US3530061A - Stable hydrocarbon lubricating oils and process for forming same - Google Patents

Description

5 Claims ABSTRACT OF THE DISCLOSURE A lubricating oil product fraction of hydrocracking comprising polycyclic hydrocarbons is made resistant to deterioration upon exposure to light and air by contacting the lube oil fraction with a solid contacting agent having hydrogenation/dehydrogenation properties under particularly selected conditions of temperature, space velocity and hydrogen pressure.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 630,221, filed Apr. 12, 1967, now abandoned.

FIELD OF INVENTION This invention relates to the preparation of stable hydrocarbon lubricating oils which are resistant to deterioration upon exposure to light and air, and to the method for obtaining the same.

DESCRIPTION OF THE PRIOR ART For many years, lubricating oils have been obtained from hydrocarbon oils of various character by fractional distillation. In order to obtain lubricants of relatively high viscosity index (V.I.), it has been the practice to subject the oils to solvent extraction to remove components serving to lower the V1. The solvent extracted lubricants are resistant to light and air; however, they are generally fortified with one or more additives in order to improve their resistance to oxidation during use and the like.

More recently, hydrocarbon lubricating oils of somewhat different character have been obtained by a variety of processes in which high boiling fractions are contacted with hydrogen in the presence of hydrogenation/dehydrogenation catalysts at elevated temperatures and pressures. In such processes, there is a consumption of hydrogen. Lubricating oil fractions are separated from the resulting products. Such lubricating oil fractions difier from those obtained by fractional distillation of crude oils and the like, since they have such relatively high V.I. values that solvent extraction treatments are generally not required to enhance their V.I. values. Lubricating oil fractions which are the products of hydrocracking suffer from the shortcoming that they are not completely stable when exposed to light (particularly, actinic rays) and air. When so exposed, sediment and lacquer formation occurs, thus lessening the commercial value of such lubricants. The present invention is directed to a method for overcoming such a shortcoming.

SUMMARY OF THE INVENTION In accordance with the present invention, there is pro United States Patent vided a method for forming lubricating oils resistant to deterloratlon upon exposure to light and air.

The process of the present invention comprises contact- DESCRIPTION OF SPECIFIC EMBODIMENTS HYDROCARBON FEED FRACTIONS The hydrocarbon feed material suitable for use in the present invention can be substantially any hydrocarbon feed material comprising polycyclic ring compounds which are susceptible to treatment with hydrogen. Generally, it is preferred to use materials boiling above about 600 F. or 650 F. Such materials include heavy gas oils, residual stocks, cycle stocks, topped crudes, reduced crudes and relatively high boiling hydrocarbon fractions of cracking derived from coal, tars, pitches, asphalts and shale oils. These materials can be obtained by fractionation, as by vacuum distillation, of crude oils identified by their source, viz.: Pennsylvania, MidContinent, Gulf Coast, West Texas, Amal, Kuwait and Barco.

HYDROGENATION/ DEHYDRO GENATION HYDROCRACKING CATALYSTS The catalysts employed to effect hydrocracking of the hydrocarbon charge material can include substantially any catalyst having cracking activity in combination with hydrogenation and dehydrogenation activity. Such catalysts are well-known in the art. The catalysts include oxides and sulfides of any metal of Group VI-B of Mendeleeffs Periodic Table, or mixture thereof, typical of which are: chromium sulfide, molybdenum sulfide and tungsten sulfide. Others include oxides and sulfides of Group VIII of said Periodic Table or mixture thereof, as illustrated by: the sulfides of iron, cobalt, nickel, palladium, platinum, rhodium, osmium and iridium. Still other catalysts include mixtures of the above oxides and sulfides of the metals of Group VI-B and VIII of said Periodic Table, typified by mixtures of: nickel sulfide and tungsten sulfide; cobalt sulfide and molybdenum sulfide; and nickel sulfide and molybdenum sulfide. These metals can be deposited upon adsorbent carriers such as alumina, silica-alumina and silica-Zirconia.

Preferred catalysts include those comprising at least one of the metals mentioned above, deposited upon a composite-like oxide of at least 2 of the elements of Groups II-A, III-B, IVA and IV-B of said Periodic Table. Additional preferred catalyst include a sulfided or unsulfided 1-8 weight percent cobalt oxide and 3-20 weight percent molybdenum trioxide on a silica-alumina or silica-zirconia base containing silica in amounts of from about 5 to about weight percent.

