DE1543194C - Process for making platinum group metal catalysts - US Pat - Google Patents

Description

with the formation of ethylene monounsaturated carbon Hydrogen with good yield. Furthermore, undesirable side reactions, for example cracking, Skeletal isomerization and aromatization and the formation of ethylene polyunsaturated hydrocarbons and of carbon is considerably reduced by the process of the invention. The usage of the catalyst according to the invention also leads to a long-lasting dehydrogenation efficiency of the catalyst.

Platinum, palladium, iridium, ruthenium, osmium and rhodium are understood as platinum group metals. All of these metals falling under the term “platinum group metals” as defined above can can be used for the preparation of the catalyst according to the invention, but are within the scope of Invention platinum and palladium preferred. In the particularly preferred embodiment of the invention The most common platinum group metal used is platinum.

The noble metal content of the catalysts produced according to the invention can be between 0.02 percent by weight and 2.0 percent by weight of the total composition. Within the scope of the invention a precious metal content above the range mentioned is due to the relatively high cost of this Metals avoided. Precious metal contents below the specified range are generally inexpedient, because only low degrees of conversion can be achieved with them. Usually the invention has Catalyst composition has a noble metal content of 0.02 to 1.0 percent by weight, based on the Total weight of the catalyst. In the preferred embodiments of the invention, in which the preferred If platinum metals are used, the catalyst has one based on its total weight Precious metal content from 0.1 to 1.0%.

To produce the catalyst, the platinum group metal is dispersed on a low-acid carrier material. As will be explained below, the acid content of the carrier is of considerable importance in the context of the invention. It has been found that when determined by many of the known, common methods of determining acid equivalent, the carriers used in accordance with the invention are usually low in acidity. However, not all carriers which have such a low acid content can be used within the scope of the invention. Therefore, to determine the acidity required, methods other than conventional methods of measuring the acidity of the carrier must be used. It has been found that a model reaction can be used to measure acidity with good success. The use of model reactions to determine the limits of the composition of a catalytic material is well known and discussed in the Journal of the American Chemical Society, Vol. 82, pp. 2471 and 2483 (1960). The acid content of the carrier according to the invention is expressed here by an "acid factor". This acid factor is determined by bringing the carrier into contact in a small reaction chamber with hydrogen and a hydrocarbon mixture consisting of 92 percent by weight n-dodecane and 8 percent by weight. Na-dodecene exists, the Mpl ratio between the hydrocarbon mixture and the hydrogen being 1: 2. A temperature of 435 to 440 ^° C., atmospheric pressure ± 0.14 kg / cm ² and a throughput rate of the hydrocarbon mixture of 4.65 liquid volumes per hour are maintained in the reaction vessel. The product of this model reaction is then passed through a gas chromatograph, the column of which is filled with a substrate that is suitable for preparing the product mixture depending on the boiling point and the polarity. A preferred substrate is obtained, for example,

ίο if you have Chromosorb W (W. Z.), one with a Flux calcined infusor earth, with Carbowachs20M, a waxy polyethylene glycol, and small amounts of silver nitrate. The percentage concentration of the material that was before the n-Dodecane eluted from the gas chromatograph represents the one used in the context of the invention Acid factor. The substances eluted from the gas chromatograph before the n-dodecane have a lower boiling point than the n-dodecane and no polarity such that it is affected by the adsorbent are preferred to n-dodecane. If the concentration of this before the n-dodecane eluted components in the product is 10%, the carrier has the acid factor 10. According to the invention The supports used for the catalyst are low in acid. In general, their acid factor is not higher than 2.0. The low-acid carriers of aluminum oxide used according to the invention preferably have an acid factor of 1.0 or less. The acid factor measurements used here are regarded as critical because carriers with an acid factor higher than indicated above in the Catalysts prepared according to the invention only after an additional pretreatment of the support or of the finished catalyst can be used. This pretreatment can consist of more as 0.01 weight percent of an alkali or alkaline earth metal in the carrier. The usage however, such supports in catalysts lead to excessively strong side reactions, in particular for skeletal isomerization and aromatization and for cracking, as well as for the formation of carbon and ethylene polyunsaturated hydrocarbons.

It has been proposed above to measure the acid factor of the non-impregnated alumina support. In the context of the invention, however, the acid factor can also be measured in the finished, noble metal-containing catalyst. In this case, too, the model reaction described above is used to determine the acid factor. The acid ^: factor of the finished catalyst is usually less than 4.0, preferably less than 2.5.

