US2937132A - Upgrading a naphtha by fractionation and reforming the fractions - Google Patents

Description

y 1960 A. VOORHIES, JR 2,937,132

UPGRADING A NAPHTHA BY FRACTIQNATION AND REFORMING THE FRACTIONS Filed June 2-7, 1957 sscouo LIGHT NAPHTHA L 424 CONVERSION zom:

l v 2| FIRST 63 LIGHT NAPHTHA CONVERSION zom-z J '2 FRACTIONATOR 1 1 I? n FRACTIONATOR ISjI WIDE CUT NAPHTHA FEED 20 J &

l5 HEAVY NAPHTHA 4HYDROFORMING ZONE Alexis Voorhies, Jr. Inventor United States Patent;

UPGRADING A NAPHTHA BY FRACTIONATION AND REFORMING THE FRACTIONS Alexis Voorhies, Jr., Baton Rouge, La., assignor to Esso Research and Engineering Company, a corporation of Delaware Application June 27, 1957, Serial No. 668,367 6 Claims. (Cl. 208-64) The present invention relates to a method for reforming or upgrading hydrocarbon fractions boiling in the naphtha or motor gasoline boiling range to produce high yields of high octane number products.

Hydroforrning 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 consumption of hydrogen and ordinarily there is a net production of hydrogen in the process. A variety of reactions occur during hydroforming including dehydrogenation of naphthenes to the corresponding aromatics, hydrocracking of parafi'ins, isomerization of straight chain paraffins to form branch chain paraffins, dehydrocyclization of paraflins, 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 and sulfur or sulfur compounds are eliminated by conversion to hydrogen sulfide or to catalytic metal sulfides, making the hydroformate burn cleaner or form less engine deposits when used as a fuel in an internal combustion engine.

Hydroforming is usually applied to a rather wide boiling range naphtha, i.e., to one having a boiling range of from about 125 F. to about 400 to 430 F. It has been 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 at page 1174, Optimum reformer utilization is obtained by not using feed stock constituents boiling much below 200 F. which do not contribute greatly to increased octane during reforming as these merely take up reformer capacity better used for high boiling materials more susceptible to octaine upgrading. In view of the continuing demand for more and higher octane number gasolines, however, it is becoming increasingly important to upgrade these lower boiling naphtha fractions in order that the octane levels of the lighter fractions will be brought more nearly into line with the octane number of the higher boiling hydroformates.

It is the object of this invention to provide the art with an improved method for reforming or upgrading naphthas.

It is also the object of this invention to produce wide boiling range naphthas having a high octane number in the front end as Well as in the back end.

It is a further object of this invention to provide the art with a method for upgrading naphthas in which the "processing of the light naphtha and of the heavy naphtha will be so integrated that a final wide boiling range prod-- net will be formed having a satisfactory octane distribu. tion.

These and other objects will appear more clearly from the detailed specification and claims which follow.

It has now been found that wide boiling range naphthas can be upgraded to form high octane number products having good octane number distribution by subjecting the naphtha to distillation to form a C to C or light naphtha cut and a C or heavy naphtha cut, hydroforming the light naphtha cut in contact with a platinum-alumina catalyst in a first reaction stage, hydroforming the heavy naphtha cut with a molybdenum oxide-alumina or platinum-alumina catalyst at pressures of from about to 400 p.s.i.g., fractionating the heavy naphtha hydroformate to separate a C minus fraction, a C -C fraction and a C,-{- fraction, combining the C to 0, fraction from the heavy naphtha hydroformate with the light naphtha hydroformate and aromatizing the resultant mixture by treatment in contact with an aromatization catalyst such as a chromium oxide-alumina or a chromium oxide-titanium oxide catalyst, in a second light naphtha conversion stage whereupon the product from the aromatization or second light naphtha conversion stage is combined with the C and the C -ifractions of the heavy naphtha hydroformate to form a final product of high octane number with high octane levels in the front end as well as in the back end.

Reference is made to the accompanying drawing which diagrammatically illustrates a flow plan in accordance with the present invention.

Referring to the drawing, 10 is the naphtha feed inlet line through which a naphtha boiling in the range of from about to 430 F. preferably from about to 360 F. is supplied to fractionator 11. A light naphtha or C to 0; cut is taken overhead from the fractionator through line 12 and supplied to first light naphtha conversion zone 13.

