DE1246918B - Process for the production of hydrocarbon oils with a reduced pour point - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

Clog

German class: 23 b -1/04

Number: 1 246 918

File number: S 88082IV d / 23 b

Filing date: October 29, 1963

Opened on: August 10, 1967

Processes for the production of hydrocarbon oils with reduced pour point are known. In these known processes, a large proportion of the starting material is converted into gaseous hydrocarbons and converted into hydrocarbons that boil within the gasoline range, but what Is disadvantageous if you have a high yield of higher-boiling components, for example for Heating or furnace oils.

It has now been found, according to the invention, that the pour point of hydrocarbon oils is only very little conversion of the feedstock into gaseous hydrocarbons and hydrocarbons from the gasoline boiling range if the treatment in question is in the presence of nitrogen compounds is carried out.

From the German patent specification 422 953 it is already known in a method for production of light oils by thermal cleavage of heavy hydrocarbons to reduce the Formation of gaseous as well as unsaturated compounds of the evaporated and to be cleaved Add ammonia to the feed.

The German Auslegeschrift 1 002 102 describes the catalytic reforming of hydrocarbons in the boiling range of light gasoline to light oil in the presence of platinum or palladium catalysts described. In this reforming treatment, naphthenes are released with the release of hydrogen converted into aromatics, with isomerization taking place at the same time, while on the other hand also Paraffinic hydrocarbons are converted into aromatics with elimination of hydrogen. Also takes place selective cracking of high molecular weight compounds takes place. By adding ammonia or an ammonia-forming compound succeeds in modifying the noble metal catalyst so that the the best conditions for the isomerization taking place during the aromatization of the naphthenes as well as for the isomerization of the paraffins can be realized at the same time. By adding of nitrogen in the form of ammonia, the formation of hydrogen is increased, which intensifies Indicates dehydration to aromatics.

In French patent 594 604, the hydrogenative cleavage of hydrocarbons is present described by steam and a catalyst consisting of activated carbon, its activity can be increased by adding metal promoters. It should also be used during the hydrating Fission hydrogen in statu nascendi be present, the z. B. can be generated from ammonia.

Process for the production of
Hydrocarbon oils with degraded
Pour point

Applicant:

Shell International Research

Maatschappij N.V., The Hague

Representative:

Dr. E. Jung, patent attorney,
Munich 23, Siegesstr. 26th

Named as inventor:

Maxwell Rodent, Pasadena, Tex. (V. St. A.)

Claimed priority:

V. St. ν. America October 31, 1962

(234 539)

US Pat. No. 1,598,973 describes the hydrogenative cleavage of heavy hydrocarbon oils with the formation of products in the gasoline boiling range. The one needed for the hydrogenation Hydrogen should be present in statu nascendi at the moment of the formation of the fission products, so as far as possible little unsaturated products are created. This hydrogen can e.g. B. in the reaction zone from ammonium halides and finely divided metals are produced, whereby the metals simultaneously in catalytically effective halogen salts are transferred.

In the process of US Pat. No. 2,872,492, the isomerization and dehydrogenation of Hydrocarbon mixtures containing five- and six-membered naphthenes in the presence of

Platinum catalysts carried out, wherein a nitrogen compound is added to prevent dehydrogenation of the five-membered naphthenes and their conversion into aromatic compounds.
The invention relates to a method for the production of hydrocarbon oils with a reduced pour point, which is characterized in that a hydrocarbon oil having a boiling range between about 175 and 455 ⁰ C in the presence of hydrogen or a hydrogen containing gas at about 340 and 455 ° C, about 31.5 and 105 atm, at a space velocity in the range of 0.5 to 5 liters of oil per hour per liter of catalyst, with one

709 620/472

molar ratio of hydrogen to oil of about 1:10 and with a hydrogen consumption of about 18 to 134 Nm ³ per cubic meter of starting material with a catalyst containing tungsten sulfide and nickel sulfide on an acidic carrier and optionally fluorine, and with one or more nitrogen compounds in Bringing such an amount in contact that about 0.005 to 0.06 percent by weight nitrogen, based on the oil used, are present, and optionally the oil obtained is then divided into a fraction with a boiling range between about 115 and 360 ° C and a further fraction with a boiling point above 36O ⁰ C and separating the latter fraction cleaves in the presence of a catalyst.

