DE102007043447A1 - Catalyst carrier, useful e.g. in the synthesis of vinyl acetate monomer, comprises an open-porous matrix formed from a material containing natural silicate layer, where elementary carbon is distributed in the matrix - Google Patents

Abstract

Catalyst carrier preferably useful in the synthesis of vinyl acetate monomer, comprises an open-porous matrix, which is formed from a material containing natural silicate layer, preferably from an acid-treated calcinated bentonite containing material, where elementary carbon is distributed in the matrix. Independent claims are included for the preparations of the catalyst carrier comprising either mixing the powder form natural silicate layer, preferably acid treated calcinated or non-calcinated bentonite with powder form graphite or a graphitizable material; forming a body from the obtained mixture or applying the obtained mixture on the carrier structure; calcinating the mixture, when the mixture contains the natural silicate layer and graphite; and graphitizing the graphitizable material contained in the mixture, when the mixture contains the natural silicate layer and the graphitizable material; or providing the natural silicate layer, preferably acid treated calcinated or non-calcinated bentonite, incorporating a carbonizable chemical compound between the silicate layers; and carbonizing the chemical compound.

Description

The The present invention relates to a catalyst carrier, especially for use in the synthesis of vinyl acetate monomer (VAM), comprising a natural phyllosilicate.

VAM is an important monomer building block in the synthesis of plastic polymers. The main application areas of VAM are u. a. the production of Polyvinyl acetate, polyvinyl alcohol and polyvinyl acetal and the Co- and terpolymerization with other monomers such as Ethylene, vinyl chloride, acrylate, maleate, fumarate and vinyl laurate.

VAM is predominantly in the gas phase of acetic acid and ethylene produced by reaction with oxygen, wherein the preferably used for this synthesis catalysts Pd and Au as active metals and an alkali metal component as a promoter, preferably potassium in the form of the acetate. In the Pd / Au system These catalysts are probably the active metals Pd and Au not in the form of metal particles of the respective pure metal but rather in the form of Pd / Au alloy particles of possibly different composition, although the Presence of unalloyed particles can not be excluded can. Alternatively to Au, for example, Cd or Ba as the second Be used active metal component.

At present, VAM is predominantly produced by means of so-called shell catalysts in which the catalytically active metals of the catalyst do not completely penetrate the catalyst support designed as a shaped body, but rather are contained only in a more or less wide outer region (shell) of the catalyst support molding (cf. For this EP 565 952 A1 . EP 634 214 A1 . EP 634 209 A1 and EP 634 208 A1 ), while the more interior areas of the catalyst support are almost free of active metal. With the aid of coated catalysts, a more selective reaction is possible in many cases than with catalysts in which the catalyst support is impregnated into the carrier core with the active components ("impregnated").

The shell catalysts known in the prior art for the preparation of VAM can be, for example, catalyst supports based on silicon oxide, aluminum oxide, aluminosilicate, titanium oxide or zirconium oxide (cf. EP 839 793 A1 . WO 1998/018553 A1 . WO 2000/058008 A1 and WO 2005/061107 A1 ). However, catalyst supports based on titanium oxide or zirconium oxide are currently barely used, since these catalyst supports are not long-term stable or relatively expensive with respect to acetic acid.

The majority of currently used catalysts for the preparation of VAM are shelled catalysts with a Pd / Au shell on a porous amorphous, formed as a ball aluminosilicate on the basis of natural phyllosilicates in the form of natural acid-treated calcined bentonites, which are impregnated with potassium acetate as a promoter , The catalyst carrier used here is predominantly a spherical carrier with the designation "KA-160" from SÜD-Chemie AG based on acid-treated calcined bentonites as natural layered silicate, which has a BET surface area of about 160 m ² / g.

The selectivities of VAM achieved by means of the known in the prior art VAM shell catalysts based on Pd and Au as active metals and KA-160 supports as catalyst support are about 90 mol .-% based on the supplied ethylene, wherein the remaining 10 mol .-% of the reaction products are essentially CO ₂ , which is formed by total oxidation of the organic starting materials / products.

The VAM synthesis predominantly occurs in so-called tube bundle reactors instead, in which a plurality of tubes aligned parallel to each other are arranged. The tubes are filled with the VAM catalyst and for VAM synthesis, the gaseous starting materials by passed the catalyst bed. In the VAM synthesis using ethene, acetic acid and oxygen as Educts are a relative strong exothermic reaction whose heat is dissipated must be in order to avoid the formation of so-called hot-spots (hotter Places) and a concomitant reduction in selectivity to counteract VAM. These are the pipes with a cooling medium flows around. Decisive for an efficient heat dissipation in the reaction in question is not only the provision of an efficient cooling system, but also ensuring an effective one Heat conduction from the reaction environment to the tube surface.

