US3544472A - Power transmission hydrocarbon oil - Google Patents

Description

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ULR/C 5. 5R4) Mom-om -Z. Ffl/NMAA/ United States Patent 3,544,472 POWER TRANSMISSION HYDROCARBON OIL Ulric B. Bray, Pasadena, and Morton Z. Fainman, Los Angeles, Calif., assignors to Bray Oil Company, Los Angeles, Calif., a corporation of California Filed Nov. 8, 1966, Ser. No. 592,944 Int. Cl. C09k 3/00; B01d 3/00 US. Cl. 25273 7 Claims ABSTRACT OF THE DISCLOSURE A hydraulic oil for power transmission particularly suited to aeronautic service having a high flash point coupled with low pour point made by alkylating benzene with normal monochlorinated hydrocarbons of 11 to 13 carbon atoms followed by distillation of the alkylate to recover a fraction in the range of 650760 F. having a viscosity of 20-30 centistokes at 100 F. and a viscosity index of 70l10.

This invention relates to a novel hydraulic oil and power transmission oil useful particularly in aircraft and missiles, and other machinery operating over a wide temperature range, and to the method of its manufacture. This novel hydraulic oil is a synthetic hydrocarbon oil of unique chemical composition which provides physical and chemical properties heretofore impossible or extremely difficult and expensive to obtain with petroleum fractions. More particularly, the invention relates to a hydrocarbon hydraulic oil having the desired physical and chemical properties to an enhanced degree, particularly high flash point, high average boiling point, high thermal stability and high viscosity index in combination with a low pour point and relatively low viscosity.

The invention is illustrated by drawings which show graphically in FIG. 1 the distillation characteristics of the product and, in FIG. 2, a diagrammatic outline of the process.

In the operation of aircraft, especially at high altitudes and high speeds over a wide range of geographic conditions, it is essential that the oil retain its fluidity at very low temperatures and provide adequate viscosity and lubricity at high temperatures in the neighborhood of 300 to 450 F. Also, it is highly desirable for the oil to exhibit minimum volatility at the highest operating temperatures in order to avoid excessive losses from vaporization and to reduce the danger of fires and explosions in the event of leakage onto hot surfaces during operation. Thus the oil must have a high flash point. Furthermore, the oil must be extremely resistant to oxidation and capable of operating for long periods of time at elevated temperatures without sludging or other changes in properties which would be detrimental to the functioning of the hydraulic system. While missiles generally do not operate for a considerable length of time, nevertheless the physical properties of the oil over a wide temperature range may be extremely critical in this service also.

The limitations of petroleum fractions employed in the production of hydraulic fluid for advanced designs of air craft and missiles are well known. Attempts to solve the problems and correct the deficiencies of such oils have generally been directed away from hydrocarbon oils and toward the halogen containing oils such as the fluorine derivatives and toward the oxygenated oils such as the esters and diesters. Besides being very costly, such oils have often introduced other problems with poor lubricity, increased density, hydrolytic and thermal instability, etc.

Treatment of petroleum oils by a combination of drastic defining, including fractionation, acid and solvent refining, and/or hydrogenation (hydrofining), either preceded or 3,544,472 Patented Dec. 1, 1970 followed by coventional dewaxing, has produced oils from paraffinic crudes with good physical properties at temperatures above 0 F. However, to obtain the pour point and fluidity at temperatures considered necessary for military a rcraft (below 70 F. pour) and supersonic commercial aircraft, additional dewaxing of a drastic and costly nature is required. Such deep refining and dewaxing are currently being practiced with relatively low viscosity oils having viscosities in the range of to 100 sec. Saybolt- Universal at 100 F. It has not yet been demonstrated commercially that par-aflinic oils of higher viscosity can be dewaxed to the necessary pour points required for military alrcraft. A substitute for the deep dewaxed parafiinic oils that has been considered is a drastically refined naphthenic base oil from a substantially wax-free crude. Such naphthenic oils as are available are limited in viscosity-temperature susceptibility, showing a maximum viscosity index of about 75. Naphthenic stocks which yield oils of higher viscosity index contain excessive wax, making the oils inoperative at the necessary low temperatures. An even greater disadvantage exhibited by the naphthenic base hydraulic fluids is their lower boiling range and greater volatility for a given viscosity at 100 F. as compared to the parafiinic oils.

