DE102009018109A1 - Preparation of a supported silver (Ag)/palladium (Pd) catalyst, useful for hydrogenation of acetylenic hydrocarbons (acetylene or propylene), comprises providing a Ag/Pd mixed oxide, and applying the mixed oxide on a catalyst support - Google Patents

Abstract

Preparation of a supported silver (Ag)/palladium (Pd) catalyst (I) comprises providing a Ag/Pd mixed oxide, and applying the mixed oxide on a catalyst support. Independent claims are included for: (1) the Ag/Pd catalyst obtained by the above method; and (2) an Ag/Pd catalyst precursor comprising a catalyst support, which is coated with Ag/Pd mixed oxide.

Description

The The present invention relates to a process for producing a supported Ag / Pd catalyst, one by the method available Ag / Pd catalyst, a precursor of an Ag / Pd catalyst as well as the use of the precursor in the preparation of a supported Ag / Pd catalyst.

ethylene and propylene are important monomers for the preparation of plastics, such as polyethylene or polypropylene. Ethylene and propylene are mainly derived from petroleum and petroleum products by thermal or catalytic cracking of long-chain hydrocarbons won. The ethylene and propylene obtained from the cracking process However, it contains an undesirably high proportion on acetylenic compounds, such as acetylene or propyne, which may adversely affect the ethene or propene polymerization. Before using the ethylene or propylene, this must therefore be largely freed of acetylenic compounds.

For For example, the polymerization of ethylene must be the acetylene concentration be reduced to a value below 5 ppm. This will be the acetylene is usually hydrogenated selectively to ethylene. To catalyst and hydrogenation are placed high demands. On the one hand the acetylene must be as complete as possible by reaction to ethylene On the other hand, the hydrogenation of ethylene has to be removed Ethan can be prevented. To ensure this, will the hydrogenation is carried out within a temperature range, by the so-called "clean-up" temperature and limited the so-called "runaway" temperature becomes. Under the "clean-up" temperature is in the understood context the temperature, starting from the one significant hydrogenation of acetylene to ethylene is observed, under the "runaway" temperature the temperature, in which a significant hydrogenation of ethylene to ethane begins. The temperatures mentioned can be determined by, for example the hydrogen consumption of a defined gas mixture, the acetylene, Contains ethylene and hydrogen, depending is measured by the temperature.

When Catalysts for the selective hydrogenation of acetylene to ethylene in hydrocarbon streams become predominant Palladium-shell catalysts used which contain silver as a promoter. The palladium and the silver are on an inert temperature-resistant Deposited carrier material. The preparation of these catalysts is carried out in such a way that suitable salts of palladium and the Silver, for example, palladium nitrate or silver nitrate, in the form aqueous solutions on a support material be applied. The impregnation can be in separate Steps with a solution of the palladium compound and a solution of the silver compound. But it is also possible, the solution of the palladium compound and the solution of the silver compound simultaneously in one apply individual impregnation step to the carrier. there it may be preferable to use a single solution in which dissolved both the palladium and the silver compound are included. The impregnated carrier will then for the transfer of palladium in palladium oxide or the silver calcined in silver oxide and then optionally one Reduction to convert the catalyst into the active form. In the reduction, the palladium and silver become the oxidation state 0 transferred. The reduction can for example also be carried out in situ in the reactor.

DE 31 19 850 A1 describes a process for the selective hydrogenation of a diolefin having at least 4 carbon atoms in a hydrocarbon mixture. The hydrogenation is carried out with hydrogen over a catalyst containing palladium and silver. The weight ratio of the catalyst from silver to palladium is 0.7: 1 to 3: 1. The catalyst is prepared by co-impregnating a support with an aqueous solution of palladium and silver salts.

US 5,648,576 A describes a process for the selective gas phase hydrogenation of acetylenic hydrocarbons (C ₂ -C ₃ ) in the corresponding ethylenic hydrocarbons. The catalyst is produced by co-impregnating the support with an aqueous solution of corresponding metal salts.