Catalyst comprised of such metals associated with molecular sieves can also be employed. Such catalysts are typified by those described in US. Pat. No. 3,173,854.

The catalyst loses some of its activity during use by deposition of carbonaceous materials thereon and, therefore, is regenerated. The spent catalyst is contacted in an oxygen containing atmosphere at an elevated temperature sufiicient to burn the carbonaceous deposits on the cata lyst. Conditions for regenerating the catalyst include a temperature between about 600 F. and about 1000 F., a pressure of from atmospheric to about 500 pounds per square inch (p.s.i.), a total gas rflow rate of from about 1 to about 20 volumes per volume of catalyst per minute and an oxygen concentration of from about 0.1 percent to 100 percent. The oxygen can be diluted with steam, nitrogen or other inert gas.

HYDROGEN Pure hydrogen can be used in the process either alone or as a supplement to hydrogen rich gases obtained from other sources. Hydrogen rich gases of varying purity obtained as a recycle gas or from other hydrogenating process sources such as reforming can be used. It is recommended that the hydrogen rich gas be subjected to purification as required so as to limit any undesirable impurities of water, sulfur compounds, methane and the like to relatively low values. The hydrogen rich gas can be circulated in the hydrocracking operation at a rate in the range of from about 1000 to about 20,000 standard cubic feet (s.c.f.) per barrel of hydrocarbon charge, and preferably 500010,000 s.c.f. per barrel of charge. Hydrogen consumption is expected in hydrocracking and can be less than about 40 s.c.f. per barrel of charge and greater. However, it is preferred to have a hydrogen consumption of 100 or more s.c.f. per barrel of charge.

HYDROCRACKI NG OPERATION The hydrocarbon charge to be cracked is passed with hydrogen in contact with a hydrocracking catalyst of the type described above, at a temperature selected from within the range of from about 500 F. to about 1000 F., preferably 600850= F. Hydrogen pressure is selected from within the range of from about 1000 to 10,000 pounds per square inch gauge (p.s.i.g.) and preferably is at least about 1500 p.s.i.g. Liquid hourly space velocity (L.H.S.V.) of charge normally falls within the range of 0.1 to 10, and preferably 0.2-3, volumes of charge (as 60 F. liquid) per volume of catalyst per hour.

The products of hydrocracking are withdrawn and cooled to a temperature at which hydrogen rich recycle gas is separated from the normally liquid product. The normally liquid product is then passed to a fractionator from which several diflerent boiling range fractions including gasoline, kerosene and lube oils are removed. A lubricating oil fraction boiling above about 600 F. and comprising polycyclic compounds constitutes one of the recovered fractions.

The recovered lubricating oil fraction boiling above 600 F. usually contains some wax products. Removal of wax, if present, can be accomplished by any suitable convenient means used for dewaxing oils to provide an oil having a pour point below about 20 F. or lower. Such dewaxing can be completed at this stage of the process or following the subsequent contact of such materials as described below.

METAL STABILIZATION CATALYSTS The metal catalysts agents contemplated herein for stabilizing the lube oil product of hydrocracking are those having primarily hydrogenating-dehydrogenating activity in combination with relatively low cracking activity and are selected from metals of Groups IIB, VIB and VIII of Mendeleeifs Periodic Table. Such metals include: zinc, chromium, iron, cobalt, platinum and palladium. Metals of Group VIII are preferred, especially platinum. These metals can be deposited upon adsorbent carriers includ ing alumina, silica-alumina, silica-zirconia and charcoal.

The catalysts lose activity during use. Activity can be restored by discontinuing hydrogen and hydrocarbon charge flow to the catalyst, followed by purging of the catalyst with flue gas or other inert gas such as nitrogen and regenerating with an oxygen containing gas such as air. Air is injected into the circulating purge gas in increasing concentration to a maximum of about 2 percent (volume), such care being taken to avoid formation of an explosive mixture. Combustible deposits on the catalyst are removed by burning. The effluent gas is analyzed to determine the carbon dioxide content thereof; when the CO value decreases to a minimal value, the reactivation operation is discontinued.

STABILIZATION OPERATION The stabilizing catalysts used according to the method of this invention are effective at different temperatures as shown hereinafter by the illustrative examples. In general, elevated temperatures ranging from about 500 F. to about 800 F. are employed, particularly about 650- 750 F. with a platinum supported catalyst of little or no cracking activity. A preferred support may be either alumina or charcoal.

