US2358129A - Distillation process - Google Patents

Description

Sept. I2, 1944. Q Rl LAKE DISTILLATION 'PROCESS Filed Sept. 29, 1941 von mwa

KNN Thi Patented Sept. 12, 1944 UNITED STATES PATENT vOFFICE DISTILLATION PROCESS George R. Lake, Long Beach, Calif., assigner to Union Oil Company of California, Los Angeles Calif., a corporation of California Application September 29, 1941, Serial No. 412,813

(Cl. Zim- 42) Claims.

This invention relates to the preparation of pure hydrocarbons from petroleum, these pure hydrocarbons being contained in'a fraction of petroleum hydrocarbons Whose components have small differences in boiling points, which renders them inseparable by ordinary fractional distillation. This application is a continuation in part of my copending application, Serial No. 360,264, led October 8, 1940.

An object of the present invention is to further the progress in preparing pure compounds from a heterogeneous petroleum mixture, using in this particular case a method which involves fewer steps than a chemical method and which yields a purer product than that produced by careful fractional distillation and/or extraction with selective solvents.

from a given fraction of petroleum, such as gasoline, kerosene, or a narrow boiling range hydro-V carbon 'fraction prepared from such materials, these fractions consisting of a mixture of parafiinic, isoparaffinic, naphthenic, olefnic and aromatic hydrocarbons, a fraction that is essentially paranic or isoparalnic or naphthenic or olenic or aromatic.

'A particular object of my invention is to separate aromatic hydrocarbons from non-aromatic hydrocarbons, by distilling the complex hydrocar'bon fraction in thc presence of a polyhydroxy alcohol, an ether of a polyhydroxy alcohol, or a derivative of an ether of a polyhydroxy alcohol.

The invention'comprises adding to such petroleum fractions from which it is desired to segregate a specific hydrocarbon or hydrocarbon fraction, a substance or a mixture of substances hereinafter disclosed having a preferential afiinity for one or more components contained in the fractions, thus causing a distunbance of the vapor pressure equilibrium that formerly existed in the fraction, in such manner that the partial vapor pressure or fugacity of at least one component in the fraction is changed sufficiently to permit its separation by controlled fractional distillation. This type of yfractional distillation will be referred to hereinafter as azeotropic distillation and the substance or substances which are added to the fraction which effect the aforementioned change will 'be referred to as azeotrope farmers.

According to my invention, the separation of a specific hydrocarbon or hydrocarbon fraction from a mixture of hydrocarbons is accomplished by azeotropic distillation wherein a polyhydroxy alcohol, an ether of a polyhydroxy-alcohol or a derivative of an ether of a polyhydroxy alcohol is added to the petroleum fraction and the mixture is subjected to controlled fractional distillation. The addition of these compounds to the petroleum fraction results in forming a more volatile azeotrope with certain of the hydrocarbon components which may then be distilled from the remaining hydrocarbon components. Thus, when it is desired to segregate naphthene hydrocarbons from aromatic hydrocarbons, the fractional distillation of this mixture to which an azeotrope former has rbeen added results in the formation of an azeotrope consisting of the naphthene hydrocarbons and the lazeotrope former which is more volatile than the aromatic hydrocarbons which may or may not contain a portion of the azeotrope former. The fractional distillation of the mixture results in distilling overhead the naphthene hydrocarbons in admixture with the azeotrope former leaving the aromatic hydrocarbons as undistilled bottoms. The same procedure may be employed to segregate paraffin and aromatic hydrocarbons in which case the paraiiin hydrocarbons form a lower boiling azeotrope with the azeotrope former. paraffin hydrocarbons may 'be separated from naphthene hydrocarbons in which case the naphthene hydrocarbons remain as the undistilled bottoms. While it is preferred to effect the fractional distillation in such manner that one of the components in the hydrocarbon fraction remains as an undistilled bottoms, it is also possible to distill the mixture of hydrocarbons completely with the azeotrope former and then by controlled fractionation in a fractionating column effect the condensation of the separate hydrocarbon components at various points in the fractionating column from which the various components may be removed. Y

