DE1224860B - Process for converting cyclic hydrocarbons to paraffinic jet fuel hydrocarbons - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
Display day:

Clog

German class: 23 b - 1/04

1224 860
U 8359IV d / 23 b
September 28, 1961
September 15, 1966

The method according to the invention is used to convert cyclic hydrocarbons into paraffinic jet fuel hydrocarbons.

The nature of jet fuel mixtures is determined primarily by their calorific value and above all determined by their luminosity or brightness number, which is based on the molecular structure of the hydrocarbons present is based in that a low brightness number indicates an extremely bright flame. Low hydrogen to carbon ratios are essential for achieving a low luminous number unfavorable. So aromatic hydrocarbons are the worst materials and when the number of As the number of condensed rings within the molecule increases, the fuel deteriorates even further. Paraffinic So hydrocarbons are the best jet fuels, followed by naphthenes and olefins in terms of quality. Furthermore, less branched hydrocarbons show a better luminous index than the more branched hydrocarbons.

Since the larger proportion of hydrocarbon distillates that boil in the jet fuel range, a Containing a remarkable amount of aromatic hydrocarbons, it is convenient to hydrogenate them to be carried out with practically simultaneous ring opening. This task is in contrast to the previously known catalytic reforming using Supported platinum-halogen catalysts.

Various hydrocarbon catalytic reforming processes in the presence of the foregoing Catalyst type and hydrogen have found extensive industrial use in the petroleum industry. Various reactions occur, including hydrogenation, cyclization, cracking, dehydrogenation, Alkylation, hydrocracking and isomerization should be mentioned. With the catalytic Reforming it is expedient to achieve a suitable equilibrium among such reactions, in order to dehydrate the naphthenes to aromatics, to dehydrocyclize the straight chain paraffins to aromatics and to effect a controlled type of hydrocracking, both in terms of Texture as well as the amount is selective. Isomerization and hydrogen rearrangement also occur to a lesser extent and disproportionation. These reforming processes are designed so that a Liquid product with large amounts of aromatics and other hydrocarbons with a high octane blending number can be obtained.

After USA. Patent 2,642,384 and French Patent 1,080,916 gasoline is at 400 to 54O ⁰ C at less than 3.5 to 80, 0.5 to 15 mol

Process for the conversion of cyclic
Hydrocarbons in paraffinic
Jet fuel hydrocarbons

Applicant:

Universal Oil Products Company,

Des Piaines, JIl. (V. St. A.)

Representative:

Dr. H.-H. Willrath, patent attorney,
Wiesbaden, Hildastr. 18th

Named as inventor:

Vladimir Haensel, Hinsdale, JU. (V. St. A.)

Claimed priority:
V. St. v. America September 29, 1960
(59 161)

Treated hydrogen in the presence of halogen which is reactive with the alumina in the catalyst under the reforming conditions. The catalyst consists essentially of alumina, 0.05 to 1.5 percent by weight platinum or palladium and less than 3 percent by weight fluorine or chlorine. According to US Pat. No. 2,689,208, gasoline or gasoline fractions are reformed by alternately contacting a light naphthenic gasoline fraction with a catalyst made of platinum, alumina and bound chlorine or fluorine under about 3.4 to 27 atm at 400 to 540 ° C and a heavier naphthenic gasoline fraction in the presence of hydrogen under a pressure of at least 34 atm at 400 to 54O ⁰ C. According to US Pat. and then at an elevated temperature at which aromatic hydrocarbons are formed from C ₅ ring naphthenes and acyclic hydrocarbons by dehydrocyclization. Also with other reforming processes, as they are, for. B. in US Pat. No. 2,849,378 or British Pat. No. 800,339, the dehydrogenation of cyclic hydrocarbons to aromatics or the dehydrocyclization of paraffins and isomerization and dehydrogenation of cycloaliphatic hydrocarbons with the formation of aromatics play an essential role.

