US2462792A - Alkylation process - Google Patents

Description

Patented Feb. 22, 1949 ALKYLATION PROCESS Francis T. Wadsworth, Texas City, and Robert J. Lee, La Marque, Tex., assignors to Pan American Refining Corporation, New York, N. Y., a

corporation of Delaware Application August 9, 1945, Serial No. 609,882

6 Claims.

This invention relates to a process for the conversion of hydrocarbons. More particularly it relates to a process for the alkylation of polycyclic hydrocarbons. In one specific embodiment this invention relates to the alkylation of polymethyl naphthalenes with olens.

One object of our invention is to provide a. process for the alkylation of alkyl polycyclic hydrocarbons with olens wherein side reactions are minimized. Another object of our invention is to provide a process for the alkylation of alkyl polycyclic aromatic hydrocarbons with olens under conditions conducive to the production of high yields of alkylation products, Which conditions avoid destruction of the alkylation catalyst. An additional object of our invention is to provide a process for the alkylation of aromatic hydrocarbons, especially naphthalene and its derivatives, under conditions and with a catalyst adapted to avoid or minimize the production of condensed ring compounds, such as binaphthyls and the like. Still another object of this invention is to provide a process for the employment of substantially anhydrous toluene sulfonic acids under carefully controlled conditions for the alkylation of polycyclic hydrocarbons with olens. An additional object of our invention is to provide novel alkylated polycyclic aromatic hydrocarbons. Further objects will become apparent as the description of our invention proceeds.

Briey, We have discovered that polycyclic hydrocarbons, such as naphthalene, methyl naphthalenes and polymethyl naphthalenes can be alkylated with oleins in the presence of substantially anhydrous toluene sulfonic acids to produce high yields of alkylated polycyclic hydrocarbons having molecular weights equal to the molecular weights of the olens and polycyclic hydrocarbons which have participated in the alkylation reaction. Particularly, We have discovered operating conditions for this alkylation process which are conducive to the obtainment of high yields of desired alkylates at high alkylation reaction rates. The operating conditions which we use obviate undesirable side reactions of the type hitherto encountered in alkylation processes of this nature, viz., olen polymerization and excessive catalyst destruction. We can use a Wide variety of alkyl polycyclic hydrocarbons in our process. Suitable sources of alkyl polycyclic aromatic hydrocarbons for use in our process are synthetic hydrocarbon fractions obtained by the catalytic conversion of petroleum oils with catalysts comprising at least one metal oxide selected from groups 2 to 6, inclusive, of the periodic table, particularly silica, although polycyclic hydrocarbons from other sources, e. g., coal tar, can also be used.

Specifically, a suitable process for the production of alkyl polycyclic aromatic hydrocarbons is the hydroforming process. In this process a petroleum naphtha, which may be a virgin or cracked naphtha or mixture of both, is converted to aromatic hydrocarbons by contact with a solid, porous dehydrogenation catalyst at a temperature in the range of about 850 F. to about 1050 F., preferably in the presence of hydrogen. Suitable catalysts are oxides of metals of groups 2 to 6 of the periodic system, particularly oxides of 6th group metals such as chromium and molybdenum, preferably supported by alumina or magnesia. Excellent catalysts can be prepared by depositing about 4 to about 10% of molybdenum oxide upon an activated alumina. Suitable space velocities for hydroforming fall Within the range of about 0.2 to about 4 volumes of the liquid charge stock per hour per volume of catalyst space. About 0.5 to about 8 mols of hydrogen can be charged to the process With each mol of naphtha feed stock. In addition to a high octane number naphtha, the hydroforming process produces a fraction which boils above the naphtha range, for example, in the range of about 425 to about 650 F., which is known as hydroformer bottoms. We can use the entire hydroformer bottoms or selected fractions thereof as feed stock for our process.

Hydroformer bottoms comprises a complex mixture of alkyland polyalkyl polycyclic aromatic hydrocarbons, including relatively large proportions of monoand polymethyl naphthalenes. Although the constitution of hydroformer bottoms fractions may vary to a minor extent, depending upon the specific catalyst, the age of the catalyst, the specific constitution of the feed stock, etc., remarkably uniform hydroformer bottoms can be produced in a commercial hydroformer plant.