None of the above publications addresses the specific technical problem, namely the production of hydrocarbon oils with a lowered pour point. Meaning of a catalytic reforming process using platinum or palladium catalysts is to produce gasoline fractions with a high octane number, which experience has shown that the starting material is not higher than about to boil 200 ⁰ C and working temperatures of at least 454 ⁰ C are used (see FIG. BL Nelson, "Petroleum Refinery Engineering ", 1958, p. 811). Another essential feature of a catalytic reforming process is that no hydrogen is consumed in the process. It is also known that a ^{feed material boiling above 200 °} C. has to be split in a platforming system so that components from the gasoline boiling range are produced, with an increased risk of gas and coke formation always existing. Such loads are therefore avoided whenever possible. According to the invention, however, just used, such higher-boiling hydrocarbon oils, which should, however, experienced only a very slight cleavage in the treatment for reducing the pour point, since it is the boiling point 115-360 ⁰ C final products for fuel oils u. Like. Of particular importance. In contrast to the platforming process, the process according to the invention consumes hydrogen, and indeed in considerable quantities. Accordingly, no platinum and palladium catalysts are used in this hydrogenating treatment by the process according to the invention, but instead catalysts with a strongly hydrogenating effect, namely catalysts containing tungsten sulfide and nickel sulfide. Another important difference compared to the reforming treatment is that, according to the invention, the work is carried out at the lowest possible temperatures, which should not exceed 455.degree.

Since in the hydrating treatment provided according to the invention, the position of the equilibrium of Aromatization and isomerization reactions on platinum or palladium catalysts are irrelevant plays, it was not obvious either, the ones described in the German Auslegeschrift 1002102 Measures to solve the different technical problem of a lowering of the pour point of heavy hydrocarbon oils to try. Only the fact that in the context of a platforming process the presence of nitrogen compounds the position of the isomerization equilibrium sets within the optimal range even under severe process conditions and thus automatically the formation of gaseous products is low, could not induce the person skilled in the art to use a corresponding measure also in the case of a hydrating treatment in the presence of tungsten sulfide and Use nickel sulfide-containing catalysts. As a starting material for the inventive Processes can include one or more hydrocarbon oils and / or one or more fractions of such Oils are used including a variety of

ίο directly distilled and catalytically split raw materials. Although these starting oils have pour points within a wide range between e.g. B. -37 and -5.5 ° C, identical results are achieved with each oil. The starting material for the process according to the invention should preferably boil in the range between about 175 and 455 ° C. If the pour point of a furnace oil, which typically has a boiling range between about 175 and 36O ⁰ C, has to be reduced by the inventive method, it is advantageous to add even gas oils the furnace oil, that boil higher than that usually present in such a furnace oil components . Such high-boiling gas oils generally contain relatively large amounts of nitrogen compounds and therefore serve as a source for the latter, whereby an optimal nitrogen content is achieved. In addition, this measure also significantly improves the yield of a furnace oil with a low pour point. This additional increase in yield is the result of the lowering of the pour point and the molecular weight of the components of the heavy gas oil, so that part of the heavy gas oil used can also be used in the furnace oil after the treatment according to the invention. By treating components of such a heavy gas oil in combination with the components of a furnace oil, for example a catalytically split or directly distilled gas oil, the yield of furnace oil can be increased by up to 15% by means of the treatment according to the invention. There are also indications that the use of a heavy gas oil in the starting material for the process of the invention improves the stability of the catalyst.

The catalyst used in the process according to the invention has a dual function because it contains a metal with high activity for hydrogenation reactions from group VI and a metal from Iron group of the periodic table, namely tungsten sulfide and nickel sulfide in combination with one acidic carrier, which has a pronounced cleavage activity.

The amount of hydrogenating metal in the catalyst is usually between about 5 and 50 percent by weight, based on the total catalyst, although higher concentrations if desired can be applied.

A catalyst containing tungsten sulfide and nickel sulfide is used for the process according to the invention used, preferably a weight ratio of tungsten to nickel between 0.2 and 4 very is suitable and this ratio is expediently between 0.4 and 0.8. A catalyst that is 6 percent by weight Nickel and 19 percent by weight tungsten is particularly suitable.