The light naphtha fraction is hydroformed in reactor 13 in contact with catalysts containing 0.01 to 1.0 wt. percent platinum or 0.1 to 2.0 wt. percent palladium dispersed upon a highly pure alumina support such as is obtained from aluminum alcoholate in accordance with US. Patent 2,636,865 or from an alumina hydrosol prepared by hydrolyzing aluminum metal with dilute acetic acid in the presence of very small catalytic amounts of mercury. A suitable catalyst comprises about 0.1 to 0.6 Wt. percent platinum uniformly dispersed upon alumina in the eta phase derived from aluminum amylate and having a surface area of about to 220 square meters per grams. A preferred catalyst for fluidized solids operation is one comprising a mixture of a platinum catalyst concentrate consisting essentially of 0.3 to 2.0 wt. percent platinum on alumina microspheres formed by spray drying an alcoholate alumina hydrosol prepared in accordance with US. Patent 2,656,321 and mixed with sufiicient unplatinized alumina to form a catalyst composition containing about 0.01 to 0.2 wt. percent of platinum. The pressure in the first light naphtha conversion zone 13 should be in the range of from about 25 to about 200 p.s.i.g., preferably about 50-150 p.s.i.g. The temperature ,of the catalyst bed in zone 13 should be in the range of from 800 to 975 F. and is preferably within the range of 875 to 950 F.

The light naphtha feed is preheated to temperatures in the range of from about 900 to 1050 F., preferably about 975 to 1000 F. preparatory to charging to the conversion zone 13. Hydrogen or hydrogen-rich process or recycle gas is preheated to 900 to 1300 F., preferably about 1175 F., preparatory to charging to the conversion zone 13. The amount of hydrogen-rich gas employed may vary from about 500 to 8000 and is preferably about 1000 to 5000 standard cubic feet per barrel .metal catalyst, preferably platinum on activated alumina.

Suitable catalysts of the first type are those containing .about 5 to '15, preferably about 10 wt. percent M dispersed upon an alumina gel, activated alumina or silicastabilized alumina support. ond type are those containing about 0.01 to 1.0 wt. per- Suitable catalysts of the seccent platinum upon alumina, preferably about 0.6 wt. percent platinum upon high purity activated alumina derived from aluminum alcoholate as per US. Pat. 2,636,865, or from an alumina hydrosol prepared by the Patrick method. Reaction conditions are about 850-975 r. and

about 150 to 400 p.s.i.g., preferably about 200 p.s.i.g., with molybdenum oxide catalysts and about 300 to 350 p.s.i.g. in the case of platinum alumina catalyst. The catalyst may contain activators or promoters, the platinum catalysts, preferably containing up to about 1.0 wt. percent of halogen such as chlorine or fluorine. If a halogen-free alumina prepared by hydrolyzing aluminum amylate with aqueous ammonia or cold water and aging to convert the hydrolysis product to beta alumina trihydrate, drying and calcining, is impregnated with sufficient chloro platinic acid to provide 0.6 wt. percent platinum in the finished catalyst, the latter will inherently contain about 0.6 wt. percent chlorine. Hydrogen-containing gas, preferably hydrogen-rich recycle gas from .the hydroforming operation is supplied to the reaction zone 15 in amounts of about 1000 through 6000 standard cubic feet per barrel. The hydroforming reaction zone 15 may be operated as a fixed bed, moving bed or fluidized solids system. The heavy naphtha or C cut is maintained under reaction conditions in hydroforming reaction zone 15 until the liquid hydroformate has a research clear octane number of 85 to 102, preferably about 90 to 98.

The heavy naphtha hydroformate is withdrawn from hydroforming zone 15 via line 16 and transferred to fractionator 17 ,Where it is distilled to separate a high octane .C to C fraction removed via line 18 and transferred to product storage or blending, an intermediate or C -C cut removed via line 19 for further treatment which will be described below and a bottoms or C fraction also of high octane number which is removed via line 20 and transferred to product storage or blending.

The light naphtha is removed from the first light naphtha conversion zone 13 at an octane number of about 75 to 90, preferably about 80 to 85, through outlet line 21. The light naphtha hydroformate is then mixed in line 22 with the C to 0; cut from a heavy naphtha hydroformate supplied through line 19 and the resultant mixture is thereupon charged to second light naphtha conversion zone 23. This mixture is further reformed or aromatized in zone 23 in contact with catalysts containing from about 5 to about 40' wt. percent, preferably about 25 wt. percent chromium oxide, upon a support such as activated alumina, alumina gel, titanium oxide gel or the like. up to about wt. percent SiO may be included in the support to improve its stability. Also, if desired, small amounts of promoters such as potassium oxide, cerium oxide, and the like may be incorporated in the catalyst.

p the catalyst.