The predominantly used in the VAM synthesis due to its excellent chemical resistance "KA-160" carrier has a relatively limited thermal conductivity, which for a certain proportion of VAM selectivity loss is the cause.

task Therefore, it is the object of the present invention to provide a natural one To provide layer silicate comprising catalyst support, especially for use in the synthesis of VAM, the has improved thermal conductivity.

These Task is solved by a catalyst carrier, comprising an open-pore matrix, which consists of a natural one Layered silicate-containing material is formed, in particular from an acid-treated calcined bentonite containing material, wherein in the matrix elemental carbon is distributed.

The The present invention thus relates to a catalyst support with an open-pored matrix that turns one into a natural one Phyllosilicate-containing material (matrix material) is formed, wherein contained in the matrix material elemental carbon is.

It has been found that the catalyst support according to the invention is characterized by a significantly improved thermal conductivity and therefore, for example, can dissipate the amounts of heat released in oxidation reactions more efficiently to the coolant surrounding the reactor. The catalyst support according to the invention can therefore contribute, for example in the VAM synthesis, to an increase in the VAM selectivity. The thermal conductivity of the catalyst support according to the invention is preferably in accordance with the standards DIN 52612 or DIN EN 12664 and DIN EN 12667 certainly.

About that In addition, it was found that the inventive Catalyst support despite the carbon content by a relatively high hardness as well chemical and thermal resistance is excellent and that of contained in the catalyst carrier elemental carbon does not adversely affect VAM synthesis.

Further allows the catalyst support of the invention due to its increased thermal conductivity, that catalysts whose high activity / heat development their use on conventional carrier oxides with low thermal conductivity forbids, now can be used in supported form.

About that In addition, the catalyst support according to the invention is characterized by a relatively low weight out.

The term "natural layered silicate", for which the term "phyllosilicate" is also used in the literature, is understood in the context of the present invention to be untreated or treated silicate mineral originating from natural deposits, in which SiO ₄ tetrahedron, which is the basic structural unit all silicates form, in layers of the general formula [Si ₂ O ₅ ] ^2- are cross-linked with each other. These tetrahedral layers alternate with so-called octahedral layers, in which a cation, especially Al and Mg, octahedrally surrounded by OH or O is. For example, a distinction is made between two-layer phyllosilicates and three-layer phyllosilicates. Phyllosilicates preferred in the context of the present invention are clay minerals, in particular kaolinite, beidellite, hectorite, saponite, nontronite, mica, vermiculite and smectites, with smectites and in particular montmorillonite being particularly preferred. Definitions of the term "sheet silicates" can be found, for example, in " Textbook of inorganic chemistry ", Hollemann Wiberg, de Gruyter, 102nd edition, 2007 (ISBN 978-3-11-017770-1) or in "Römpp Lexikon Chemie", 10th edition, Georg Thieme Verlag by the term "phyllosilicate." Typical treatments to which a natural layered silicate is subjected prior to use as a catalyst support material include, for example, acid treatment and / or calcining A particularly preferred natural sheet silicate in the present invention is a bentonite In the present case, therefore, in the case where the natural sheet silicate is a bentonite, it is to be understood that the natural sheet silicate in the catalyst support is in the form of or as part of a bentonite is present.

The catalyst support according to the invention can be prepared, for example, by grinding a pulverulent (uncalcined) acid-treated bentonite as phyllosilicate with powdered graphite with the addition of water and then intimately mixed to homogeneity, the resulting mixture under compression to give a shaped body by means familiar to the person skilled in the art, such as For example, extruders or tablet presses, is molded and then the uncured molded body is calcined to form a stable shaped body. The calcination is carried out at temperatures at which results in a solid structure. The size of the specific surface area (BET) of the catalyst support depends on this special on the quality of the (raw) bentonite used, the acid treatment process of the bentonite used, ie, for example, the nature and relative to bentonite and the concentration of the inorganic acid used, the acid treatment time and temperature, the compression pressure and the calcination and temperature and the calcination atmosphere.

Acid-treated bentonites can be obtained by treating bentonites with strong acids, such as sulfuric acid, phosphoric acid or hydrochloric acid. A definition of the term bentonite which also applies in the context of the present invention is given in Römpp, Lexikon Chemie, 10th ed., Georg Thieme Verlag , stated. Bentonites which are particularly preferred in the context of the present invention are natural aluminum-containing sheet silicates which contain montmorillonite (as smectite) as the main mineral in a proportion of 60-85% by mass. After the acid treatment, the bentonite is usually washed with water, dried and ground to a powder.

