DE2065211B2 - Process for the catalytic dehydrogenation of paraffinic or alkyl aromatic hydrocarbons to the corresponding olefinic hydrocarbons - Google Patents

Description

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The invention relates to a process for the catalytic dehydrogenation of paraffinic hydrocarbons having 2 to 30 carbon atoms or of alkyl aromatic hydrocarbons having 2 to 6 carbon atoms in the alkyl group to the corresponding olefinic hydrocarbons on a catalyst, the at least one platinum group metal component impregnated on an aluminum oxide carrier, a t> o Contains alkali or alkaline earth metal component and another metal component and after Impregnation has been dried and calcined.

The dehydrogenation of paraffinic to olefinic hydrocarbons is because of the large and b5 ever increasing need for olefinic hydrocarbons for use in manufacture numerous chemical products, e.g. B. detergents, plastics, synthetic rubber, pharmaceuticals Products, high-knock petrol, fragrances, perfumes, drying oils, ion exchange resins and various other products known in the art, an important technical one Process. As an example of this need, consider the manufacture of high octane gasoline under Use of Ci and Q monoolefins for Called alkylation of isobutane. Another example is the dehydration of n-paraffin hydrocarbons for the production of n-monoolefins with 4-30 carbon atoms per molecule; these n-monoolefins are suitable for the production of biodegradable detergents. Furthermore, these monoolefins for example for the production of alcohols are hvdratisiert, which in turn for the production of Plasticizers and / or synthetic lubricating oils are suitable.

The dehydrogenation of alkyl aromatic hydrocarbons to the corresponding alkenyl aromatic Hydrocarbons is important for the production of further products in the application Petroleum, petrochemical, pharmaceutical, detergent, plastics and tire industries. For example Ethylbenzene can be dehydrogenated to styrene, which is used in the manufacture of polystyrene plastics and styrene-butadiene rubber is used. Isopropylbenzene is dehydrated to Λ-methylstyrene, which in turn is at the production of polymers, drying oils, ion exchange resins and similar materials Applies.

The technical production of such dehydrogenation products mostly takes place by selective dehydrogenation of the Starting hydrocarbons on a catalyst. The most important parameter for the performance of the Dehydration is the achievement of the desired conversion with the least possible impairment through side reactions over long periods of operation. The ability of a catalyst to fulfill this task is expressed by its activity, selectivity and stability. Activity is a measure of the ability of the catalyst to convert the hydrocarbon used under the given reaction conditions (Operational acuity) to convert into products. The selectivity results from the amount of obtained desired products in terms of the amount of hydrocarbon converted. The stability is characterized by the temporal change in activity and selectivity, with a lower one Change / unit of time indicates a more stable catalyst.

It is known (US-PS 34 15 737) in a process a catalyst for the catalytic reforming of heavy gasoline in the presence of hydrogen use, on an aluminum oxide carrier material 0.01 to 3 percent by weight of platinum and 0.01 to 5 Contains percent by weight rhenium. The catalyst can contain other components, e.g. B. halogens, however, an intentional alkali or alkaline earth content is not intended. When implementing on this Catalyst, the usual reforming reactions are aimed for and brought about, in particular the production of aromatics by dehydrocyclization of paraffins and aromatization of naphthenes as well as isomerization and hydrocracking, d. H. Reactions that are provided in a dehydrogenation process according to the invention Species should graze as suppressed as possible. Conversely, dehydration of

paraffinic or alkyl aromatic hydrocarbons to the corresponding olefinic hydrocarbons, as they are in a dehydrogenation process of the type provided according to the invention is sought, not in any way in the known method brought about significant extent, but because it is a reforming and olefinic Hydrocarbons in a reformate are undesirable, on the contrary, just suppressed.

The same applies to another known method (US-PS 34 38 888) for reforming Heavy gasoline that contains less than 25 percent by volume of aromatics in the presence of hydrogen using a catalyst containing platinum and rhenium on a porous support material for ι> Obtaining a gasoline with an improved octane number, with the particular way of working there characterized isi that the catalyst is preconditioned before the reforming treatment by it at least 0.5 hours of exposure to a highly aromatic hydrocarbon material containing more than 50 Contains aromatics in percent by volume, exposed to reforming conditions. Again, it's an intentional one Alkali or alkaline earth content of the catalyst is not provided and it is again a 2-5 Reforming of heavy gasoline with the usual octane number-improving reactions, in which, however a dehydrogenation of paraffinic or alkyl aromatic hydrocarbons to the corresponding olefinic hydrocarbons in a notably so significant extent is not brought about but is currently suppressed.

It is also known (DT-PS 10 70 160) for the selective hydrogenation of unsaturated aldehydes in specially prepared, a platinum metal component and an alkali metal component on one Use catalysts containing aluminum oxide carriers. This is an implementation in which hydrogen is attached to an olefinic double bond, i.e. just the opposite of this is to be what is aimed at in the dehydrogenation provided according to the invention.