A representative hydroformer bottoms fraction exhibits the following physical properties:

A.P.I. gravity l1. 0 Refractive indexND2D l. 5911 Specific dispersion.o 264 Specific gravity 2%0 989 It Will be noted that the hydroforrner bottoms have a rather narrow boiling range except for the last 20%. Distillation of the bottoms with fire and steam accompanied by some fractionation was carried out, 8 volume percent distillate fractions of the bottoms being separated. The refractive indices and specific dispersions of the distillate fractions of the hydroformer bottoms are shown in the following table:

Percent of Refractive Specific 4 Tractlon Prgffrlller Index, N D20 .Dispersion The precise chemical characterization of hydroformer bottoms or specific fractions thereof constitutes a difficult analytical problem. The general nature of the hydrocarbons present in hydroformer bottoms Was revealed by extraction of the bottoms with nitromethane, which is a solvent having high solvent capacity for polycyclic and alkyl polycyclic aromatic hydrocarbons under conditions of temperature and solvent/oil ratios under which it dissolved Vsubstantially no non-aromatic or monocyclic aromatic hydrocarbons. The hydroformer bottoms were fractionally extracted and the boiling points, refractive indices and specific dispersions of the extracts were determined. From the data so obtained, together with distillation analyses and chemical characterization, it appears that the hydroformer bottoms have the following composition (by volume) z Anthracene and alkylated anthracenes 1Dimechyl and higher alkyl groups.

It is to be remembered that the above values are only approximate and are given as our best estimate of its composition.

A variety of olens which may be either normally gaseous or liquid, can be employed in our alkylation process. Normally gaseous olefins constitute a preferred feed stock in our process when it is desired to produce alkylates having value as plasticizers for high molecular Weight resins and plastics, for example, natural rubber, butadiene rubbers such as butadiene-styrene copolymerizates (GR-S) or butadiene-acrylonitrile copolymerizates (GR-N), polystyrene, polyvinyl halide resins, cellulose and cellulose derivatives, etc. We can use clef-ins such as propylene, butylenes, amylenes, hexenes, and the like. We can 4 also use mixtures containing two or more olens and/or other hydrocarbons, such as are found in Ipetroleum refinery hydrocarbon fractions.

The catalyst employed in our alkylation process is a substantially anhydrous toluene sulfonic acid. The catalyst may be ortho,V meta, or para-toluene sulfonic acid, but We prefer to use a technical toluene sulfonic acid which contains more than one isomer and may contain all three. We have found that the substantially anhydrous toluene sulfonic acids are much more soluble in hydrocarbons than hydrous toluene sulfonic acids and `can be used as homogeneous catalysts under conditions Where hydrous toluene sulfonic acids are'quite immiscible with hydrocarbonA feed stocks. Furthermore, anhydrous toluene sulfonic acids appear to induce higher reaction rates than the hydrated acids. In fact, in many instances, hydrated toluene sulfonic acid has been found to be substantially devoid of catalytic alkylation activity. Typical toluene sulfonic acids which We have employed as catalysts for the alkylation of alkyl polycy-clic aromatic hydrocarbon with olens vhave the following properties:

Neutralization equiv. (theory: 172) Density, grams/inl. at 84.9 F

Refractive index: y

(a) Of 11.4% aqueous solution 1.352

brown color `We have found that although we may use as little as 1 mol percent, it is desirable to use at least 3 mol percent, preferably 10 mol percent of toluene sulfonic acid based on the alkyl polycyclic hydrocarbon employed as feed stock. Increased yconcentration of toluene sulfonic acid in the reaction zone increases the rate of the alkylation reaction. Thus, Vthe Yemployment of 10 mol percent of toluene sulfonic acid induced a higher rate of alkylation than 3 mol percent. We can use 20 mols of toluene sulfonic acid per 100 mols of alkyl polycyclic hydrocarbon, or-even more.

The rate of alkylation is also affected by the specic olefin feed stock. We have found that the rate of alkylation is reduced with increasing molecular weight of the olen feed stock. Thus, propylene alkylates an alkyl polycyclic aromatic hydrocarbon at a considerably faster rate than `butene-l, and butene-l alkylatesy more rapidly than pentene-l. Data illustrating the effects of catalyst concentrationY and specific oleiins on the rates of alkylation are set forth vin Table I. In the experiments which yielded the data -set forth in Table I, a Well-stirred solution of technical toluene sulfonic acid in a fraction of hydroformer bottoms boiling in the range of about 480 to 530 F. was in each case maintained at 265 F., While the pure olefin was introduced in slight excess of the reaction rate. The fraction ofAhydroformer bottoms that Was used comprised' a substantial proportion of dimethyl naphthalenes. The maximum rate rof olefin introduction was 0.006 cubic foot per minute for a 15 mol aromatic hydrocarbon charge containing 10 mol Ypercent of technical ytoluene sulfonic acid. The data presented inTable I show that 10'mo1 percent toluene -sulfonia acid induced an enhanced rate of alkylation as compared with 3 mol percent of toluene Sinfonie acid.