609 660/381

3 4

In contrast, the main object of the invention. The method according to the invention can be used in any

the conversion of hydrocarbon mixtures can be carried out in a suitable plant. Particularly

while avoiding the main reactions of Dehy- preferred is the use of the known system with

dration and dehydrocyclization, as they are for a pinned layer in which the catalyst is in the

successful reforming process are required, 5 reaction zone is deposited and the hydrocarbon

A finished product with such physical substances in the upstream, downstream or radial flow

and to gain chemical properties as they are passed through. The entire reaction zone

are required for jet fuel. For this purpose, the outlet is in a separation zone for the purpose of separation

a catalyst selected, which passed a low-melting a hydrogen-rich gas stream leading to the

Inorganic oxide, especially alumina, mixed with fresh and fresh hydrogen

a small amount of a platinum group metal, hydrocarbon feed to the reaction zone

especially platinum, and a small amount of bound is returned. The light paraffin hydro

Contains chlorine and which is highly selective for the substances methane, ethane, propane and butane are made by Desired reactions to the formation of paraffinic dementia warnings

Hydrocarbons removed from cyclic hydrocarbons 15 suitable fractionation or distillation zone,

is, while at the same time under such reactions - All unconverted cyclic hydrocarbons,

expresses which have a detrimental effect on the soil that remains in the liquid product stream,

Generation of unsuitable for jet fuel can be removed from this and mixed with the

would have components. original hydrocarbon feed and

The method according to the invention consists in circulating hydrogen. Other that cyclic hydrocarbons in a nozzle-suitable systems in which the process according to the fuel range boiling and at least vorr- Invention can be carried out consist of consisting of a fluidized bed system consisting of cyclic hydrocarbons, in which the carbon-hydrocarbon charge with added hydrogen and the catalyst in a fluidized fluid on a catalyst, which in addition to a platinum layer state under hindered settling conditions group metal content of 0.1 to 2 percent by weight are kept in fluidized bed operation with solid Chlorine content of at least 0.75 and at most a horizontal layer, which is not the catalyst 1.5 percent by weight of the catalyst is withdrawn from the reaction zone as in the a pressure of at least 68 at and one to 300 actual fluidized bed process, in operation up to 400 ° C limited temperature by ring opening 30, with a compact moving layer, in which the and hydrogenation to paraffinic jet fuel hydrocarbons and agitated catalyst hydrocarbons are transferred and these layers are separated together in countercurrent or cocurrent from the effluent of the reaction zone are passed to one another, and in suspensoid mode, and that optionally unreacted cyclic in which the catalyst in the reaction zone as Hydrocarbons from the outlet of the reaction sludge in admixture with the hydrocarbon zone after separation of the hydrogen-rich gas feed is performed.

separated therefrom and the separated cyclic The cyclic hydrocarbons containing carbon

Hydrocarbons and the hydrogen-rich gas hydrogen feed are fed into the reaction zone

then to the reaction zone along with fresh _w ith an hourly Flüssigkeitsraumgeschwindig-

Hydrogen and fresh hydrocarbon charge 40, defined as liquid volume fractions of hydrocarbons

to be led back. Preferably, the conversion material is charged per hour per room proportion of catalyst

Development on a catalyst causes the except alumina inside the reaction zone, from 0.5 to 10.0

and 0.1 to 2 weight percent platinum which passed to 0.75. Lower and medium space velocities

1.5 percent by weight limited amount of chlorine as the only items within this range are preferred,

Contains halogen component. _{45 and} d. these are generally in the range of 1.0

The one for use in the method according to the Er- up to 3.0. As stated above, it becomes a hydrogen-rich one The preferred catalyst is also circulated through its gas stream to keep up with the fresh Production method marked to combine the hydrocarbon feed therein. Of the stands that one becomes a fluoride-free, aqueous aluminum-hydrogen in a sufficient amount oxide prepared, this glows, the platinum component 50 recycled and to a molar ratio of and chlorine combined with the calcined alumina, the hydrogen to hydrocarbon corresponding to 4: 1 Accruing mass in the range from 204 to 316 ° C out to 50: 1 in the circuit. In terms of oxidized long enough to reduce their volatile content of relatively high pressures, under which the decomposition to a value below about 5.0 percent by weight drive according to the invention will be carried out to decrease, and thereafter in the range of 371 to relatively small amounts of hydrogen within this 538 ° C further oxidized sufficiently long to the molar ratio range preferred to the load Volatile content to a value below approximately that for the cycle of such a gas stream 2.0 percent by weight. used plant to facilitate. Preferably