The synthetic hydrocarbon oil of this invention possesses both a high viscosity index and a low pour point, and in addition shows a higher boiling range and less volatility for a given viscosity than even theparafiinic oil. The chemical composition and methods of synthesis of the novel hydraulic fluid are shown hereinafter.

Many attempts have been made in the past to use various synthetic hydrocarbon oils as the base component for aircraft hydraulic fluids, but none of the synthetic hydrocarbon fluids produced in the past have been satisfactory. Low molecular weight isobutylene polymers do not have sufiicient thermal stability and generally exhibit only fair temperature-viscosity characteristics. The heavy residues produced in the manufacture of gasoline alkylate (as, for example, alkylation of isobutane with butylene using either H or HF catalyst) have also been found unsatisfactory. When alkylated benzene (commonly called polypropyl benzene or dodecyl benzene) became commercially available as a raw material for the manufacture of water soluble detergents, it was thought that the high boiling fractions from the alkylation reaction might provide suitable base oils for the manufacture of hydraulic fluids, but such residues were not found useful for this purpose. Such detergent base hydrocarbons have been commonly produced by alkylating benzene with polymers of propylene containing lesser amounts of ethylene and butylene polymers. In preparation for the alkylation, the propylene polymer is fractionated to give, on the average, 10 to 14 carbon atoms per molecule, depending on the desired properties of the alkylate. In commercial operations, the alkylation of benzene with the polypropylene fraction is conducted with the aid of either A101 or HP catalysts.

With either alkylating agent, a portion of the reaction product boils above the range acceptable in the water soluble detergent base. Such residues have been used successfully in the manufacture of secondary plasticizers for vinyl resins, and as raw material for sulfonation to produce oil soluble sulfonates. These heavy residues, and fractions therefrom, exhibit fairly good thermal stability but their outstanding deficiency as regards their use as hydraulic fluids is their exceptionally poor viscositytemperature characteristics as illustrated by viscosity indexes generally less than zero. Also their volatility for a given viscosity is quite high and appears to be in keeping with their low viscosity index. Thermal stability has also been deficient.

It is generally believed that synthetic oils produced by polymerizing olefins such as butylene, consist of highly branched chain structures and are substantially devoid of cyclic structures. Where the polymerized olefin is used to alkylate benzene, regardless of whether the alkylation is conducted with AlCl or HF catalyst, the side chain has a branched structure. In the course of alkylation, it is apparent that some of the olefin polymerizes further before the alkylation actually takes place, with the result that high boiling residues are formed. It also appears that some of the high boiling residues are the result of poly-alkylation giving di or tri alkyl benzenes. In any case, the side chains have highly branched structure.

We have now discovered that functional fluids and particularly hydrocarbon oils having the properties required in a hydraulic oil to a high degree can be made by a process of alkylation wherein a normal or straight chain (linear) hydrocarbon of the paraffin series of controlled chain length is halogenated and then condensed with excess'benzene in the presence of anhydrous aluminum chloride catalyst followed by fractionation to a selected narrow boiling range. Following the alkylation reaction, the AlCl catalyst is removed by hydrolysis and water washing, neutralization with caustic alkali, and then recovery of excess benzene by distillation. Following this, a mono alkyl benzene fraction having about 16 to 19 carbon atoms and an average molecular weight of about 240 is removed by distillation to a temperature of about 575 F. The ASTM distillation of this oil is shown in FIG. 1, curve No. 1. This fraction can be. used in the manufacture of household detergents by sulfonation and neutralization with sodium hydroxide.

The residue from the above distillation, amounting to about 10 to 30% of the weight of the paraffin halogenated, is characterized by the distillation curve No. 2 in FIG. 1. Analysis by mass spectrometer shows it to consist principally of the following hydrocarbons:

Example Range Dialkyl benzenes, percent 48. 5 40-60 Dialkyl tetralin, percent 22. 3 15-25 Dialkyl diphenyl, percent 13. 9 10-15 Unidentified hydrocarbons, percent 15. 3 1015 topped, leaving 57.8% bottom (curve No. 5), which is the desired specific narrow boiling range hydrocarbon power transmission oil of our invention as will be described hereinafter in greater detail. Other schemes can be employed for fractionating out the narrow boiling cut desired for our hydraulic oil such as conventional fractionating towers, etc.