Catalyst concentration can vary considerably, as from about 0.25 to about 20 percent by weight of metal on the alumina or charcoal base.

Contact of the lubricating oil fractions with the metal catalyst is accomplished from atmospheric pressure up to about 50 p.s.i.g. hydrogen pressure. However, higher pressures up to about p.s.i.g. can be employed in some special operations. When hydrogen is used with the oil charge at pressures up to about 50 p.s.i.g. under the particular temperature and space velocity conditions defined herein, there is a net production of aromatics in the lube oil fraction. Thus the polycyclic compounds in the oil charge are believed to be stabilized by removing loosely bound hydrogen from the molecule.

The liquid hourly space velocity of the lubricating oil fraction being stabilized may range from about 0.1 to 3, and particularly 1.2 to 3, volumes of charge (as 60 F. liquid) per volume of catalyst per hour. It is preferred to employ relatively high space velocities for the purpose of reducing cracking to products boiling below 600 F. to a low minimum.

When temperatures are in the range of 700 F. to 800 F. at hydrogen pressures of from atmospheric to about 50 p.s.i.g., the space velocities are preferably in the range of 1.2 to 3.0 L.H.S.V. range. When the lower temperatures and lower pressures of the specified ranges are employed, the space velocities may be selected from the lower end of the range It is preferred, however, to operate the stabilizing contacting step at a pressure from atmospheric pressure up to about 50 p.s.i.g. hydrogen pressure and prefer ably at the higher pressure to obtain improved catalyst activity retention and stability.

ILLUSTRATIVE EXAMPLES Example 1 A Kuwait-Barco propane deasphalted raffinate was treated with hydrogen as described below. The charge stock had the following properties:

Gravity, API 22.4 Vacuum assay, F.:

IBP 637 5% 989 10% 1016 30% 8 50% 1100 70% 1136 Viscosity index 85 Viscosity at 210 F.:

Kinematic viscosity, cs. 34.34 Saybolt seconds Universal 162 Pour point, F. Flash point, F. 606 Carbon residue, weight percent 1.09 Nitrogen, weight percent 0.08 Sulfur, weight percent 1.93

The catalyst comprised a silica-zirconia support containing approximately 11 percent by Weight of ZrO The support was then spray impregnated with 10 percent M as a water solution of ammonium molybdate, (NHQ Mo O -4H O, drying at 220 F. for 16 hours and calcining 3 hours at 1000 F. in air. The resulting composite was then impregnated with 3 percent CoO as a water-solution of cobalt nitrate, Co(NO -6H O, dried at 230 F. for 3 hours and calcined 10 hours at 1000 F. in air. The resulting catalyst was sulfided with a 50 percent H --50% H S mixture employing 2 volumes per volume of catalyst per minute for hours at 800 F. Further details of the preparation and character of this catalyst are available in US. Pat. 3,182,012, issued May 4, 1965.

The liquid product obtained by contact with hydrogen and the catalyst under the following conditions was fractionated, thereby providing approximately 57 percent by volume of the lubricating oil fraction having a boiling point above about 650 F.

Temperature, F. 772 Pressure, p.s.i.g 2000 LHSV 0.8 H circulation, s.c.f./bbl. 8000 Conversion (100-products boiling above 650 F.,

in volume percent) 43 0.4 fresh charge and 0.4 liquid recycle, 4004350 F. fraction.

The lubricating fraction was then dewaxed at about 0 F., with 3 volumes of 50/50 (volume) methyl ethyl ketone (MEK)/toluene.

A variety of dewaxed lubricating oil fractions were so obtained, as illustrated by the fraction identified by the properties given below:

API gravity, 60 F 34.0 Vacuum assay at mm., F.

vol. percent at 760 mm.:

IBP 627 958 1026 Viscosity index, ASTM D-567 123 Viscosity at 210 F. SSU 57.2 Pour point, F. 20 Flash point, F 470 Carbon residue, Conradson 0.03 Nitrogen, p.p.m 2 Sulfur, wt. percent 0.09 Color, ASTM 6.0

Other fractions employed had viscosity indices ranging from about to 125.