Catalytic dehydrogenation processes of the type specified at the outset are in US Pat. No. 3,293,319.33 10,599 and 33 79 786. In the process of the first-mentioned patent specification, a catalyst is used worked, the on an aluminum oxide carrier a lithium component, a metal component of the group VIII of the periodic table, preferably platinum, and a metal component from the arsenic group, Contains antimony, bismuth or their compounds. It has been shown that dehydration using these catalysts is not yet fully satisfactory. A further increase in the performance of the Dehydrogenation by means of further improved catalysts is desirable. In the case of the arsenic-containing catalyst are the toxic properties of arsenic and arsenic compounds both in terms of operational Use of the Katplysators and its production disadvantageous, even if satisfactory Results in terms of activity, selectivity and stability in the dehydration can be achieved. With the Catalysts containing antimony became less favorable in corresponding studies on dehydrogenation Results than obtained with the arsenic-containing catalyst, in particular with regard to the Catalyst life. The bismuth-containing catalyst has proven to be something else in the dehydrogenation Proven unfavorable, so that accordingly already in the said US-PS of those considered there Metal components arsenic, antimony and bismuth which bismuth is called the least suitable.

In the catalytic dehydrogenation process of the aforementioned US Pat. No. 3,310,599, the dehydrogenation of paraffinic hydrocarbons carried out with a catalyst on an alumina support a lithium component, a noble metal component of group VIII of the periodic table, in particular palladium or platinum, and a metal component from the group of tellurium, selenium or their Contains connections. It has been shown that with these catalysts no better results than with the arsenic-containing catalysts can be achieved. Also the catalysts containing selenium or tellurium are disadvantageous in that they pose additional operational and manufacturing difficulties because of the toxicity of these materials.

In the catalytic dehydrogenation process of the abovementioned US Pat. No. 3,379,786, alkyl aromatic Hydrocarbons having at least two carbon atoms in the alkyl side chain using of a catalyst dehydrated on an aluminum oxide carrier containing a lithium component a metal component of group VIII of the periodic table, especially platinum, and a metal component from groups Vb and VIb of the periodic table with an ordinal number from 33 to 52, d. H. Arsenic, antimony, selenium, tellurium or their compounds contains. As the cheapest embodiment is the dehydration using platinum and arsenic on the lithium-containing aluminum oxide carrier containing catalyst highlighted. Here, too, it is again true that even with satisfactory results the toxic properties of the arsenic component in terms of activity, selectivity and stability in the dehydrogenation in operational terms and in relation to the necessary catalyst manufacture and handling are at a distinct disadvantage. For the less than the preferred arsenic-containing catalyst anyway For cheap catalysts with antimony, selenium or tellurium or their compounds, the above applies in Link with the other two U.S. patents on operating procedures using Catalysts with these metal components analogously to what has been said.

The invention was based on the object of creating a method of the type specified at the beginning, which does not have the abovedescribed and similar shortcomings of the known working methods and in particular by operating with a further improved catalyst of high activity, selectivity and stability leads to a further increase in the efficiency of the dehydrogenation process without thereby with the difficulties and disadvantages of operating with a catalyst, the one contains highly toxic component, such as arsenic, to be afflicted.

To achieve this object, the invention relates to a process for catalytic dehydrogenation of paraffinic hydrocarbons with 2 to 30 carbon atoms or of alkyl aromatic ones Hydrocarbons with 2 to 6 carbon atoms in the alkyl group to the corresponding olefinic ones Hydrocarbons on a catalyst impregnated at least one on an aluminum oxide carrier Platinum group metal component, an alkali

or alkaline earth metal component and another metal component and after impregnation Has been dried and calcined, which is characterized according to the invention in that one Catalyst used, which is made by impregnating the ί aluminum oxide carrier in any order with the solution of a compound of a platinum group metal, an alkali or alkaline earth metal and of Rhenium in amounts of 0.01 to 1.0 percent by weight platinum group metal, 0.01 to 5.0 percent by weight of the in Alkali or alkaline earth metal component and 0.01 to 1.0 percent by weight rhenium, calculated as elements and based on the final catalyst composition, and preferably after the calcination has been produced by reduction and sulphidation, and the dehydrogenation on this catalyst a temperature in the range of 371 ° to 677 ° C, a pressure in the range of 0.1 to 10 atmospheres, one hourly space velocity of the liquid in the range from 1 to 40 and in the presence of Hydrogen with a hydrogen / hydrocarbon molar ratio in the range of 1: 1 to 20: 1.

The solution to the problem outlined above represents a significant advance in the field. As evidenced by the examples listed below, 2 ~> are used in carrying out the process according to the invention The method achieved very good results and as evidenced by the specified comparative tests the invention of a method implementation using the prior art discussed in in Technology superior to the preferred arsenic catalyst. This is all the more true compared to process implementation with the catalysts, which are less favorable according to the state of the art, which instead has an antimony, bismuth, selenium or contain tellurium component. A highly toxic component such as arsenic or its compounds is not required in the catalyst for the process of the invention. In addition, the catalyst for the process of the invention can be prepared in a simpler manner than the arsenic-containing catalyst and it a significantly higher yield of the desired olefins is achieved even with a significantly lower one Platinum content of the catalyst achieved, as also from the comparative tests listed below emerges.

The following are features and preferred embodiments of the method of the invention further explained.

