US2635123A - Reforming of hydrocarbons - Google Patents

Description

Patented Apr. 14, 1953 2,635,123 REFORMING F HYDROCARBONS Robert M. Kennedy, Newtown Sduare, Pa., as-

signor to Sun0il Company, Philadelphia, Pa., a corporation of New Jersey No Drawing.

. 1 This invention relates to a process for reforming gasoline, and more particularly to a process for reforming a gasoline havinga low octane j nuinber into a gasoline having a high octane number;

Gasoline fractions derived from petroleum, such as straight run gasoline fractions, are of sufficiently low octane number to be unsuitable 'for'use" in spark-type internal combustion engines. Such fractions have heretofore been subjected to various treatments in order to increase the octane number. Such processes are generally known as reforming, since the object thereof is to' reform, or convert, gasoline constituents of low octane number into high octane number constituents.

' Processes heretofore employed include the dehydrogenation of naphthene constituents to aromatics using a molybdenum oxide catalyst, and isomerization to convert straight-chain to branched-chain parafiins using a Friedel-Crafts catalyst such as aluminum chloride. Theseprocesses are subject to difficulties including excesslve coke formation, rapid catalyst deactivation, complicated operating manipulations, and the necessity of conducting each such process as an individual operation. It is also known that the removal'of sulfur compounds, such as mercap tans, enhances the lead susceptibility of gasoline,

and desulfurization has heretofore been accomplished, e. g. by extracting with caustic soda or treatment with sulfuric acid. A still further known processfor reforming gasoline involves the use of a catalyst containing a minor but substantial proportion of platinum, or palladium, which makes the use of a process employing this catalyst relatively expensive, and in some instances prohibitively expensive. In general, reforming processes heretofore employed involve a substantial amount of cracking whereby the higher molecular weight hydrocarbons of the charge are converted to lower molecular weight hydrocarbons, frequently forming substantial quantities of normally gaseous hydrocarbons, so that the volatilityof the product is substantially lower than the volatility of the charge. In such processes it is apparent that the charge must be of a higher boiling range than the boiling range of the desired product, or, if a gasoline boiling within the desired range of the product is employed, it is necessary to blend the product with higher boiling hydrocarbons in order to increase the boiling range to the value desired. Accordingly, where reformation, i. e. an increase in octane number, of-a gasoline boiling within the Application November 28, 1950, Serial No. 198,035

v 11 Claims. (01:.260-668) range desired for the product is required,--the cracking Observed in prior processes presents a t al disadvantage. 4

An object of the present invention is to pro- ,vide an economical process for reforming gasoline. Another object is to provide a process for reforming gasoline wherein the several reactions which enhance the octane number and lead susceptibility of gasoline occur simultaneously. A still further object is to convert a straight run gasoline to a higher octane number gasoline without substantially changing thevolatility of the gasoline. Other objects appear hereinafter.

It h asnow been discovered that by contacting a, gasoline fraction with a catalyst consisting of a major proportion of silica and minor proportions-of alumina and nickel, as hereinafter described, under certain conditions of operation, a reformation of the gasoline occurs wherein the constituents exhibiting a low octane number are converted to high octane number constituents, 'so that the octane number of the gasoline is greatly enhanced, and that the volatility characteristics of the product substantially coincide with those of the charge. Other advantages achieved by the present process are discussed hereinafter.

In accordance with the present invention, a gasoline fraction is contacted with a catalyst comprising silica, alumina, and nickel at an elevated temperature and under a high pressure of hydrogen. The resulting gasoline fraction exhibits an increased octane number and lead susceptibility. These advantages result from several simultaneous reactions which occur in the present process, each of which contributes to the'enhanced properties of the product. The most important of these reactions is the dehydrogenation of naphthenes to form aromatics, but the isomerization of straight chain paraffins to their branched chain isomers and desulfurization substantially contribute to the enhanced properties of the product.