In the process according to the invention, the acidic support for the catalyst preferably contains silica and aluminum oxide, magnesium oxide and /

I 246 918

or zirconium oxide. A silica-alumina carrier, preferably about 5 to 40 percent by weight Contains aluminum oxide, has been found to be the carrier of the catalyst for the process according to the invention proved to be particularly suitable. The catalyst support can also contain only fluorine, for example in one Amount from 0.1 to 2 percent by weight, based on the total catalyst. Other suitable support materials consist of only one heat-resistant oxide, such as silica or aluminum oxide and Fluorine.

The process according to the invention works very well using a fixed catalyst bed carry out. The catalyst is therefore advantageously in the form of lumps, shaped pieces or Granules, the size of which is preferably between about 1.6 and 4.8 mm.

The catalyst used in the process according to the invention can be prepared in any suitable manner, simple impregnation being preferred. If the catalyst has to be sulphided, a mixture of H ₂ S and hydrogen, which preferably contains 10 percent by volume H ₂ S, is passed over the catalyst for a sufficient period of time, the sulphidation generally being terminated by means of a breakthrough of H ₂ S can be recognized by the catalytic converter. Another possibility is to have been injected the catalyst with a sulfur-containing hydrocarbon such as a hydrocarbon oil is used as starting material in which 2 to 3 volume percent CS ₂ or methyl disulfide to bring at an initial temperature of about 90 ⁰ C in contact and these gradually over to allow a certain period of time to rise to the reaction temperature.

The method according to the invention is carried out at a temperature in the range from approximately 340 to 455 ^° C. and in particular from 370 to 430 ^° C., at a pressure in the range from approximately 31.5 to 105 atm, in particular from 52.5 to 70 atm, at a liquid hourly space velocity in the range from about 0.5 to 5 liters and in particular from about 1 to 41 oil per hour per liter of catalyst and with a molar ratio of hydrogen to oil in the range from about 1 to 10, preferably from about 2 to 5 , carried out.

The hydrogen consumption in the process according to the invention is in the range from about 18 to 134 Nm ^{3 of} hydrogen per cubic meter of fed starting material, which, however, depends at least in part on the type of starting material.

In the case of low-boiling distillates, the hydrogen consumption is preferably about 18 to 54 Nm ³ / m ³ , while in the case of heavy distillates, e.g. B. heavy, catalytically cracked gas oils which contain a substantial proportion of polyaromatics, the hydrogen consumption is preferably in the range between about 96 and 117 Nm ³ / m ³ .

In the process of the invention, the hydrocarbon oil comes with the catalyst in the presence of nitrogen compounds in contact, the amount of which is controlled so that about 0.005 to 0.06 percent by weight and preferably 0.01 to 0.03 percent by weight of nitrogen, based on the supplied Starting material, are available. The optimal nitrogen content depends on the type of starting material itself, the specific catalyst used and the other process conditions. An excess of nitrogen tends to reduce the catalyst activity. Though most, if not all hydrocarbon distillates contain naturally occurring nitrogen compounds, the Nitrogen content fluctuate considerably and in many cases only have a relatively low value. In such cases, the nitrogen content can be increased by adding suitable nitrogen compounds to the Distillate are increased, for which in particular the

ίο cheap and readily available organic amines suitable. Also cyclic compounds that contain nitrogen atoms inside or outside the ring, are suitable for this purpose, but are generally more expensive. Even more volatile nitrogen compounds, such as ammonia, are effective in the process of the invention and can the Starting material can be added. If hydrogen is recycled back into the process the ammonia content of the returned hydrogen must be used when calculating the amount to be added Amount of nitrogen compounds must also be taken into account.

In the treatment according to the invention, the volatility of the hydrocarbon oils used is increased, their pour point and their cloud point lowered and sulfur and nitrogen compounds are practically completely removed from them. The pour point should be at least around 3 ° C and preferably be reduced by at least 4 ° C.

According to the invention it is even possible to reduce the pour point to about 6 ⁰ C. The nitrogen is practically completely removed, even when starting materials with a high nitrogen content are used. The simultaneous lowering of the cloud point is also important, since the commercial tools for lowering the pour point are generally ineffective with regard to a simultaneous lowering of the cloud point of distillates. In addition, the invention

according to the treated oils a much better filterability and pumpability at low temperatures than can be achieved by adding auxiliaries. Furthermore, the stability of the invention ' according to treated oils good.