The carriers used according to the invention are not only subject to a restriction with regard to their acid content, but they must also meet various other requirements. The supports which can be used in the context of the invention generally have a specific surface area of at least 10 m ² / g, preferably of at least 30 ^{m 2} / g. The carriers used according to the invention generally have a macropore volume of at least 0.05 cm ³ / g, preferably of at least 0.07 cm ³ / g. The macropore volume is the total volume of the pores present in the aluminum oxide with a pore size

radius of more than 350 Å per unit weight of aluminum oxide designated. The use of carriers that meet these requirements with regard to the Macropore volume and the specific upper

Fulfill the surface, contributes considerably to the maximum utilization of the precious metal content of the catalyst at. This maximum utilization of the precious metal means that in many cases the total amount of in the precious metal required for the catalyst is reduced very considerably. The macropore volume is made with an Aminco-Winslow mercury porosimeter, Model 5-7107 (American Instrument Co.) or an equivalent device that measures the penetration of mercury, determines and represents the internal volume into which the mercury penetrates between 0 and 176 atmospheres. The determination of the macropore volume is dealt with in Industrial and Engineering Chemistry, Vol. 17, p. 787 (1945).

The support of the catalyst contains an aluminum oxide, which is preferably heat-stabilized, that is, it should be grown long without substantial reduction of the specific surface area at temperatures in the range of 400 to 500 ⁰ C in the presence of oxygen or an oxygen-containing gas from 1 to 12 hours. If an aluminum oxide which is not heat-stabilized is used to produce the catalysts, considerable amounts of the noble metal are occluded during the final calcination as described below, so that these amounts do not come into active contact with the reactants in the process according to the invention and the effectiveness of the catalyst is reduced.

For the preparation of the catalysts is generally the support of aluminum oxide in a solution of a platinum group metal salt in a suitable one Immersed in solvent. When manufacturing the catalytic converter, care must be taken to ensure that a uniform dispersion and distribution of the platinum group metal guaranteed on the carrier and the acidity of the carrier is maintained. Practical Each of these noble metal salts can be dissolved in a suitable solvent and used for impregnation of the carrier. In general, however, it is preferred to use a platinum group metal salt, which is either thermally decomposed or can be reduced, so that that with the noble metal impregnated carrier is essentially free of acid ions. For example, halogen-containing platinum group metal salts, the chloroplatinic acid, less convenient, although they can be used when the catalyst is a treatment to eliminate-. is subjected to residual acid and / or to ensure strong dispersion. The residual acid can by known methods, for example steam treatment, washing with alkaline solutions and the like can be removed. When the platinum group metal salts For example, containing a halogen, the precious metal is often on the outer surface of the The carrier is undesirably highly concentrated, so that a uniform dispersion on the outer and inner surfaces of the wearer is prevented. The use of competing adsorbates, as suggested by R. W. M a t m a η in "Industrial and Engineering Chemistry", Vol. 51, p. 913 (1959) leads to a process in which, with the help of the halogen-containing noble metal salts, a better Dispersion of the noble metal can be obtained / Even if the aluminum oxide is longer in the impregnation solution is immersed is obtained when using halogen-containing platinum group metal salts a better dispersion of the precious metal on the aluminum oxide. As a result of this need one The halogen-containing platinum group metal salts are subjected to additional treatment or longer immersion time somewhat less preferred in the preparation of the catalysts according to the invention. Preferred platinum group metal salts are for example platinum diaminonitrite, palladium diaminodinitrite, platinum tetramino hydroxide, Platinum dioxide diamine, palladium dioxide diamine and the like. Through the reduction With such compounds, the metal is obtained on the catalyst without residual acid ions being present are. Such compounds can be dissolved in any suitable solvent, preferably does not increase the acidity of the catalyst. A particularly suitable solvent for such Precious metal salt is an aqueous solution of ammonium hydroxide.

In the platinum group metal-containing one produced according to the invention Catalyst is strong and noble metal on the alumina support low in acid evenly dispersed. It has been shown that there is a high degree of dispersion of the noble metal on the carrier. Alumina is relatively critical to the invention. A high dispersion of the precious metal on the catalyst carrier contributes to maximum utilization of the noble metal in the catalyst composition and to a high efficiency of the catalyst. at. It also contributes to a high efficiency of the catalyst the strong dispersion of the noble metal, which impairs the effectiveness of the catalyst Agglomeration of the precious metal is prevented.

