE TO THE MOLECULAR SIEVE TREATMENT FOR THE RECOVERY OF BRANCH CHAIN PARAFFINS IN THE AROMATICS THEREIN WITH THE NON-NORMAL PARAFFINS IN THE HEAVY NAPHTHA HYDROFORMATE, SEPARATING THE OLEFIN-CONTAINING DESORPTION GASES FROM THE MOLECULAR SIEVES, POLYMERIZING THE SEPARATED OLEFINS TO FORM ADDITIONAL GASOLINE BOILING RANGE PRODUCTS AND PASSING THE RESULTANT POLYMERIZATE, THE LIGHT NAPHTHA PRODUCTS AND HEAVY NAPHTHA PRODUCTS TO BLENDING AND STORAGE.

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