As feedstock paraffin hydrocar- jo are bons having 2-30 carbon atoms per molecule, contain at least one pair of adjacent carbon atoms bonded thereto are hydrogen, and to an evaporation at the applied Dehydriertemperaturen able and alkylaromatic v, hydrocarbons, in which the alkyl group Has 2 to 6 carbon atoms is used. Examples include: alkanes such as ethane, propane, n-butane, isobutenes, n-pentane, isopentanes, η-hexane, 2-methylhexane and similar compounds; Alkyl aromatics such as ethylbenzene, n-butylbenzene, 1,3,5-triethylbenzene, isopropylbenzene, ethylnaphthalene and similar compounds.

It is preferably one or more normal paraffinic hydrocarbons with 4-30 and in particular about 10-15 carbon atoms per molecule. Preferred feedstocks for the production of intermediate non-corrosive diameters reveal a mixture of 4 or 5 adjacent normal paraffin homologues, for example CiI ₁ -Cn, Cn-Cm, Cn-C, 5 and similar mixtures.

Preferably, the alumina support used for the catalyst has a surface area of 25 to 500 m ² / g or more. Suitable aluminum oxides are the crystalline gamma-, eta- and theta-aluminum oxides, gamma- or cta-aluminum oxide, in particular the former, being preferred. Particularly preferred is a carrier material with an apparent bulk density of about 0.30 to 0.70 g / cm ³ , an average pore diameter of about 20 to 300 Angstrom units, a pore volume of about 0.10 to 1.0 ml / g and a surface area of about 100 to 500 m ² / g. In general, particularly favorable results are obtained with a gamma-alumina carrier in the form of spherical particles of e.g. B. about 1.6 mm in diameter, an apparent bulk density of about 0.5 g / cm ¹ , a pore volume of about 0.4 ml / g and a surface area of about 175 m ² / g educate.

The alumina carrier can be synthetically manufactured or naturally occurring Trade material. Before use, the aluminum oxide can be treated with one or more treatments, like drying, calcination or steam treatment, can be activated and it can be in forms exist as known as activated alumina, porous alumina or alumina gel are. For example, the aluminum oxide carrier can be produced by adding an alkaline one Substance, e.g. B. ammonium hydroxide, to an aluminum salt, z. B. an aluminum chloride or aluminum nitrate solution in such an amount that an aluminum hydroxide gel is formed, which by drying and Calcination is converted into aluminum oxide. The alumina can be formed into a desired shape will. z. B. balls, pills, cakes. Tablets. Extrudates, powders, granulates. A particularly preferred one Shape are spheres. Alurniniumoxide spheres can continuously according to the known oil drop method getting produced. It has also proven useful to subject the resulting and then calcined spheres to a steam treatment at high temperature to subject to undesirable acidic ingredients as far as possible to remove. This treatment causes conversion of the alumina hydrogel to that preferred crystalline gamma alumina.

Platinum, palladium, rhodium, ruthenium, osmium and iridium come into consideration as platinum group metals. The platinum group metal, preferably platinum, can be in the final catalyst in the form of a compound. z. B. as oxide, sulfide or halide, or in the elemental state. The platinum group metal makes 0.01 to 1.0 and preferably 0.1 to 0.9 weight percent of the final catalyst composition, calculated as an element, from.

The platinum group metal is with the aluminum oxide carrier by impregnation with a soluble decomposable compound of the platinum group metal combined. For this purpose, for example, the carrier can an aqueous solution of hexachloroplatinum (IV) acid are mixed. Other useful water soluble ones Platinum compounds are z. B. ammonium chloroplatinate, platinum chloride and dinitro-diamino-platinum. The usage a platinum chloride compound, e.g. B. hexachloroplalin (IV) acid is normally preferred. Farther it is usually preferred to use the

rial to impregnate after it has been calcined, the risk of washing away part of the valuable platinum compounds is as small as to make possible. In some cases, however, it can also be advantageous to apply the carrier in the gel state impregnate.

The rhenium component can be in the form of the elemental metal, as a chemical compound, e.g. B. as oxide, Sulphide, halide, or in physical or chemical association with the aluminum oxide carrier and / or the other components of the catalyst are present. The rhenium component is in a introduced in such an amount that the final analyzer composition is 0.01 to 1.0 percent by weight Contains rhenium, calculated as an elemental metal. The rhenium component can be in any Step of the preparation of the catalyst are introduced. In general, it is preferred to use the rhenium to introduce in a late stage of manufacture To avoid losses in subsequent processing measures, such as washing and cleaning equipment. The rhenium component is preferably introduced by impregnating the aluminum oxide carrier either before, during or after the introduction of the remaining components. With the impregnation solution it can be an aqueous solution of a rhenium salt, e.g. B. ammonium perrhenate, sodium perrhenate, Kaliumperrhcn.it, or an aqueous one Solution of a rhenium halide, e.g. B. of chloride, but preferably an aqueous 3 " Perrhcnic acid solution used. The rhenium component can before, simultaneously with or after Introduction of the platinum group metal component are impregnated into the carrier material, particularly preferred becomes an impregnation concurrently with the platinum group metal component.