The distribution of the platinum group metal in the catalyst particles of the finished catalyst according to the invention is also of great importance. The noble metal should be evenly distributed throughout the aluminum oxide. In the context of the invention, the distribution is indicated by the local concentration of the noble metal on the aluminum oxide carrier. To meet the requirements of the invention, a catalyst particle of the finished catalyst must contain at least 50 percent by weight of the total noble metal content in a local noble metal concentration which is not greater than twice the total noble metal concentration of the particle. For example, if the total noble metal content of a catalyst particle is 0.1% of the particle weight, at least 0.05% by weight of the noble metal of the particle is distributed such that in any given segment of the catalyst particle the concentration of noble metal in that segment or location is not higher than 0.2 ° / _0, based on the weight of the segment. The local precious metal concentration in any given segment of a catalyst particle can be determined by electron probe microanalysis. This procedure is described in

1. "The Microscan X-Ray Analyzer Mark II" Cambridge Instrument Co. Ltd., London and Cambridge, England (1961);

2. C o s 1 e 11, V. E., “Proceedings of the X-Ray Colloquium Spectroscopiumc Internationale, "Spartan Books, Washington, D. C, pp. 357-381 (1963);

.3. Melford, D. A., and D u η c ο m b, P., Metallurgica, Vol. 16, No. 367, pp. 205-212 (May 1960).

The even distribution of the platinum group metal in the aluminum oxide carrier contributes significantly contributes to good efficiency and a long service life of the catalytic converter.

Process for obtaining a high degree of dispersion and uniform distribution of the noble metal in the finished catalysts are known. In many cases, these known methods can be used as the strongest Dispersion and uniform distribution of the noble

Alumina further 12 hours was then calcined in air at 500 ⁰ C and reduced at 450 ° C in pure hydrogen. The catalyst prepared in this way contained about 0.3 g weight percent platinum. The average local distribution of platinum was 0.3%. The acid factor of the alumina carrier was determined by mixing the alumina in the presence of hydrogen with a hydrocarbon mixture of 92 percent by weight

metal in the catalyst produced according to the invention, n-dodecane and 8 percent by weight of dodecene in the case of sator, in accordance with the information given above, at a temperature of 435 to 440 ° C. A particularly useful method for
Preparation of the catalyst is in the present
Description given.
To the invention

atmospheric pressure (-f 0.14 kg / cm ² ) and a flow rate of the hydrocarbons of 4.65 liquid volumes per hour in contact with the catalyst, the molar ratio of hydrogen to hydrocarbon being 2: 1. The products obtained were ^{condensed at 20 °} C., collected and analyzed by gas chromatography as follows: A 366 cm long column with a through

Making the

In most cases, the catalyst support is made with a solution of the platinum group metal salt
brought into contact. The metal salt is in that
Solvent usually dissolved in such an amount that the desired amount of metal used on the 20 knife of 6.4 mm, which comes with 18% of a carrier made of alumina. This metal salt wax-like polyethylene glycol (commercially available under the amount can easily be determined by the person skilled in the art, designation Carbowax 2OM) and 1%. In many cases it can be advisable to move the silver nitrate on a carrier made from a flux impregnation solution in order to obtain the infusoric earth (commercially available under the contact between this solution and the carrier from Chromosorb W - WZ) ) to support with aluminum oxide. After touching a screen size of 30 to 60 mesh was filled. • The aluminum oxide with that from the solvent Helium was used as the carrier gas. The temperature and the noble metal salt existing impregnation temperature of the column was from 110 to 230 ⁰ C program solution until its absorption is controlled by the impregnated. Those components whose dwell time of the carrier in air or a similar atmosphere at 30 was shorter than that of the n-dodecane corresponded to 0.1% of a temperature of 100 to 300 ^° C. when dried. According to the product. It is said that the aluminum during this drying period the catalyst oxide had an acid factor of 0.1,
residential calcined in air or other oxygen-containing To illustrate the usefulness of this Kataly gas at 300 to 600 ⁰ C. The calcination is sators about 29 g of the catalyst was completed in one usually in 1 to 12 hours. The calcium reaction chamber was introduced, and the catalyst, which was about 102 cm long, was then generally on and had a diameter of about 7.9 mm. Essence of hydrogen or another redu- A Cn-Cii-n-paraffin mixture which reduces 99.2% n-paraffin-effecting gas so that the noble and 0, '% aromatic hydrocarbons contained metal is obtained in reduced form . The reductive was then cocurrently with hydrogen in the tion temperatures are usually in the range of 4 ° reaction chamber, keeping the molar ratio of 300 to 450 ⁰ C., in the context of the invention the

Reduction also take place in the reaction chamber under the reaction conditions, as the conditions of the dehydrogenation process according to the invention promote the reduction.