Instead of, as stated in the prior art *, a hydrogen cycle is used in the dehydrogenation of naphthenes and / or the 60 an amount that has a molar ratio of water dehydrocyclization from paraffins to effect, substance to hydrocarbon within the frosting which in the process according to the invention also results in from 6: 1 to 15: 1. As follows Applied working conditions for advantageous conversion is illustrated in special examples, the reaction conversion of aromatic hydrocarbons in zone under a pressure of at least, advantageous paraffinic hydrocarbons. 65 but held over 68 at and up to about 170 at. at

The production of the pressures used according to the invention below about 68 at contains the outlet

Catalyst is the subject of the German design - the reaction zone does not have a sufficient amount of paraf-

scripture 1211 606. Finnish hydrocarbons, as they are necessary,

to meet the luminance specification, notwithstanding the fact that a significant amount of ring opening is caused at the lower pressures. The temperature at which the catalyst is maintained must necessarily be controlled within certain limits in order to avoid the temperature sagging which would inevitably lead to an excessive degree of hydrocracking of the paraffinic hydrocarbons into gaseous light paraffins. On the other hand, the temperature must be such that sufficient ring opening is effected to match or exceed the marking in terms of the luminous number. It has been found that the catalyst to be maintained at a temperature substantially within the range of 300 to 400 ⁰ C. At this temperature, unusually high volumetric yields of a product with the required luminosity are produced. In general, the cyclic hydrocarbon feed to the reaction zone boils above 52 ° C. and mostly in the range of 52 to 231 ° C. Distillates having, for example, a boiling range of 93 to 177 ° C. can also be used. The hydrocarbon feed to the reaction zone can be direct recovered gasoline fraction, a thermally or catalytically cracked gasoline fraction, a "heavy heavy gasoline" fraction, or a mixture thereof. Before entering the reaction zone, the hydrocarbon feed can be subjected to a suitable decomposition to remove normal paraffinic hydrocarbons. The use of molecular sieves is extremely advantageous for this purpose , by means of which a hydrocarbon fraction practically free of normal paraffins is obtained When cyclic hydrocarbons are formed with simultaneous hydrogenation of them to straight and slightly branched paraffinic hydrocarbons, it would be expected that any catalyst known to have hydrocracking and hydrogenation activity would be suitable for use in this process. For such catalysts it is indicated in the prior art that they contain one or more metals from group VI-A and the iron group of the periodic table. These catalysts generally have one or more of the following metal components: chromium, molybdenum, tungsten, iron, cobalt and / or nickel. A well known hydrogenation catalyst with hydrocracking properties is a nickel-diatomaceous earth catalyst which consists of about 50 weight percent nickel. As will be explained in a specific example below, such catalysts are in fact unsuitable for use in the process. When such catalysts are used, the operating temperature required to produce a high degree of ring opening is such that

ίο a run through of the temperature with the inevitable The result is that excessive amounts of light paraffinic hydrocarbons are generated and the catalyst due to the deposition of excessive amounts of coke and other carbonaceous substances Material is deactivated. At temperatures above 300 ° C, the demethylation reaction becomes predominant and causes the deposition of carbonaceous material that forms the effective surfaces and centers shields the catalyst from the materials to be processed.

The following examples serve to illustrate and illustrate the process according to the invention the benefits of using the catalyst in the manufacture of a jet fuel carbon-hydrogen fraction can be achieved with a suitable and excessively high luminosity.

example 1

This example illustrates the inappropriateness of a typical hydrocracking hydrogenation catalyst for use in the process of the invention. The catalyst used in this example was a nickel-diatomaceous earth catalyst in the form of cylindrical pills of 3.2 mm with 55.5 percent by weight nickel. The reaction zone was maintained at a pressure of 34 atmospheres or higher. The fuel velocity was 2.0 and the hydrogen to hydrocarbon molar ratio was 5: 1. The operating temperature fluctuated between the limits of 200 and 425 ^° C. in a succession of operating periods and the results of the various operations are shown in Table I below ⁰ C and a specific gravity of 0.7674. The hydrocarbon feed contained 31% paraffins, 57% naphthenes and 12% aromatics by volume, with no olefinic hydrocarbons in the feed.

An initial analysis showed that this hydrocarbon feed had a luminous number of 70.

Table I.

Product quality

Nickel-diatomite catalyst

working conditions

Pressure, at

Temperature, ⁰ C

Product investigation

Paraffins in percent by weight.