EP 0 064 301 A1 discloses a catalyst for the selective gas phase hydrogenation of acetylene. The preparation of the catalyst is carried out by a two-stage application of palladium and silver.

EP 0 780 155 A1 describes the preparation of hydrogenation catalysts using solutions of palladium nitrate and silver nitrate in a nitrogen-containing acid for the impregnation of the carrier.

It there is a need, selectivity and activity of Ag / Pd catalysts in the hydrogenation of acetylenic hydrocarbons continue to improve.

task It is therefore an object of the present invention to provide a method can be obtained with the supported Ag / Pd catalyst, which is characterized by a relatively high Selectivity and activity in the hydrogenation Distinguish acetylenic hydrocarbons.

• – Bereitstellen eines Ag/Pd-Mischoxids;
• – Auftragen des Ag/Pd-Mischoxids auf einen Katalysatorträger.

This object is achieved by a method for producing a supported Ag / Pd catalyst comprising the steps

• Providing an Ag / Pd mixed oxide;
• - Applying the Ag / Pd mixed oxide on a catalyst support.

It could be shown that by means of the invention Process-supported Ag / Pd catalysts are produced can be characterized by a relative high selectivity and activity in the hydrogenation Distinguish acetylenic hydrocarbons.

In the process according to the invention is an Ag / Pd mixed oxide applied to a catalyst support. In contrast to impregnation methods known from the prior art using appropriate metal salt solutions has the use of mixed oxide in the use of porous Bear the advantage that this is not in the carrier penetrates, but rather on the outer surface the carrier remains. Accordingly, on procedural terms simple way, namely about the amount of applied Mixed oxide, the thickness of the resulting catalytically active layer adjusted become. For example, can be by means of the invention Procedure by a small order quantity on mixed oxide relatively thin produce catalytically active layers, thereby increasing the selectivity of the catalyst can be further increased.

The improved selectivity and activity by means of of the process according to the invention produced Ag / Pd catalysts is probably u. a. on one compared to conventional prepared Ag / Pd catalysts improved mixing of Attributed to Ag and Pd.

The to be used in the process according to the invention Mixed oxide is preferably a binary mixed oxide, i. H. a mixed oxide, in addition to Ag and Pd to usual impurities contains no further metals. In this context it is further preferred that in the mixed oxide Ag and Pd in the oxidation state +1 or +2 are present.

• – x eine Zahl größer 0 ist;
• – y eine Zahl größer 0 ist;
• – das Verhältnis von x zu y 2,1 bis 3 beträgt;
• – z eine Zahl ist, die eine derartige Größe aufweist, dass das Mischoxid elektroneutral ist.

According to a preferred embodiment of the method according to the invention, it is provided that the Ag / Pd mixed oxide of the general formula (I) Ag _x Pd _y O _z (I) is enough, in which

• - x is a number greater than 0;
• - y is a number greater than 0;
• The ratio of x to y is 2.1 to 3;
• Z is a number having a size such that the mixed oxide is electroneutral.

According to one further preferred embodiment of the invention Procedure, it is provided that the ratio of x to y is 2.3 to 2.6.

With obtainable by the process according to the invention Ag / Pd catalysts are characterized by an Ag / Pd atomic ratio from 2.3 to 2.6 by a relative high selectivity and activity the hydrogenation of acetylenic hydrocarbons. Therefore it is inventively preferred that in the to be used mixed oxide, the ratio of x to y 2.3 to 2.6.

Corresponding a further preferred embodiment of the invention Method is provided that the Ag / Pd mixed oxide is amorphous.

Ag / Pd mixed oxides with different Ag / Pd atomic ratio fall in the Precipitation from aqueous solution in amorphous Shape. A crystallization of the mixed oxides is only by consuming measures possible. The mixed oxide in amorphous form is thus less expensive, why by means of the same comparatively inexpensive Ag / Pd catalysts can be prepared. Corresponding is it according to a further preferred embodiment the process of the invention provided that the Ag / Pd mixed oxide in amorphous form in the inventive Method is used.