The following exemplary embodiments serve to further explain the subject matter of the invention :

Example I.

To produce a catalyst, 3.2 mm large, cylindrical pellets of a support made of aluminum oxide with a specific surface area of 74 m ² / g and a macropore volume of

hydrogen to hydrocarbon was 2: 1. The temperature in the reaction chamber was maintained in the range of about 420 to 435 ° C, whereby the lower temperature at the beginning of the experiment and the higher temperature at the end of the experiment prevailed. A pressure of about 0.32 atm was maintained in the reaction chamber. The contact time between the slack wax and the catalyst was about 2 seconds and the surface space velocity was about 14 cm per second. After about The reaction was terminated for 132 hours and the total product was collected and analyzed. This Product corresponded to a liquid yield of 99.2 percent by weight. Analysis of this liquid

0.12 cm ³ / g as well as an acid factor of 0.1 in a 55 product showed that the conversion was immersed in monoolefin solution of platinum diaminodinitrite. The approximately 13.2% and average production of platinum diaminodinitrite solution was made by
in distilled water this salt in such a
Amount was heated that a platinum concentration
of 0.0030 g of platinum per cm ^{3 of} the catalyst (rubble 60
volume) was obtained. Then per g of platinum

Monoolefin was about 0.096 grams per gram of catalyst. This liquid product had the following analysis:

salt 10 ml of concentrated ammonium hydroxide added. After the salt had dissolved, the volume of the solution was increased to one by adding water A sufficient amount is set for complete saturation of the aluminum oxide. After diving was the impregnated aluminum oxide was dried in the air at 100 ° C. for 12 hours. The impregnated

82% paraffinic hydrocarbons, 13.2% monoolefinic hydrocarbons 1.6% diolefin hydrocarbons

3.2% triolefin and aromatic hydrocarbons

Example II

A second catalyst was prepared in the manner described in Example I, except that the

309 618/157

Aluminum oxide was impregnated with an aqueous solution of chloroplatinic acid. The drying, calcining and reducing were carried out as described in Example I. To compare this catalyst with the catalyst described in Example I with respect to the dehydrogenation effect, 145 ml of each catalyst were introduced into a reaction tube which had a diameter of 35 mm and a length of 51 cm. A feed consisting of purified n-dodecane was brought into contact with each of the catalysts in cocurrent with hydrogen, the molar ratio of hydrogen to n-dodecane being 2: 1. The contact temperature was kept at 440 ^° C. and the pressure at essentially atmospheric pressure. The product of each of the two runs was continuously collected and analyzed periodically during the run. The conversion to monoolefin for each catalyst is given for different ages of each catalyst in the table below:

Conversion and yield results using the with the various carriers The platinum-containing catalysts produced are shown in the table below:

A In IO A. acid macro Speci total mono- Aluminum B. factor pore fishes umwand olefin minium
oxide C. volume surface lung yield D. (cm ³ / g) (m ² / g) (%) ■ (Vo) IS E 0.2 F. 0.1- 0.227 202 17.7 74.0 G 0.1 0.108 83 16.3 . 75.4 H 0.5 0.119 72 16.9 74.5 0.7 0.054 160 15.1 71.0 0.3 0.027 268 14.7 70.1 2.9 0.014 175 13.5 65.2 6.9 0.107 292 12.5 60.8 0.160 438 18.5 31.9

catalyst

Made from platinum diaminodinitrite
Catalyst according to Example I.

From chloroplatinic acid
manufactured catalyst
according to example II

old
(Hours)

8th.
12th
16
24

12th
16

conversion

12.5
12.1
11.8
11.3

10.4
9.7
9.3

The table above shows that the platinum diaminodinitrite. manufactured catalyst dem made from chloroplatinic acid is somewhat superior. The initial dehydration effectiveness of the after the preferred embodiment of the invention produced catalyst is significantly higher than that of the catalyst made from chloroplatinic acid and remained higher throughout the experiment.