The yield of liquid end products in the procedure according to the invention is high and is often about 100 percent by volume. The yield of oil products having a boiling range between about 115 and 36O ⁰ C, which represent an excellent furnace oil is preferably at least 85 volume percent, more preferably 90 percent by volume, and especially 95 percent by volume. Only a small proportion of the starting material is converted into low-boiling products, preferably less than 10 percent by weight and in particular less than 5 percent by weight. This distinguishes the process according to the invention from other known hydrogenation processes, in particular from hydrogenating cleavages.
If the starting material is a heavy gas oil or a heavy gas oil fraction contains, as the accumulating in the inventive process, liquid final product is preferably separated into a fraction having a boiling range of about 115 to 36O ⁰ C and a further fraction with a boiling point above 360 ⁰ C. The first-mentioned fraction represents an excellent furnace oil, while the second-mentioned fraction is very suitable as a feed for a hydrogenative cracking process or a catalytic converter.

tisch.es splitting process because it is practically free from Is nitrogen. For this reason, the second fraction is preferred to be present split of a catalyst. For example, a product obtained as a process product according to the invention is obtained heavy gas oil yields less coke and more gasoline than a product resulting from a conventional hydrogenation process.

The inventive method can be carried out for a longer period of time, though the catalyst activity gradually decreases and thereby corresponding increases in the working temperature be required to achieve the desired lowering of the pour point of the treated oil to achieve. In general, the use of high partial pressures of hydrogen enables catalyst activity maintain.

Ultimately, however, it will always be necessary to regenerate the catalyst by means of a regeneration treatment to bring it back to its old activity. For this purpose one can use the catalyst one Subject to oxidation treatment with, for example, diluted air, in order to remove the deposits, whereupon the catalyst preferably re-sulphided and then the method of treatment according to the invention resumed and resumed.

example 1

The importance of the presence of nitrogen compounds in the inventive process results in the following table I, in which the results are presented to a hydrogenating treatment of cetane with a catalyst comprising nickel sulfide and tungsten sulfide (6.5 ° / ₀ nickel, 10% tungsten) Contains deposited on a silica-alumina carrier. The catalyst is kept in the sulfided state by adding 1% sulfur in the form of dimethyl disulfide. The hydrogenating treatment is carried out with and without the addition of triethylamine, the nitrogen concentration in the first case being adjusted to 0.01 percent by weight in the starting material. It can be seen from the table that somewhat higher working temperatures are used when using the nitrogen-containing starting material.

Table I.

Nitrogen content of the starting material in percent by weight

Yield in percent by weight

C ₁ to C ₅

C ₆ to C ₁₃

ISO-C ₁₆

temperature
352 ⁰ CI 399 ° C

30.5

25.9

5.4

38.1

6.2 12.6 21.8 58.5 silicotungstic acid impregnated in an amount such that it contained 6.5 percent by weight nickel and 10 percent by weight tungsten. The impregnated catalyst granules were allowed to stand for 16 to 20 hours and then dried under a heat lamp. The catalyst was constantly stirred in the first drying phase. The catalyst was then subjected to an additional 3 hour drying treatment in vacuo at 130 ^° C.

ίο then calcined it for 20 hours at 26O ⁰ C and a further 5 hours at 46O ⁰ C. Before use, the catalyst was sulfided by injecting 3 percent by volume of carbon disulfide or dimethyl disulfide into the starting material at a temperature of 93 ⁰ C, whereupon the temperature at a rate of 28 to 56 ° C / hour. was gradually increased up to the actual reaction temperature.

For the production of the invention

Process used catalysts is in the Rah-υ No protection is claimed for the invention.

B e i s ρ i e 1 2

The activity and stability of the catalyst were determined by means of an oil mixture which consisted of 65 volume percent of catalytically cracked light gas oil and 35 ° / ₀ of a mixed acid, straight run gas oil. These components are considered to be representative of the main components of a furnace oil. This mixture, which had a total nitrogen concentration of 200 parts per million, was used for an extended period of time with the catalyst described above. treated with hydrogenation. The liquid reaction product was distilled in a distillation column with a diameter of 25.4 mm and 30 trays at a reflux ratio of 10: 1. The process conditions and the results obtained are summarized in Table II below.

Table II

From the above numerical values it follows that the presence of nitrogen compounds to achieve a high yield of iso-cetane and a low yield of low-boiling components is very essential.