TABLE I Efect of catalyst concentration and nature of l olefin on the allez/lation of dimethyl naphtha- Zenes Temperature: 265 F.Charge stock: 480-530 F. fraction of hydroformer bottoms Mols of Olefln Absorbed/Mol of Hydrocarbon] Hour Time Hours 3% catalyst 10% catalyst Propylene Butene-l Butene-l olefin/mol of Aromatic 1. 81 1. 82 2. 04 58 Total time 25 47. 5 14 12 The optimum temperatures for the use of substantially anhydrous toluene sulfonic acid catalysts for alkylating alkyl polycyclic hydrocarbons with olens lie within the range of about 265 Penetene-l to about 300 F. We have found that in admixture with alkyl polycyclic hydrocarbons and olens, toluene sulfonic acids begin -t-o decompose at a substantial rate at temperatures above about 300 F., although in the absence of polycyclic hydrocarbons and `oleiins considerably higher decomposition temperatures are indicated. It is probable that decreased alkylation rates observed at temperatures in excess of 300 F. are attributable to the decomposition of toluene sulfonic acids. However, we do not intend to be bound by any theory regarding the alkylation reactions.

Representative data indicating the effect of temperature on the rate of alkylation of alkyl polycyclic hydrocarbons with olens are illustrated in the graph on the accompany drawing. The data were obtained by again alkylating a fraction of hydroformer bottoms boiling in the range of about 480 to about 530 F., comprising a substantial proportion of dimethyl naphthalenes, using a concentration of 10 mol percent of technical toluene sulfonic acid per mol of dimethyl naphthalene in the feed stock. Butene-l was introduced into the alkylation zone at a rate slightly in excess of its absorption (reaction) rate. From the graph on the accompanying drawing it will be evident that alkylation proceeded at a slow rate at 212 F. and at a rapid rate at 302 F. However, at 392 F., the alkylation rate was appreciably lower than the rate at 302 F. The optimum alkylation rate' is achieved and the recovery of toluene sulfonic acid catalyst for recycle to the alkylation zone is maximum at temperatures in the range of about 265 to about 300 F.

The data in Table II are advanced as practical illustrations of the results obtainable by our improved alkylation process, but are not intended unduly to li-mit our invention.

TABLE II Preparation and properties of propylated and butt/lated alkyl naphthalenes Era'mple l 2 3 4 5 Product. mono and dibutyldibutyl crrgl t11110110 and mono and dibutyldipropyl.

Reactor 5 liter glass 5 liter glass 2 gallon steel 50 gallon steel 3 liter glass. Alkylation Conditions:

Mol percent toluene sulfonic acid 8.

catalyst. Pressure Atm 70 mm. Hg. Temperature, F 26o-265.

Time, hours 80 Mols olen absorbed/mol hydroormer bottoms. Charge Stock:

Olefm Hydroiormer bottoms fraction, boiling range (F.) at 1 atm.

92 (in excess). 2.14.

Butene-l Mixed B-B 1 Mixed B-B 1 Refinery propylenes (47.9% propylene). 7-554.

Total 143 Dialkylated Product, Wt. Percent oi Theoretical Yield. Product 1- 3 2 4 5. o 248-338/1 mm. 608-622/760 mm 6l2-653/772 mm. Bolling Ranger F mm }336383/2 111m- 541'633/760 mmh- {gggogs/l mm" ggggS/l mm .5 0.9489 0.944 0.9390. Light Yello Light Yellow (1% Light Yellow (1V 92ASTNI). 9 ASTM). Weight percent Aromatics by sul- 98.6 96.6 8 5 fonction i. Iodine No. (Wijs) 0. Viscosity at 100 F., Centistokes 46.5. Saybolt Viscosity, Universal (sec,- 215.

ands/100F.)

l Renery butane-butylene stream containing 41% olefms. 2 Method tends to give low values in the high ranges of aromatic t 3 Average molecular Wight 256. The theoretical molecular weight of a dibutyl dimethyl naphthalene is 268.