Portions of the dewaxed lubricating oil fractions were contacted with a variety of metal catalysts at atmospheric pressure as shown in Table I below. Each run was conducted in a continuous flow reactor in which the liquid charge rate, inert gas (N rate of approximately 50 cc. per minute, temperature and pressure were controlled. The resulting products were fractionated in order to obtained lubricating oil fractions having boiling points above 600 F.

The lubricating oil fractions were exposed to air and an ultraviolet light source and rated at various time intervals, as 24, 48 and 72 hours. Equipment utilized in the ultraviolet light test was such as described in ASTM Test Method D 529. The operating temperature was approximately -120 F. The light source was a xenon lamp (6000 watts). Samples of the oil fractions were contained in 4 dram glass vials during the test.

The dewaxed lubricating oil fraction before contact with a metal catalyst, formed a heavy precipitate in the test in less than 24 hours.

In the test, precipitates formed are rated visually in the following order:

0 None. 1 Very slight. 2 Slight. 3 Medium. 4 Heavy. 5 Very heavy.

The metal catalysts used in this example included catalyst A comprising 0.5 percent (Weight) of platinum on activated alumina containing 0.55 percent of chloride ion. This is a commercial catalyst, RD of Baker Sinclair.

Catalyst B is catalyst A which has been reduced with hydrogen at 750 F. before use in this example.

Catalyst C comprises a composition similar to catalyst A but is essentially free of chloride ion. This was prepared by washing 92 grams of catalyst A with four portions of 5 percent ammonium hydroxide, each 125 milliliters, then with water until free of ammonia. The water-washed material was then dried in an oven at F. for 16 hours. The temperature was increased gradually to 340 F. during 8 hours and the material was heated at 340 F. for 16 hours. It was then cooled and retained in a desiccator. Catalyst C, so prepared, contained 0.03 percent of chlorine.

Catalyst D comprises platinum on activated charcoal. This catalyst is prepared by vacuum spray impregnation of 930 grams of activated charcoal with an aqueous solution of chlorplatinic acid to provide 0.6 percent by weight of platinum on the carbon. Four portions, each 500 cc., of the acid were used. The resulting material was wet aged at 230 F. for 20 hours and then dried at 230 F.

Catalyst E comprises 0.5 percent (weight) of palladium on activated alumina. It is a commercial catalyst, Pd-- 0501 of Harshaw Chemical.

Catalyst F is another palladium catalyst, 1 percent (weight), on activated alumina. The method for its preparation involves the use of eta alumina which had been heat treated at 950 F. for 5 hours; 530 grams were so reduced to 499 grams. The heat treated alumina was vacuum spray impregnated with an aqueous solution of palladium chloride to provide a composite containing one percent by weight of palladium on the alumina. The impregnated material was dried at 230 F. for 20 hours, then reduced with steam at 450 F. for 2 hours, heated at 950 F. for 12 hours and purged with nitrogen. It was then treated five times with a 5% ammonium chloride solution, the total of which was one liter. It Was washed with water and then dried at 23 0 F.

Catalyst G comprises 7 percent (weight) of cobalt on activated alumina. It is a commercial catalyst, Co-0501 of Harshaw Chemical.

Catalyst H comprises 7 percent (weight) of iron on activated alumina. This is Fe-030l of Harshaw Chemical.

Catalyst I comprises a mixed chromium oxide-zinc oxide on activated alumina which has been treated with hydrogen at 750 F. The chromium and zinc contents are 7 and 8 percent (weight), respectively, for the hydrogen-treated composition. The mixed oxide-activated alumina is Zn-0602 of Harshaw Chemical.

The following charge stocks were employed in the runs reported in Tables I, II and III.

CHARGE STOCK Preei itate Wtz. percent p VI aromatics 24 48 72 Results of runs made with catalysts A-F and the dewaxed lubricating oil fractions are given in Table I.

TABLE I.DEI-IYDRO GENATION, METAL CATALYSTS AT ATMOSPHERIC PRESSURE Total liquid product Prccipitatc O.H., Wt. K.V., 210

percent 1 #WONQTOOIQIUOOOOlOUIOb-PQTUIUIOQ UIOONNUOOOOOOOOONQOWMUI oon co D000 1 O.H.=Overhead or product boiling 600 F.

