DE977657C - Process for the production of platinum-on-aluminum oxide catalysts - Google Patents

Description

(WiGBl. P. 175)

ISSUED JANUARY 25, 1968

U 599IVa / is g

Availed

Platinum-on-alumina catalysts and various methods of making them are available known, but these catalysts are because of their relatively high manufacturing costs only limited commercial use. For example, it is from U.S. Patent 2,184,235 known a platinum-on-alumina catalyst by soaking aluminum oxide with a platinum solution and then annealing. In US Pat. No. 2,319,452, on the other hand, the selection of certain aluminum oxide modifications, such as γ-aluminum oxide or activated alumina, as a carrier for compounds of Vanadium, niobium and tantalum have been described. On the other hand, the activation is also natural or artificial clays, which are known to be something other than clay, with hydrogen fluoride or hydrofluoric acid for use as catalysts.

The essential principles for the manufacture of a catalyst that is used to carry out catalytic Hydrocarbon conversion reactions are suitable are described in the British patent 558 294. According to this, it is important that the catalyst support has a large surface has to increase the available catalytic surface, furthermore, the catalyst should have a promoter effect have, which is why chrome

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oxide on clay. Finally, a stabilizing effect is required, along with the supported catalyst also has a long service life in operation; z. B. has chromium oxide per se desired activity, which it quickly loses with use. To solve this problem is the use of an aluminum oxide, which is obtained from the in the manufacture of alumina according to the Bayer process accruing hard crystalline Alumi-IQ nium oxide products has been obtained by dehydration to a water content of 0.2 to 5%, and proposed its impregnation with an aqueous chromic acid solution, whereupon the impregnated The catalyst is quickly dried and the chromic acid is converted into chromium oxide. Numerous compounds are used as impregnants, including also halides of metals of the transition series of the periodic table, among others too Called platinum. The catalyst should be 0.5 to 40%, preferably 0.5 to 20% by weight, active Metal included.

It is also known from British Patent 452 095, the catalytic ^ treatment of Distillable carbonaceous material with the addition of hydrogenation gases in contact with metals or metal compounds (but excluding silicon compounds) to carry out their Activity has been increased by treatment with fluorine or fluorine compounds. For example granular active clay is treated with 10% hydrofluoric acid for about 15 minutes and then dried, whereupon ammonium thiotungstate is deposited on the clay and in a stream of hydrogen is heated to convert the tungsten compound to tungsten disulfide. The finished catalyst contains approximately 90 parts of alumina and 10 parts of tungsten disulfide. Treatment becomes general with sulfides of the heavy metals of groups IV to VIII of the periodic table, e.g. B. the WoIfram, Molybdenum, chromium or cobalt, as well as oxides of the metals of the VI. Group recommended. If the catalyst activity has been reduced during the subsequent washing with water, should this by sulfiding treatment of the catalyst to be restored. As an application area of these catalysts is primarily Line the destructive hydrogenation of carbonaceous material and further the improvement of Properties of motor fuels called aromatization or hydroforming.

About the fluorine content of the finished catalyst nothing can be found in the publication. Treatment with fluorine compounds should result in a Etching of the material occur, with a loss of 5 to 3o% of the activated material occurs, which obviously requires extensive washing out, but this can be omitted if desired can be. Tests have shown that when alumina is treated with 5 to 10% aqueous If hydrofluoric acid is not washed out, a very significant weight gain occurs and that Dried alumina product contain up to 20% fluorine can.

Furthermore, US Pat. No. 2,184,235 a process for the catalytic dehydrogenation of butane to butylene or other paraffins to olefins known in the commercial alumina activated as a catalyst with at least one oxide or Sulphide of the metals of the first transition row of the periodic table is used. In addition to nickel oxide or iron oxide is said to be particularly beneficial chromium oxide. The procedure or the catalyst can be applied to motor fuels to increase their olefin content.