Around a sufficiently high mechanical stability of the invention To ensure catalyst support, it is according to a preferred embodiment provided that the proportion the matrix of natural layered silicate, in particular acid-treated calcined bentonite, at least 50 Mass .-% is, preferably at least 80 Mass .-%, preferably at least 90% mass%, more preferably at least 95 mass%, and especially preferably at least 99% by mass.

It could be found that the thermal conductivity the catalyst support according to the invention the higher the content, the higher the salary the catalyst support is of elemental carbon, being in terms of achieving a significant increase the thermal conductivity of the catalyst carrier preferred is when the content of the matrix of carbon at least 0.05 mass%, preferably at least 0.1 mass% based on the mass of the catalyst support. Indeed is the mechanical stability of the invention Catalyst carrier the lower, the higher its Carbon content is. According to a preferred embodiment it is envisaged that the proportion of the matrix of elemental carbon up to 50% by mass, preferably up to 20% by mass, preferably up to 10% by mass and more preferably up to 5% by mass. This measure can be a relatively high thermal conductivity of the catalyst support ensured with sufficiently high mechanical stability become.

In In the above context, it may further be preferred that the proportion of matrix of elemental carbon 0.05 to 30 mass% is preferably 0.1 to 20 mass% and preferred 0.15 to 5 mass%.

In order to the catalyst support according to the invention via its dimensions a largely uniform thermal conductivity It is further preferred that the elemental carbon is evenly distributed in the matrix, preferably distributed homogeneously.

Corresponding a further preferred embodiment of the invention Catalyst support it is envisaged that the carbon embedded between layers of the layered silicate. Through intercalation between layers of the layered silicate, the carbon is largely Shielded from carbon-degrading influences, so this measure the increased thermal conductivity of the catalyst carrier over proportionately guaranteed for long periods of time. The intercalation of the carbon between silicate layers, for example by means of Powder diffractometry can be detected. Probably the intercalated Carbon in amorphous form before or in the form of a single graphite plane (graphene layer) embedded between two silicate layers is.

alternative to an intercalation of the carbon between silicate layers it is according to another embodiment provided that the carbon is in the form of graphite particles, which are evenly distributed in the matrix are. Carbon in the form of graphite is characterized by a particularly high thermal conductivity, so with a relatively high low carbon content a desired thermal conductivity can be achieved. In addition, it could be shown that in the matrix of the catalyst support according to the invention contained graphite is characterized by a high thermal and chemical Resistance, which is why this measure increased the Thermal conductivity of the catalyst carrier over relatively long periods of time also under thermal and chemical guaranteed in demanding conditions. Further became found that the chemical and thermal resistance of the catalyst support the higher the crystallinity, the higher of graphite.

If, as described in one of the processes according to the invention, the catalyst support is prepared by calcining a mixture comprising a phyllosilicate and graphite, then it has in the catalyst Carrier contained graphite usually largely on the quality of the graphite used. On the other hand, when the catalyst carrier is prepared by graphitizing an organic compound, the carbon material contained in the resulting carrier is usually a mixture of graphite and amorphous carbon which still contain hydrogen to some degree. It is preferred if the carbon material contains more than 80% by weight of graphite, less than 10% by mass of amorphous carbon and less than 10% by mass of hydrogen.

It may also be preferred that part of the carbon between Layers of the layered silicate intercalated and the other part in Form of graphite particles is distributed in the matrix.

It it was found that the thermal conductivity of the catalyst support according to the invention its uniformity is even, the smaller the graphite particles are, the use being nanoparticulate Graphits essentially no adverse effect on the chemical and thermal stability of the catalyst support shows. Accordingly, it is according to another Embodiment provided that the graphite particles a average diameter of less than 100 nm, preferably one from 10 to 80 nm.

The Acidity of the catalyst support according to the invention For example, the activity of a VAM catalyst favorably influence. According to a further preferred Embodiment of the invention Catalyst carrier has this an acidity of between 1 and 150 μval / g, preferably one of between 5 and 130 μval / g, preferably one of between 10 and 100 μval / g, and more preferably one of between 10 and 60 μval / g. The acidity of the catalyst support is determined as follows: 1 g of the finely ground catalyst support is added with 100 ml of water (with a pH blank) and under Stir for 15 minutes. Subsequently, will titrated with 0.01 N NaOH solution at least until pH 7.0, wherein the titration is gradual; and that will be first 1 ml of the NaOH solution was added dropwise to the extract (1 drop / second), then waited 2 minutes, read the pH, again 1 ml of NaOH dropped, etc. The blank value of the water used is determined and corrected the acidity calculation accordingly.