In such cases where the hydrocarbon fraction contains more than two components of different chemical characteristics, as for example, aromatics, naphthenes and parafns, and it is desired to separate one or more of these components from the other component or components, the separation may be accomplished by stage fractional distillation to remove first one component and then another component.` For ex. ample, an azeotrope former such as ethyl ether of ethylene glycol may be added to a mixture of aromatics, naphthenes and paraflins having a boiling range of 300 to 340 F. and the mixture then distilledv to remove as overhead fractions, first an azeotrope of the parains with ethyl ether of ethylene glycol and then an azeotrope Likewise nent, the paraillns, for example, is substantially completely distilled from the remaining components may be observed by a rise in distillation temperature in order to effect further distillation of the material in the still.- Thus, in the above example, if the distillation is initially carried out at an overhead temperature of 255 F. at which temperature the parailln hydrocarbons together with azeotrope former distill from the remaining hydrocarbon components, then when substantially all of the paramn components have been evaporated from the mixture, it' will be necessary to raise the distillation temperature so that the overhead temperature will be increased to, for example 265 F., in order to effect further removal of hydrocarbon components. 'I'his increase in temperature indicates that all of the paramns were previously distilled .fromthe mixture and that the next hydrocarbon components, for example, the naphthenes, are being distilled at the increased temperature. By thus observing and controlling the distillation temperature,I it is possible to remove the various components present in the original feed stock as separate fractions. While the invention is adapted for the separation of hydrocarbons of characteristics different from each other, I have found that this process is particularly useful for producing toluene having a very high degree of purity from gasoline fraction produced from straight run or synthetic gasolines such as those produced by cracking, polymerization or reforming. The production of substantially pure toluene is highly important when it is to be used in the manufacture of explosives by nitrating the toluene since small amounts of impurities seriously impair the nitration process. 'I'he process is also particularly useful for producing specific aromatic hydrocarbons of higher boiling points or mixture of such hydrocarbons which are very useful as solvents of high solvency power, as for example, lacquer and paint solvents. Also the process may be used to produce lubricating oils, spray oils and Diesel engine fuel oils of improved quality. In the latter, the desired hydrocarbon fraction is taken overhead with the polyhydroxy alcohol as an azeotrope from which the desired fraction may be separated from the polyhydroxy compound.

Polyhydroxy alcohols which may be employed as azeotrope formers include ethylene glycols such as mono, di, tri, tetra, hexa and nona-ethylene glycols, the ethers of these ethylene glycols, such as monomethyl, monoethyl and monobutyl ethers of mono, di, tri, etc., ethylene glycols and the esters of the ethers of ethylene glycols such as for example, the acetate of the monomethyl ether of ethylene glycol. pounds which may be used as azeotrope formers are the propylene glycols and the ethers of propylene glycols and the esters of the ethers of propylene glycols. Examples of these include propylene glycol and di-propylene glycol. In addition to the di-hydroxy alcohols mentioned above, the other polyhydroxy alcohols which may be used include the tri-hydroxy, tetra-hydroxy, etc. Examples of the latter include glycerine and erythritol. The polyhydroxy alcohol should be chosen with respect to the boiling point of the hydrocarbon fraction, the higher the boiling point of the hydrocarbon fraction, the higher assenso the boiling point of the p01yhydroxy alcohol will be to effect the azeotropic distillation. The boiling point of the polyhydroxy alcohol should be not more than F., preferably, not more than 30-50 F. lower than the average boiling point of the hydrocarbon fraction. The polyhydroxy alcohol should preferably be employed in the anhydrous state, although small quantities of water may be tolerated, particularly in the lower boiling polyhydroxy alcohols.

The type of distillation to be used depends somewhat on the quantity of polyhydroxy alco hol used. I may take any proportion of the petroleum fraction to the added mixture that I desire, depending on the emciency of the operation or the purity of the product desired, and the technique to be used in the distillation. 'I'he proportion of the polyhydroxy alcohol may readily be adjusted on an ideal point, the definition of this point again depending on whether I desire the portion high in aromaticity to remain as bottoms in the boiler in a practically pure state, i. e. free from non-aromatic hydrocarbons, or whether I wish to distill a portion of the non-aromatic hydrocarbons, leaving a portion of the non-aromatic hydrocarbons as bottoms together with the aromatic hydrocarbons. Also, the distillation temperature and amount of azeotrope form-` er may be adjusted to eil'ect the distillation of all of the non-aromatic hydrocarbons together with a portion of the aromatic hydrocarbons. In other words, the emciency of separation of the aromatic from non-aromatic hydrocarbons is dependent upon the proper adjustment of the amount of polyhydroxy alcohol used since a small amount may result in incomplete separation of the non-aromatic hydrocarbons while the use of an excess .of the polyhydroxy alcohol together with a relatively higher distillation temperature may cause distillation of a portion of the aromatic hydrocarbons.