Olefins in percent by weight ...

Naphthenes in percent by weight

Aromatics in percent by weight
Luminous number

2 3 4th period 6th 7th 1 34 34 34 5 34 35.4 34 220 260 303 34 400 300 200 35 37 37 310 33 41 36 - - - 35 1 - __ 65 63 63 - 53 59 64 65 13th 95 99 98 73 99 98 102

The eight operating periods given in Table I illustrate the inappropriateness of the nickel-diatomaceous earth catalyst for producing a suitable luminous number jet fuel hydrocarbon fraction. . Regulations have indicated that the luminous figure can not be "lower than 132 so that a 'hydrocarbon fraction has the desired focal properties of a suitable nozzle fuel in Table I can be seen, an operating temperature of 300 ⁰ C very low ring opening caused when exceeding, ^and: for For all practical purposes, the liquid product effluent was identical to the original hydrocarbon feedstock, and increasing temperature had no apparent beneficial effect on the increase in luminosity, and it should be noted that increasing the pressure to 68 atm did not improve operation to any extent It can be seen that this type of catalyst is not applicable for use in the process of the invention because it does not promote ring opening to the required extent while hydrocracking the so formed paraffinic hydrocarbons would be prevented.

Example 2

This example serves to explain the influence of the operating pressure on the method according to the

ίο invention. The hydrocarbon feed used was identical to that used in Example 1 above, "space velocity was 1.0 to 1.5 and the molar ratio of Hydrogen to hydrocarbon to about 10: 1 held. Two periods were each at three different pressure levels, namely 34, 61 and 68 at, carried out. At each pressure level, two periods with different temperature levels were carried out. The working conditions for the six periods can be found in the following table II:

Table II Influence of Pressure

10 ' period 11 12th 13th 14th 9 34 61 61 68 68 34 370 360 330 325 300 320 45 65 50 85 69 38 0 0 0 0 0 0 48 35 50 15th 31 62 7th 0 0 0 0 0 79 111 105 146 124 99

working conditions

Pressure, at

Temperatures, ⁰ C

Product investigation
Paraffins in percent by weight.
Olefins in percent by weight
Naphthenes in percent by weight
Aromatics in percent by weight.

Luminous number

The catalyst used to achieve the values given in this table consisted of a mass of alumina, 0.375 percent by weight of platinum and 4.0 percent by weight of bound fluoride, calculated as the element. The influence of the pressure increase to 68 at can easily be determined from the values given in Table II. At a pressure of 34 at a temperature rise resulted from 320 ⁰ C to 370 ⁰ C in a decrease in the luminous number from 99 to 79. The latter is only slightly different from the value of 70, the exit load possessed. Further, at 34 and were at a temperature of 37o C ⁰ containing 7.0 weight percent of aromatic hydrocarbons and naphthenes 48 percent by weight in the product. At 61 at, there was an increase in the production of paraffinic hydrocarbons as evidenced by the increase in luminosity to 111 and 105. Operation at 68 atm and a temperature of 325 ° C resulted in a product with a luminosity of 146 and this was the only attempt that resulted in a suitable jet fuel hydrocarbon fraction. -

Analyzes that were carried out to obtain the product distribution showed, however, that the presence of fluoride within the catalyst mass leads to an excessive degree of hydrocracking so that the weight fraction of pentanes and heavy hydrocarbon product is only 77.2% of the original hydrocarbon feed. This deleterious influence of fluoride in the catalyst is shown even more clearly in the following example ".

Example 3

This example serves to compare the results obtained by using catalytic masses with different amounts of platinum and different amounts of -bound -fluoride- or -bound chloride. The hydrocarbon feed used was a mid-continent heavy gasoline with 56 volume percent cyclic compounds and a luminosity of 71. The hydrocarbon feed had a boiling range of 119 to 196 ° C. The reaction zones were under a pressure of 136 atmospheres for all six periods with the hydrocarbon feed being fed with a liquid hourly space velocity of 2.0. The molar ratio of hydrogen to hydrocarbon was maintained at a level of 10: 1 and the reaction temperature varied from 280 to 39O ⁰ C,