2 Viscosity and Viscosity Index (V .L) of product boiling above about 600 F.

As indicated by the results in Table I, catalyst A is eifective for the purposes of this invention when employed in the temperature range of 400800 F. and 0.33.0 LHSV. However, the lubricating oil fractions from operations at 650 F. and 750 F. are generally more stable than the corresponding fractions obtained at 400 F. and 500 F. At the higher temperatures of the range, greater cracking to 600 F. material occurred and the lubricating oil fractions had lower viscosities but higher viscosity indices.

Catalyst B is also highly effective at 650-750" F. Hydrogen and nitrogen are equally suitable carrier gases.

Catalyst C was also efficient at 650-75 0 F. The absence of chloride ion from the catalyst composition appears to have no appreciable effect upon cracking conversion.

Catalyst D is effective at 500-750 F., with less cracking conversion than with catalysts A-C. Not only was the catalyst composite effective in cooperating to provide a stable lubricant, but substantial improvement in color was realized. The charge oil had a color value of L 6.0, in contrast with the lubricant having a color value of 2.5.

Palladium (0.5%) catalyst E is ineffective at 400- 650 F. but efficient at 750 F. Catalyst F containing 1% of palladium is elfective at 400750 F., with superior results being obtained at 650-750 F.

Cobalt-containing catalyst G is effective at 750 F., no benefit being realized at 500650 F.

Some improvement is achieved at 650 F. with the iron-containing catalyst H; however, greater stability is realized at 750 F.

Similarly, the chromium-zinc catalyst, I, provides improvement at 500650 F. Superior results are obtained, however, at 750 F.

Comparative Example A TABLE II.DEHYDROGENENATION, INERT BASES AT ATMOSPHERIC PRESSURE Total liquid product Compara- Precipitate Charge tive eata Inert Oil, Temp., O.H., wt. K.V., 210 Aromatics Run No. stock lyst gas LHSV F. percent 1 F. V1. 24 48 72 wt. percent I None I a N2 0. 6 I a Na 0. 6 III 83 III b N 0.6 III b N2 06 III b Ni 0.6 III 12 N: 0.6 III b NZ 0.6 III 0 Hz 0.3 69 III c 112 0.3

K O.H.=Overhead or product boiling 600 F. 2 Viscosity and Viscosity Index (V.I.) of product boiling above 600 F.

Aromatics 72 wt. percent Example 2 A dewaxed lubricating oil fraction boiling above about 600 F. was obtained following the procedure described in Example 1. The fraction had a kinematic viscosity at 210 F. of 7.50 and a viscosity index (V.I.) of 112.

Portions of this fraction were contacted with metal catalysts under hydrogen pressure. The ratio (volume) of hydrogen to oil charge was 30:1. The same continuous unit was used as in connection with Example 1. Lubricating oil products were subjected to the ultraviolet light test.

Catalyst A and D were used. As indicated by the presentation of the test results in Table III, below, a fresh charge of catalyst was used in Run No. 112, following Run No. 109. Also, the charge stock used in all Runs following Run No. 109 was the stock used in connection with Table I.

Comparative Example B Conventional antioxidants for lubricating oils have proven to be ineifective for stabilizing the foregoing oils which had not been contacted with a metal catalyst. This is illustrated with an oil of the character of that described in Example 1., before treatment with a metal catalyst. Onetenth percent (0.1%) of 2,6-ditertiary butyl-4-methyl phenol was incorporated in the oil. The resulting product was tested in the ultraviolet light test. There was no appreciable improvement as shown by a comparative test with the oil alone in the ultraviolet light test.

Having thus given a general description of the process and means of this invention and provided by way of example specific embodiments thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof, and minor modifications may be made thereto without departing from the scope thereof.

What we claim is:

TABLE III.V-DEHYDROGENATION, Pt CATALYSTS UNDER Hz PRESSURE Total liquid product Precipitate Pressure 011, Temp, O.H., wt. K.V., Aromatics, Catalyst p.s.i.g. LHSV F. percent 1 210 F. V1. 24 48 72 wt. percent 5 D 50 2. 0 A 250 3. 0 0 A 250 3. 0 0 A 500 3. 0 0 A 500 3. 0 0 A 500 2. 0 0 7. 50 112 A 250 0. 6 650 0. 3 7. 115 4 A 100 0. 6 650 0.0 7. 23 117 4 A 250 0. 6 750 4. 6 5. 65 120 4 A 100 0. 6 750 6. 1 4. 90 115 0 A 250 0. 6 850 16. 9 3. 51 105 1 A 100 0. 6 800 14. 6 3. 59 88 0 9. 37 123 5 A 1. 2 0 A 50 0. 6 0 A 50 0.9 0 A 50 0. 9 0 A 50 1. 2 0 A 50 1. 2 g A 50 l. 2 0 A 50 1. 6 0 A 50 2. 0 1 A 50 l. 2 0 A 50 2. 4 1 A 50 3. 0 0 D 50 0. 6 0 D 50 1. 2 4 D 50 1. 2 0 D 50 0. 6 0 D 50 1. 2 0 D 50 2. 4 0