In order to separate the polyhydroxy alcohol from the azeotropic distillate, it is merely necessary to extract the condensate mixture -with a solvent adapted to extract or dissolve the polyhydroxy alcohol and substantially none of the hydrocarbons. By allowing this mixture to settle, two distinct layers are formed, an upper layer consisting of the hydrocarbon and a lower layer of polyhydroxy alcohol dissolved in the solvent. Solvents for this purpose include hydrocarbons having a greater aromaticity than the hydrocarbons contained in the azeotropic distillate since the polyhydroxy alcohols have a greater aillnity for the relatively aromatic hydrocarbons than they have for the relatively non-aromatic hydrocarbons. Preferably, the aromatic hydrocarbon solvents for eil'ecting the separation should have a considerably different boiling point, i. e. lower or higher, than the hydrocarbons to be separated since a portion of the aromatic hydrocarbon solvents may become dissolved in the non-aromatic hydrocarbons during the extraction and thus, these may be separated by simple distillation. Aromatic hydrocarbon solvents useful for the above include benzene, toluene, xylenes, etc. `Other solvents for the purpose include the nitroparaillns such as nitromethane, nitroethane, nitropropane, phenolic compounds, ketones, monohydroxy alcohols and even polyhydroxy alcohols having different boiling points than the hydrocarbons to be separated from the azeotropic distillate. In some cases, the separation of the polyhydroxy alcohols from the hydrocarbons may be accomplished by cooling the assenso azeotropic distillate or bottoms sufficiently, as for example, 125 F, in the case of ethyl ether of ethylene glycol. in order to reject the hydrocarbons from the polyhydroxy alcohol Most of the polyhydroxy alcohols, such as ethyl ether of ethylene glycol are water soluble and these are preferably extracted from the azeotropic distillate with water at an appropriate temperature to effect the desired result. The polyhydroxy alcohol may be recovered from the non-aqueous solvent or water by simple distillation, the overhead being either the ypolyhydroxy alcohol or the solvent depending upon the relative boiling points of .these two materials. When water is employed to effect the aforesaid separation, the overhead will be water and the bottoms will be the polyhydroxy alcohol.

Other objects, features and advantages of my invention will be apparent to those skilled in the art from the following description of the invention which represents a diagrammatic arrangement of apparatus for carrying out my invention. In the following example, the invention will be described as applied to the separation of aromatic hydrocarbons boiling between 310 and 340 F. from a hydrocarbon fraction employingA ethyl ether of ethylene glycol as the azeotrope former. However, it will be observed that thisv example is not to be taken as limiting my invention since the process is applica-ble to separate other components from complex substances employing the other azeotrope formers disclosed herein for effecting the desired separation.

In the drawing, the hydrocarbon feed to be resolved into its component parts, such as for example, a hydrocarbon fraction obtained by fractionation of a catalytically reformed gasoline, said fraction having a boiling range of about 300 to 330 F. and consisting of substantially 52% by volume of aromatic hydrocarbons (iso-propyl benzene, methyl ethyl benzene, tertiary butyl benzene, etc.) 5% by volume of olens and the remainder paraffin and naphthene hydrocarbons, is taken from tank l via line Il and is pumped by pump I2 through line I4 controlled by valve I5 into line i6. Ethyl ether of ethylene glycol, preferably substantially anhydrous, is taken from tank l1 via line I8 controlled -by valve t9 and is pumped by pump through lines 2l and 22 and valve 23 into line IB where it is mixed with the hydrocarbon feed from tank l0. The mixture of hydrocarbon feed and ethyl ether of ethylene glycol in the ratio of approximately equal volumes of the ethyl ether of ethylene glycol and hydrocarbon feed is passed into fractionating column 2d which is provided with heater 25 and reflux cooling coil 26 where the mixture is subjected to fractionation. If desired, ethyl ether of ethylene glycol may be introduced directly into the fractionating column at any other point as near the top of the column in which case it will act in part as reflux for the fractionation. In the fractionation column, the distillation is controlled so as to distill overhead an azeotrope consisting of the parainic, naphthenic and olenic hydrocarbons together with substantially all of the ethyl ether of ethylene glycol. This is accomplished at an overhead temperature of approximately 265 F. and at atmospheric pressure. If desired, the azeotropic distillation may be carried out either at atmospheric or superatmospheric pressure or under a vacuum. The above overhead mixture'` is removed from the fractionating column via'line 21, controlled by valve 28, condensed in condenser 29 and may be passed via line 30 contillate is cooled sumciently in condenser 26 to permit separation of the mixture into two liquid phases. In the case of the example herein described, cooling of the azeotropio distillate to a temperature below F., the condensate will separate when allowed to settle into an upper phase comprising a mixture of substantially all of the non-aromatic hydrocarbons and a portion of the ethyl ether of ethylene glycol and a lower phase consisting of substantially pure ethyl ether of ethylene glycol. In such case, the cooled azeotropic condensate from condenser 26 may be passed through line 33 controlled by valve 34 into a separator 35 where the mixture is allowed to stratify into the two layers. The lower layer is withdrawn via line 36 and pumped by pump 31 either via line 38 controlled by valve 36 into stora-ge tank I1 or via line 40 controlled by valve 4I through lines 22 and I6 to fractlonating column 24. The upper layer is withdrawn via line 42 controlled by valve,43 and passed via line 32 to the ethyl ether of ethylene glycol recovery system.