mn to obtain finished products with various Leuehtzahl and to modify the degree of hydrocracking effected in the reaction zone. One of the catalysts evaluated under these conditions contained 0.750 percent by weight platinum and 0.90 percent by weight bound chloride, calculated as the element which was the only halogen constituent of the composition. This catalyst is the preferred catalyst for use in the process of the invention and was prepared in the following manner: An aluminum chloride hydrosol was converted into 1.6 µm spheres by the oil drop method illustrated in U.S. Patent 2,620,314. The alumina spheres were dried at a temperature of approximately 204 ^° C. and then annealed in an air atmosphere for approximately 1 hour at a temperature of approximately 510 ^{° C.} The annealing temperature was then raised to a height of about 6SS ⁰ C and the Calcinrerung continued for about 2 hours at the elevated temperature had fallen until the content of volatiles in the alumina balls at a level of 1.98 percent by weight. The calcined alumina spheres were mixed in a rotary evaporator with water, hydrochloric acid and sufficient chloroplatic acid to result in a finished catalyst with 0.75 percent by weight of platinum. Based on approximately 271.2 kg of the annealed alumina spheres of 1.6 mm, 5161 of water and 15.7 kg of 34.6 weight percent hydrochloric acid were added to the rotary evaporator. The alumina spheres were dried in the rotary evaporator at a vapor pressure of about 3.4 atm for 6 hours. The dried spheres were then subjected to at a temperature of 288 ⁰ C for 1 Stuade a high temperature oxidation, to. the volatile content had fallen to about 4.5 percent by weight. The temperature was then increased to a height of 590 ° C. and the oxidation was further stirred at this increased temperature for 2 hours until the volatile content had fallen to a value of 1.7 percent by weight. The finished catalytic mass was free of fluoride and contained 0.150 percent by weight of platinum and 0.90 percent by weight of bound chloride, calculated as elemental chlorine.

For the production of the according to the invention used Catalyst is not claimed in the context of the invention.

As indicated in Table HI below the evaluated catalysts except for the catalyst just described with masses of alumina a) 0.375 percent by weight platinum and 4.0 percent by weight bound fluoride, b) 0.750 percent by weight Platinum and 0.25 percent by weight lithium, c) 0.375 percent by weight platinum, d) 0.750 percent by weight Platinum and 0.22 percent by weight combined chloride. For each catalyst tested, the amounts were cyclic hydrocarbons in the product, the luminosity number and the amount of light paraffin hydrocarbons produced plotted against temperature as the variable. As indicated in table ΪΙΙ the catalysts were compared at two levels of hydrocracking; initially at a level that too 13.35 normal liters of light paraffinic hydrocarbons (gaseous) per liter of fresh liquid hydrocarbon feed and then at a hydrocracking level of 39.16 normal liters of light paraffinic hydrocarbons per liter of fresh liquid hydrocarbon feed.

1Θ

Table III
Catalyst evaluation

catalyst

0.375% Pt, 4.00% F ..
0.750 ⁰ Z ₀ Pt, 0.25% Li ..

0.375% pt

0.7507 ₀ Pt, 0.22% CL.
0.750% Pt, 0.90% CL.

At 13.351 / 1
cy- I luminous clic [number

42
40
37
33
23

107
112
121
126
140

At 39.161 / 1

cyclic

28
29

16

Luminous number

123
119

138
151

At the lower level of hydrocracking, the only catalyst that resulted in a product with a Luminous number led above the prescription of 132, which was preferred for use in accordance with the invention and catalyst prepared as set forth above. At the higher hydrocracking level, the catalyst yielded with 0.22 percent by weight of bound chloride as the only Haiagen ingredient, a product with a Luminous number of 138, however, it should be noted that this catalyst required an increase in the severity of the operation, which inevitably became stronger Hydrocracking and, accordingly, a lower volumetric yield.

Another catalyst was prepared using 1.6 mm alumina spheres according to FIG U.S. Patent 2,620,314 containing

3.0 0.35 percent by weight combined chloride. The spheres were intimately mixed with a sufficient amount of an aqueous hydrogen fluoride solution to combine therewith 0.35 percent by weight bound fluoride. The halide-containing spheres were then dried and subjected to a single calcination at a temperature of. about 482 ⁰ C subjected. The calcined spheres were impregnated with an aqueous chloroplatinic acid solution in an amount sufficient to provide a finished catalyst containing 0.750 percent by weight of platinum, calculated as its element. The impregnated spheres were dried at a temperature of about 149 ⁰ C and then calcined for 2 hours approximately in an air atmosphere at a temperature of about 482 ° C until at which time the content of volatiles in the catalyst is below a value of approximately 2.0 Weight percent was. This catalyst is characteristic of a present-day platinum-containing reforming catalyst with associated bound halogen. This catalyst is compared to a catalyst containing 0.750 percent by weight platinum and 0.90 percent by weight combined chlorine and prepared as described above for use in accordance with the invention.