In 'Table II, the hydroformer bottoms fraction boiling in the range of 437 'to .554 F. comprised predominantly a mixture of mono-, di, and trlmethyl naphthalenes. The hydroformer .bottoms fraction boiling at 482 to 527 F. comprised predominantly dimethyl naphthalenes. Details of operating procedures used in obtaining the data set forth in Table II will be Set forth below.

Example 1 A sample of butylated hydrofor-mer bottoms was prepared by alkylation at 265 F. of la 3 mol percent solution of technical toluene sulfonic acid in dimethylnaphthalenes (482-527 F. fraction from hydroformer bottoms). The solution was placed in a liter, 3 neck ask fitted with an eicient mechanical stirrer, a water Condenser and a gas distributor which introduced the gas through small holes beneath the surface of the liquid. The gas was metered in at a rate slightly faster than that at which it was absorbed. Alkylation was continued until 1.2 mols of olen per mol of hydroformer bottoms, calculated as dimethylnaphthalene, had been absorbed. Beyond this point the absorption of butylenes was slow. Alkylati'on was `then stopped and when flask contents had cooled the catalyst was washed out with dilute alkali and then with water. When vacuum distillation of the dried mixture was attempted, the presence of a white crystalline solid was noted in the distillate; some had also solidied in the condenser. It is believed vthat this solid is formed by the decomposition of esters of toluene sulfonic acid at the high pot temperatures. The distillation was continued, however, at total take-off, allowing the remaining esters to decompose until the temperature reached 410 F. at 3 to 4 mm. mer-cury pressure. v The toluene sulfonic acid was washed out of the distillate with dilute alkali and nonalkylated .and unreacted hydrocarbons were removed by topping-this distillate through a 60 x 2.5 cm. column packed nwith A1/3 inch Fenske helices to an overhead temerature of 450 F'. at 200 mm. mercury pressure. The product was diluted with isopentane and decolorized by filtering through clay. After solvent removal the mixed mcnoand dibutyl dimethylnaphthalene yield based on crude butylat- 50 ed product was 75 weight percent. Physical properties were determined and are listed in Table II under product 1.

Example 2 Product 2 of Table II was prepared bythe alkylation of a wider cut of hydroformer bottoms (mono, di, and tri-methylnaphthalenes, boiling range 437-554 F.) with Dure butene-l, us-

ing v mol percent of anhydrous 'toluene sulfonic acid catalyst. In this preparation, butylation was continued until the product contained an aver` Example J3.

For this alkylation a refinery stream `of `butanes-butylenes was used in place of pure butene-l, and found Ato be satisfactory. `The refinery stream, containing 41% of oleiins, was dispersed well beneath the surface of the liquid aromatic hydrocarbons by means of a distributor tube. The exhaustgas, from which most ofthe olens had been removed, was allowed to escape from a pressure reducing Valve located at the top of the reactor. After the injection of the olenic gas stream was discontinued, the contents of the alkylation reactor were maintained with stirring at the reaction temperature between 3 and 4 hours. The reactor contents were thereafter withdrawn, cooled, and free toluene sulfonic acid was removed by Washing with an aqueous vsolution of caustic soda. The specific constants listed in Table II for product 3 are for the crude unfractionated material which contains a small amount of unreacted feed stock; hence they are at slight variance 4with other product samples.

Example 4 The liquid charging stock was 17.5 gals. (66.7 kg.) of a mixed mono, di-, and trimethyl naphthalene fraction of hydroformer bottoms. To this charging stock there was added 10 mol percent (7.35 kg.) of technical toluene sulfonic acid. The butano-butenes gas stream was first introduced at the rate of 0.2 cubic feet per minute. Shortly 3- thereafter the rate was increased to 0.5 cubic feet per minute. A small proportion of polymer having an average molecular weight of .126 was produced. The mol ratio of olefin converted vto polymer to olen converted to alkylate was 0.0645. 40 The products were worked up in the manner described in Example 3 and were then fractionated.