The chemistry involved in the formation of these hydrocarbons is obscure, but it appears that hydrogen transfer between hydrocarbons occurs in the presence of the aluminum chloride catalyst. The power transmission oil of our invention possesses a combination of properties not heretofore found in any functional hydrocarbon fluid. It boils entirely within the range of 650 to 760 F. and is generally characterized as follows:

Gravity, API-28-33 Viscosity, centistokes at 100 F.-20-30 Viscosity, centistokes at 210 F.3.8-4.9 Viscosity index-70-110 Flash point, C.O.C.above 400 F. Pour point, ASTMbelow -70 F.

In the manufacture of our new power transmission fluid, the paraflin halide, preferably the chloride, is prepared from the normal paraflin hydrocarbon fraction boiling in the range of decane to tri-decane. Chlorination under pressure is preferred, for example, 25-50 p.s.i., and an excess of the hydrocarbon is used to avoid formation of dichlorides, trichlorides and other polychlor hydrocarbons as far as economically feasible. A mol ratio of 2 to 5 mols of hydrocarbon per mol of chlorine is favorable. At least 70% of the chlorinated oil should be monochlor, usually 75-90%. The reaction is catalyzed by ultra violet light, for which mercury vapor lamps are suitable. During chlorination, the temperature may rise from about F. to 250 F. by the heat of reaction. After separation of by-product HCl gas, the product can be fractionated to recover the unchlorinated paraflin to be recycled to the chlorination step. It is preferred, however, to omit recovery of unchlorinated parafiin hydrocarbon at this stage and proceed directly to the alkylation stage of the process, after which the paraflin hydrocarbon is recovered by fractionation.

The paraffin hydrocarbon employed for chlorination will have a molecular weight in the range of about to 170, for example, 160, a boiling point of about 340-450 F. and density of 0.74-0.75. It is conveniently derived from a petroleum naphtha fraction boiling in the range of about 300 to 460 F. by separation of the normal hydrocarbons, employing a molecular sieve, i.e.: porous alumino silicates and similar materials prepared especially to adsorb selectively the normal or straight chain hydrocarbons which are then subsequently displaced, usually by steaming at elevated temperature.

The chlorinated parafiin (alkyl chloride) with or without unchlorinated paraffin, is thoroughly dried and mixed with benzene, also dry and free of thiophene, in the mol ratio of 2 to 5 mols benzene to 1 mol of alkyl chloride. A ratio of about 1 to 1.5 volumes benzene to 1 volume of alkyl chloride is satisfactory. The mixture is cooled to a temperature of 30-50 F. and rapidly agitated while anhydrous AlCl is introduced. The reaction can be promoted by saturating with HCl gas if desired and, when the chlorination reaction product is employed directly in the alkylation stage without paraflin separation, the HCl produced in the reaction can be allowed to remain. The amount of AlCl required is about 2 to 10 percent of the weight of alkyl chloride, 2 to 3% being elfective when sufiicient HCl is present. Addition of AlCl should be gradual to avoid excessive temperature rise, cooling of the reaction mixture being provided. HCl pressure of 5 to 100 p.s.i. can be held on the reaction to promote the catalytic action of the aluminum chloride. After all AlCl has been introduced, the temperature is allowed to rise to 100 F.- F.

When the reaction is complete, a sludge layer is settled and discarded. HCl gas is removed as far as practicable and the remaining aluminum chloride catalyst is removed by washing with cold water, after which the oil product is neutralized with caustic soda solution. Excess benzene is then distilled off and the product is fractionated by steam distillation or in vacuum to remove the unreacted parafiin hydrocarbons when present and the monoalkylated benzene fraction. The heavier fraction boiling above mono alkyl benzene is the source of the desired hydraulic oil (curve 2, FIG. 1).

In an alternative method of alkylation, the reaction product from the chlorination is cooled to 100-150 F. and undissolved HCl is gassed 013?. The liquid mixture of unreacted parafiin, chloroparafiin, and dissolved HCl then passes to the alkylation stage where it is fed continuously into a large excess of benzene with good agitation. Finely powdered AlCl .catalyst is fed in simultaneously in an amount of 2 to 5 percent by weight of the chlorparaffin. As before, about 2-5 mols of benzene is employed per mole of chlorparafiin. HCl evolved in the alkylation is recovered. After discarding sludge, the Oil layer is neutralized, water washed and distilled into four fractions, V12:

(1) Unreacted benzene (2) Unchlorinated paraifin (3) Alkylate16 to 19 carbon atoms (curve 1, FIG. 1)

(4) Residueupwards of 19 carbon atoms (curve 2,

FIG. 1)

Fraction 1 is recycled to the alkylation stage of the process. Fraction 2, completely freed of benzene, is recycled to the chlorination step of the process.