The titration curve (ml 0.01 NaOH versus pH) is then plotted and the point of intersection of the titration curve at pH 7 is determined. The molar equivalents are calculated in 10 ^-6 equiv / g carrier, which results from the NaOH consumption for the point of intersection at pH 7.

in the With regard to low pore diffusion limitation during use in a synthesis reaction can according to another preferred embodiment be provided that the catalyst support has an average pore diameter of 8 to 30 nm, preferably one from 9 to 20 nm and preferably from 10 to 15 nm.

When using the catalyst support of the invention as a support of a coated catalyst with a Pd / Au shell in the VAM synthesis, it has been observed that the smaller the surface area of the catalyst support, the higher the VAM selectivity. In addition, the smaller the surface area of the catalyst support, the greater the thickness of the Pd / Au shell can be, without having to accept significant losses of VAM selectivity. According to a preferred embodiment, therefore, the catalyst support has a surface area of less than or equal to 160 m ² / g, preferably one of less than 130 m ² / g, preferably one of less than 120 m ² / g, more preferably one of less than 110 m ² / g, more preferably one of less than 100 m ² / g, even more preferably one of less than 95 m ² / g, and more preferably one of less than 90 m ² / g. In the context of the present invention, the term "surface area" of the catalyst support is understood to mean the BET surface area of the catalyst support, which adsorbs by means of adsorption of nitrogen DIN 66132 is determined.

Furthermore, it may be preferred for the catalyst support to have a surface area of from 160 to 60 m ² / g, preferably from 140 to 65 m ² / g, preferably from 135 to 70 m ² / g, more preferably from 120 to 70 m ² / g, more preferably from 110 to 70 m ² / g, and most preferably from 100 to 70 m ² / g.

The catalyst support according to the invention is usually processed into a catalyst by subjecting a large number of catalyst supports in the form of shaped bodies to a "batch" process in whose individual process steps the shaped bodies are mediated, for example, by stirring and mixing tools, subject to relatively high mechanical loads. In addition, the inventor Catalyst carriers according to the invention are subjected to high mechanical stress during the filling of a reactor, which can lead to undesirable dust formation and damage to the catalyst carrier. In particular, in order to keep the abrasion of the catalyst support according to the invention within reasonable limits, the catalyst support has a hardness greater than or equal to 20 N, preferably greater than or equal to 25 N, more preferably greater than or equal to 35 N and most preferably one of greater than or equal to 40 N. The hardness is determined by means of a tablet hardness tester 8M from Dr. Ing. Schleuniger Pharmatron AG on 99 pieces of catalyst support (balls with a diameter of 5 mm) as an average determined after drying the catalyst support at 130 ° C for 2 h, the device settings are as follows: Hardness: N Distance to the molded body: 5.00 mm Time Delay: 0.80 s Feed type: 6 D Speed: 0.60 mm / s

The Hardness of the catalyst carrier can be, for example by varying certain parameters of the process for its production influenced by, for example, the selection of the natural one Phyllosilicate, calcination / carbonization time and / or calcination / carbonization temperature one of a mixture formed, uncured Shaped body, or by certain additives such as Methylcellulose or magnesium stearate.

It was found that the VAM selectivity of a Pd / Au coated catalyst prepared using the catalyst support of the invention is dependent on the integral pore volume of the catalyst support. According to a further preferred embodiment of the catalyst support according to the invention, therefore, the catalyst support has an integral pore volume to BJH of between 0.25 and 0.7 ml / g, preferably one of between 0.3 and 0.55 ml / g and preferably one of 0 , 35 to 0.5 ml / g. The integral pore volume of the catalyst support is determined by the method of BJH by means of nitrogen adsorption. The surface of the catalyst support and its integral pore volume are determined by the BET method or by the BJH method. The BET surface area is determined according to the BET method according to DIN 66131 ; a publication of the BET method can also be found in J. Am. Chem. Soc. 60, 309 (1938) , To determine the surface area and the integral pore volume of the catalyst support, the sample can be measured, for example, with a fully automatic nitrogen porosimeter from Micromeritics, type ASAP 2010, by means of which an adsorption and desorption isotherm is recorded.

To determine the surface area and the porosity of the catalyst support according to the BET theory, the data according to DIN 66131 evaluated. The pore volume is determined from the measurement data using the BJH method ( EP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73 (1951, 373) ). This procedure also takes into account effects of capillary condensation. Pore volumes of certain pore size ranges are determined by summing up incremental pore volumes, which are obtained from the evaluation of the adsorption isotherm according to BJH. The integral pore volume according to the BJH method refers to pores with a diameter of 1.7 to 300 nm.