Finally, the French patent specification 878 760 describes a catalytic cracking process, in which the catalyst as a carrier natural or activated artificial clays or bauxite or a Contains gel of silica and alumina, with the alumina-containing material with Hydrofluoric acid or hydrofluoric acid can be pretreated. The carrier is 0.3 to 5 percent by weight of oxides of metals of the IV., V., VI. or VIII. Group of the Periodic Table, in particular soaked in oxides of vanadium, chromium, molybdenum, tungsten, cobalt or nickel. Even this patent gives nothing about the level of the fluorine content of the catalyst.

Although platinum has long been a known catalytic metal for hydrogenation reactions, was because of the high price of platinum, experts are striving to become independent of platinum. Acquaintance namely, platinum catalysts in practical use contained about 2 to 5% platinum, for example on activated coconut charcoal, and as a result were in practice for dehydration of cyclohexane-like naphthenes and cyclization of paraffins Chromium oxide-alumina catalysts has been used as particularly suitable during molybdenum oxide-alumina catalysts in contrast to the catalytic reforming of heavy gasoline under hydrogen pressure proved to be the most appropriate.

In contrast, the invention has set itself the task of a platinum-on-aluminum oxide catalyst to produce, which despite an extremely low platinum content is an extraordinarily good activity for carrying out the various catalytic hydrocarbon reactions has and has a very substantial service life, d. H. especially over longer periods Periods can be in use without its regeneration would be required. This goal will according to the invention achieved in that one in the known soaking of aluminum oxide with the solution of a platinum compound and subsequent annealing the solution in an amount the finished catalyst has a content of 0.01 to ι weight percent platinum as the only catalyst Satormetall granted, and a halogen-containing aluminum oxide used, which is obtained by treating aluminum oxide with a halogen or a platinum-free halogen compound and after annealing, 0.1 to 3 percent by weight of fluorine or 0.2 to 8 percent by weight of chlorine and one

Maximum total halogen content of 8 percent by weight, based on the aluminum oxide as dry substance, having.

In the process according to the invention it is essential that the aluminum oxide corresponds to the above-defined Contains fluorine or chlorine, which does not come from the platinum compound used for impregnation originates. As a result, it is possible to obtain a catalyst that is very low. Platinum content has a relatively high fluorine or chlorine content.

Comparative tests with a catalyst made according to the invention and a Catalyst otherwise of the same composition, but with a range below the stated range lying content of halogen, namely fluorine, or with an aluminum oxide catalyst same fluorine content, but impregnated with cobalt nitrate instead of platinum using this ao catalysts in the isomerization of normal butane or in the hydrocracking of a light one Gas oil fraction under excess pressure showed that the catalyst with the prescribed according to the invention Halogen content converted a 2-fold higher percentage of normal butane into isobutane as the catalyst with the too low halogen content and that in hydrocracking the hydrogen production in the case of the cobalt-containing catalyst was not sufficient to maintain the pressure without extraneous hydrogen to maintain, while operating with the catalyst according to the invention, a hydrogen supply was not required. Furthermore, that was produced with the catalyst according to the invention liquid product considerably richer in aromatic hydrocarbons and it contained um half more gasoline hydrocarbons than the product made with the cobalt-containing catalyst was obtained from the same fluorine content.

In a preferred embodiment of the invention, a substrate formed of an aluminum salt is used, and alumina, the finished catalyst annealed at about 425-650 ⁰ C. It has been shown that such an aluminum salt z. B. aluminum oxide obtained by precipitation is far superior to a catalyst made from natural alumina, and the calcination at about 425 to 650 ^° C. ensures particularly good activity.

According to the invention, it is very particularly expedient to use one made of aluminum chloride Aluminum oxide gel with a lowered by washing out chlorine ions with ammonia-containing water Chlorine content of less than 0.1 percent by weight, based on dry aluminum oxide, to be treated with an aqueous solution of hydrogen fluoride or hydrogen chloride. on in this way, the desired content of the catalyst can be achieved with a particularly high degree of certainty Adjust fluorine or chlorine, and you get more reliable results than with the formation of the aluminum oxide from aluminum chloride by partial washing out and selective restraint of chlorine. If, for example, the aluminum oxide is so far with preferably ammonia-containing Water washes so that about 0.2 to 5 percent by weight of chlorine is retained, so there is no need the need to add chlorine or fluorine at a later stage of manufacture, but it is generally difficult to control the washing process in this way.