The Ag / Pd mixed oxide to be used in the process of the present invention can be prepared (at any Ag / Pd atomic ratio), for example, by dissolving appropriate amounts of Ag (NO ₃ ) and Pd (NO ₃ ) ₂ in water containing nitric acid and from this solution the mixed oxide is precipitated by means of an aqueous alkali or alkaline earth metal hydroxide solution.

According to one further preferred embodiment of the invention Method is provided that the application of the Ag / Pd mixed oxide on the catalyst support by means of a suspension of Ag / Pd mixed oxide takes place. As suspending agent may in principle any pure solvent or solvent mixture used, the expert for the purpose of the invention is known as suitable. For cost reasons and from ecological However, water is preferred as the suspending agent.

According to a further preferred embodiment of the method according to the invention, it is provided that the proportion of the suspension of Ag / Pd mixed oxide is from 0.01% by weight to 0.1% by weight. This will make the production of relatively ig thin catalytically active layers with relatively uniform thickness procedurally simple guaranteed.

According to one further preferred embodiment of the invention Method, the method further comprises drying the with the Ag / Pd mixed oxide suspension loaded catalyst support.

The Drying may occur after application of the Ag / Pd mixed oxide suspension carried out on the catalyst support or already during the application of the suspension. One Dry already during the application of the suspension is inventively preferred because such a bleeding the applied suspension is avoided and accordingly catalytically active layers with relative uniform layer thickness can be obtained. The drying after the application of the suspension can, for example be carried out by means of a furnace, the dry during the order by placing the suspension on a heated support is applied. The drying temperature is preferably in the Range of 25 ° C to 120 ° C, especially in the range from 40 ° C to 100 ° C.

According to one further preferred embodiment of the invention Method, the method further comprises the transfer the metal components of the Ag / Pd mixed oxide in the oxidation state 0th

The conversion of the metal components of the Ag / Pd mixed oxide into the oxidation state 0 serves to activate the catalyst and can be carried out by conventional means known to those skilled in the art. According to the invention, the conversion into the oxidation state 0 is preferably carried out in situ or ex situ at a temperature of 100 ° C. to 250 ° C. by means of a reducing gas, preferably by means of a gas mixture of hydrogen and an inert gas, preferably N ₂ .

Corresponding a further preferred embodiment of the invention Procedure, the application of the Ag / Pd mixed oxide suspension on the catalyst support by adding the catalyst support is sprayed with the suspension. This will be a special uniform application of the mixed oxide to the carrier guaranteed.

According to one further preferred embodiment of the invention Procedure, it is provided that the Ag / Pd mixed oxide suspension on the catalyst support is applied by adding the suspension sprayed into a fluidized bed of catalyst supports is, preferably in a fluidized bed, in which the catalyst support orbiting on an elliptical or toroidal path. This can a variety of catalyst units with a substantially uniform Layer thickness of the catalytically active layer to be applied simultaneously getting produced.

In order to produce the fluidized bed, it is further preferred according to the invention to use a device which is set up to produce a fluidized bed of a particulate material by means of a gas, the particles of the material moving in an elliptical or toroidal path in the fluidized bed. Such devices are for example in the documents WO 2006/027009 A1 . DE 102 48 116 B3 . EP 0 370 167 A1 . EP 0 436 787 B1 . DE 199 04 147 A1 . DE 20 2005 003 791 U1 whose contents are incorporated by referencing in the present invention. In such devices, the suspension of Ag / Pd composite oxide is sprayed into a fluidized bed of catalyst supports, with the catalyst supports in the fluidized bed orbiting elliptically or toroidally. According to the invention particularly preferred devices are those Innojet Technologies, stones, Germany, which are sold under the names Innojet ^® Ventilus or Innojet ^® AirCoater.