Preferably the weight ratio of rhenium to platinum group metal, calculated as elements, in the range from 0.05: 1 to 2.75: 1 and in particular in the region of 1: 1. This is especially true when the total content of rhenium plus platinum group metal in the catalyst to a value in the range of about 0.2 to 1.5 percent by weight, particularly preferably to about 0.4 to 1.0 percent by weight, calculated as Elements, is set.

The alkali or alkaline earth metal component can be of cesium, rubidium, potassium, sodium or lithium or calcium, strontium, barium or magnesium are formed. You can get in the form of the catalyst a relatively stable connection, e.g. B. as an oxide or sulfide, or in combination with one or several of the other components of the catalyst, or in combination with the alumina support, z. B. in the form of a metal aluminum. As the catalyst before use for dehydrogenation is always calcined by hydrocarbons in air or a gas containing oxygen, this is the case Component is very likely to be in an oxidic state during dehydration. The amount of alkali or Alkaline earth component is chosen so that the final value> o gc catalyst 0.01 to 5.0 and preferably about 0.05 contains up to 2.5 percent by weight of the alkali or alkaline earth metal. Compounds of lithium or potassium are particularly preferred.

The alkali or by Erdalkalikomponenlc can b ^r> impregnation either before, during barren be introduced after the introduction of the other components in the Trägermalerial. In general, it is added after the other metal components in order to simultaneously neutralize the acid which may be used when the platinum group metal and the rhenium are introduced. decomposable salt of the desired alkali or alkaline earth metal or metals. For example, the halides, sulfates, nitrates, acetates, carbonates and phosphates are suitable. Excellent results will be ζ. Β obtained if the aluminum oxide carrier is impregnated with an aqueous solution of lithium or potassium nitrate after the introduction of the platinum group metal and the rhenium component. After impregnation, the material is dried and preferably calcined in air.

Drying is expediently carried out at a temperature of 93 ° to 316 "C over a period of 2 to 24 hours. Thereafter, preferably at a temperature of 316 ° to 593 ° C in air over a period of 0.5 to 10 and in particular 1 up to i hours caicinieri to convert the metal components largely into the oxidic form.

If acidic components are present in one of the impregnation solutions, the catalyst mass can be a High temperature treatment with steam can be subjected, either after or before the calcining tion to remove the unwanted acidic components as much as possible.

It is preferred that the calcined catalyst be used in the dehydrogenation of coals Hydrogen is subjected to reduction in the substantial absence of water. These Treatment serves to ensure an even and fine distribution of the platinum group metal and the rhenium component in the entire aluminum oxide carrier. Preferably this is essentially pure and dry hydrogen, d. H. with a content of less than 20 parts by volume per million H2O used as a reducing agent. The reducing agent is with the calcined catalyst at one Temperature of about 427 ° to 649 ° C. for a period of about 0.5 to 10 hours or more ir Brought into contact, so that a substantial or complete reduction of both the platinum group metal as well as the rhenium component in the elemental state. This reduction treatment Treatment can be carried out in the dehydrogenation reactor or outside as a separate treatment stage.

Furthermore, in some cases, the reduced catalyst may advantageously be subjected to a sulfidation treatment in order to introduce about 0.05 to 0.60 percent by weight of sulfur, calculated as the element, into the catalyst. This presulfiding treatment is preferably carried out in the presence of hydrogen and a sulfur-containing compound, ζ. Β Hydrogen sulfide, low molecular weight mcrcaptans, or other organic sulfides. A treatment of the reduced catalyst with an H ₂ / H ₂ S mixture with a molar ratio of about 10: 1 at a temperature of 10 ° to 593 ° C. has proven successful. This presulfiding treatment can also be carried out in the dehydrating reactor or outside the reactor.

Hydrocarbon dehydration can be used of the catalyst in a l'cstbclt, a moving bed, a fluidized or fluidized bed or in batch mode.

A fixed bed system is preferably used in order to avoid catalyst abrasion. The dehydration zone can be from one or more reactors with intermediate heating devices are formed, the latter to ensure that the desired at the entrance to each reactor Temperature is present. The reactants can pass through the catalyst bed in upward, downward, or Radial flow and be passed in liquid, mixed liquid-vapor or vapor phase. A conversion i < > Use in the vapor phase is preferred.

The dehydrogenation is carried out in the presence of hydrogen. Additional diluents, e.g. B. water vapor, methane, carbon dioxide, can be used. The hydrogen reduces the partial pressure of the i ^r j dehydrogenated hydrocarbon and suppresses the formation of carbonaceous deposits on de: n catalyst. The hydrogen is used in such amounts that a hydrogen / hydrocarbon molar ratio in the range from 1: 1 to 20: 1, preferably 1.5: 1 to 10: 1, results. The hydrogen is expediently recycled.

Dehydrogenation conditions known per se can be met. The temperatures are in the range of 371 ° C to 677 ³ and appropriately values in the lower portion of this range for the more readily dehydrogenatable hydrocarbons z. B. the long-chain normal paraffins, and values in the upper section of this range for the harder to dehydrogenate j »hydrocarbons, z. B. propane and butane can be selected. For example, for the dehydrogenation of Cb-Cjo normal paraffins, a temperature in the range from 427 ° to 510 ° C. is recommended. The pressure is normally kept as low as possible from a catalyst stability standpoint and is in the range of 0.1 to 10 atmospheres, with particularly favorable results usually being obtained in the range of about 0.5 to 3 atmospheres. The liquid hourly space velocity, ie the volume of hydrocarbon feed added in liquid form to the dehydrating zone per hour divided by the volume of the catalyst bed, is in the range from 1 to 40 and preferably from 25 to 35.