Ce O as promoters. Numerous aluminas of commerce are acceptable as catalyst bases. The silica stabilized alumina produced by mixing minor amounts of sodium silicate with sodium aluminate and then reacting with an aluminum sulfate solution such that the resultant slurry is at pH l01l is particularly. desirable. Other commercial aluminas, such as are prepared from gelatinous alpha alumina monohydrate are also suitable. Titanium oxide gels, particularly those stabilized with 210% silica or alumina, are also suitable bases for chromium oxide catalysts.

The pressure in the aromatization zone 23 should be in the range of from atmospheric pressure to about 100 p.s.i.g. If desired, hydrogen-containing process gases may be recycled through the aromatization zone at a rate of from about 500 to 3000 cu. ft. per barrel of liquid feed. The temperature of the catalyst bed reactor 23 should be in the range of about 950 to 1075 F. and is preferably within the range of 980 to 1050 F. The reactants are maintained under these reaction conditions in reaction zone 23 for a period suflicient toraise the octane number of the liquid product to about 90 to 102, preferably about 95 to 100 research clear. The aromatized product is withdrawn from conversion zone 23 via line 24 and is passed to product storage or blending. By

blending the aromatized product from conversion zone 23 with the C to C and the C -lfractions of the heavy hydroformate a motor fuel is produced having a clear research octane number in excess of 95 and having the high octane components distributed throughout the en- .tire boiling range of the final fuel product.

It is noted that the drawing herein is entirely diagrammatic and omits many items of equipment such as furnaces, pumps, valves, condensers and the like, which would be obvious to those skilled in this art. In so far as the conversion zones are concerned, they may be operated as a fixed or moving bed or as a fluidized solids system and when a moving bed or fluidized solids system is used, the conversion zone shown in the diagram will ordinarily comprise 2 or more separate vessels through which the catalyst particles are circulated. For example one vessel may be the reactor in which the desired conversion takes place, and a second vessel' may be the regenerator, where the carbonaceous deposit is burned from Moreover what is shown as a conversion zone may in fact be two or more reactor vessels in series with or without reheating means between.

The following example is illustrative of the present invention.

Example a and a research clear O.N. of 47.8.

The light naphtha fraction is subjected to hydroforming in contact with a catalyst containing 0.6 wt. percent platinum and about 0.7 wt. percent chlorine on a high surface area alumina derived from aluminum alcoholate.

The reaction zone is maintained at 50 p.s.i.g. and 900 F. and the naphtha is charged at 3.0 w./hr./w. and

hydrogen-rich recycle gas is charged at 5000 s.c.f./bbl.

42 parts of light naphtha charged yields 36.4 parts of If desired, small amounts of silica, i.e.,

A highly effective aromatization catalyst comprises a a I C hydroformate having a research clear O.N. of 80.5.

The heavy naphtha fraction (58 parts) is charged to fluid molybdenum oxide hydroforming reaction zone charged with finely divided catalyst containing 10 wt. percent M00 2 wt. percent SiO and 88 wt. percent The reaction zone is maintained at 200 p.s.i.g. and 900 F. and the naphtha is charged at 0.27 w./hr./w.

V and hydrogen-rich recycle gas is charged to the hydro- 7 5 forming reaction zone at 7000 s.c. f./bbl. The catalyst to oil ratio charged to the reaction zone is 1.1. The 58 parts of heavy naphtha charged to this unit produces 40.1 parts of C hydroformate having a research clear O.N. of 96.2.

The heavy naphtha hydroformate is subjected to fractionation to give 4.0 parts of mixed pentanes, 7.9 parts of C -200" F. naphtha of 75.6 research clear ON. and 28.2 parts of 200 F.+ naphtha of 100.8 research clear O.N.

The 7.9 parts of C -20O F. hydroformate from the heavy naphtha hydroforming are combined with the 36.4 parts of (1 product from the light naphtha hydroforming to give 44.3 parts of naphtha of 79.6 research clear O.N. This naphtha is fed to a chromium oxide 1 aromatization zone which is charged with a catalyst containing 100 parts A1 29 parts Cr O 2 parts K 0 and 0.86 part Ce O The aromatization reactor conditions are 1025 F. and 50 p.s.i.g. The feed rate is 0.57 w./hr./w. and the recycle rate is 2000 s.c.f./b. and the unit is operated on a four-hour cycle. The yield from the chromium oxide aromatization zone is 36.5 parts of C naphtha of 95.0 research clear O.N. This product combined with the mixed pentane and the 200 F.+ naphtha from the heavy naphtha hydroforming gives 68.7 parts of C naphtha of 97.2 research clear ON.