A cleavage catalyst made of silica-aluminum oxide (Al ₂ O ₃ content about 25%) was tabletted and treated with an aqueous solution of nickel nitrate and hydrogenation conditions

Pressure, atm

Liquid hourly space velocity
(Liters of oil / hour / liter of catalyst

Molar ratio H ₂ : oil

Temperature, ⁰ C

H ₂ consumption, Nm ³ / m ³

Flow time in hours

Yield in percent by volume,

based on the supplied oil

H ₂ S (Nm ³ cm ³ )

Methane (Nm '/ m ⁸ )

Ethane (Nm ³ cm ³ )

propane

Isobutane

η-butane

Isopentane

n-pentane

Cyclopentane

C ₆ ⁺

C _e -116 ° C

63

3.9
382
71
326

1.72
1.12
0.89
0.6
0.3
0.2
0.5
0.3
0.1
102.9
4.6
98.3

4.4 385
76
710

2.03 0.96 0.80 0.4
0.3
0.4
0.6
0.4
0.1
102.2
4.6
97.6

properties

Density, kg / m ³

Flash point, ⁰ C

Pour point, ⁰ C

Cloud point, ⁰ C ..
Diesel index

ASTM distillation
Initial boiling point,
⁰ C

10 ¹ Vo

50 ° / ₀

90 ° / o

Final boiling point, ⁰ C
Total sulfur,

in percent by weight.
Total nitrogen,

Parts per million. ..

Source material

869
103

-12
-5.5
43.6

223
257
291
326
341

0.98
200

116 ° C + product

842
62.5
-16.5
-9.5

52.3

170

215.5

273.5

316

319

<1

841
63

-9

52.6

184.5

229.5

270.5

318

339

0.05

IO

From the above numerical values, it can be seen that the specifications for a furnace oil are essentially could be met after the reaction product in a distillative cut 116 ° C had been subjected to the conditions with regard to the flash point, without an addition of larger quantities of luminous oil is necessary

was. The separated light gasoline fraction, ie, the C ₆ -116 ° C fraction contained about 60 ° / ₀ of cyclic hydrocarbons and therefore provided an excellent feedstock. for a catalytic reforming process.

Example 3

Mixtures of light and heavy gas oil were treated in a hydrogenating manner corresponding to the catalyst of Example 2 over a sulfided tungsten-nickel catalyst with a silica-aluminum oxide support. The starting material A, which consisted of 80 percent by volume of light gas oil and 20 percent by volume of heavy gas oil, had to be cut by distillation at 329.5 ° C. to achieve a pour point of -18 ° C. The yield of furnace oil from such a distillation cut was 78 percent by volume. The starting material B comprising 60 volume percent light gas oil and 40 percent by volume heavy gas oil contained, required to achieve the same pour point of -18 ⁰ C a distillation section at 325 ° C, whereby the yield of the furnace oil was 69 volume percent in this case. The process conditions and results obtained are summarized in Table III below. The total nitrogen concentration in starting material A was 0.021 percent by weight and that in starting material B was 0.026 percent by weight.

Table III

80 percent by volume light

Gas oil
20 percent by volume heavy

Gas oil

60 percent by volume light

Gas oil 40 percent by volume

Gas oil

Hydrogenation conditions

: Reactor temperature ^{, 0 C}

Reactor pressure, atm;

■ Liquid hourly space velocity

(Liters of oil / hour / liter of catalyst)

Molar ratio H ₂ : oil

Catalyst life in hours

Hydrogen consumption, Nm ³ / m »

Yield in percent by volume, based on the starting oil

H ₂ S

Methane (Nm ³ / m ³ )

Ethane (Nm ³ / m ³ )

propane

Isobutane

η-butane

Isopentane

n-pentane

C ₆ -116 ° C

116 to 357 ⁰ C
116 to 338 ⁰ C

357 ⁰ C +

338 ° C

All in all. . .