The catalysts prepared according to the invention are suitable for converting hydrocarbon compounds. This term should be understood here to mean both hydrocarbons themselves and their oxygen compounds. The catalysts are not only particularly advantageously suitable for isomerization of normal paraffin or the hydrocracking of oil fractions to convert heavier oils into lower-boiling products, such as in particular gasoline. The halogen content should preferably be used for cracking of the catalyst are within the upper limits of the ranges mentioned, because these more halogen-containing catalysts are more effective at triggering decomposition reactions. Furthermore, the catalyst according to the invention can be used for hydrogenations including hydrogenation unsaturated aliphatic hydrocarbons, such as from monoolefins and diolefins to corresponding more highly saturated hydrocarbons, hydrogenation of unsaturated cyclic hydrocarbons, unsaturated Alcohols, ketones, acids and similar compounds can be used. Other implementations, in which these catalysts can be used are oxidations, such as oxidation from olefins to the corresponding oxides, e.g. B. Oxidation of ethylene to ethylene oxide, of Propylene to propylene oxide, the oxidation of alcohols and ketones. For reactions such as hydrogenation, Oxidation or condensation should preferably be the halogen content of the catalyst lie within the lower limits of the ranges mentioned in order to minimize side reactions impede.

However, the usefulness of the catalyst prepared according to the invention is particularly advantageous for reforming gasoline into a motor fuel with improved knock resistance. This reforming involves a number of chemical reactions, such as the dehydration of naphthenic hydrocarbons to aromatics, cyclization of straight-chain paraffins under Formation of aromatics, isomerization of paraffin hydrocarbons, regulated hydrocracking, d. H. a breakdown of long-chain hydrocarbon molecules in sections, but without the formation of gaseous hydrocarbons or hydrogen rearrangement. When using a catalyst prepared according to the invention, these can be Coordinate reactions to one another in a particularly favorable manner, and this makes one surprising achieve a high increase in the octane values of gasoline if one considers the halogen content of the Catalyst adjusts accordingly, while the platinum content can be extremely low and for example is only 0.1%.

Platinum hydrochloric acid is suitable for carrying out the catalyst preparation process, primarily hexachloroplatinum (IV) acid, also tetrachloroplatinum (II) acid, however, solutions of other platinum-containing compounds can also be used, such as such of ammonium platinum chloride, trimethylbenzylammonium platinum chloride, tetramine platinum chloride, ammonium platinum nitrate and dinitrodiaminoplatinum. ίο During the production of the artificial aluminum oxide In some cases it may be useful to add an organic acid. One special Acetic acid has shown a favorable influence on the catalyst in order to peptize the aluminum oxide and thereby bringing it into a better condition for union with the platinum. Also serves they partly serve to fix the platinum on the aluminum oxide, so that the migration of the platinum is minimized during the subsequent heating. The one to be used if necessary The amount of acetic acid is generally from about 0.05 to about 0.5 moles of acetic acid per mole Aluminum oxide.

Aluminum oxide represented in the above manner After washing and filtering, it is usually mixed with water to a paste. If the halogen is added separately, this is preferably done in this stage of the catalyst preparation, d. H. before the platinum is mixed with the aluminum oxide. The halogen can be added in any suitable manner, however, the halogen should be added in a form which easily mixes with the aluminum oxide implements to get the desired results, and there should also be no unwanted deposits left in the catalyst. It is therefore appropriate to use the halogen in the form an acid such as hydrogen fluoride and / or hydrogen chloride to be added. In particular, will Fluorine added as an aqueous solution of hydrogen fluoride to facilitate handling and to regulate the amount to be added. Another suitable source for the addition of the halogen is in a volatile salt such as ammonium chloride. The ammonium ions are during the following Heating removes the catalyst and therefore does not leave any unwanted deposits in this. In another mode of operation, the halogen can be elemental, e.g. B. as fluorine added will; in view of the fact that fluorine and chlorine are normally gases, it is convenient to use them to use in the form of a solution for easier handling.