The catalyst of the present invention consists of a major proportion of silica and minor proportion of alumina and nickel. This catalyst and its preparation is described in U. S. Patent 2,452,190 wherein it is described as useful for the polymerization of olefins. The catalyst which maybe used in the present process may contain alumina and nickel in somewhat larger quantities than describedin this patent. The present catalyst contains from to 99.98% of silica, from 0.01 to 25% alumina, and from-0.01 to 15% nickel, and it is important,-

order to achieve the advantages of the present invention that the constituents of the catalyst be maintained within the stated ranges in order to prevent undesired reactions, such as cracking, from becoming predominant. Thus, while the presence of Only relatively small amounts of alumina and nickel are required, it isessential to the present process that theybe present within the concentrations stated. It is preferred to employ a catalyst consistin of from 75 to 99% silica, from 0.5 to% alumina, and from 0.5 to 10% nickel, since with the constituents of the catalyst within these com centrations, good results are obtained throughout the defined limits for temperature .and pressure.

,n-ickelni-trate, Ni(NO3J,2.6l-I20, and 75 grams of aluminum nitrate, AHNOB) $9320, 1:0 2 kilograms of silica gel (i-8 mesh) .inian evaporating dish. .The .mixture was evaporated to dryness, with stirring, and then ignited .at :a temperatureof about 300 C. afor about nine .hours to convert the nitrates to their .respectiveoxides. Prior to use, the catalystmass was chargedintoacatalyst tube and ignited ior one hour with air at 400 C. toensure completeconversion tothe-oxides and to remove traces-of water. It wasthen reduced with a slow stream of hydrogen forrabout nine hours at some. to convert thenickel oxide to nickel; Also, for starting materials in the preparation of the catalyst composition :any com pound of aluminum, which upon ignition will yield alumina inactivated form upon si-lica gel, and nickel salt, which will yield nickel oxide whichcan be subsequently reduced tolnickel on the silica gel, .can be employed. Ber-example, freshly precipitated aluminum hydroxide can be admixed with nickel hydroxide (and-added to silica gel rand the wholeigni-ted then reduced as set forth herein. :Or, ifdesired an aluminum compound and a nickel compound can be-distributed on silica gel and the entire massignited in air followed by reduction of the ignited mass. As stated, other methods ofpreparation, which will beapparent toithose versedin the art,'can also .be -'employed.

:above described, the preferred catalyst of the present invention consists of silica, alumina, and nickel .However, chromia may besubs'tituted for alumina,- and: cobalt may be substituted for nickel, andgood 1 results obtained therewith where the.concentration.of the chromia is the same asstated for alumina and the concentration .for cobalt ,is .the .same as expressed for nickel. Thus, catalytic compositions consisting of silica, chromia, and nickel; silica, alumina, and cobalt; silica, alumina, and nickel; and silica, chromia, and'cobalt may be employed in the present process. Also, with silica as the predominating element, both alumina and chromia may be'employed either with'nickel or cobalt, or with both nickel and'cobalt, or both nickel and cobalt may be employed with either alumina or chromia.

The gasoline fraction which may be reformed in the present process is a petroleum gasoline fraction boiling in the range of from-60 Fpto 400 F. and which contains-at least 5% naphthenes. The gasolinetreated may containzfrom 0% to 40% aromatics and from 0% to olefins. A. substantial advantagecf theipresent In order to illustrate the preparation of the 'fractionbciling' in the range or from about 150 F. to 390 F. and containing from 20% to by volume of naphthenes, from about 4% to 30% by volume of aromatics, the remainder of the "charge being paraffins including isoparaffins.

instances the charge stock will con- .itain'sulfur-compounds, say up to about 1%, and ,in-the presentprocess the concentration thereof will bereduced, usually to negligible quantities,

:thecactual reduction depending upon the initial concentration. and the operating conditions. This desulfurization enhances the lead susceptibility of the gasoline product thereby forming an especially valuable pro duct.