Eample 5 Table II indicates that dipropylation of ahydroformer bottoms fraction can be effected under conditions similar to those employed with butylenes to yield a similar product. Upon completion of the desired alkylation reaction, propylene injection was discontinued and the `reaction mixture was stirred at the alkylation temperature for an additional 4 hours to decompose yesters of toluene sulfonic acid which are present in the alkylation reaction mixture. Thereafter thereaction mixture was allowed to cool :to room temperature and finished as described in Example 3. From the data of Table II, it will be seen that monoor dialkylation of hydroformer bottoms fractions can Ibe accomplished quite read-ily under '60 mild reaction conditions in the presence of substantially anhydrous toluene sulfonic acids. The specific catalyst used was a mixture of technical `toluene sulfonic acids, whose properties 'have lbeen described above. It will also be observed that petroleum refinery mixtures of butenes-butanes vcan be used Aas alkylating agents with substanv.tially as good results as those obtained when pure butene-l is used.

From a comparison of Vthe data in Table II it will be observed that the butylated product is characterized by high viscosity (-300 seconds Saybolt Universal at 100 F.) and low volatility or high boiling range at 1-2 mm. .mercury pres- Our alkylation process can be operated batch wise, multistage, or continuously. The toluene sulfonic acid catalyst can be separated from the alkylation products intermittently or continuously, and recycled to the alkylation reactor. A particularly suitable method for recovering the toluene sulfonic acid catalyst from the reaction mixture, especially where relatively large quantities of catalyst are used, e. g., 10 to 20 mol percent, comprises diluting with a saturated aliphatic material in the liquid state, e. g., a hydrocarbon such as liquid propane, butanes, pentanes, hexanes, heptanes, cyclohexane, etc., or mixtures containing two or more of these hydrocarbons, paranic naphthas, kerosene, gas oil or the like. Upon the addition of a suiiicient volume of saturated aliphatic material, usually between about 0.25 and about 3 volumes per volume of the alkylation reaction mixture, the toluene sulfonic acid catalyst separates as a lower layer in substantially anhydrous condition and can be recycled as an alkylation catalyst without modification. Layer separation can be eiected conveniently at temperatures within the range of about 50 to about 150 F. e. g., at room temperature. The small proportion, e. g., 1 to 3% of toluene sulfonic acid which remains in solution in the alkylate can be removed by washing with water or alkalies prior to fractionating the alkylate. Unconverted feed stocks can be recovered and recycled in proper proportions to the alkylation reactor. Over-alkylation can be avoided by recycling products of undesirably high molecular weight to the alkylation reactor.

Although our invention has been described with specific reference to the alkylation of hydroormer bottoms, it is not thus limited and can be applied to the alkylation of alkyl polycyclic Ihydrocarbons from diierent sources. Thus, it may be applied to alkyl polycycylic hydrocarbons derived from certain crude petroleum oils by extraction with selective solvents. Alkyl polycyclic hydrocarbons derived from coal tars, e. g., alkyl naphthalene fractions, are desirable feed stocks for our improved alkylation process. Alkyl polycyclic aromatic hydrocarbons are also present to a considerable extent in cracked cycle stocks produced by cracking high boiling petroleum oils such as gas oils, preferably with catalysts. Cracking with solid cracking catalysts comprising one or more oxides of metals selected from groups 2 6, inclusive, e. g., silica, of the periodic table may be eiected at temperatures of the order of about 850 to 1050 F. and pressures of atmospheric to 50 p. s. i. or even higher. A suitable cracking catalyst is active silica promoted with about 5 to about 30% of active alumina or magnesia. Also, activated clays may be used as catalysts. A lkyl polycyclic aromatic hydrocarbons may be concentrated from cracked cycle stocks by a variety of selective solvents. Suitable selective solvents include nitromethane, nitroethane, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene triamine, dipropylene glycol, methanol, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, morpholine ethanol, triethylene tetramine, tetraethylene pentamine, etc.

The physical properties of aromatic hydrocarbons extracted by a selective solvent from a cycle 'stock produced by catalytically cracking 35 A. P. I. Mid-Continent gas oil are:

A.P.I. gravity 9.6 Refractive index ND20 1.5960 Specific dispersion 267 Speclc gravity l-o-C 1.007 A.S.T.M. distillation (F.):