Thebottoms in the fractionating column 24 consisting of the aromatic hydrocarbons are withdrawn via line 44 controlled by valve 45 and are pumped by pump 46 through line 41 into storage tank 48.

The hydrocarbons obtained in tank 48 may be treated with clay which may be accomplished at a temperature of about 230 F. employing 1 to 5 pounds of clay per barrel of the hydrocarbon fraction. In place of clay treatment, the hydrocarbon fraction may be cooled and then treated with 1 to 10 pounds of sulfuricacid per barrel of the hydrocarbons followed byv neutralization with clay or caustic alkali, If desired, the acid and/or clay treated stock may be fractionated to remove undesirable hydrocarbons and/or products of reaction,

The azeotropic distillate passing through line 32 is passed into the bottom of washer 49 which is provided with packing material, such as broken tile 50, where the mixture is countercurrently washed with water obtained from tank 5| via line 52 controlled by valve 53 and pumped by pump 54 into the top of the Washer via line 55. The washing procedure dissolves the ethyl etherof ethylene glycol from the hydrocarbons. The solution of water and azeotrope former is withdrawn via line 56 controlled by valve 51 and is pumped by pump 58 through line 59 and heater 60 into fractionating column 6I where the distillation is controlled to separate substantially all of the water as overhead vapor. The fractionation is aided by heater 62 and reflux cooling coil 63. The water distilled in the fractionating coiumn 6I is withdrawn via line 65 controlled by valve 66, condensed in condenser 61 and passed via lines 68 and 36 into storage tank 5l.

The unvaporized ethyl ether of ethylene glycol at the bottom of the fractionating column 6i is withdrawn via line 69 controlled by valve 10 and is pumped by pump 1| through line 12 into storage tank I1. The washed hydrocarbons are withdrawn from the top of the washer 49 via line 13 controlled by valve 14 'and are pumped by pump 'l5 through line 16 into storage tank 11.

In the foregoing example, a bottoms hydrocarbon fraction was produced representing about 38% of the original feed to the azeotroplc distillation having a gravity of 30 A. P. I., a solubility in 99% sulfuric acid of 100% and boiling range of 310 to 330 F. This hydrocarbon mixture is particularly useful in formulating solvents for use in making dyes, paints and lacquers.

The above method may be applied to the production of Diesel engine fuel oils, spray oils and lubricating oils of improved quality, An example of such method is as follows:

A lubricating oil distillate obtained from the vacuum distillation of a Santa Fe Springs crude oil having a gravity of 21.8 A. P. I., a viscosity of 57 seconds (Saybolt Universal at.210 F.) and 'a viscosity gravity constant of 0.866 was fractionated into two cuts of substantially equal quantities. The lighter fraction having a viscosity of 51 seconds, a gravity of 22.4 A. P. I. and a viscosity gravity constant of 0.865 was subjected to fractional distillation in the presence of approximately an equal volume of tetraethylene glycol at an overhead temperature of about 275 F, which gradually increasedto about 325 F. towards the end of the run and under relatively high vacuum. 'I'he overhead oil which was separated from the azeotrope former had a gravity of 28.7 A. P. I., a viscosity of 45.5 seconds and a viscosity gravity constant of 0.823 and was obtained in a yield of 63% by volume. The distillation bottoms representing 37% had a gravity of 7.9 A. P. I., a viscosity of 142 seconds and a viscosity gravity constant of 0.968.

