US2418534A - Hydrocarbon conversion process - Google Patents

Description

April 8, 1947- c. w. WATSON HYDROCARBON CONVERSION PROCESS Filed Aug. 18, 1944 Sn 2o @165mm NNM lull

Patented Apr. 8, 1947 HYDROCARBON CONVERSION PROCESS Claude W. Watson, Scarsdale, N. Y., assigner to The Texas Company, New York 17, N. Y., a. corporation of Delaware Application August 18, 1944, Serial No. 550,101

3 Claims.

This invention relates to the manufacture of gasoline to produce gasoline of improved quality from naphtha hydrocarbons.

The presentapplication isa continuation-inpart of Serial No. 500,599, filed August 31, 1943, for Hydrocarbon conversion process, and which is now Patent No. 2,400,795, dated May 21, 1946.v

The invention has to do with the catalytic conversion of cracked and straight run naphtha, or fractions thereof, into gasoline of increased parailin and aromatic content and of improved octane value. It involves a continuous method for effecting dehydrcgenation of straight run naphtha andV hydrogenation of cracked naphtha in a common reaction zone.

The invention provides a method for the conversion of olefinic petroleum hydrocarbons of motor fuel range into motor fuel components of low potential gum content, high anti-knock value and excellent lead susceptibility, especially suited for use in aviation fuels or other motor fuels for high compression engines. It provides a process for the production of motor fuel of aviation grade from a relatively unsaturated cracked naphtha and a relatively saturated naphthenic hydrocarbon fraction.

AsV disclosed in Patent No. 2,400,795, liquid olefinic hydrocarbons are subjected to catalytic isomerization and the resulting isomerizate is reacted, under hydrogen transfer conditions, with cyclic hydrocarbons containing alicyclic methylene groups. The hydrogen transfer reaction effects hydrcgenation of the olefins and dehydrogenation of the cyclic hydrocarbons. By this combination of reactions, a petroleum hydrocarbon fraction of high olen content, such as a catalytically cracked naphtha, may be converted to a parainic blending stock of high anti-knock value. If a naphthenic fraction of motor fuel range is employed in the hydrogen transfer reaction with the cracked naphtha isomerizate, the naphthenes are dehydrogenated, and the resulting aromatic hydrocarbons further improve the anti-knock characteristics of the reaction product. By this means it is possible to obtain a product having an octane number at least as high as that of the original cracked naphtha, and usually substantially higher than that of the cracked naphtha, and also having alow bromine number and ability to meet the most stringent specications as to accelerated gum formation.

Also, as disclosed in Patent No. 2,400,795, the isomerized olens are reacted with hydroaroniatic hydrocarbon constituents of straight run naphtha by contact with a solid hydrogenation-dehydrogenation catalyst of the oxide or sulfide type at temperatures ranging from 750 to 950 F. and under pressures ranging from 50 to 1500 pounds per square inch. Also, as described in the parent application, straight run naphtha hydrocarbons heated to the desired temperature are passed through a reaction tower packed with the hydrogenation-dehydrogenation catalyst, while thel cracked naphtha hydrocarbons following :lsomeri. zation are introduced to the tower at a plurality of succeeding points intermediate the inlet and the outlet of the reaction tower.

The present application is concerned particularly with the procedure employed in carrying out the combined dehydrogenation and hydrogenation reactions so as to effect transfer of hydrogen from hydroaromatic constituents of the straight run naphtha to unsaturated constituents of the cracked naphtha.

More specifically, the invention of the present application involves maintaining a reaction tower or other elongated reaction zone packed with the hydrogen transfer catalyst in solid granular form. Dehydrogenation of naphthene hydrocarbons is effected in one region, while hydrogenation of olenic hydrocarbons is effected in another region of the reaction zone.

The procedure thus involves passing the straight run hydrocarbons through a dehydrogenating section of the reaction zone at a temperature in the range about 840 to 900 F. and preferably at about 850 to 860 F. The products of dehydrogenation then pass through a hydrogenating section wherein they are brought into contact with the cracked naphtha hydrocarbons at a temperature in the range about 600 to 800 F. and preferably at a temperature about 650 to 700 F. Advantageously, the cracked naphtha hydrocarbons are introduced directly to the hydrogenating section at a plurality of succeeding points in the direction of straight run hydrocarbon iiow therethrough. The temperatures and proportions of the successive streams of cracked hydrocarbons are correlated so as to maintain the desired temperature within the hydrogenating section, which temperature should not exceed a maximum of about 800 F.