Corresponding a further preferred embodiment of the invention Process, it is provided that the catalyst support heated during the application of the Ag / Pd mixed oxide suspension is, preferably to a temperature of more than 40 ° C, more preferably at a temperature of more than 50 ° C and especially preferably at a temperature of more than 60 ° C. The upper temperature limit is preferably less than 150 ° C and more preferred less than 100 ° C.

is the catalyst support during application of the Ag / Pd mixed oxide suspension heats, so volatilized the suspending agent is relatively fast, thereby avoiding bleeding of the applied suspension and correspondingly the formation of a catalytically active layer with relatively uniform Layer thickness is favored. Will the Ag / Pd mixed oxide suspension applied to a fluidized bed of catalyst supports, Thus, the catalyst support by means of heated Process gas, which is the generation of fluid bed condition the carrier serves to be tempered. This can be a continuous drying of the carrier over the throughout the period of the suspension job What makes the formation of catalytically active layers with particularly uniform Layer thickness favors.

According to one further preferred embodiment of the invention Process, it is provided that the catalyst support is formed as a shaped body.

Especially with regard to the preparation of Ag / Pd shell catalysts the catalyst support is preferred as a shaped body educated. The formed as a shaped body catalyst support can in principle have any shape that the expert suitable for the purpose of the invention is known. For example, the catalyst support as sphere, cylinder, perforated cylinder, trilobus, tetralobus, tablet, Torus or ring, star, cartwheel, inverse cartwheel or as a strand be educated. However, it is preferred according to the invention that the shaped body is formed as a tablet or ring.

Corresponding a further preferred embodiment of the invention Process it is envisaged that the supported Ag / Pd catalyst an Ag / Pd shell catalyst and that the invention A method according to the step of recovering the Ag / Pd shell catalyst includes.

According to one further preferred embodiment of the invention Procedure, it is provided that the molded body a maximum Dimension of 1 mm to 25 mm, preferably a maximum Dimension from 2 mm to 10 mm.

According to one further preferred embodiment of the invention Procedure, it is provided that the shaped body as a tablet is formed, preferably with a dimension of 3 × 3 mm to 5 × 5 mm.

According to a further preferred embodiment of the method according to the invention, it is provided that the catalyst support is formed from Al ₂ O ₃ . Al ₂ O ₃ is largely inert with respect to the hydrogenation reaction of acetylenes.

In principle, any material which is known to the person skilled in the art for the purpose according to the invention can be used as the catalyst support in the process according to the invention. It is crucial that the carrier material is substantially or completely inert with respect to the hydrogenation reaction of acetylenes. According to the invention it is preferred that the catalyst support consists of Al ₂ O ₃ or steatite.

According to one further preferred embodiment of the invention Process, it is provided that the Ag / Pd mixed oxide has an average particle size from 0.5 μm to 20 μm.

If the mean particle size of the mixed oxide in the range is from 0.5 microns to 20 microns, is a relatively good adhesion of the mixed oxide and the resulting catalytic active layer on the support and a slight abrasion of the same guaranteed as well as a protrusion largely avoided. Accordingly, the mixed oxide according to the invention is preferred a mean particle size of 0.5 microns to 20 microns, more preferably an average particle size from 1 μm to 18 μm and more preferably one average particle size from 3 μm to 10 μm.

The Determination of the average particle size takes place Preferably according to the invention by means of laser diffraction methods with a Fritsch Particle Sizer Analysette 22 Economy (Fa. Fritsch, DE) according to the instructions of the manufacturer also regarding the Sample pretreatment, wherein the sample in deionized water without Addition of auxiliaries homogenized and sonicated for 5 minutes is treated.