A typical sample of heavier alkylate made in the foregoing manner had the following properties:

The exceptionally low pour point of this oil, coupled with its high flash point, makes it unique for low temperature service in power transmission machinery. Incorporation of a small amount of an antioxidant such as ditertiary butyl phenol, prevents deterioration on aging in storage and in service. Phenolic antioxidants are most desirable from the standpoint of color. Amounts of about 0.1% to 2% are usually suflicient. Typical antioxidants are polybutylated bisphenol A and octylated diphenylamines, octyl and nonyl phenols, alkylphenol ethers (Tenox BHA), and zinc dialkyl dithiophosphate (Paranox l4) and 2,6-ditertiarybutyl paracresol (Parabar 441). Other additives, rust inhibtors, antifoam agents (silicones) and extreme pressure agents can be incorporated in the oil in amounts suflicient for the purpose desired. Tricresyl phosphate in the amount of 0.2 to 2% is sometimes added to increase lubricity of the oil and decrease wear.

All hydrocarbon oils undergo deterioration when held for prolonged periods of time at high temperatures, above about 400 F. Although our linear alkylate oils are unusually stable at high temperatures, we have discovered that certain less stable constituents thereof can be removed by reacting them with S Inasmuch as these alkylates are aromatic in nature, it would be expected that S0 would efiect complete sulfonation and destruction of the oil in accord with the classical reaction:

However, we have discovered that this reaction can be controlled to remove only the less thermally stable compounds in the oil by employing S0 in solution in sulfuric acid containing from 2 to 10% S0 holding the temperature at about 90 to 115 F. and employing rapid agitation to effect proper contact. Under these conditions, the extent of the reaction can be controlled by varying the ratio of acid used to oil treated. When using 30% by volume of acid containing 5% S0 we remove about 45% of the oil, leaving 55% to be recovered after neutralization and washing. Because the acid produces some oil soluble sulfonic acids which remain in the oil, serious emulsions are formed when the oil is neutralized and contacted with water. These are'broken by use of an emulsion breaking solvent, such as butyl alcohol or other light alcohols up to 6 carbon atoms, glycol mono ethyl ether, etc. Secondary butyl alcohol is very effective and can be recovered easily in the form of its aqueous phase containing about 72% alcohol and 28% water.

We prefer to control the S0 treatment to remove from 40% to 50% by volume of the linear alkylate fraction which has been previously distilled to meet the required narrow boiling range for our power transmission oil. Surprisingly enough, the S0 reaction has little, if any, effect on the vaporization characteristics of the oil, from which it appears that the less stable hydrocarbon constituents are evenly distributed throughout the molecular weight range of the alkylate. This is indicated by the ASTM distillation of the oils as shown in the following table. Dealkylation taking place in the S0 reaction appears to be followed by sulfonation of the de-alkylation products, both aromatic and paraffinic. There is a significant increase in both the flash point and viscosity index following the S0 reaction.

Alkylate after Alkylate S03 reaotion stock 56% yield Gravity, API 28. 8 32. 0

Viscosity, F. cs 20. 47 20. 98

Viscosity, 210 F. cs 3. 81 3.92

Viscosity index 74 82 Flash point, 410 430 Pour point, F 75 80 Aniline point; 123. 4

Color, ASTM (D1500) l. 0 Distillation ASTM:

Initial F 662 664 1 Water white.

Where unusually high thermal stability is not required, we can reduce the severity of the S0 treatment and supplement it with a clay treatment. For this purpose, we can employ an acid treated bentonite or montmorillonite clay, for example, Filtrol, Grade 13 which has an acid number of 16 mg. KOH equivalent per gram. Clays having an acid number in the range of about 5 to 20 are suitable. The clay treatment is carried out by contacting or percolating at 300-500 F. in an inert atmosphere. Air can be conveniently excluded with a C0 or nitrogen blanket. The clay treatment may precede or follow the S0 treatment. If S0 precedes the clay, it is possible to omit the steps of neutralization and washing following the S0 reaction. In either case, it is preferred to strip the oil with steam at about 500 F. to remove de-alkylation products or any low boiling substances which would adversely affect the flash point of the finished oil. The stripped oil is then given a final clay treatment or polish with a neutral clay (less than 2 acid value) to absorb color and remove a trace of acid derivatives left by the S0 treatment. A temperature of 200300 F. is satisfactory for this operation.