The hydrogenating reaction is of exothermic character and therefore succeeding streams of cracked naphtha may be introduced at progressively lower temperatures, or in different proportions at substantially the same temperature, in order to control the over-al1 temperature prevailing within the hydrogenating section..

Free hydrogen is maintained present in both sections of the reaction zone in excess of 'that required for completely hydrogenating the olefinic 3 or other unsaturated constituents of the cracked naphtha feed and also in excess of that required for hydrogenating any sulfur available from the naphtha feed for reaction with hydrogen to vform hydrogen sulfide.

' Free hydrogen is produced in the dehydrogenating section wherein naphthenic hydrocarbons are converted to aromatic hydrocarbons with lib'- eratlon of hydrogen. Provision may be made for recycling hydrogen ,through the reaction tower.

Advantageously, hydrogen gas is separated from the products of the process and recycled to the dehydrogenating section of the reaction zone. The recycled gas can be heated to temperatures suiciently elevated to provide the heat required in effecting the endcthermic dehydrogenation reaction..

The ratio of cyclic hydrocarbons to olefins for 'the hydrogen transfer reaction will depend upon the degree of unsaturation of the oleiinic charge stock and the available hydrogen in the cyclic hydrocarbons. It is desirable to employ an excess of the cyclic hydrocarbons over that theoretically required to supply all of the hydrogen necessary for saturation of olens and for hydrogenation of available sulfur. Ratios of cyclic hydrocarbons to olens in the charge may suitably range from 1.1 to 1.5 times the theoretical ratio.

The process of the invention is especially adapted for the treatment of olelnie' hydrocar.- bon mixtures such as cracked petroleum fractions including naphtha hydrocarbons derived from either thermal cracking or catalytic cracking. The relatively lower boiling portion. namely, boiling in the range below about 250 or below 300 F., of catalytically cracked naphtha, is particularly suitable since it contains a relatively high proportion of branched chain olefin hydrocarbons. While mention is made of oleilnic naphtha obtained from cracking ,of petroleum, nevertheless it is contemplated that the olenic naphtha mentioned cycloparaifins, cyclooleiins, terpenes/ and polycyclic hydrocarbons of alicyclic or mixed alicyclic-aromatic character. The hydroaromatic hydrocarbons are preferred as hydrogen donors for the hydrogenation of the oleiins since they are dehydrogenated to aromatics. Naphthenic hydrocarbons, consisting essentially of cyclohexane and its derivatives, boiling at a temperature not higher than the end boiling point of the desired gasoline product, are especially desirable.

Straight-run naphtha such as derived from naphthene base crudes may be used as the source of the naphthene hydrocarbons required in the process as hydrogen donors. It is preferred to use a naphthene stock high in Cs ring naphthene hydrocarbons boiling within the range of aviation gasoline, that is, boiling in the range below 250 or 300 F. A naphthenic gasoline having a C. F. R. M. octane number of 60 to 70 or in excess of 55 is preferred. v

In order to describe the invention in more detail, reference will now be made to the accompanying drawing illustrating a method of flow suitable for carrying out the hydrogen transfer reaction irrespective of whether or not the olelnic feed stock has been subjected previously to isomerization.

The numeral I designates a vertical reaction tower packed with a plurality of beds of catalyst 2, each bed being supported by a perforated tray 3. The catalyst may be of the molybdena-alumina type in which the oxides of molybdenum amount to about 9% by weight of the catalyst.

Straight run naphtha from a source not shown is conducted through a pipe 4 and a. heater 5 wherein it is heated to a temperature of at least 850 F. .and not in excess of about 925 F. The heated naphtha passes through a pipe 8 to the top of the reaction tower I. The straight run naphtha, advantageously boiling` in the range -about to 300 F., enters the top of the tower in vapor phase and ows downwardly through the catalyst beds in series. y Recycled gas, from a source which will be referred to later, is heated in the heater 8 to a temperature which may range as high as `1200 F. or to a temperature sumciently high to provide the heat of reaction required for effecting dehydrcgenation of straight run naphtha. The heated gas is passed through pipe 8 which communicates with branch pipes I0, II and I2. These branch pipes extend into the upper portion of the tower I, in which portion dehydrogenation is effected.' The heated gases are thus introduced at a .plurality of succeeding points and the proportions and temperatures of the several entering gas streams are correlated so as to maintain substantially the same temperature throughout the' catalyst mass in the dehydrogenating section of the tower.