According to a further preferred embodiment of the method according to the invention, it is provided that a binder is contained in the suspension, wherein as a binder preferably a sol, preferably an Al ₂ O ₃ sol, a TiO ₂ sol, a ZrO ₂ sol and / or a SiO ₂ sol is used, particularly preferably an Al ₂ O ₃ sol. If a binder is present in the suspension, relatively good adhesion of the Ag / Pd mixed oxide to the catalyst support and relatively high mechanical stability of the applied Ag / Pd mixed oxide layer and the resulting catalytically active layer are achieved. In addition, the porosity of the catalytically active layer can be adapted to the respective requirements via the type and amount of the binder.

The The present invention further relates to a supported one Ag / Pd catalyst, available according to the inventive method. The inventive Catalyst comprises a catalyst support, preferably coated with a layer containing Ag and Pd.

One according to the invention Process obtainable Ag / Pd catalyst has a relatively high selectivity and activity in the hydrogenation acetylenic hydrocarbons.

According to one preferred embodiment of the invention Catalyst it is provided that the Ag / Pd layer of the catalyst has a layer thickness of 3 microns to 50 microns, more preferably a layer thickness of 5 microns to 30 microns and particularly preferably a layer thickness of 10 μm to 20 μm. If the catalyst of the invention has a Layer thickness in the aforementioned interval, so this is by a relatively high selectivity characterized in the hydrogenation of acetylenes in comparatively high activity.

According to a further preferred embodiment of the catalyst according to the invention it is provided that the catalyst support is open-pore and the inner surface of the support is free or substantially free of Ag and Pd. Accordingly, the noble metals are substantially only or only on the outer surface of the catalyst support.

The The present invention further relates to an Ag / Pd catalyst precursor, in particular for the production of an inventive Catalyst comprising a catalyst support, wherein the catalyst support is coated with an Ag / Pd mixed oxide. The Ag / Pd catalyst precursor according to the invention is preferably by means of the invention Process produced. The precursor can be through the transfer of Ag and Pd in the oxidation state 0 are activated.

Corresponding a preferred embodiment of the invention Ag / Pd catalyst precursor has the Ag / Pd mixed oxide coating Layer thickness of 3 microns to 50 microns, more preferably a layer thickness of 5 microns to 30 microns and especially preferably a layer thickness of 10 microns to 20 microns.

According to one further preferred embodiment of the invention Precursor is provided that the catalyst support is porous and the inner surface of the carrier is free or substantially free of the Ag / Pd mixed oxide. Corresponding the mixed oxide is essentially only or only on the outside Surface of the catalyst carrier.

Corresponding a further preferred embodiment of the invention Ag / Pd catalyst precursor is in the Ag / Pd mixed oxide coating contain a binder.

The The present invention further relates to the use of a method according to the invention Ag / Pd catalyst precursor in the preparation of a supported Ag / Pd catalyst, in particular an inventive Ag / Pd catalyst.

The The following examples serve to explain the invention.

Example 1: Preparation of an Ag / Pd mixed oxide

255 mmol of commercially available silver nitrate and 100 mmol of commercially available Palladium (II) nitrate was immersed in 40 ml of deionized water Add 1 ml of concentrated nitric acid (65%). By adding 40 ml of a 5 molar potassium hydroxide solution to the solution of the precious metals became a black solid like, which was filtered off. The filter cake was washed with deionized water to neutrality and then for a period of 12 hours Dried at 20 ° C in the air. The black obtained in this way Ag / Pd mixed oxide is (X-ray) amorphous while both analogous precipitated silver oxide and palladium oxide crystalline is.

Example 2: Preparation of an Ag / Pd mixed oxide

245 mmol of commercially available silver nitrate and 100 mmol of commercially available Palladium (II) nitrate was immersed in 40 ml of deionized water Add 1 ml of concentrated nitric acid (65%). By adding 40 ml of a 5 molar potassium hydroxide solution to the solution of the precious metals became a black solid like, which was filtered off. The filter cake was washed with deionized water to neutrality and then for a period of 12 hours Dried at 20 ° C in the air. The black obtained in this way Ag / Pd mixed oxide is (X-ray) amorphous.