Extraction of the oil with selective solvents such as furfural, phenol, dichlor ethyl ether, etc., can be employed to improve color and increase viscosity index. We prefer to employ such solvent refining as a preliminary to $0 treating. Thus, We can extract 30 to 50 percent of the oil with furfural, preferably in stages, then contact the partially refined oil with S0 to give a yield overall of 35 to 65% in a typical operation.

FIIG. 2 of the drawings is a flow diagram of the S0 treating operation applied to the linear alklate oil of curve 5, FIG. 1. It will be seen that, in this case, a charge of 68 gallons yielded 38 gallons of treated oil or 56% of the oil charged. Time of stripping-1 to 2 hours.

, Another example of the eifect of S treatment of the alkylate oil is further illustrated by the following data:

1 Below 80 F.

The 80;, treated sample had received 30% (volume) of H SO containing 5% S0 followed by neutralization and washing. The untreated oil boiled within a narrow range, 90% within 46 F., indicating that the synihetic hydrocarbons of which it is composed have a relatively uniform molecular weight and type.

We believe the increase in API gravity obtained by the S0 treatment can be the effect of removing naphthalene derivatives and polyphenyl compounds, particularly diphenyl alkanes, contained in the heavy alkylate. We prefer to fractionate the oil, either before or after solvent extraction, to a boiling range of about 675 to 750 F. Still closer fractionation will provide an oil boiling in the range of 700 to 725 F. with still higher flash point. However, it is often desirable to merely strip the oil with steam or other inert gas after the chemical treatment to obtain the flash point.

The S0 treated oil of the foregoing example was compounded to consist of 96.0% oil, 1.0% tricresyl phosphate, 0.5% Parabar 441 (alkylated phenol oxidation in- .hibitor sold by Enjay Chemical Company), and 2.5%

Paratone N (polybutene concentrate sold by Enjay Chemical Company). The finished oil had the following physical properties:

Gravity, API at 60 F. 31.5 Pounds per gallon 7.228 Viscosity at -40 F., cs. 9,263 Viscosity at 100 F., cs 25.66 Viscosity at 210 F., cs 4.68 Viscosity index 110 Flash point, COC, F. 4.15 Fire point, COC, F. 450 Pour point, F. 80 Color, NPA 1 The compounded oil was tested for thermal stability by heating a 100 ml. sample in a glass tube under nitrogen for 72 hours at 500 F. with no significant change in appearance or properties. The compounded oil was also subjected to an extremely severe test by a leading manufacturer of supersonic aircraft. The oil was pumped at 4,000 p.s.i. pressure in a simulated supersonic aircraft hydraulic system at 425 F. for 1,500 hours. The pump, servo mechanisms and other parts of the system in contact with the oil were judged to be in excellent operating condition at the end of the test. The oil after this extremely severe test showed no significant change in properties other than a slight darkening in color. All other hydraulic fluids (including hydrocarbon, silicone, silicate ester, and polyol ester based fluids) failed this performance test in unsatisfactorily short periods ranging from 5 to 200 hours. The superior performance of our linear alkylate oil under these severe conditions, which must be met to satisfy the requirements for 1,800-2,000 miles per hour airplanes, constitutes a notable contribution toward the practical operation of such aircraft in both military and civilian use.

In addition to additives shown in the foregoing examples, other oxidation inhibitors, wear reducing agents, and viscosity index improvers may be used in our oil in minor amounts where special conditions require them. Also our oil may be blended with compatible fluids such as refined natural petroleum oils, diesters such as di-2- ethyl hexyl sebacate, polyol esters such as tri-methylol propane pelargonate or pentaerythritol heptanoate, polyphenyl ethers, phosphate esters such as hexyl dicresyl phosphate, silicate esters, siloxanes and silicones.