A vfurther significant advantage of the present piocessis that the Volatility characteristics of theproduet do notdiffersubstantially from the charge stock. Thus, while a small amountof cracking occurs, as evidenced by theformation of aminor amount of.nor-ma1ly gaseous hydrocarbons, it isinot apredominant facton- .Accordingly,,a preferredembodiment of the present invention'is the treatmentofa gasoline-to increase the octane number thereof without substantially changing the .ycilat'ility characteristics. This emphasizes the importance o'f thedefined upper boiling limit ror the charge gasoline. fIf higher boiling fractions aremployed, say agas oil or kerosene fraction, considerably cracking may occur. atthe expense of the desired dehydrogenation of naphthenes.

The temperature to employ in the present precessmay be varied from 600 F. m 1,200 F. .andpreferabl-y is within the range of 800 F.- to 'LOOOFF'. Pressures-of from 50 to 1,500, pxs. i., and. preferably from 250.to 1,000 p.:s. i., give good results, such pressures-being obtained and maintaiiied by supplying'an atmosphere of, hydrogen. Ithas been round that the use of an elevated hydrogen pres s'uiieis essential to the successful operation ofthe present process. Theoptim-um pressure and temperature to employ :depends somewhat on the particular gasoline fraction beingtr'eatd and also the hourly liquid space Velocity used which maybe variedyfrom 0.1 to 10 volumes of liquid hydrocarbon 011 :1381 volume or catalyst per'hour.

In the present process, at leastabout 30%-of the naphthene content of the charge gasoline is converted to aromatic hydrocarbons, and under preferredoperative conditions a much larger percent maybe so converted. Hence, the product obtainedhas adecreased naphthene content or atleast 30% and .a correspondingly increased aromatic content, Also, under preferred conditions .of operation, the paramn content remains substantially unchanged, but substantial isomeri zation of normal to branched chain par'affins may be observed, which alsoserve's'to increase the octane number of the roduct.

The following examples, presented to facilitate an understanding of the present invention, illustrate preferred embodiments thereof, and are not necessarily to be considered as limiting the present invention.

Example 1 A straightrun-gasolinehaving az-boiling range of'from 170F'. to 370F.and a'na'phthen'e con- 3 tent-01 43 volume percentwas contacted with a catalyst consisting of 98% silica, 1% alumina, and

- 1% nickel at a liquid hourly space velocity of 1.

A hydrogen pressure of 1,000 p. s. i. and a tem- --perature of 878 F. was maintained. Properties and. compositions of the charge and product are internal combustion engines. 1

Example 2 Example 1 was repeated using the same charge Tga'solin'egbut a pressure of 500 p. s. i. and a'temperatu'reof 806 F. were employed. An increase inaromatic concentration in the product of over 36% was observed, with a corresponding decrease in the naphthene concentration, the concentration of parafilns remaining substantially unchanged.

Based on the liquid recovered, the gasoline yield was 97.2% and the yield of condensible normally gaseous hydrocarbons was 2.8%.

The above examples illustrate preferred embodiments of the present invention; when chromia is substituted for alumina, and when cobalt is substituted for nickel in the catalyst, substantially similar results are obtained.

A further important advantage of the present process is the production of relatively pure hydrogen from the dehydrogenation of naphthenes. since cracking is not an important reaction in the present process, the hydrogen produced is relatively pure, i. e. is not contaminated with substantial amounts of normally gaseous hydrocar-- bons, such as methane and ethane. Hence, the hydrogen produced may be recovered and employed in hydrogenation processes, such as the hydrogenation of catalytic gas oil, usually without purification. In some hydrogenation processes an especially pure hydrogen i desired, in which case if necessary the hydrogen produced by the present process may be subjected to purifying operations as known to the art.