According to a further preferred embodiment of the catalyst support according to the invention, it may be provided that the water absorbency of the catalyst support is 40 to 75%, preferably 50 to 70% calculated as weight increase by water absorption. The absorbency is determined by soaking 10 g of the carrier with deionized water for 30 minutes until no more gas bubbles escape from the carrier sample. Then, the excess water is decanted and the soaked sample is blotted with a cotton cloth to free the sample from adherent moisture. Then the water-loaded carrier is weighed and the absorbency calculated according to: (Weight (g) - weight (g)) × 10 = water absorbency (%)

According to a further preferred embodiment of the catalyst support according to the invention, it may be preferred if at least 80% of the integral pore volume of the catalyst support according to BJH is formed by mesopores and macropores, preferably at least 85% and preferably at least 90%. This counteracts a reduced activity of a catalyst produced by means of the catalyst support of the invention caused by diffusion limitation, in particular in the case of Pd / Au shells with relatively large thicknesses. In this regard, under the terms micropores, mesopores and Macropore pores having a diameter of less than 2 nm, a diameter of 2 to 50 nm and a diameter greater than 50 nm.

In order to ensure a very high chemical resistance of the catalyst support according to the invention, the natural phyllosilicate present in the support has an SiO ₂ content of at least 65% by mass, preferably at least 80% by mass and preferably from 95 to 98% .-% based on the mass of the layered silicate.

In the gas-phase synthesis of VAM from acetic acid and ethene, a relatively low Al ₂ O ₃ content in the natural sheet silicate hardly has a disadvantageous effect, while at high Al ₂ O ₃ contents a considerable decrease in the pressure hardness of the catalyst support must be expected. According to a preferred embodiment of the catalyst support according to the invention, the natural layered silicate therefore contains less than 10% by mass of Al ₂ O ₃ , preferably 0.1 to 3% by mass and preferably 0.3 to 1.0% by mass, based on the Mass of natural phyllosilicate.

Of the catalyst support according to the invention preferably formed as a shaped body. It is preferred if the catalyst carrier as a ball, cylinder (also with rounded end faces), perforated cylinder (also with rounded off Front surfaces), trilobus, "capped tablet", tetralobus, Ring, donut, star, cartwheel, "inverse" cartwheel, or as a strand, preferably as Rippstrang or star train, trained is, preferably as a ball.

Of the Diameter or the length and thickness of the catalyst support is preferably 2 to 9 mm, depending on the reactor tube geometry, in which the catalyst support should be used. Is the Catalyst support designed as a sphere, so has the catalyst support preferably a diameter greater than 2 mm on, preferably a diameter greater than 3 mm and preferably a diameter of 4 mm to 9 mm.

• a) Vermischens eines pulverförmigen natürlichen Schichtsilikats, insbesondere eines säurebehandelten kalzinierten oder unkalzinierten Bentonits, mit pulverförmigem Graphit oder mit einem graphitisierbaren Material;
• b) Bildens eines Körpers aus dem gemäß Schritt a) erhaltenen Gemisches oder des Auftragens des Gemisches auf eine Trägerstruktur;
• c) Kalzinierens des Gemisches, wenn das Gemisch das natürliche Schichtsilikat und Graphit enthält;
• d) Graphitisierens des in dem Gemisch enthaltenen graphitisierbaren Materials, wenn das Gemisch das natürliche Schichtsilikat und das graphitisierbare Material enthält.

The present invention further relates to a first process for preparing a catalyst support, in particular a catalyst support according to the invention, comprising the steps of

• a) mixing a powdered natural layered silicate, in particular an acid-treated calcined or uncalcined bentonite, with powdered graphite or with a graphitizable material;
• b) forming a body from the mixture obtained according to step a) or applying the mixture to a support structure;
• c) calcining the mixture if the mixture contains the natural layered silicate and graphite;
• d) graphitizing the graphitizable material contained in the mixture when the mixture contains the natural layered silicate and the graphitizable material.

through of the first method according to the invention prepared using graphite catalyst support be in their matrix, the graphite evenly is distributed. When using the graphitizable material however, catalyst supports can be prepared of which also the inner surface of the porous Matrix is occupied by graphite particles.

The Calcining or graphitization is preferably in a Temperature of 300 to 650 ° C performed. at These temperatures can be a stable solid structure of Layered silicate and graphite particles are obtained.

Furthermore, it may be preferred that the calcination or the graphitization is carried out in a non-oxidizing or in a reducing atmosphere, for example in a nitrogen or in a noble gas atmosphere. By using a non-oxidizing or reducing atmosphere, losses of carbon can be avoided, for example by total oxidation. If a graphitizable material is used, the application of a non-oxidizing or reducing atmosphere is almost mandatory, since otherwise a high conversion of the material to CO and CO ₂ threatens. However, graphitization can also be carried out in an oxidizing atmosphere, wherein the graphitization times should be chosen to be relatively short in order to limit the loss of carbon.