The total halogen content in the finished catalyst is 0.1 to 8% of the dry weight of the Alumina. The fluorine appears to be more active and therefore only 0.1 to 3% related on the dry weight of the alumina required. The chlorine content is preferably 0.2 to 8% 0.5 to 5% of the dry weight of the aluminum oxide. Amounts of halogen below these lower Limits do not provide the desired improvement and, on the other hand, halogen concentrations affect Above the upper limits, the selectivity of the catalyst is disadvantageous, as this Side reactions occur to a greater extent than desired.

After the aluminum oxide and the halogen have been intimately mixed, the platinum solution can can be added. A preferred mode of operation is to form a separate solution of Platinum hydrochloric acid in water and introduction of hydrogen sulfide into this solution Room temperature until the platinum hydrochloric acid solution assumes a constant color has, d. H. no color change occurs when further hydrogen sulfide is added. Normally the platinum hydrochloric acid solution is pale yellow and evidently takes gas with formation when hydrogen sulfide is introduced one or more chemical complex compounds turns dark brown in color. The best results were obtained by bubbling in the hydrogen sulfide at room temperature. the Initiation at an elevated temperature of e.g. B. 80 ° C apparently provides less favorable catalysts. The brown solution of platinum hydrochloric acid and hydrogen sulfide can then be mixed with the pulp from moist aluminum oxide gel are intimately mixed at room temperature.

The platinum hydrochloric acid solution the pulp of halogenated! Alumina gel was added and then hydrogen sulfide was passed into the mixture will. It has been shown that the hydrogen sulfide at room temperature or an increased Temperature of 8o ° C can be fed.

In some cases, satisfactory resultant catalysts can thereby be produced that the platinum hydrochloric acid solution with the slurry of the halogen-containing aluminum oxide gel mixed and the mass is then dried and heated without adding hydrogen sulfide will. However, experiments have shown that the addition of hydrogen sulfide is preferable because it works to make the platinum stronger in the form of an insoluble compound on the aluminum oxide to fix, so that the platinum compound is not no can hike. In general, the best results are obtained when using the platinum solution the aluminum oxide is brought together before this is significantly heated or dehydrated will.

After the alumina has been impregnated with the platinum solution, the mixture is preferably at a temperature of about 95 to about 205 ° C or more up to about 300 ⁰ C for about 4 to 24 hours or longer dried. In some cases it is convenient to prepare the catalyst in the form of pills of the same size and shape, e.g. B. the partially dried catalyst together with a suitable lubricant such as stearic acid, resin, hydrogenated coconut oil or graphite, in a suitable tabletting device

is deformed. Pills of about 3 x 3 mm to 6.5 x 6.5 mm or more are particularly useful. In some cases, however, it may also be appropriate to use the catalyst as a powder or grains more irregularly Size and shape to use.

The catalyst is preferably calcined ^{at about 425 to about 650 °} C. for about 2 to 8 hours or more. Also the catalyst with hydrogen or a hydrogen containing gas is about 4 to 12 hours or more can be reduced at about 150 to about 315 ⁰ C, may preferably followed by calcination at about 425 connects to about 650 ⁰ C. In another procedure, the catalyst can be reduced with hydrogen or a hydrogen-containing gas for about 2 to 10 hours or more at a temperature of about 425 to about 65 ° C.

In some cases, the lubricant can be removed during the high temperature heating.

In other cases, e.g. B. when using graphite, the separate stage of high temperature heating can be used omitted, and the effective heat treatment of the catalyst can be done in one plant for the treatment of hydrocarbons before or during such treatment.

Although the catalyst according to the invention has a long service life, it may be necessary to replace the catalyst after prolonged periods of use, e.g. B. by treatment with air or other oxygen-containing gas, to revive it in order to separate carbon-containing deposits. Generally, the regeneration temperature should preferably not exceed about 650 ⁰ C. In some cases it can be useful to follow the oxidation with a treatment with a hydrogen-containing gas at about 370 to about 595.degree.