Initial 420 5 10% 464 20 478 30 494 40 512 50 526 6o 544 10 70 570 80% 600 90 658 Max 732 The alkylation products, particularly the mono- 15 and dibutylated methyl naphthalenes, produced by the process of our invention are novel and useful. Because of their low volatility and high viscosity, they are especially adapted for use as plasticizers in high molecular Weight resins and plastics such as natural rubbers, butadienestyrene rubbers, butadiene-acrylonitrile rubbers, cellulose plastics, etc. Alkylated methyl naphthalenes, e. g., dipropyl, dibutyl, and diamyl dimethyl naphthalenes, can be used in combination with other plasticizers, e. g., ester type plasticizers such as dibutyl phthalate, in plasticizing rubbers, e. g., butadiene-acrylonitrile rubbers. Alkylated methyl naphthalenes, as produced by the process of our invention, can also be employed in compositions for impregnating wood and other brous materials to prevent or inhibit attack by termites or by marine organisms. Suitable imprcgnating compositions can contain creosote or coal tar in addition to the alkylated methyl naphthalenes. Alkylation products of our invention can also be used as insecticides, e. g., for chinch bugs and termites, alone or in combination with other insecticidal materials. The alkylated methyl naphthalenes can also be sulfonated to yield sulfonates whose salts, e. g., the sodium and potassium salts are wetting, re-wetting, detergent or emulsifying agents. The alkylated methyl naphthalenes can also be employed as lubricants alone or in combination with other lubricants. Alkylated methyl naphthalenes can be employed in quenching oils. As to the foregoing description of uses for the alkylation products which can be produced by our process, it will be understood that chemical derivatives of the alkylation products can also be employed, e. g., halogenated derivatives, alkoxy derivatives, chloromethyl derivatives, etc.

It will be evident that we have set forth a highly advantageous process for the alkylation of alkyl polycyclic hydrocarbons characterized by high yields of desirable alkylates, low catalyst consumption and the avoidance of undesirable side reactions.

We claim:

1. A process for the alkylation of polycyclic aromatic hydrocarbons which comprises introducing an olefin into an alkylation Zone and contacting said olen in said alkylation zone with polycyclic aromatic hydrocarbons and at least 3 mol percent of a substantially anhydrous toluene sulfonic acid at a temperature in the range of about 265 to about 300 F. under suiiicient pressure to maintain a liquid phase in said alkylation zone, diluting alkylation reaction products with a saturated hydrocarbon, and separating a phase comprising substantially anhydrous toluene sulfonic acid.

2. A process for the alkylation of a polycyclic aromatic hydrocarbon which comprises contacting an olen in an alkylation Zone with a polycyclic aromatic hydrocarbon and a substantially anhydrous toluene sulfonic acid catalyst at an alkylation temperature underv suflicient pressure to maintain. a liquid phasev in said ralkyl'aton zone, diluting the alkylation reaction mixture with a saturated hydrocarbon and separating a distinct phase comprising substantially anhydrous toluene sulfonic acid.

3. The process of claim 2 wherein the olen is a normally gaseous olefin containing at least three carbon atoms in the molecule.

4. The lprocess of claim 2 whichv comprises the additional step of recycling substantially anhydrous toluene sulfonic acid recovered from the alkylation reaction mixture to said alkylation zone.

5'. 'The process of claim 1 wherein the polycyclic aromatic hydrocarbons are contained in a fractioncomprising a substantial proportion of methylnaphthalenes, said fraction boiling between about 437 F. and about 554 F. at 1 atmosphere.

6. The process of claim 2 wherein the polycyclic I2 Y aromatic hydrocarbons: aref contained in a. fraction comprising a substantial proportion of inethylnaphthalenes,f said fraction boiling between about 437 F. andk about 554 F. at 1 atmosphere.

FRANCIS T. WADSWO-RTH. ROBERT J'. LEE.

REFERENCES CITED The following references are ofr record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,741,472 Michel 1 Dec. 31, 1929 2,014,766 Isham Sept. 17, 1935 2,385,303 Schmerling Sept. 18, 1945 2,386,892 Schaad Oct. 16, 1945 2,390,835V Hennion et al. Dec. 11, 1945 2,390,836 Hennion et al Dec. 11, 1945 2,395,976 Shankland Mar- 5, 1946 2,411,578 Lieber Nov. 26, 1946 Certificate of Correction Patent No. 2,462,792. February 22, 1949.

FRANCIS T. WADSWORTH ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Columns 5 and 6, Table Il, column numbered 4, opposite Boiling Range, OF. for 608-622/760 mm read 608-662/760 mm;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the ease in the Patent Ofice.

Signed and sealed this 28th day of June, A. D. 1949.

THOMAS F. MURPHY,

Assistant ommssz'oner of Patents.

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