It could be found that if the inventive Method under graphitization of the graphitizable material micropores of the layered silicate with carbon be occupied. This is advantageous in the VAM synthesis, as free Micropores in the VAM synthesis lead to coking reactions can.

Prefers is a graphitizable material an organic material. There relatively organic polymer materials Simply graphitize, it is according to one further preferred embodiment of the invention Provided that the graphitizable material is an organic Polymer material is, preferably in powder form or in can be used dissolved in a solvent. Preferred polymeric materials are plastic polymers, saccharides as well as tarry materials. Particularly preferred plastic polymers are polybutadienes, polyesters, polyamides, polyethers, polyols, etc. In addition But polymer materials can also be other organic compounds like organic acids like fatty acids or paraffins, Aromatics, aldehydes, alcohols, ketones or polymerizable monomers such as acrylic acid, acrolein, vinyl acetate, styrene or acrylonitrile be used. Preferred saccharides are starches, cellulose and dextrans.

• a) Bereitstellens eines natürlichen Schichtsilikats, insbesondere eines säurebehandelten kalzinierten oder unkalzinierten Bentonits;
• b) Einlagerns einer carbonisierbaren chemischen Verbindung zwischen Schichten des Schichtsilikats;
• c) Carbonisierens der chemischen Verbindung.

The present invention further relates to a second process for the preparation of a catalyst support, in particular a catalyst support according to the invention, comprising the steps of

• a) providing a natural layered silicate, in particular an acid-treated calcined or uncalcined bentonite;
• b) incorporating a carbonizable chemical compound between layers of the layered silicate;
• c) carbonating the chemical compound.

The Carbonation is preferably carried out at a temperature of 300 to 650 ° C performed. At these temperatures will be a largely complete carbonation of the chemical Ensures connection without the structure of the layered silicate adversely affect.

Further it may be preferred that the carbonation in a non-oxidizing or reducing atmosphere performed is, for example in a nitrogen or in a noble gas atmosphere. through the use of a non-oxidizing atmosphere can Losses of carbon, for example, by total oxidation of the chemical compound are avoided.

According to a further preferred embodiment of the method according to the invention, the chemical compound is selected from the group of organic solvents or from the group of carboxylic acids. In particular, carboxylic acids such as, for example, acetic acid, propionic acid, acrylic acid, citric acid, tartaric acid, malic acid, glyoxylic acid, glycolic acid, lactic acid, pyruvic acid, gluconic acid, maleic acid, fumaric acid and fatty acids can be procedurally relatively easily intercalated between silicate layers and converted into carbon. The intercalation of the chemical compound can be carried out, for example, by reacting a solution of the chemical compound, preferably the solution of a carboxylic acid, over a prolonged period, optionally at elevated temperature and temporary mechanical treatment, for. B. in wet mills, can act on the sheet silicate (see. US 5,952,095 ).

The The present invention further relates to the use of the invention Catalyst support as a catalyst support for a shell catalyst, in particular for a shell catalyst, in its shell metallic Pd and Au, Pd and Pt or Pt and Ag is included.

The The following embodiments serve to explain the invention:

Comparative Example:

500 g of an acid-treated dried powdery Bentonite as a natural layered silicate with the main component Montmorillonite became fine in a ball mill Grinding powder.

The resulting bentonite powder was made into a dough with the addition of water by means of a mixer, from which spherical shaped bodies were produced under pressure by means of a tablet press. For curing, the balls were calcined at a temperature of 600 ° C over a period of 5 h. The moldings thus obtained have the characteristics listed in Table 1: Table 1: Geometric shape Bullet diameter 5 mm moisture content <2.0 mass% Compressive strength > 25 N bulk weight 570 gl ^-1 Wassersaugvermögen 59% specif. Surface (BET) 130 m ² g ^-1 SiO ₂ content 94% by mass Other oxides Residual mass in mass% Ignition loss 1000 ° C <0.4 mass% acidity 30 μval / g BJH pore volume N ₂ 0.37 cm ³ g ^-1 Thermal conductivity λ 0.16 Wm ^-1 K ^-1 (at room temperature)

The thermal conductivity of the catalyst support of the comparative example and of Examples 1 and 2 was determined on a bed of beads at room temperature and 0% relative humidity according to DIN 52612 certainly.