The effluent from the dehydrogenation zone normally contains unconverted feed hydrocarbons, Hydrogen and reaction products of the dehydrogenation reaction. He is chilled and in a Separation zone separated into a hydrogen-rich vapor phase and a liquid hydrocarbon phase. The unreacted feed hydrocarbon from this liquid phase is expedient recovered and returned to the reaction zone together with the recycled hydrogen. These Recovery can be done in a manner known per se, / .. B. by adsorption on a fixed bed, liquid extraction or fractionation. It can also be a selective chemical conversion of the contained olefin can be used for separation. t> <>

If, for example, long-chain n-paraffin hydrocarbons are dehydrogenated to the corresponding n-monoolefins, an alkylation reaction can be carried out to carry out this hydrocarbon separation. The liquid hydrocarbon phase discharged from the separation zone is mixed with an aromatic compound and (.Uis (ionic is introduced into an alkylation zone which contains a strongly acidic catalyst, e.g. a non-aqueous solution of hydrogen fluoride. In the alkylation zone, the monoolefins react with the alkylatable aromatic compound, while the unconverted normal paraffins remain essentially unchanged. The effluent from the alkylation zone can then be easily separated, for example by fractionation, so that the non-unconverted normal paraffins can be easily recovered returned to the dehydration zone.

The following examples to further illustrate the invention were carried out in a dehydrogenation plant carried out on a laboratory scale. The one containing the hydrocarbon to be dehydrogenated Feed stream was combined with a stream of hydrogen and the resulting mixture was added to the desired conversion stamp naturally heated; below this is the one maintained at the inlet / around the reactor To understand temperature. The heated mixture was then passed through a fixed bed of the catalyst particles in the Reactor headed. The pressures indicated were measured at the outlet of the reactor. The reactor effluent was cooled and in a separator, into a hydrogen-rich gas phase and a liquid hydrocarbon phase separated; the latter contained the dehydrogenated hydrocarbons, unconverted feed hydrocarbons and a small amount of by-products. Part of the water-loft-rich The gas phase was drawn off as excess circulating gas, the remainder was passed through a compression device continuously returned to the heater and mixed with the feed. The liquid phase was withdrawn from the separator and analyzed to determine the values given in the examples Conversion and selectivity to be determined. The values shown for the conversion are all calculated from the disappeared amount of the dehydrogenatable hydrocarbon and expressed as all in mole percent. The values for the selectivity are calculated accordingly and given as the number of Moles of dehydrogenated hydrocarbon produced per 100 moles of hydrocarbon converted.

All catalysts used in the examples were according to the following method, with appropriate modifications of the proportions to achieve the composition given in the respective example. First an aluminum oxide carrier in the form of spheres with a diameter of about 1.6 mm was made from an aluminum oxychloride sol, formed by dissolving pure aluminum pellets in a hydrochloric acid solution with addition from hexamethylenetetramine to your sol. The balls were made by dropping the sol into a Oil bath for the formation of spherical particles from an aluminum oxide hydrochloric acid, aging and washing of the particles obtained with an iimnioniacal color Solution, as well as drying, calcining and steaming the aged and washed Particles made. Spherical particles of gamma-alumina were obtained, which were essential contained less than 0.1 weight percent bound chloride. These were then treated with an impregnation solution brought into contact, the I lcxachloroplalin (IV) -siiurc, It contained ammonium acid and nitric acid in such amounts that it was a definitive catalyst composition with the desired content-ii; in Platinum and rhodium. The AlkiilikompoiiLMiic

was oxidized in the. Containing platinum and rhenium Introduced catalyst in a separate impregnation stage, in which the particles with a aqueous solution of lithium nitrate or potassium nitrate were impregnated. The amount of the alkali salt became "> each chosen so that a final catalyst of the desired composition resulted. The impregnated Balls were then dried at a temperature of 149 ° C. for one hour and then in air Calcined at 260 to 538 ° C for 2 to 10 hours. Thereafter, the balls were blown with an air stream of 10 up to 30% water vapor, treated at a temperature of 538 ° C for an additional 5 hours in order to obtain the to further reduce residual bound chlorine contained in the catalyst. r>

In all examples, the catalyst was treated with hydrogen during start-up increased temperature and then ir Mixture of H2 and H2S in an amount for introduction from 0.1 to 0.5 percent by weight of sulfur is sulfided.

example 1

The reactor was charged with 100 cm ^{3 of} a catalyst which - calculated as elements - contained 0.375 percent by weight platinum, 0.375 percent by weight rhenium, 0.8 percent by weight lithium and 0.15 percent by weight bound chloride. The feedstock stream consisted of technical grade n-dodecanese. The dehydrogenation reactor was operated at a temperature of j <> 466 ° C., a pressure of 7 ° C., an hourly space flow rate of the liquid of 32, and a hydrogen / hydrocarbon molar ratio of 8: 1. After steady-state conditions were reached, a 20-hour test period jj was carried out; The average conversion of the n-dodecane was 18%, with a selectivity for the formation of n-dodecene of 94%.