It is advantageous to avoid a substantial temperature drop in this section of the tower. It is preferred to maintain a uniform temperature within the range about 840 to 870 F.

Higher temperatures are avoided so as to prevent hydrocarbon cracking or other undesirable reactions. On the other hand, at temperatures below 840 F. the dehydrogenation reaction is relatively slow. At a temperature of about 850 to 860 F. the reaction is about 90% completed provided the proper time of contact is realized.

The time of contact is dependent upon space velocity, which in turn is` maintained within the range about 0.1 to 0.5 volume of straight run naphtha measured as liquid at 60 F. per volume of catalyst per hour.

The pressure maintained within the reaction tower ranges from about 400 to 800 pounds and preferably about 700 pounds.

As indicated in the drawing, the dehydrogenating reaction is substantially completed during passage of the hydrocarbons through the rst bed of catalyst or section of the tower. The products of dehydrogenation then pass on through the succeeding catalyst bed or beds comprisingv the hydrogenating section.

Cracked naphtha, boiling in the range up to about 300 F., is conducted from a source not shown through a pipe I5, whichv in turn communicates with branch pipes I6 and I1. These branch pipes may lead to separate heaters or heat exchangers I8 and I9 respectively, wherein the naphtha streams are heated t0 the desired temperature or temperatures.

The portion of the cracked naphtha, passing from the heater I8 through pipe 20, may enter the reactor I at comparatively -low temperatures, for example at a. range from 100 to 200 or 300 F. It is thus used to reduce the temperature of the products of dehydrogenation passing to the hydrogen section of the tower. If desired, the cracked naphtha hydrocarbons may enter through pipe 20 in liquid phase so that their chiasso.'

heat of vaporization is utilized'within the reaction tower to cool the products of dehydrogenation to a temperature of about 700 F. or to a, temperature below about 800 F. The cracked'naphtha and the dehydrogenated naphtha, together with free hydrogen, ow in the presence. of each other through the hydrogenating sections of the tower, so that hydrogenation oi' the unsaturated constituents of the cracked naphtha occurs.

Since the hydrogenating reaction is expthermic, it is advantageous to employ split feed of the cracked naphtha. Therefore a succeeding stream is introduced from -the exchanger I9 through pipe 2l. The proportions of cracked naphtha entering at each succeeding point, the spatial distribution of the several streams, and the temperature at which each stream enters are correlated so as to maintain a temperature about 650 to '700 F. within the hydrogenating section. As previously indicated, each stream may enter at substantially the same temperature, control of reaction temperature being effected by adjusting the relative proportions of the streams.

The straight run naphtha introduced to the top of the tower may range from about 35% to '75% by volume of the combined straight run and cracked naphtha feed. i

The products of reaction are continuously 1 drawn off from the bottom of the reactor through a pipe 30 to the lower portion of the fractionator 3l. The fractionation is carried out so as to remove a distillate fraction containing gasoline hydrocarbons boiling up to about 300 to 320 F.

The distillate is removedr through a pipe 32 and condenser 33 to a receiver 34. The condensate collects therein and is continuously drawn off through a pipe 35.

The gas is vented oi through a pipe -36 from which it may be discharged, at least in part, through pipe 31. n

Since it is usually desirable to carry on the process with hydrogen recycle, provision is made for conducting the gas from the pipe 36 through the pipe 38 leading to the heater 8, previously mentioned and wherein the recycle gas is heated prior to return to the reaction tower. The amount of gas recycled usually ranges from about 5,000 to 10,000 cubic feet per barrel of straight run or donor feed, the gas being measured under standard conditions.

When the gas contains a relatively large amount of hydrogen sulfide, provision may be made for scrubbing it prior to recycling. In such case, the gas is passed through pipe 40 into a scrubber 4|, wherein it is scrubbed with soda ash solution or other scrubbing medium to effect removal of hydrogen sulfide. The resulting scrubbed gas is then returned through pipe 42 which communicates with pipe 38. Since the bulk of the hydrogen sulfide is removed from the system in the condensate leaving the receiver 34, such scrubbing is usually unnecessary.