Example 3: Preparation of an Ag / Pd mixed oxide

235 mmol of commercially available silver nitrate and 100 mmol of commercially available Palladium (II) nitrate was immersed in 40 ml of deionized water Add 1 ml of concentrated nitric acid (65%). By adding 40 ml of a 5 molar potassium hydroxide solution to the solution of the precious metals became a black solid like, which was filtered off. The filter cake was washed with deionized water to neutrality and then for a period of 12 hours Dried at 20 ° C in the air. The black obtained in this way Ag / Pd mixed oxide is (X-ray) amorphous.

Example 4: Preparation of an Ag / Pd catalyst

On 95 g of commercial Al ₂ O ₃ tablets (size: 4.5 mm × 4.5 mm) were 200 ml of an aqueous suspension containing 0.21 g of Ag / Pd mixed oxide according to Example 1 and 1.05 g of an aluminum oxide sol as a binder (Nyacol AL20; solid content: 20 wt .-%) in a fluidized bed coater (type: Innojet ^® Aircoater 25; company: Innojet Herbert Hüttlin, Steinen, Germany) at a temperature of 70 ° C over a period of 1 h applied by spraying.

The thus obtained, loaded catalyst carrier tablets were to transfer the silver and palladium in the oxidation state 0 at a temperature of 200 ° C with a mixture of 5 vol .-% hydrogen treated in nitrogen. The catalyst thus prepared contained 295 ppm Pd and 610 ppm Ag (determined by ICP (Ionic Coupled Plasma)).

Example 5:

The catalyst prepared according to Example 4 tor was tested in the hydrogenation of acetylene. The hydrogenation of acetylene to ethene started at 50.5 ° C and the hydrogenation of ethene to ethane at 53 ° C.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3119850 A1 [0005]
• US 5648576A [0006]
• EP 0064301 A1 [0007]
• - EP 0780155 A1 [0008]
• WO 2006/027009 A1 [0030]
• - DE 10248116 B3 [0030]
• EP 0370167 A1 [0030]
• EP 0436787 B1 [0030]
• DE 19904147 A1 [0030]
• - DE 202005003791 U1 [0030]

Claims (13)

Process for the preparation of a supported Ag / Pd catalyst, full Providing an Ag / Pd mixed oxide; - Instruct of the Ag / Pd mixed oxide on a catalyst support. A method according to claim 1, characterized in that the Ag / Pd mixed oxide of the general formula (I) Ag _x Pd _y O _z (I) is sufficient, in which - x is a number greater than 0; - y is a number greater than 0; The ratio of x to y is 2.1 to 3; Z is a number having a size such that the mixed oxide is electroneutral. Method according to one of the preceding claims, characterized in that the method further comprises - Transfer the metal components of the Ag / Pd mixed oxide in the oxidation state 0th Method according to one of the preceding claims, characterized in that the application of the Ag / Pd mixed oxide on the catalyst support by means of a suspension of Ag / Pd mixed oxide takes place. Method according to claim 4, characterized in that that the application of the Ag / Pd mixed oxide suspension on the catalyst support takes place by the catalyst support with the suspension is sprayed. Method according to one of the preceding claims, characterized in that the catalyst carrier as Shaped body is formed. Method according to one of the preceding claims, characterized in that the mixed oxide has an average particle size from 0.5 μm to 20 μm. Method according to one of claims 4 to 7, characterized in that in the suspension a binder is included. Method according to claim 8, characterized in that that the binder is a sol. Ag / Pd catalyst, available after one Method according to one of the preceding claims. Ag / Pd catalyst precursor comprising a catalyst support, wherein the catalyst carrier with an Ag / Pd mixed oxide is coated. Precursor according to Claim 11, characterized in that the Ag / Pd mixed oxide coating contains a binder is. Using an Ag / Pd catalyst precursor after one of the preceding claims in the production a supported Ag / Pd catalyst.