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 of preparing high octane number motor ,fuels which comprises fractionating a wide boiling range naphtha feed into a light naphtha cut and a heavy naphtha cut, subjecting the light naphtha cut to hydroforming under low severity conditions to convert the light naphtha to a 75 to 90 octane number product, subjecting the heavy naphtha to hydroforming under relatively severe conditions to produce an 85 to 102 octane number product, fractionating the heavy naphtha hydroformate into a C to C fraction, a C to C fraction, and a C fraction, combining the C to C fraction from the heavy naphtha hydroformate with the light naphtha hydroformate, aromatizing said mixture in contact with a chromium oxide catalyst to an octane number in the range of 90 to 102 and blending the aromatized product with the C to C and the C fractions of the heavy naphtha hydroformate to produce a motor fuel having a research clear octane number in excess of 95 and having high octane components distributed throughout the entire boiling range of the said motor fuel.

with a moiybdenum oxide-alumina catalyst at 850-975 F. to 400 p.s.i.g. and in the presence of about 1600 to 6000 cubic feet of hydrogen-rich gas per barrel of heavy naphtha feed.

4. The process as defined in claim 1 in which the heavy naphtha fraction of the feed is hydroformed in contact with a platinum-alumina catalyst at 850-975 F. and at about 300 to 350 p.s.i.g. and in the presence of about 1000 to 6000 cubic feet of hydrogen-rich gas per barrel of heavy naphtha feed.

5. The process as defined in claim 1 in which the light naphtha fraction of the feed is hydroformed in contact with a platinum-alumina catalyst at 25 to 200 p.s.i.g., 800-975 F. in the presence of 500 to 8000 cubic feet of hydrogen-rich gas per barrel of light naphtha feed and the heavy naphtha fraction of the feed is hydroformed in contact with a molybdenum oxide-alumina catalyst at 850975 F. and 150 to 400 p.s.i.g. and in the presence of about 1000 to 6000 cubic feet of hydrogenrich gas per barrel of heavy naphtha feed.

6. The process as defined in claim 1 in which the light naphtha fraction of the feed is hydroformed in contact with a platinum-alumina catalyst at 25 to 200 p.s.i.g., 800-975 F. in the presence of 500 to 8000 cubic feet of hydrogen-rich gas per barrel of light naphtha feed and the heavy naphtha fraction of the feed is hydr0- formed in contact With a platinum-alumina catalyst at 850975 F. and at about 300 to 350 p.s.i.g. and in the presence of about 1000 to 6000 cubic feet of hydrogen-rich gas per barrel of heavy naphtha feed.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,695 Laughlin Oct. 22, 1946 2,653,175 Davis Sept. 22, 1953 2,740,751 Haensel et al. Apr. 3, 1956 2,758,062 Arundale et al. Aug. 7, 1956 OTHER REFERENCES Progress in Petroleum Technology, Am. Chem. Soc., Washington, D.C., Aug. 7, 1951, pages 365 to 371,

Claims (1)

1. A METHOD OF PREPARING HIGH OCTANE NUMBER MOTOR FUELS WHICH COMPRISES FRACTIONATING A WIDE BOILING RANGE NAPHTHA FEED INTO A LIGHT NAPHTHA CUT AND A HEAVY NAPHTHA CUT, SUBJECTING THE LIGHT NAPHTHA CUT TO HYDROFORMING UNDER LOW SEVERITY CONDITIONS TO CONVERT THE LIGHT NAPHTHA TO A 75 TO 90 OCTANE NUMBER PRODUCT, SUBJECTING THE HEAVY NAPHTHA TO HYDROFORMING UNDER RELATIVELY SEVERE CONDITIONS TO PRODUCE AN 85 TO 102 OCTANE NUMBER PRODUCT FRACTIONATING THE HEAVY MAPHTHA HYDROFORMATE INTO A C4 TO C5 FRACTION, A C6 TO C7 FRACTION, AND A C8+ FRACTION, COMBINING THE C6 TO C7 FRACTION FROM THE HEAVY NAPHTHA HYDROFORMATE WITH THE LIGHT NAPHTHA HYDROFORMATE, AROMATIZING SAID MIXTURE IN CONTACT WITH A CHROMIUM OXIDE CATALYST TO AN OCTANE NUMBER IN THE RANGE OF 90 TO 102 AND BLENDING THE AROMATIZED PRODUCT WITH THE C4 TO C5 AND THE C3+ FRACTIONS OF THE HEAVY NAPHTHA HYDROFORMATE TO PRODUCE A MOTOR FUEL HAVING A RESEARCH CLEAR OCTANE NUMBER IN EXCESS OF 95 AND HAVING HIGH OCTANE COMPONENTS DISTRIBUTED THROUGHOUT THE ENTIRE BOILING RANGE OF THE SAID MOTOR FUEL.

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