Example 1:

495 g of an acid-treated dried powdery Bentonite (the same bentonite as in the comparative example) and 5 g of commercial graphite particles were under the same Conditions as in the comparative example in a ball mill milled to a fine powder mixture.

The resulting powder mixture was processed analogously to the comparative example with the addition of water by means of a mixer to a dough, from which by means of a tablet press under pressure spherical moldings were prepared. For curing, the spheres were calcined at a temperature of 600 ° C over a period of 5 h under a nitrogen atmosphere. The moldings thus obtained have the characteristics listed in Table 2: TABLE 2 Geometric shape Bullet diameter 5 mm moisture content <2.0 mass% Compressive strength > 25 N bulk weight 565 gl ^-1 Wassersaugvermögen 58% specif. Surface (BET) 128 m ² g ^-1 SiO ₂ content 93% by weight graphite content 1 mass% Other oxides Residual mass in mass% Ignition loss 1000 ° C <1.4 mass% acidity 29 μ / g BJH pore volume N ₂ 0.37 cm ³ g ^-1 Thermal conductivity λ 1.04 Wm ^-1 K ^-1 (at room temperature)

Example 2:

500 g of an acid-treated dried powdery Bentonite (the same bentonite as in the comparative example) were under the same conditions as in Comparative Example in one Grind ball mill to a fine powder. The powder was dissolved in 1 L of a 10% aqueous solution of Acrylic acid was suspended and the solution was allowed to stand For 24 h at a temperature of 50 ° C act on the bentonite.

To the action of the bentonite was separated from the solution and washed extensively with water.

The resulting loaded bentonite was analogously to the comparative example with the addition of water by means of a mixer processed into a dough, from which by means of a tablet press under pressure spherical moldings were prepared. To cure the spheres and to carbonize the acrylic acid, the spheres were calcined at a temperature of 600 ° C over a period of 5 h in a nitrogen atmosphere. The moldings thus obtained have the characteristics listed in Table 3: TABLE 3 Geometric shape Bullet diameter 5 mm moisture content <2.0 mass% Compressive strength > 25 N bulk weight 568 gl ^-1 Wassersaugvermögen 59% specif. Surface (BET) 128 m ² g ^-1 SiO ₂ content 94% by mass Carbon content 0.3 mass% Other oxides Residual mass in mass% Ignition loss 1000 ° C <0.7 mass% acidity 30 μval / g BJH pore volume N ₂ 0.36 cm ³ g ^-1 Thermal conductivity λ 0.41 Wm ^-1 K ^-1 (at room temperature)

Based a powder diffractogram of the carbon loaded bentonite it could be determined that the majority of the stored in the bentonite carbon between silicate layers is.

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

• - EP 565952 A1 [0004]
• - EP 634214 A1 [0004]
• EP 634209 A1 [0004]
• EP 634208 A1 [0004]
• - EP 839793 A1 [0005]
• WO 1998/018553 A1 [0005]
• WO 2000/058008 A1 [0005]
• WO 2005/061107 A1 [0005]
• US 5952095 [0053]

Cited non-patent literature

• - DIN 52612 [0013]
• - DIN EN 12664 [0013]
• - DIN EN 12667 [0013]
• - Lehrbuch der anorganischen Chemie ", Hollemann Wiberg, de Gruyter, 102nd Edition, 2007 (ISBN 978-3-11-017770-1) [0017]
• - "Römpp Lexikon Chemie", 10th edition, Georg Thieme Verlag [0017]
• - Römpp, Lexikon Chemie, 10th ed., Georg Thieme Verlag [0019]
• - DIN 66132 [0032]
• - DIN 66131 [0036]
• - J. Am. Chem. Soc. 60, 309 (1938) [0036]
• - DIN 66131 [0037]
• EP Barret, LG Joiner, PP Haienda, J. Am. Chem. Soc. 73 (1951, 373) [0037]
• - DIN 52612 [0058]

Claims (27)