In carrying out the process it will be apparent, from the foregoing, that the space velocity in the hydrogenating section of the tower is relatively greater than that prevailing in the dehydrogenating section. In the dehydrogenating section, the space velocity does not exeed 0.5, while in the hydrogenating section it will range from about 1 to 3 and is preferably maintained at about 2 liquid volumes of combined naphtha (exclusive of gas) per volume of catalyst per hour.

The procedure described is particularly advantageous for the treatment of naphtha, contain- V catalyst used in this process, particularly at the temperatures most effective for carrying out dehydrogenation. It is therefore important to maintain a high partial pressure of hydrogen present* in order to keep the catalyst free from sulfur. The available sulfur reacts with free hydrogen to produce hydrogen sulfide whichv is discharged from the system. The present process therefore permits maintaining a large amount of 'hydrogen present in the dehydrogenating section so as to prevent catalyst degradation due to the sulfur contained in the feed naphtha.

It is for this reason that the olefinic feed is not introduced with the straight run naphtha. Instead, it is not introduced until a point in the path of travel of the straight run hydrocarbons through the reaction zone is reached where the dehydrogenating reaction is substantially entirely completed. The reduction in the amount of hydrogen present, which would occur as a result of having olens present in the dehydrogenating section is thus avoided.

The hydrogenating reaction is effected, in accordance`with the present invention, at a lower range of temperature, such that the sulfur has relatively low affinity for the catalyst. The process thus provides a means for effecting desulfurization as well as hydrocarbon conversion.. It is useful for effecting both desulfurization and hydrogenation of cracked naphtha.

It is contemplated that with straight run feed stocks containing lless than .01% sulfur, the process may be operated without substantial hydrogen recycle. On the other hand, with straight run feed stocks containing sulfur in excess of .05% by weight, provision may be made for desulfurizing the straight run naphtha prior to the hydrogen transfer treatment. In this ease, the straight run naphtha hydrocarbons of high sulfur content may be subjected to the action of a catalyst of the fullers earth or bauxite type, at a temperature in the range 650 to 900 F., to effect desulfurization. The desulfurized naphtha from which the sulfur has been removed is then passed to the hydrogen transfer reaction.

It is contemplated carrying out the hydrogen transfer reaction process so that no hydrocarbon cracking occurs as evidenced by the obtaining of a liquid hydrocarbon recovery of at least 98% by weight and preferably at least 99% of the liquid feed hydrocarbons. The C4 hydrocarbon, and lighter gas fraction of the eiuent stream of reaction products, consists essentially of hydrogen. In other words, the hydrogen is in excess of and is usually not less than 97% by weight of this fraction.

'I'his is in contrast with the conventional hyy ananas merization of oieilns with subsequent cracking of products formed by polymerization; cyclization of .parai1ins,` lcondensation of aromaticsw; etc. These l.destructive conversion reactions are. so pronouneed that in the conventional operation, even with a, large amount of hydrogen gas recycle, the

catalyst is'rapidly fouled so that regeneration is necessary after to 1.2 hourson stream.

The hydrogen' transfer catalyst used in the process of this invention advantageously comprises a mixture` of aluminum oxide in any of its various forms with from 1 to 50 Weight per cent naphthenic hydrocarbons in the `presence of the hydrogenation-dehydrogenation vcatalyst nevertheless it is also contemplated that the' process may have`application tothe treatment of unsaturated hydrocarbons derived from other sources and also to the treatment of other unsaturated materials such as contained in fatty oils and fatty acids or derivatives thereof obtained from vegetable, animal. or fish oil sources. Thus theprocess may be used for effecting saturation of these unsaturated fatty oil or fatty acid substances by reaction with naphthenic hydrocar- A bons derived from straight-run naphtha.

of an oxide or sulde of a metal selected from reaction zone corresponds to a space velocity of about .5, while the flow through the hydrogenating section corresponds to a space velocity of about 2.

The operation is carried out with a gas recycle rate of about 8,000 cubic feet per barrel of combined naphtha feed so as to maintain a hydrogen partial pressure in the eiiluent product stream from'the reaction of about 400 to 700 pounds per square inch gauge.

The liquid product obtained, after a minimum of 100 hours continuous flow without interrup tion for catalyst reactivation, amountsto about 98.7% by weight of the combinednaptha feed. The following tabulation sets forth the characteristics vof the feed naphtha fractions and the resulting product, including those of a blend of the feed naphthas in the proportion as actually charged, namely 35% cracked naphtha to 65% of straight run naphtha by weight.