Oven oil, final boiling point, ⁰ C

Pour point, ° C

Specific weight, kg / 1

Flash point, ⁰ C

399
63

1.0
5.0
2050
89

Starting oil

89.5
10.5

100.0

product

1.3
1.2
0.4
0.5
0.1
0.3
0.1
1.6
90.7

102.5

357

0.8682
165

413 63

1.0 5.0 2220

77

Starting oil

71.1 28.9

100.0

338 +6

product

3.5 3.2 0.9 0.6 0.6 0.3 0.1 2.2

78.5 19.3

102.5

338 0 0.8676

709 620/472

Be i s ρ i e 1 4

A furnace oil with those given in Table IV Properties was used for hydrating treatment

by means of a sulfided tungsten-nickel catalyst used on a silica-alumina support, the catalyst with the in Example 1 described was identical.

Table IV

Density, kg / 1 0.821

ASTM distillation, ⁰ C

Initial boiling point 171

10% 209

. 50% 243

90% 292

Final boiling point 310

Sulfur in percent by weight 0.15

Nitrogen, parts per million by weight 29

Pour point, ⁰ C -32

Cloud point, ⁰ C -26

Diesel index 60.6

An organic nitrogen compound, namely triethylamine or tri-n-butylamine, was added to this furnace oil added in varying amounts in order to obtain different nitrogen concentrations. the Hydrating treatment was carried out at a pressure of 63 atm, a temperature of 385 ° C with a hourly space velocity of 11 oil per hour per liter of catalyst and a molar ratio Hydrogen to oil = 5 carried out. From the numerical values in Table V below, the The influence of the various nitrogen concentrations can be read off.

Table V

Nitrogen, parts per million by weight

Hydrogen consumption, Nm ³ / m ³

45 to 116 ⁰ C, percent by volume

116 ° C + yield, volume percent

Pour point, ° C

Cloud point, ⁹ C .;.

Sulfur content in percent by weight

Nitrogen, parts per million by weight

Comparative experiment

For comparison purposes, a mixture of components of a furnace oil was treated with hydrogenation using a commercially available hydrodesulphurisation catalyst, which is made from cobalt molybdenum to 300
28
4.8
95.3

04

-33

100
36
5.8
93.2
-35
-29
0.01
1

50

85.7
-38
-33

Aluminum oxide. The pour point of this mixture amounted to -14 ° C and the cloud point at -9 ⁰ C. From Table VI below shows that the pour point and the cloud point of the starting material are little affected by such a hydrotreating.

Table VI

Temperature, ⁰ C

Pressure, atm

Liquid hourly space velocity
(Liters of oil / hour / liter of catalyst) ...

Molar ratio H ₂ : oil

Pour point, ⁰ C

Cloud point, ° C

343 343 371 371 48 52.5 52.5 52.5 3.3 3.3. 3.3 3.3 2.0 2.0 2.0 2.0 -14 -14.5 -13.5 -15 - 9.5 _ -

371

52.5

-14.5

Claims (4)

Patent claims: 1. A process for the production of hydrocarbon oils with a reduced pour point, characterized in that a hydrocarbon oil with a boiling range between about 175 and 455 ° C in the presence of hydrogen or a hydrogen-containing gas at about 340 and 455 ° C, about 31.5 and 105 Atm, at a space velocity in the range of 0.5 to 5 1 oil per hour per liter of catalyst, at a molar ratio of hydrogen to oil of about 1:10, with a hydrogen consumption of about 18 to 134 Nm ³ per cubic meter of starting material with a Catalyst which contains tungsten sulfide and nickel sulfide on an acidic reacting carrier and optionally fluorine, and brings it into contact with one or more nitrogen compounds in such an amount that about 0.005 to 0.06 percent by weight of nitrogen, based on the oil used, is present, and optionally the oil obtained then into a fraction with a boiling range between about 115 and 360 ⁰ C and a another faction with one separates and
Presence of one Boiling point above 360 ^° C
last mentioned group in
Catalyst splits. 2. The method according to claim 1, characterized in that a catalyst is used for the reaction in which the weight ratio of tungsten to nickel is approximately in the range between 0.2 and 4 lies. 3. The method according to claim 1 and 2, characterized in that a catalyst is used whose carrier component consists of silica and aluminum oxide. 4. The method according to claim 1 to 3, characterized in that a catalyst is used is, the carrier component of which is about 5 to 40 percent by weight of aluminum oxide, based on the Carrier material, contains. Considered publications: German Patent No. 422 953; German Auslegeschrift No. 1 002 102; French Patent No. 594,604; U.S. Patent Nos. 1,598,973, 2,872,492. A priority document was displayed when the registration was announced.