The heavier fraction having a viscosity of 60 seconds, a gravity of 21.6 A. P. I. and a viscosity gravity constant of 0.866 was subjected to fractional distillation in the presence of approximately an equal volume of hexaethylene glycol at an overhead temperature of about 425 F. which gradually increased to about 475 F. towards the end of the run and under a relatively high vacuum. The overhead which was separated from the azeotrope former had a gravity of 27.6 A. P. I., a viscosity of 57.7 seconds and a viscosity gravity constant of 0.821 and was obtained in a yield of 65% by volume. The distillation bottoms representing 35% had a gravity of 6.0 A. P. I., a viscosity of 305 seconds and a viscosity gravity constant of 0.974.

The overhead light and heavy fractions recovered in the foregoing azeotropic distillations were blended. 'The blended material representing 64% by volume based'upon the original 21.8 A. P. I. lubricating oil distillate had a gravity of 28.1 A. P. I., a viscosity of 51.5 seconds and a viscosity gravity constant of 0.821. The bottoms from each of the azeotropic distillations were blended and the blend showed a gravity of 7.0, a'viscosity of 224 seconds and a viscosity gravity constant of 0.968.

In another example a catalytically treated or reformed gasoline was fractionated to produce a fraction having a boiling range of 210 to 250 F., a gravity of about 44 A. P. I. and a solubility in 99% H2SO4 of 58%. This fraction contained approximately 53% toluene, 5% olens and the remainder paralns and naphthenes. This fraction was mixed with approximately one-half volume of methyl ether of ethylene glycol and the mixture was fractionally distilled at an overhead temperature of approximately 220225 F. whereupon a mixture of hydrocarbons and methyl ether of ethylene glycol was obtained as an overhead fraction which was condensed. The condensate was extracted with water at a temperature of about 100 F. which separated the hydrocarbons from a solution of water and the polyhydroxy assenso alcohol derivative. The residue remaining in the still after being washed with water represented 40% of the charging stock and had a gravity of 31.1, A. P. I.. a solubility in 99% sulfuric acid of 100%, a zero olefin content and a refractive index of 1.4968 at 20 C. for the D line of sodium. It will be noted in this example that the temperature of distillation was approximately 200- 225 F., .while the average boiling point of the stock was only 230 l". and yet substantially efiicient separation of toluene was obtained. Thus, with methyl ether of ethylene glycol it is possible to effect the desired separation of toluene even though the azeotrope former boils slightly above the average boiling point of the stock.

The foregoing description ofmy invention is not to be taken as limiting my invention but only as illustrative thereof since many variations may be made by those skilled in the art without departing from the scope of the following claims.

I claim:

1. A process for the treatment of a hydrocarbon fraction containing aromatic and non-aromatic hydrocarbons to separate the aromatic hydrocarbons from the non-aromatic hydrocarbons contained therein which ordinarily distill from said hydrocarbon fraction in the same temperature range as the aromatic hydrocarbons distill therefrom which comprises azeotropically distilling said hydrocarbon fraction in the presence of a sumcient amount of a compound selected from the class consisting of polyhydroxy alcohols, ethers of polyhydroxy alcohols and esters of ethers of polyhydroxy alcohols to vaporize the non-aromatic hydrocarbons together with said compound, the said compound having a boiling point lower than the average boiling point of the hydrocarbon fraction but within 100 F. of said average boiling point, thereby leaving aromatic hydrocarbons in the residue substantially completely separated from the hydrocarbons other than the aromatic hydrocarbons.

2. A process for the treatment of a complex hydrocarbon fraction having a narrow boiling range to separate toluene therefrom from the other components contained therein which ordinarily distill from the hydrocarbon fraction in the same temperature range as toluene distills therefrom which comprises azeotropically distilling said complex hydrocarbon fraction having a narrow boiling range in the presence of a sufiicient amount of a compound selected from the class consisting of polyhydroxy alcohols, ethers of polyhydroxy alcohols and esters of ethers of polyhydroxy alcohols to vaporize the hydrocarbons other than the toluene together with said compound, the said compound having a boiling point lower than the average boiling point oi the hydrocarbon fraction but within 100 F. of said average boiling point, thereby leaving toly uene in the residue substantially completely separated from the hydrocarbons other than toluene.