The addition of a small amount of shear stable, thermally stable polymer appears especially beneficial in reducing leaking with certain designs of mechanical seals. The addition of 2.5% of the polybutene concentrate sold under the name of Paratone N made a marked improvement in seal leakage in rigorous high pressure recycling tests. Other oil soluble polymer viscosity index improvers having molecular weights in the range of 10,000 to 20,000 can be employed in amounts of 1 to 5 percent by weight.

Having thus described our invention, what we claim is:

1. The process of making power transmission oils having high flash points above 400 F. and low pour points below 70 F. wherein a normal paraflin hydrocarbon of 10 to 13 carbon atoms and 140 to 170 molecular weight is chlorinated to produce a mixture of monochlor and polychlor paraffins wherein at least 70% is monochlor paraffin, alkylating benzene with said chlor paraflins in the presence of 2-10 percent of aluminum chloride alkylation catalyst and excess benzene in the mo] ratio of 2-5 mols benzene per mol of chlor paraflin to maximize formation of mono alkyl benzene hydrocarbons, distilling the alkylation product to remove a major fraction consisting of mono alkyl benzenes, and continuing the distillation to recover a power transmission oil fraction boiling substantially entirely within the range of 650 to 760 F., whereupon the said power transmission oil fraction is treated at about to F. with the sulfur trioxide in solution in sulfuric acid at a concentration of about 2-10 percent to remove polyphenyl compounds and naphthalene derivatives, washed and neutralized.

2. The process of claim 1 wherein the said power transmission oil fraction is treated with a selective solvent to remove polyphenyl compounds and naphthalene derivatives before sulfur trioxide treating.

3. The process of claim 1 wherein the said S0 treated oil is decolorized by contacting with adsorbent earth.

4. The power transmission oil made by the process of claim 1 containing in solution therein from 0.1 to 1% of an antioxidant consisting of a phenolic compound.

5. The power transmission oil made by the process of claim 1 containing in solution therein from 1 to 5% of an oil soluble polymer viscosity index improver having a molecular weight of 10,000 to 20,000.

6. A synthetic, functional hydrocarbon oil consisting essentially of aromatic rings substituted with linear paraffin side chains, made by alkylating benzene with a monochlorinated normal hydrocarbon of the paraflin series having about 10 to 13 carbon atoms by the action of aluminum chloride catalyst in the amount of 2 to 10 percent of the weight of the chlor parafiin, and distilling the resulting alkylation product to remove undesired lower boiling alkylates boiling below about 650 F., and higher boiling alkylates boiling above about 760 F., said oil having the following characteristics:

said oil distilling substantially entirely within the range of 650 to 760 F. and consisting essentially of the following hydrocarbons:

Percent Dialkyl benzenes 40-60 Dialkyl tetralin 15-25 Dialkyl diphenyl 1015 Unidentified hydrocarbons 10-15 7. The process of making power transmission oils having high flash points above 400 F. and low pour points below 70 F. wherein a normal parafiin hydrocarbon of 10 to 13 carbon atoms and 140 to 170 molecular weight is chlorinated to produce a mixture of monochlor and polychlor paraflins wherein at least 70% is monochlor paraflin, alkylating benzene with said chlor parafiins in the presence of 2-10 percent of aluminum chloride alkylation catalyst and excess benzene in the mol ratio of 2-5 mols benzene per mol of chlor parafiin to maximize formation of mono alkyl benzene hydrocarbons, distilling the alkylation product to remove a major fraction consisting of mono alkyl benzenes, and continuing the distillation to recover a power transmission oil fraction boiling substantially entirely within the range of 650 to 760 F., whereupon the said power transmission oil fraction is treated in an inert atmosphere with an acidic adsorbent earth at 300-500 F., then cooled and treated References Cited UNITED STATES PATENTS 3/1965 Pappas et al. 252-59 X 9/1968 Feighner et a1. 260-671 LEON D. ROSDOL, Primary Examiner D. SILVERSTEIN, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 544,472 December 1 Ulric B. Bray et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, line 5, "a

corporation of California" should read a limited partners of California Column 1, line 71, "defining" should read refining Column 6, lines 30 to 40, the second column c figures should appear as shown below:

Column 8, line 30, cancel "the". Column 10, line 4, "adbsorbent should read adsorbent Signed and sealed this 27th day of April 1971.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. WILLIAM E SCHUYLER, J Attesting Officer Commissioner of Patent

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