example 1

An aluminum hydroxide prepared by adding aluminum hydroxide to aluminum chloride hexahydrate (181 g AlCl ₃ · 6 H ₂ O) was washed very carefully in order to reduce its chlorine content to below 0.1% of the dry weight. This washing process comprised six separate washes with large amounts of water containing a small amount of ammonium hydroxide (each 1250 cm ³ H ₂ O + 7.5 cm ³ NH ₄ OH), and finally an additional wash with pure water (1250 cm ³ ). The washed aluminum oxide was impregnated with a 4.8% strength aqueous hydrogen fluoride solution (13.2 g) so that the finished catalyst contained 1.5% by weight of fluorine. Hydrogen sulfide was passed through an aqueous solution of platinum hydrochloric acid _{(0.108 g H 2 PtCl 6} · 6 H ₂ O in 25 g H ₂ O) at room temperature until the solution had a constant dark brown color. This resulting solution was added to the fluorine-containing aluminum oxide, so that a finished catalyst with 0.1 percent by weight of platinum, based on dry matter, was produced. This mass was then ^{dried at 150 °} C. for 17 hours and then reduced with hydrogen ^{at 500 °} C. for 3 hours.

Example 2

An aluminum hydroxide formed by adding ammonium hydroxide (581 g of a 28% strength aqueous solution of NH ₄ OH) to aluminum chloride hexahydrate (724 g AlCl ₃ · 6 H ₂ O in 1500 cm ³ H ₂ O) was washed 4 times with water, each time 1600 cm ³ water with 10 cm ³ NH ₄ OH were used to selectively retain chlorine in the aluminum hydroxide in this way. The washed aluminum hydroxide gel was intimately mixed with a solution of platinum hydrochloric acid (0.434 g of H ₂ PtCl ₆ · 6H ₂ O in 300 cm ^{3 of} H ₂ O) with a small amount of glacial acetic acid (20 cm ³ ) and hydrogen sulfide was passed ^{through the mixture at 60 °} C. until it was saturated directed. The mixture was then heated 17 hours dried and closing borrowed for 3 hours at 500 ⁰ C at about 150 ⁰ C. The resulting catalyst contained approximately 3.5 percent by weight chlorine and 0.1 percent by weight platinum.

Claims (4)

PATENT CLAIMS: 8S 1. Process for the production of platinum-on-aluminum oxide catalysts for the conversion of hydrocarbon compounds by soaking aluminum oxide with the solution go a platinum compound and subsequent annealing, optionally in the presence of Hydrogen, characterized in that the solution in an amount that the finished Catalyst a content of 0.01 to 1 percent by weight Platinum granted as the only catalyst metal, and a halogen-containing aluminum oxide used, obtained by treating aluminum oxide with a halogen or a platinum-free halogen compound and after annealing 0.1 to 3 percent by weight of fluorine and / or 0.2 to 8 percent by weight Chlorine and a maximum total halogen content of 8 percent by weight, based on the Aluminum oxide as a dry substance. 2. The method according to claim 1, characterized in that there is used a substrate formed of an aluminum salt of aluminum oxide and the final catalyst annealed at about 425-650 ⁰ C. 3. The method according to claim 2, characterized in that an aluminum oxide is used, that by treating an alumina gel formed from aluminum chloride with one formed by washing out chlorine ions with ammonia-containing water, reduced chlorine content of less than 0.1 percent by weight, based on dry aluminum oxide, with an aqueous solution of hydrogen fluoride or hydrogen chloride has been obtained. 4. Departure according to claim 2 or 3, characterized characterized in that the halogen-containing aluminum oxide with platinum hydrochloric acid solution soaks and introduces hydrogen sulfide into the resulting mixture or first into the platinum hydrochloric acid solution for other 709 752/4 near room temperature introduces hydrogen sulfide, then the aluminum oxide with this Solution soaks and the products obtained in both cases glow. Considered publications:
French patent specification No. 814712, 760, 921 021; French additional patents No. 46816 (Addition to French patent specification No. 781543), 44 183 (addition to French patent specification No. 750 296);
British Patent Nos. 467470, 452095, U.S. Patents Nos. 2319452, 2403375, 2184235, 2411726, 2255399, 2336165, 2437531. 2 411 829, 2317683, 2428741, 1938452, 2045794; Gmelin's manual of the inorganic. Chemie, 8th Edition, 1939, Part C, Platin, pp. 104 and 105. O 709 752/4 1.68