Example 4 Example 2

4 (1

fcis was the same catalyst as in Example 1 used. The feed stream consisted of n-tetiadodecane. The operating conditions were one Temperature of 449 ° C, a pressure of 1.4 atm, an hourly space velocity of the liquid of 32 and a hydrogen / hydrocarbon molar ratio of 8: 1 is observed. After reaching steady-state conditions, a mean conversion of 12.0% and w a selectivity for n-Tctradodecene of 93.0% was found.

Example 3

ίί

The catalyst contained, calculated as the elements, 0.30 percent by weight platinum, 0.30 percent by weight rhenium and 0.6 percent by weight lithium, the combined chlorine content being less than 0.2 percent by weight. The salt maicrialslrom consisted of essentially pure η-butane. The operating conditions include a temperature of 510 ⁰ C, a pressure of I aiii, an hourly Raumslrömungsgcschwindigkcit Iler liquid of 4.0 and a hydrogen / Kohlcnwiissersluff-Molvcrhältnis of 4: 1 were observed. In a h ^r> 20stündigcn test period, the average conversion of the η-butane 3 () "/ o and the selectivity to n-Biileii94.0%, respectively.

The catalyst contained 0.1 5 calculated as elements Weight percent platinum, 0.15 weight percent rhenium, 0.6 weight percent lithium and less than 0.2 Weight percent combined chlorine. The feed stream consisted of technical grade ethylbenzene. The operating conditions were: a pressure of I atü, an hourly space air velocity Liquid of 32, a temperature of 566 ° C and a hydrogen / hydrocarbon molar ratio of 8: I. During a 20 hour test period, the equilibrium conversion of the ethylbenzene was 80%. the Selectivity to the formation of styrene was 98.0%.

Example 5

The reactor was charged with a catalyst which, calculated as elements, contained 0.375 percent by weight platinum, 0.375 percent by weight rhenium, 2.4 percent by weight potassium and less than 0.2 percent by weight combined chlorine. The feed stream consisted of a mixture of Cn - Ci <normalpai;) fl'inen with a content of 0.4 weight percent nd ,,. 27.2 percent by weight n-Ci ,, 30.7 percent by weight n-Ci2, 25.0 percent by weight n-Cn, 13.0 percent by weight n-Ci4, 0.5 percent by weight n-Ci5 and 3.2 percent by weight non-normal hydrocarbons. As operating conditions, a pressure of 2.1 atm were, an hourly space velocity of the liquid 32, a hydrogen / hydrocarbon mole ratio of 8: 1 and a temperature of 460-475 C ¹³ observed. After equilibrium was reached, the plant was operated at 460 ° C. for an initial period of 12 hours; the mean conversion of the normal paraffins was 6.4%, the selectivity for the formation of the n-mopoolefins was 99.0%. The plant was then operated for 120 hours at 466 ° C., an average conversion of 8.4% being achieved with a selectivity of 97.5%. The final study period had a duration of 22 hours at 470 ⁰ C, during this, the mean conversion Zeilraums 8.6 Molprozeni at a selectivity to the corresponding N-mono-olefins of 98%.

Example 6

The catalyst contained calculated as elements. 0.375 percent by weight platinum, 0.375 percent by weight rhenium, 1.5 percent by weight potassium and less than 0.2 percent by weight combined chloride. The feed stream and the operating conditions used, apart from the temperature, were the same as those of Example 5. The service run was divided into four sections: the first section had a duration of 12 hours at 460 "C, the second portion has a duration of 126 hours at 466 ° C, the third portion of a period of 30 hours at 470 ^u C and the fourth Section a duration of 54 hours at 475 "C. The conversions observed in the four sections were 7.4%, 8.4%, 8.5% and 8.7%, respectively. The observed in the four sections selectivities for the formation of the corresponding n-Monoolefinc amounted to 98.5%, 96 ¹ Mi, 99 "/ (i, 98 ° / '.

Example 7

The catalyst contained, calculated as elements, 0.37% by weight platinum, 0.375% by weight rhenium, 0.75% by weight potassium and less than

0.2 percent by weight bound chloride. The I-Ünsat / -Muitcriiilstrom lind the operating conditions, apart from the Tem pern I Ii r, were the same as in Example 5. The service run was divided into 2 portions, the first portion was 12 hours at a temperature of> 460 ⁰ C and the second section carried out for 54 hours at a temperature of 465 ° C. The conversions observed were 7.4% and 8.1%, respectively. The selectivities for the corresponding n-monoolefins were 94.5% and 92.5%. κι

Example 8

The catalyst contained, calculated as the elements, 0.375 percent by weight platinum, 0.375 percent by weight r, rhenium, 0.6 percent by weight lithium and less than 0.2% combined chlorine. The feed material and the operating conditions, apart from the temperature, were the same as those of the example. The service run was divided into three sections: the first section was carried out for 90 hours at 47o ⁰ C for 12 hours at 460 ° C, the second portion 126 hours at 465 ° C and the third portion. The results of the studies were as follows: an overall conversion of 8.3% with a selectivity to r> n monoolefins of 93% in the first section, a conversion of 9.2 mole percent with a selectivity of 89% in the second section, and a conversion of 9.5 mole percent with a selectivity of 93% in the last section. "1