Catalyst support, in particular for use in the synthesis of vinyl acetate monomer, comprising an open-pored matrix formed from a material containing a natural layered silicate, in particular from a material containing an acid-treated calcined bentonite, characterized in that elemental carbon is distributed in the matrix is included. Catalyst support according to claim 1, characterized characterized in that the proportion of the matrix of natural sheet silicate, in particular acid-treated calcined bentonite, is at least 50 mass%, preferably at least 80 Mass .-% and preferably at least 90% Mass .-%. Catalyst support according to one of the preceding Claims, characterized in that the proportion of Matrix of elemental carbon is up to 50 mass%, preferably up to 20% by mass and preferably up to 10% by mass. Catalyst support according to one of the preceding Claims, characterized in that the proportion of Matrix of elemental carbon is 0.05 to 30 mass%, preferably 0.1 to 20% by mass and preferably 0.15 to 5% by mass. Catalyst support according to one of the preceding Claims, characterized in that the carbon embedded between layers of the layered silicate. Catalyst support according to one of the preceding Claims, characterized in that the carbon in the form of graphite particles, which are uniform in the matrix are distributed. Catalyst support according to claim 6, characterized characterized in that the graphite particles have a mean diameter of less than 100 nm, preferably one of 10 to 80 nm. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support has an acidity of between 1 and 150 μval / g, preferably one of between 5 and 130 μval / g, preferred one of between 10 and 100 μval / g and more preferred one of between 10 and 60 μval / g. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support has an average pore diameter of 8 to 30 nm, preferably one from 9 to 20 nm and preferably from 10 to 15 nm. Catalyst support according to one of the preceding claims, characterized in that the catalyst support has a surface area of 160 m ² / g or less, preferably one of less than 130 m ² / g, preferably less than 120 m ² / g, more preferably one of less than 110 m ² / g, more preferably one of less than 100 m ² / g, even more preferably one of less than 95 m ² / g and particularly preferably less than 90 m ² / g. Catalyst support according to one of the preceding claims, characterized in that the catalyst support has a surface area of from 160 to 60 m ² / g, preferably from 140 to 65 m ² / g, preferably from 135 to 70 m ² / g, more preferably one from 120 to 70 m ² / g, more preferably from 110 to 70 m ² / g, and most preferably from 100 to 70 m ² / g. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support has a hardness greater than or equal to 20 N, preferably one of greater than or equal to 25 N, more preferably one of greater than or equal to 35 N and most preferred one of greater than or equal to 40 N. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support has an integral pore volume to BJH of 0.25 to 0.7 ml / g, preferably one from 0.3 to 0.55 ml / g and preferably one from 0.35 to 0.5 ml / g. Catalyst support according to one of the preceding Claims, characterized in that at least 80% of integral pore volume of the catalyst support of mesopores and macropores are formed, preferably at least 85% and preferably at least 90%. Catalyst support according to one of the preceding claims, characterized in that the natural layered silicate contained in the matrix has an SiO ₂ content of at least 65% by mass, preferably one of at least 80% by mass and preferably from 95 to 98%. -%. Catalyst support according to one of the preceding claims, characterized in that the natural layered silicate contained in the matrix contains less than 10 mass% Al ₂ O ₃ , preferably 0.1 to 3 mass% and preferably 0.3 to 1.0 Mass .-%. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support is formed as a shaped body, in particular as a ball, Cylinder, perforated cylinder, trilobus, ring, star or strand, preferably as Rippstrang or star string. Catalyst support according to one of the preceding Claims, characterized in that the catalyst support as a sphere with a diameter greater than 2 mm is formed, preferably with a diameter of larger than 3 mm, and preferably with a diameter of greater than 4 mm. Method for producing a catalyst support, in particular a catalyst support according to one of the preceding Claims comprising the steps of a) mixing a powdery natural layered silicate, in particular an acid-treated calcined or uncalcined Bentonites, with powdered graphite or with a graphitizable Material; b) forming a body from that according to step a) obtained mixture or the application of the mixture to a Support structure; c) calcining the mixture, if the mixture contains the natural layered silicate and graphite; d) Graphitisierenens of graphitizable contained in the mixture Materials, if the mixture is the natural phyllosilicate and containing the graphitizable material. Method according to claim 19, characterized that calcining or graphitizing at a temperature from 300 to 650 ° C is performed. Method according to one of the preceding claims, characterized in that the calcining or graphitization in a non-oxidizing or reducing atmosphere is carried out. Method according to one of the preceding claims, characterized in that the graphitizable material is an organic Material is, preferably a polymer material. Method for producing a catalyst support, in particular a catalyst support according to one of the preceding Claims comprising the steps of a) Provide a natural layered silicate, in particular an acid-treated calcined or uncalcined bentonite; b) storing a carbonizable chemical compound between layers of the layered silicate; c) Carbonizing the chemical compound. Method according to claim 23, characterized Carbonating at one at a temperature of 300 to 650 ° C is performed. Method according to claim 23 or 24, characterized that carbonizing in a non-oxidizing or reducing acting atmosphere is performed. Method according to one of claims 23 to 25, characterized in that the compound selected is from the group of organic solvents or from the group of carboxylic acids, aldehydes, alcohols and the polymerizable monomers. Use of a catalyst support after one of the preceding claims as a catalyst support for a shell catalyst, in particular for a shell catalyst, in whose shell metallic Pd and Au, Pd and Pt or Pt and Ag is included.