B e i s ρ i e 1 III

A number of catalysts have been prepared on various alumina supports to demonstrate the effect of acid factor, macropore volume and specific surface area of the support on the conversion of acyclic saturated hydrocarbons. In each case the catalyst was prepared as described in Example I. All of the catalysts produced contained 0.003 g of platinum per ml of catalyst. To demonstrate the effectiveness of these catalysts, 145 ml of each catalyst was placed in a cylindrical reaction vessel 51 cm long and 35 mm in diameter. A mixture of n-dodecane and hydrogen in a molar ratio of 0.5 of n-dodecane to hydrogen was brought into contact with the catalyst ^{at a temperature of about 440 ° C. and essentially atmospheric pressure.} The contact time was 0.3 seconds. The support, its acid factor, macropore volume, its specific surface and the Er-If one looks at the results of the catalysts prepared with the aluminum oxides G and H, one recognizes how crucial the acid factor of the catalyst according to the invention is. In the case of aluminum oxide G, both the degree of conversion and the yield are lower than in the case of the catalysts which meet the requirements according to the invention with regard to the acid content. In the case of aluminum oxide H, the yield is greatly reduced. The results obtained with the catalysts based on alumina D, E and F show the effect of the macropore volume, since both the degree of conversion and the yield are considerably lower when the macropore volume of the support is below this specified range. The catalysts produced with aluminum oxides B and C give significantly better degrees of conversion and monoolefin yields than the catalysts produced with one of the other aluminum oxides.

Example IV

Three catalysts, each containing 0.3 ° / ₀ platinum and had a support of alumina, but various local Platinkonzentra-.tionen had were, as tested in the same manner and with the same use in Beispiel'III to their dehydrogenation activity. The table below shows the average local platinum concentration and percentage conversion to monoolefin for each of these three catalysts.

catalyst local
Platinum concentration Degree of conversion
V. A.
B.
C. 0.3
0.4
0.9 12.7
11.4
. 8.0

Since the catalyst contains 0.3 percent by weight of platinum, the local concentration of platinum may not be higher than 0.6 ° / ₀ according to the invention definition of a uniform distribution. The catalysts A and B are within the scope of the invention, while the catalyst C is outside this scope. A comparison of the results achieved with the catalyst C with those obtained with the catalysts A and B shows that in the inventively produced

The distribution of the noble metal on the aluminum oxide support is crucial.

The catalyst prepared according to the invention is used in the known processes for the dehydrogenation of acyclic hydrocarbons, d. H. used by branched and straight chain paraffinic hydrocarbons. However, a particularly advantageous application of the invention consists in the dehydration of straight-chain paraffinic hydrocarbons. It has surprisingly been found that the dehydration of straight-chain hydrocarbons an alkylate for the production of biodegradable ones Cleaning compositions based on alkylaromati see sulfonates obtained will. The dehydrogenation process can be useful for the dehydrogenation of acyclic hydrocarbons any molecular weight can be used. But it is best for dehydrating hydrocarbons with 6 to 30 carbon atoms are suitable. In its preferred application, the invention is used for Dehydrogenating acyclic hydrocarbons containing 8 to 20 carbon atoms per molecule.

The products of the dehydrogenation process are ethylene

monounsaturated hydrocarbons. The inventive dehydration of essentially straight-chain paraffin hydrocarbons you get a product that is especially useful for the production of biodegradable cleaning agents. In any case, the products of the invention stand out Process in that they are much purer than those with previous processes and catalysts. The salary

ίο in aromatics and polyolefins is much lower, and fewer skeletal isomers are formed by the dehydrogenation reactions. In the dehydration reaction vessels used the surface space velocities are generally 61 to 457 cm per

ι s second. Surface space velocities in the uppermost Part of this range are preferred.

The invention is not restricted to the use of a catalyst of any particular shape or size. However, catalysts are preferred

ao of small particle size is used. The particles preferably have a shape such that they do not lead to a noticeable pressure drop in the dehydrogenation reaction vessel.