Example 9

Calculated as the elements, the catalyst contained 0.30 percent by weight platinum, 0.30 percent by weight rhenium, 0.6 percent by weight lithium and less than 0.2 percent by weight combined chlorine. The feed material flow consisted of a mixture of normal paraffins with 11 to 14 carbon atoms inclusive, namely 0.1 percent by weight η-do paraffins, 32.3 percent by weight n-Cn, 31.1 percent by weight n-C'12, 23.8 percent by weight n- Cu, 11.1 percent by weight n-Ci4, 0.1 percent by weight n-Cis and 1.5 percent by weight non-normal components. The operating conditions used, apart from the temperature, 4-, were the same as those of Example 5. The service run consisted of four sections: the first section was 12 hours at a temperature of 460 ° C, the second portion 132 hours at a temperature of 465 ° C, the third portion w 30 hours at a temperature of 470 ⁰ C and the last Section carried out for 54 hours at a temperature of 475 ° C. The results were as follows: a conversion of 7.7% in the first section, 9.2% in the second section, 9.7% in the third section, and γ, of 9.9% in the last section. The associated selectivities for n-monoolcfinc were 93.5%, 74.5%, 84.5% and 90%, respectively.

Example 10 «'

The catalyst contained, calculated as elements, 0.05 percent by weight platinum, 0.05 percent by weight rhenium, 0.6 weight percent lithium and less than 0.2 weight percent bound chloride. The Hetricbshe- ι, ί conditions and the sirom used were the same as in Example 9. The test comprised four sections: a first section of 12 Hours at a temperature of 460 "C, a second segment of 132 hours at a temperature of 465 C. a third section of 24 hours at a Temperature of 470 "C and a final section of 54 hours at a temperature of 475" C. the (Total unimplementation was 5.3%, 7.6%, 6.4% b / .w. 7.8%. The associated selectivities for n-monoolcfins were 96%, 96%, 97.5% and 96%, respectively.

Comparison attempts

Comparative experiments were carried out using catalysts according to the prior art (US Pat 32 93 3! 9 and 33 10 599) on the one hand and the inventive Catalyst, on the other hand, carried out under exactly the same dehydrogenation conditions.

The conventional catalyst contained platinum, lithium and arsenic supported on aluminum oxide (US-PS 32 93 319) and was used in an operational approach in an amount of 272 kg in the following Way made:

(1) Platinum impregnation: 267 kg of the alumina carrier in the form of spherical particles were obtained impregnated with a chloroplatinic acid solution obtained from 473 liters of water, the calculated amount of Chloroplatinic acid solution to bring about a platinum content in the final catalyst of 0.75 percent by weight, 13.4 liters of 70 percent by weight nitric acid corresponding to 0.059 mol HNOj per mol AliOj, and sufficient water to make a total volume of the solution of 568 liters. the Impregnation was carried out in a rotary dryer with steam heating. First was the aluminum oxide carrier was circulated in the impregnation solution for 30 minutes at normal temperature. Thereafter was evaporated to dryness with the addition of steam. This was followed by 2 hours at 316 ° C in a steam-free atmosphere, 4 hours at 538 "C in a steam-free atmosphere and 5 hours at 538 "C in a water vapor containing 20 mole percent Atmosphere calcined.

(2) Lithium impregnation: The platinum-impregnated particles were impregnated with a lithium nitrate solution which was mixed from 473 liters of water, 16.66 kg of 97.0 percent by weight LiNOj and further water to make up the solution to 568 liters. The impregnation was carried out in the same way as the platinum impregnation. The obtained particles were 1 hour at 316 ° C in a 10 mole percent and 2 hours at 510 ⁰ C in a 20 Molprozcnt steam-containing atmosphere calcinicri.

(3) Arscine impregnation: The platinum-Lilhium-impregnation Particles were impregnated with a solution consisting of 473 liters of water, 363 g of arsenic acid (HjAsO.1) with an arsenic content of 52.8 percent by weight and additional water to make up to 568 liters of solution with the addition of ammonium hydroxide solution (28 percent by weight NIIj) to adjust the pH was prepared. The impregnation was carried out in the same way as the platinum impregnation and the Ctilcinicrung was done in the same way as that Ciilcinierung carried out after the lithium impregnation.

In the production of the catalyst to be used according to the invention, the platinum, rhenium and lithium Contained on the aluminum oxide carrier, the platinum and the rhenium components were by common Impregnation in the aluminum oxide carrier

brings. Chloroplalic acid and proprhenic acid were used for this purpose in quantities corresponding to a content of de *. final catalyst of 0.3 weight percent platinum and 0.3 weight percent rhenium, calculated as Elements given in the definition of the impregnation solution. In addition, the impregnation solution was in prepared in the same manner as that described above in connection with the preparation of the catalyst the prior art for platinum impregnation is described. Also the impregnation itself and the subsequent calcinations were carried out in exactly the same way. The same goes for that Measures that are described above for lithium impregnation with subsequent calcination. the The measures described above for arsenic impregnation are of course not necessary. This already results a simplification in the manufacture of the catalyst.