A further embodiment of the present invention comprises the treatment of substantially pure naphthenes, or mixtures thereof, to produce by dehydrogenation the corresponding aromatic or mixture of aromatics. For example, cyclohexane, methyl cyclohexane, and the dimethyl cyclohexanes, and mixtures thereof, may be treated to produce, respectively, benzene, toluene, and the xylenes, and mixtures thereof. Where it is desired to recover the pure aromatic, it may be separated from the naphthene by methods known to the art, such as by silica gel adsorption, and the recovered naphthene may be recycled to be further converted to the corresponding aromatic.

- shown below:

- I Product Charge 1 Run 1 Run 2 boiling poiiif'ois'rmx F 216 210 261 50% boiling point (ASIM), F 246 j 242 242 70% boiling point (ASTM), F 270 268 .268 90% boiling point'(ASTM), F 812 300 308 Refractive index m}? l. 4192 1. 4223 1, 4202 Density d4" 0. 7476 0. 7518 0. 7487 Percent acid absorption l0. 9 21. 4 l8. 5

Composition:

Volume percent aromatics- 11 21 18 Volumeepercent naphthene 48 34 30 Volume percent paraflins 46 45 52 6 In obtaining the data described in the above examples, and in further operation of the present process, no decrease in the activity of the catalyst of regeneration when necessary, are additional advantages of the present invention over heretofore known processes. i

The invention claimed is:

1. Process for reforming a gasoline fraction boiling in the range of from 60 F. to 400 F. and containing atleast 5% naphthenes which comprises subjecting said fraction, at a temperature of from 600F. to 1,200 F. and a hydrogen pressure of from 50 p. s. i. to 1,500 p. s, i., to contact with acatalyst consisting of from 60 to 99.98%

silica, from 0.01 to 25% of a material selected from the group consisting of alumina and chromia, and from 0.01'to 15% of a material selected from the group consisting of nickel and cobalt.

2. Process for reforming a gasoline fraction boiling in the range of from 60 F. to 400 F. and containing from 20% to 70% naphthenes which comprises subjecting said fraction, at a temperature of from 800 F. to 1,000 F. and a hydrogen pressure of from 250 p. s. i. to 1,000 p. s. i., to contact with a catalyst consisting of from 75 to 99% silica, from 0.5 to 15% alumina, and from 0.5 to 10% nickel.

3. Process for reforming a gasoline fraction boiling in the range of from 60 F. to 400 F. and which contains at least 5% naphthenes which comprises subjecting said fraction, at a temperature of from 600 F. to 1,200 F. and a hydrogen pressure of from 50 p. s. i. to 1,500 p. s. i., to contact with a catalyst consisting of from 60 to 99.98% silica, from 0.01 to 25% alumina, and from 0.01 to 15% nickel.

4. Process for reforming a gasoline fraction boiling in the range of from 60 F. to 400 F. and which contains at least 5% naphthenes which comprises subjecting said fraction, at a temperature of from 600 F.-to 1,200 F. and a hydrogen pressure of from 50 p. s. i. to 1,500 p. s. i., to contact with a catalyst consisting of from 60 to 99.98% silica, from 0.01 to 25% alumina, and from 0.01 to 15% nickel, and recovering a gasoline product of increased octane number having substantially the same volatility characteristics as said gasoline fraction.

5. Process for increasing the aromatic content of a straight run gasoline fraction boiling in the range of from about F. to 370 F. and which contains from about 20% to about 70% naphthenes which comprises subjecting said fraction, at a temperature of from about 800 F. to about 1,000 F. and a hydrogen pressure of from about 250 p. s. i. to about 1,000 p. s. i., to contact with a catalyst consisting of about 98% silica, about 1% alumina, and about 1% nickel, and recovering a gasoline product having substantially the same volatility characteristics as said gasoline fraction, said gasoline product having an aromatic content at least 30% greater than said gasoline fraction.