Claims (4)

1 2 to such a degree that the processes, claims: in which these side reactions occur, and the catalysts used in them are uneconomical 1. Process for making a platinum group are. A further, economically very serious, low-acid, possibly heat-stable, disadvantage of many of the known noble metal-containing supports made of aluminum oxide with large catalysts is that the noble metal content of the surface and large macropore volume in the catalyst is not is used to the maximum. Applied in a very fine distribution and the catalyst is in many cases a large part of the noble metal content is calcined and reduced, so that the catalyst is arranged on and in this in such a way that 0.02 to 2.0 Ge of this part is obtained is never exploited. In view of the high weight percentage of platinum group metal in terms of cost, it is very desirable to allow maximum off-dissolution on alumina whose acid factor utilizing the noble metal content of the catalyst is not greater than 2.0 and which has specific compositions. .
A surface area of at least 10 m ² / g and a macro- 15 A purpose of the invention is to produce pore volume of at least 0.05 cm ³ / g of a precious metal-containing catalyst, in which the sits, dispersed so that at least 50 weight - Noble metal content of the catalyst is utilized to the maximum percentage of the total platinum group metal content. Furthermore, it is a purpose of the invention to have a hold of a catalyst particle in a local catalyst for dehydrogenating straight-chain concentration which is not higher than 20 paraffinic hydrocarbons to form ethylene twice the total concentration of platinum monounsaturated hydrocarbons with minimal group metal in this particle, and the acid conversion to aromatics and ethylene polyunsaturation factor of the finished catalyst to create less than 4.0 hydrocarbons,
wearing. The invention is a method for 2. The method according to claim 1, characterized in 25 production of a platinum group metal catalyst, indicates that 0.1 to 1.0 percent by weight platinum, in which the metal is on a low-acid, grouped metal is applied. if necessary, heat-stabilized support made of aluminum 3. The method according to claim 1 and 2, characterized nium oxide with a large surface and large macro, that aluminum oxide with a pore volume in a very fine distribution applied acid factor of at most 1, a specific 30 and the catalyst is calcined and reduced, da-surface of at least 30 m ² / g and one characterized in that 0.02 to 2.0 weight macropore volume of at least 0.07 cm ³ / g percent platinum group metal is used in the form of a solution. on aluminum oxide, the acid factor of which is not greater 4. Use of the according to claims 1 to 3 as 2.0 and that a specific surface area of the prepared catalyst for dehydrogenation acy- 35 at least 10 m ² / g and a macropore volume of clic, saturated hydrocarbons for selec- of at least 0, 05 cm ³ / g, dispersed in such a way that tiven production of monoolefins. at least 50 percent by weight of the total platinum group metal content of a catalyst particle is present in a local concentration that is not - 40 is higher than twice the total concentration of the platinum group metal in that particle, and the acid factor of the finished catalyst is less than 4.0 The invention relates in particular to a catalyst. more for the dehydrogenative conversion of acyclic In the German patent 960 894 is indeed saturated hydrocarbons to äthylenmonoun- 45 an acidic catalyst carrier described, but not saturated hydrocarbons. stipulates that the carrier has a certain acid For the dehydration of saturated hydrocarbons it must have, and it is not mentioned, substances for the purpose of the formation of unsaturated carbons - that the certain acid factor together with a Hydrogen are already many catalysts and certain macropore volumes are special driving has been suggested. Among the proposed 50 technical advances yields. It is true that the Catalysts include those that have a large, effective surface area and benefit from precious metals ^ like Platinum and palladium, and a carrier, for example a precious metal content that is in the range Aluminum oxide, silicon dioxide or combinations of the invention may be; not recognized these compounds contain. The investigation, on the other hand, examined the importance of local these known catalysts or their use. Application in the known processes has shown that the German Äuslegeschrift 1 115 700 often refers to the an excessively strong coke or carbon formation large pores of the catalyst, but without the and a rapid decrease in the effectiveness of the size of the macropore volume with certain Catalyst is observed. It is even more important to determine the diameter. The amount of on-fact that these known catalysts lead to undesirable catalyst metal is similar to that desired by the invention Side reactions lead, especially according to, without being identical to it; not recognized for aromatization, skeletal isomerization and on the other hand, the importance of the local concentrate cracking, as well as for the generation of undesirable tration, for which the use of certain precious amounts polyunsaturated hydrocarbons, metal salts offers greater advantages than the usual for example serving and serving. If the desired 65 chlorine-containing precious metal salts. Dehydrogenation product an ethylene monounsaturated The catalyst and the process according to the Er hydrocarbon is, it has been shown that the discovery lead to an improved conversion Side reactions reduce the efficiency of the process in from acyclic unsaturated hydrocarbons