The hydrocarbon feed used for the dehydrogenation experiments was a mixture of normal paraffins with 11 to 14 carbon atoms per molecule used. The composition is given below:

Weight percent Non-normal hydrocarbons 1.1 Light parts 0.1 Normal paraffins 98.8 Composition of normal paraffins Cio 0.1 Cn 19.9 Cl2 32.8 Cl 3 33.2 Cl4 13.9 Cl5 0.1

The attempts were made in exactly matching 4n Manner carried out in the above-mentioned dehydration device of laboratory scale. It was each worked with an amount of catalyst of 20 cm '. The reactants were passed through the fixed catalyst bed in a downward flow. The pressure on The outlet from the reactor was 3 atm. absolutely. The temperature was as indicated in the following Table changed. The hydrogen / hydrocarbon molar ratio was 8: 1 and the hourly space velocity the liquid was 32.

The comparison tests were not aimed at optimal results, such as the greatest possible yields or the like, driven, but according to the investigation method given above, which intentionally involved conversions of the starting material in the range shown in the table below and is based on strict comparability.

The results compiled in the table come from an investigation period of 248 hours duration. ho

catalyst

State of
technology

invention

Carrier material AI2O3 AI ₂ O ₃ Pt, weight percent 0.75 0.3 Li, percent by weight 0.6 0.6

b5 catalyst

State of
technology

invention

Further metal components
Weight ratio of
further metal component
to platinum

N-olefins produced,
averaged,%

As
0.3

re
1

2 (1

at 460 ⁰ C 7.9 9.2 at 465 ° C 8.6 9.6 at 470 ° C 9.2 10.3 at 475 ° C 9.7 10.6 Increase in abnormal Hydrocarbons in the outflow, averaged,% at 460 ° C 0.6 0.5 at 465 ° C 0.5 0.8 at 470 ^° C 0.6 0.6 at 475 ° C 0.6 0.6

It can be seen from the above results that the dehydrogenation according to the invention can be carried out with the for this purpose prescribed catalyst of the dehydrogenation with the catalyst of the prior art is clearly superior. According to the invention are considerably higher yields of the desired Obtain n-olefins. This improve the bulging is obtained without lowering the selectivity as from the values for the increase in abnormal ones Hydrocarbons in the effluent, which are a direct measure of the selectivity, emerges.

In addition, it was found that the invention The catalyst used has a longer service life and is easier to regenerate.

Furthermore, again with the same hydrocarbon feed and under the same operating conditions, the dehydration on a conventional one Catalyst carried out with the above prior art catalyst in all other points agreed but contained antimony instead of arsenic in the same amount. The results were less favorable than with the arsenic-containing catalyst, in particular went to more useful Initial activity, the production of n-olefins decreases relatively quickly, so that the life was unsatisfactory. The superiority of the method implementation according to the invention over a Execution of the process with the antimony-containing catalyst is thus even more pronounced.

A process carried out using a conventional catalyst that uses bismuth instead contains arsenic as a further metal component, the method implementation according to the invention is still more inferior.

Investigations of the dehydrogenation using conventional catalysts, the selenium resp. Contained tellurium instead of arsenic, antimony or bismuth as a further metal component (US-PS 33 10 599), have shown that no better results than obtained with the arsenic-containing catalysts can be. In addition, the selenium or tellurium-containing catalysts prepare special additional ones Difficulties due to the toxicity of these materials.

809 512/121

Claims (4)

Patent claims: 1. Process for the catalytic dehydrogenation of paraffinic hydrocarbons with 2 to 30 ^r , carbon atoms or of alkyl aromatic hydrocarbons with 2 to 6 carbon atoms in the alkyl group to the corresponding olefinic hydrocarbons over a catalyst which has at least one platinum group metal component impregnated on an aluminum oxide carrier, an alkali - Or contains alkaline earth metal component and another metal component and has been dried and calcined after impregnation, characterized in that ι -> a catalyst is used, which is impregnated by impregnation of the aluminum oxide support in any order with the solution of a compound of a platinum group metal, an alkali - Or alkaline earth metal and of rhenium in amounts of 0.01 to 1.0 percent by weight of platinum group metal, 0.01 to 5.0 percent by weight of the alkali or alkaline earth metal component and 0.01 to 1.0 percent by weight of rhenium, calculated as elements and related gene on the final catalyst composition, and preferably has been prepared after the calcination by reduction and sulfidation, and the dehydrogenation on this catalyst at a temperature in the range from 37 ° to 677 ° C., a pressure in the range from 0.1 to 10 atmospheres , a liquid hourly space velocity in the range from 1 to 40 and in the presence of hydrogen with a hydrogen / hydrocarbon molar ratio in the range from 1: 1 to 20: 1 !. j5 2. The method according to claim 1, characterized in that one has a catalyst, the Platinum group metal composed of platinum or a platinum compound is used. 3. The method according to claim 1 or 2, characterized in that a catalyst whose ' Aluminum oxide carrier aius gamma aluminum oxide consists, used. 4. The method according to any one of claims 1 to 3, characterized in that a catalyst, its alkali component made of lithium or a lithium compound or of potassium or a Potassium compound is used.