1 O.H.=Overhead or product boiling 600 F.

2 Viscosity and Viscosity Index (V .I.) of product boiling above about 600 F.

3 Continuous run for 7+ days (total hours, 184).

Among the results provided in Table III, those for Run Nos. 102-109 indicate that hydrogen pressures at 100 250 p.s.i.g. at 650-800 F. lead to products little improved over the charge, the dewaxed lubricating oil fraction. With such H pressures at 800-850" F., substantial improvement is realized but at the expense of excessive cracking.

H pressure of 50 p.s.i.g. and temperatures of 750- 800" F. are suitable for forming stable products without excessive cracking.

A continuous run for approximately 7 days at 50 p.s.i.g. H 750 F. and 1.2 LHSV provided excellent lubricating oil products. Approximately 2-3 percent cracking occurred. Viscosity decreased from 57.0 to 49.7 SSU at 210 F., but the viscosity index increased from 123 to 126. Additional runs (119-123) With the same catalyst demonstate that space velocity can be increased to 3.0 without sacrificing stability. Little cracking occurred.

Results set forth in Table III also indicate that: space velocity is from about 0.6-6, preferably 1.2-3; and temperature is from about 500 F. to about 850 F. Higher space velocities are employed with the higher temperatures, and lower space velocities with the lower temperatures recited here.

1. A method for stabilizing a lube oil product of hydrocracking having an initial boiling point above 600 F. and subject to deterioration upon exposure to light and air which comprises passing such a lube oil product of hydrocracking before or after dewaxing in contact with a catalyst having hydrogenation-dehydrogenation activity provided by one or more elements selected from Groups II-B, VI-B, and VIII of the Periodic Table in combination with a support material of relatively low cracking activity and hydrogen at a pressure in the range of from atmospheric up to about p.s.i.g. under conditions of temperature maintained in the range of 400 F. to about 800 F. and space velocity in the range of 0.3 to 3.0 LHSV selected to limit conversion of the lube oil product to materials boiling below 600 F. while simultaneously increasing the aromaticity of the lube oil during said contact and recovering lube oil product from said contacting significantly more stable upon exposure to light and air.

2. The method of claim 1 wherein the temperature is selected from within the range of 650 F. to about 750 F. and the space velocity is selected so as to limit conversion to product boiling below 600 F.

3. The method of claim 1 wherein the hydrogen pres- 1 1 l 2 sure is maintained below 50 p.s.i.g. while the space ve- 2,915,452 12/1959 Fear 208-57 locity is in the range of 1.2 to 3 and the temperature is 2,967,147 1/ 1961 Cole 208-18 maintained in the range of 700 to 800 F. 3,142,634 7/1964 Ireland et a1. 20818 4. The method of claim 1 wherein the support ma- 3,242,068 3/1966 Paterson 208-48 terial is selected from the group including alumina, sil- 5 3,308,055 3/ 1967 Kozlowski 208--18 ca-alumina, silica-zirconium and charcoal. 3,328,289 6/1967 Streed 20815 5. The method of claim 1 wherein the hydrogenation- 3,372,108 3/ 1968 Epperly et a1. 208l5 dehydrogenation catalyst comprises a Group VIII metal distributed on a support of little or no cracking activity HERBERT LEVINE, y Examiner such as provided by alumina and charcoal. 10

US. Cl. X.R.

References Cited 2 1 97 141 UNITED STATES PATENTS Patent: No.

Dated October 12, 1970 ln fl BERNARD A. ORKIN and MILTON BRAID It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 65 Column 7, Table II,

last line Cole. 9 Table III and 10 Cols. 9 Table III and 10 M M 1!. 1 m Ir- Auesfing Officer After "above" insert --about-- After "above insert --about-- Under heading "v.1. (2)" (Run No. 120) "126" should be a blank.

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