Table IV

Catalyst evaluation

catalyst

0.750% Pt, 0.35% F,

0 35 ° / Cl
0.750% Pt, 0.90% Cl. 1

At 13.35 IA
Luminous number

cyclic

26th
16

130

142

At 39.161 / 1 luminous number

cyclic

12th
4th

142
164

For the purposes of this example, the normal paraffinic hydrocarbons did not come from the hydrocarbon feed before their introduction to the

609 660/381

Reaction zone removed. By comparing the values in Table IV with those in Table III, it can be seen that the inclusion of normal paraffins within the feed mass has no detrimental effect on the The end result, and indeed it appears, is the production of a jet fuel hydrocarbon fraction to increase something with a luminous number over 132. Table IV also states that the inclusion Bound fluoride in the catalyst mass increases the sharpness of the operation The resulting lower yield of liquid product forces a comparable and produce acceptable jet fuel hydrocarbon fraction. On the other hand, the catalyst performed with 0.90 percent by weight bound chloride as the only halogen component to a finished product, which at the lower hydrocracking level is perfectly usable for use as jet fuel and was a superior jet fuel at the higher hydrocracking level, which was obtained in a yield of 96 volume percent of the hydrocarbon feed.

Claims (4)

Patent claims: 1. Process for converting cyclic hydrocarbons to paraffinic jet fuel hydrocarbons at elevated temperature and overpressure in the presence of hydrogen over a catalyst which is a difficult to melt inorganic oxide, especially alumina, a small amount of a platinum group metal, especially platinum, and contains a small amount of bound chlorine, with separation of one hydrogen-rich gas and a liquid hydrocarbon product from the effluent of the Reaction zone, characterized in that that cyclic hydrocarbons boiling in a jet fuel range and at least hydrocarbon feed consisting predominantly of cyclic hydrocarbons with added hydrogen on a catalyst, which in addition to a platinum group metal content from 0.1 to 2 percent by weight a chlorine content of at least 0.75 and at most 1.5 percent by weight of the catalyst, at a pressure of at least 68 atm and a pressure of 300 to 400 ° C limited temperature by ring rupture and hydrogenation into paraffinic jet fuel hydrocarbons are transferred and these are separated from the effluent of the reaction zone and that optionally unreacted cyclic hydrocarbons from the outlet of the reaction zone after separation of the hydrogen-rich Gas separated therefrom and the separated cyclic hydrocarbons and the hydrogen-rich gas then to the reaction zone be recycled along with fresh hydrogen and fresh hydrocarbon feed. 2. The method according to claim 1, characterized in that the conversion on a catalyst, in its manufacture a synthetic, fluoride-free, water-containing, low-melting one Oxide combined with a metal component from the platinum group and with chlorine and the volatility content this composition by oxidizing in the range of 204 to 316 ° C initially below 5 percent by weight and then by oxidation in the range from 371 to 538 ° C to less than 2 percent by weight has been decreased. 3. The method according to claim 2, characterized in that the conversion on a catalyst, in the manufacture of which a synthetic clay was used, its volatility content by an initial calcination for at least 1 hour at a temperature of 454 to 566 ° C and subsequent calcining at a temperature of 593 to 760 ° C to less than 2 percent by weight before their combination with the metal component and the chlorine has been carried out. 4. The method according to claim 1, characterized in that a predominantly cyclic Hydrocarbon fraction consisting of naphthenic and aromatic hydrocarbons, which was initially essentially freed from normal paraffins, as a hydrocarbon feed along with 6 to 15 moles of hydrogen per mole of feed hydrocarbon is introduced into the reaction zone. Considered publications:
French Patent No. 1080 916;
British Patent No. 800,339;
U.S. Patent Nos. 2,642,384, 2,915,458, 849,378, 2,689,208.