StraightRun Cracked Blend Product Gravity API 57. 4 67. 7 62. 3 62. 5 B ur, Wt. .01 Bromine No 0.6 105 35 1 Distillation:

I. Biolly. 168 er E. P l300 Aromatics, Wt 85. 4 Octanes:

AFD-IC C1ear Below 71.2 72.4 AFD1C+4cc- TEL. 88. 82. 0 85 87. 3

catalyst such as aluminum chloride-hydrocarbon complex.

While mention has been made of reacting olefinie hydrocarbons derived from petroleum with Obviously many modicationsand variations of the invention, as hereinbefore setaforth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap pended claims. l

- I claim:

l. A continuous method of preparing gasoline rich Ain aromatic hydrocarbons and saturated aliphatic hydrocarbons from straight run and cracked naphtha hydrocarbons boiling within the range about to 300 F. and containing sulfurbearing compounds in substantial amount involv..

1 ing dehydrogenation of hydro-aromatic constituents of straight run naphtha and hydrogenation of oleiinic constituents of cracked naphtha which comprises maintaining an elongated reaction zone containing Ya substantially stationary mass of hydrogenation-dehydrogenation catalyst and through which straight run hydrocarbons undergoing treatment flow from the inlet through a.

dehydrogenating section and thereafter through a hydrogenating section to the outlet of the reaction zone, continuously introducing a stream of straight run hydrocarbons vto said inlet, effecting contact between introduced hydrocarbons and catalyst in the dehydrogenating section at an elevated temperature of about 850 to 860 F., under a pressure within the range about 400 to 800 pounds and with a space velocity in the range about 0.1 to 0.5 liquid volumes of naphtha per hour per catalyst, and in the absence of oleflnic constituents of the cracked naphtha hydrocarbons such that dehydrogenation of said hydroaromatic constituentsoccurs with liberation of hydrogen in substantial amount, continuously introducing to the hydrogenating section of the reaction zone cracked hydrocarbons, causing the products of dehydrogenation and the introduced cracked hydrocarbons to iiow concurrently and in direct contact through the hydrogenating section at an elevated temperature in the range about 650 to 700 F. and with a space velocity in the range about 1 to 3 liquid volumes of combined naphtha per hour per catalyst such that hydrogenation of cracked hydrocarbons with said liberated hydrogen occurs, correlating the proportion of straight run hydrocarbons to cracked hydrocarbons charged so that the cyclic hydrocarbons are present in an amount equal to about 1.1 to 1.5 times the molecular equivalent of the olens and such that free hydrogen in substantial amount is maintained in the reaction zone, continuing the flow of hydrocarbons through the reaction zone for substantially in excess of 100 hours without catalyst regeneration, continuously discharging from the outlet hydrocarbon products of reaction and free hydrogen, the liquid hydrocarbons contained in said products amounting to at least about 98 weight per cent of the combined naphtha feed and the C4 hydrocarbon and lighter constituents of said products consisting of not 9 less than about 97 weight per c'ent hydrogen separating hydrogen gas from the discharged products, heating the separated gas and introducing the heated gas at a plurality of succeeding points in the dehydrogenating section of the reaction zone to thereby maintain substantially uniform temperature throughout said section.