3. A process for the treatment of a hydrocarbon fraction containing toluene and non-aromatic hydrocarbons to separate toluene from the non-aromatic hydrocarbons contained therein which ordinarily distill from said hydrocarbon fraction in the same temperature range as toluene distills therefrom which comprises azeotropically distilling said hydrocarbon fraction in the presence of a sufficient amount of methyl ether of ethylene glycol to vaporize the non-aromatic hydrocarbons-together with the methyl ether of ethylene glycol thereby leaving toluene in the residue substantially completely separated from the hydrocarbons other than the toluene.

4. A process as in claim 3 in which the compound comprises hexaethylene glycol.

5. A process as in claim 3 in which the compound comprises methyl ether of ethylene glycol.

6. A process as in claim 3 in which the com- Pound comprises the acetate of monomethyl ether of ethylene glycol.

'7. A process for the treatment of a hydrocarbon fraction containing aromatic and nonaromatic hydrocarbons to separate the aromatic hydrocarbons from the non-aromatic hydrocarbons contained therein which ordinarily distill from said hydrocarbon fraction in the same temperature range as the aromatic hydrocarbons distill therefrom which comprises azeotropically distilling said hydrocarbon fraction in the presence of a suiilcient amount of a compound selected from the class consisting of polyhydroxy alcohols. ethers of polyhydroxy alcohols and esters of ethers of polyhydroxy alcohols to vaporize the non-aromatic hydrocarbons together with said compound, the said compound having a boiling point lower than the average boiling point of the hydrocarbon fraction but within 100 F. of said average boiling point thereby leaving a residue substantially enriched in aromatic hydrocarbons.

8. A process for the treatment of a. complex hydrocarbon fraction having a narrow boiling range to separate toluene therefrom from the other components contained therein which ordinarily distill from the hydrocarbon fraction in the same temperature range as toluene distills therefrom which comprises` azeotropically distillmg said complex hydrocarbon fraction having a narrow boiling range in the presence of a sumcient amount of a compound selected from the class consisting of polyhydroxy alcohols, ethers of polyhydroxy alcohols and esters of ethers oi' polyhydroxy alcohols to vaporize the hydrocarbons other than the toluene together with said compound, the said compound having a boiling point lower than the average boiling point of the hydrocarbon fraction but within F. of said average boiling point thereby leaving a residue substantially enriched in toluene.

9. A process for the treatment of a hydrocarbon fraction containing toluene and nonaromatic hydrocarbons to separate toluene from the non-aromatic hydrocarbons contained therein which ordinarily distlll from said hydrocarbon fraction in the same temperature range as toluene distills therefrom which comprises azeotropically distilling said hydrocarbon fraction in the presence of a suiilcient amount of methyl ether of ethylene glycol to vaporize the non-aromatic hydrocarbons together with the methyl ether of ethylene glycol thereby leaving a residue substantially enriched in toluene.

10. A process as set forth in claim 7, in which the said hydrocarbon fraction is distilled in the presence of a polyhydroxy alcohol.

l1. A process as set forth in claim 7, in which the said hydrocarbon fraction is distilled in the presence of an ether of a polyhydroxy alcohol.

12. A process as set forth in claim 7, in which the said hydrocarbon fraction is distilled in the presence of an ester of an ether of a polyhydroxy alcohol.

13. A process as set forth in claim 8, in which the said hydrocarbon fraction is distilled in the presence of a polyhydroxy alcohol.

14. A process as set forth in claim 8, in which the said hydrocarbon fraction is distilled in the presence of an ether of a polyhydroxy alcohol.

15. A process as set forth in claim 8, in which the said hydrocarbon fraction is distilled in the presence of an esser of an ether of a polyhydroxy alcohol.

GEORGE R. LAKE.

CERTIFICATE OF CORRECTION. Patent no. 2,558,129. september 12, 191m.

GEORGE R. LAKE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows Page 5i first:A column, lines 5, 5 and 7, claims LL, 5 and 6 respectively, for the claim reference numerl "5 read 1; a'nd that the said Letters Patent should be read with this correction therein that the sameAmay conform to the record of the case in the Patent Office.

Signed and seaied this 50th day of January, A. D. 1911.5.

Leslie Frazer (S8111) Acting Commissioner of Patents.

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