6. Process for the dehydrogenation of a naphthene to the corresponding aromatic which comprises subjecting said naphthene, at a temperature of from 600 F. to 1.200 F. and a hydrogen tpressureof from50. p. s. i.to 1,500 p. s. i., to contact with a catalyst consisting of from 60 to 99.98% 'silica,.fro'm 0. 1 to 25% of a material selected from the group consisting of alumina and chromia, and from 0.01 to 15% of a material selected from the group consisting of nickel and cobalt.

7. Process for reforming a gasoline fraction boilingin therange of from 60 F. to 400 F. and whichcontains at least 5% naphthenes which comprises subjecting said fraction, at a temperature of from 600 F. to 1,200 Rand a hydrogen pressure of from 50 p. s. i. to 1,500 p. s. i., to contact with a catalyst consisting of from 60 to 99.98% silica, from 0.0.1 oo-25% chromia, and

from .0.01"to cobalt.

.8. Process for reforming "a gasoline fraction boiling in the range of-from 60 F. to 400 F. and which contains at least 5% naphthenes which comprises subjecting said fraction, at a temperature'of from 600 F. to .1,200 F. and a hydrogen pressure of from 50 p. s. i. to 1,500 p. s. i.,i to contact with-a catalyst consisting of from 60 to 99.98% silica, from 0.01t0 chromia, and

from'0.01-to 15% cobalt, and recovering a'gaso- 1 line product of increased octane number having substantially the same volatility characteristics as said gasoline fraction.

9. Process for increasing the aromatic content of a straight run gasoline fraction boiling in the range of from about 170 F. to 370 F. and which contains from about 20% to about 70% naphthenes which comprises subjecting said fraction, at atemperature of from about 800 F. to about 1,000 F. and a hydrogen pressure of from about 250 p. s. i. to about 1,000 p. s. i., to contact with a catalyst consisting 'oflabout 98% silica, about 1% chromia, and'about 1% cobalt, and recovering a gasoline producthaving substantially the same vola'tility characteristics as said gasoline I fraction, said gasoline .from 0.0 1 to 15% nickel.

11. .Process iorsreforminga gasoline fraction boilingin the range of from 60 F. to .4009 F. and

which contains at least 5% naphthenes which comprises subjecting said fraction, at a. temperature of fr0m600" F. to 1,200 F. andra'hydroge'n pressure of from p. s. i. to'1,500 ps. i., to contact with a catalyst consisting of from to 99.98% silica, from 0.01 to 25% alumina, and-from 0.01 to 15% cobalt.

ROBERT M. KENNEDY.

References Cited in the me or this patent UNITED STATES PATENTS Number Name Date 2,078,946 Houdry' May 4, 1937 2,324,762 Calhoun et al. July 20, 1943 2,330,090 Thomas et a1 Sept. 21, 1943 2,336,900 Taylor et al. Dec. 14, 1943 2,382,582 Ruthruff "is-(Aug. 14, 1945 2,401,246 Hull Mai/'28, 1946 2,452,190 'I-Ietzel et a1 'Oct. 26, 1948 2,495,700 Corson et al. Jan. 31, 1950 OTHER REFERENCES Forziati et al. Proceedings of 24th Annual Meeting, American Petroleum Institute, vol. 24, III (1943) pp. 3448.

Claims (1)

1. PROCESS FOR REFORMING A GASOLINE FRACTION BOILING IN THE RANGE OF FROM 60* F. TO 400*F. AND CONTAINING AT LEAST 5% NAPHTHENES WHICH COMPRISES SUBJECTING SAID FRACTION, AT A TEMPERATURE OF FROM 600*F. TO 1,200*F. AND A HYDROGEN PRESSURE OF FROM 50 P.S.I. TO 1,500 P.S.I., TO CONTACT WITH A CATALYST CONSISTING OF FROM 60 TO 99.98% SILICA, FROM 0.01 TO 25% OF A MATERIAL SELECTED FORM THE GROUP CONSISTING OF ALUMINA AND CHROMIA, AND FROM 0.01 TO 15% OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF NICKEL AND COBALT.