2. A continuous method of preparing gasoline rich in aromatic hydrocarbons and saturated aliphatic hydrocarbons from straight run and cracked naphtha hydrocarbons boiling Within the range about 100 to 300 F. and containing sulfur bearing compounds in substantial amount involving dehydrogenation of hydro-aromatic constituents of straight run naphtha and hydrogenation -of olenic constituents of cracked naphtha which comprises maintaining an elongated reaction zone containing a substantially stationary mass of hydrogenation-dehydrogenation catalyst and through which straight run hydrocarbons undergoing treatment flow from the inlet through a dehydrogenation section and thereafter through a hydrogenating section to the outlet of the reaction zone, continuously introducing a stream of naphthene straight run gasoline having a C. F. R. M. octane number of substantially in excess of 55 to said inlet, effecting contact between introduced hydrocarbons and catalyst in the dehydrogenating section at an elevated temperature of about 850 to 860 F., under a pressure within the range about 400 to 800 pounds and with a space velocity inthe range about 0.1 to 0.5 liquid volumes of. naphtha per hour per catalyst and in the absence of oleflm'c constituents of the cracked naphtha hydrocarbons such that dehydrogenation of said hydro-aromatic constituents occurs with liberation of hydrogen in substantial amount, continuously introducing to the hydrogenating section of the reaction zone cracked hydrocarbons, causing the products of dehydrogenation and the introduced cracked hydrocarbons to now concurrently and in direct contact through the hydrogenating section at an elevated temperature in the range about 650 to 700 F. and with a space velocity in the range about 1 to 3 liquid volumes of combined naphtha per hour per catalyst such that hydrogenation of run naphtha and hydrogenation of olenic coni y stituents of cracked naphthawhich comprises maintaining an elongated reaction zone 'contain-v ing a mass of hydrogenation-dehydrogenation catalyst and through'which straight run hydrocarbons undergoing treatment flow from .the inlet through 'a dehydrogenating section and thereafter through a hydrogenating section to the outlet of the reaction zone, continuously 'introducing a stream of straight run hydrocarbons to said inlet, effecting contact between introduced hydrocarbons and catalyst in the dehydrogenating section at an elevated temperature of about 840 to 870 F., `under a pressure within the range about 400 to 800 pounds and with a space velocity in the range about 0.1 to 0.5 liquid volumes ofnaphtha per volume of catalyst per hour, and in the absence of olenic constituents of the cracked naphtha hydrocarbons such that dehydrogenation of said hydro-aromatic constituents occurs with liberation of hydrogen in substantial amount,

continuously introducing to the hydrogenating cracked hydrocarbons with said liberated hydroent in an amount equal to about 1.1 to 1.5 times the molecular equivalent of the olens and such that free hydrogen in substantial amount is maintained in the reaction zone, continuing the iiow Aof hydrocarbons through the reaction zone for substantially in excess of 100 hourswithout cata lyst regeneration, continuously discharging from the outlet hydrocarbon products of reaction and free hydrogen, .the liquid hydrocarbons contained in said products amounting to at least about 98 Weight per cent of the combined naphtha feed and the C4 hydrocarbon and lighter constituents of said products consisting of not less than about 97 weight per cent hydrogen, separating hydrogen gas from the discharged products, heating the separated gas and introducing the heated gas at a plurality of succeeding points in the dehydrogenating section of the reaction zone to thereby maintain substantially uniform temperature throughout said section.

3. A continuous method of preparing gasoline rich in aromatic hydrocarbons and saturated aliphatic hydrocarbons from straight run and cracked naphtha hydrocarbons boiling Within the section of the reaction zone cracked hydrocarbons, causing .the products of dehydrogenation and the introduced cracked hydrocarbons to now concurrently and in direct contact through the hydrogenating section at an elevated temperature not in excess of about 800 F. and with a space velocity in the range about 1 to 3 liquid volumes of combined naphtha per volume of catalyst per hour such that hydrogenation of cracked hydrocarbons with said liberated hydrogen occurs, correlating the proportion of straight run hydrocarbons to cracked vhydrocarbons charged to the reaction zone so that the cyclic hydrocarbons are about 1.1 to`1.5 times the molecular equivalent oi the olefins and such that free hydrogen in substantial amount is maintained in the reaction zone. continuing the now of hydrocarbons through the reaction zone for substantially in excess of hours without catalyst regeneration, continuously discharging from the outlet hydrocarbon products of reaction and free hydrogen, the liquid hydrocarbons contained in said products amounting to at least 98 weight per cent of the combined naphtha feed and the C4 hydrocarbon and lighter constituents of said product consisting of not less than about 97 weight per cent hydrogen, separating gas from the discharged products, heating said gas and introducing the heated gas at a plurality of succeeding points in the dehydrogenating section of said reaction zone to therebyI maintain substantially uniform temperature throughout said section.

CLAUDE W.y WATSON.

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

UNITED STATES PATENTS Number Name Date 2,241,393 Danner ..-Ma-y 13, 1941 2,303,075 Frey Nov. 24, 1942 2,283,854 Friedman May 19, 1942` 2,293,759 Penisten Aug. 25, 1942 2,289,716 Marschner July 14, 1942 2,335,684 Mayer Nov. 30, 1943 2,341,269 Day Feb. 8, 1944 2,367,530 Ruthrui Jan. 16, 1945 OTHER REFERENCES Egioff et a1. pubucaun 1n the on and Gas Journal, May 21, 1931, pages 40 and 155.

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