HK1190112A - Catalyst and method for the production of chlorine by gas phase oxidation - Google Patents

Description

Catalyst and process for producing chlorine by gas phase oxidation

The invention proceeds from a known process for producing chlorine by the catalytic gas phase oxidation of hydrogen chloride with oxygen, wherein the catalyst contains tin dioxide as support and at least one halogen-and/or oxygen-containing ruthenium compound. The present invention relates to a catalyst composition and its use.

The process developed in 1868 by diken for the catalytic oxidation of hydrogen chloride with oxygen in an exothermic equilibrium reaction is the beginning of industrial chlorine chemistry:

4HCl+O₂＝2Cl₂+H₂O

however, chlor-alkali electrolysis strongly disfavors the Deacon process. Almost all chlorine production is carried out by electrolysis of aqueous salt solutions [ Ullmann Encyclopedia of industrial chemistry, seventh edition, 2006 ]. Recently, however, the Deacon process has become increasingly attractive because the global chlorine demand has grown more strongly than the sodium hydroxide solution demand. This development caters for the manufacture of sodium hydroxide solutions by the oxidative manufacture of chlorine by hydrogen chloride. In addition, in the phosgenation reaction, for example in the production of isocyanates, large amounts of hydrogen chloride are produced as by-product.

The oxidation of hydrogen chloride to form chlorine is an equilibrium reaction. As the temperature increases, the equilibrium position moves in a direction that is detrimental to the desired end product. It is therefore advantageous to use catalysts having as high an activity as possible, which allow the reaction to be carried out at relatively low temperatures.

As the current state of the art, ruthenium-based catalysts are used for HCl oxidation. In 1965, a first catalyst for the oxidation of hydrogen chloride with ruthenium as the catalytically active component was described in DE1567788, in this case, from RuCl supported on silica and alumina, for example₃And (5) starting. Further ruthenium-based catalysts having as active material ruthenium oxide or ruthenium mixed oxides and various oxides such as titanium dioxide, zirconium dioxide and the like as support materials are described in DE-A19748299, DE-A19734412 and EP 0936184A 2.

Furthermore, documents WO 2007/134772a1 and WO 2007/134721a1 disclose ruthenium-based catalyst systems which are supported on tin dioxide and whose activity is clearly highlighted in the prior art.

However, a disadvantage of the catalyst systems described in WO 2007/134772A1 and WO 2007/134721A1 is that under the reaction conditions of HCl gas phase oxidation, tin may form as a volatile compound SnCl₄Is discharged from the carrier. This is particularly negative for the lifetime of the catalyst, since the mechanical stability is gradually reduced by the continuous loss of tin. An additional factor is that the effluent must be chlorinatedTin is separated from the product. There is therefore a need for a process which increases the chemical stability of the catalysts known from WO 2007/134772a1 and WO 2007/134721a1 with respect to the expulsion of tin without impairing their excellent activity.

The object of the present invention is therefore a process for increasing the chemical stability of the catalysts known from WO 2007/134772a1 and WO 2007/134721a1 with respect to tin emissions without impairing their excellent activity. This object is achieved by doping tin dioxide prior to applying the catalytically active material.

It has now surprisingly been found that the chemical stability and the activity of the catalyst under the conditions of the HCl gas phase oxidation can be increased by doping tin dioxide with the selected metal before applying the catalytically active material.

The subject of the invention is a catalyst composition containing at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active material, characterized in that the support material contains a compound of an element selected from the group consisting of: nb, V, Ta, Cr, Mo, Au, In, Sc, Y and lanthanides, In particular La and Ce, preferably niobium or a niobium compound, particularly preferably niobium oxide.

The minor constituents are present in particular in doped form. Doping is preferably understood here to mean a homogeneous distribution of the minor constituents in the lattice structure of the matrix material (e.g. tin dioxide).

A further subject of the invention is a process for the manufacture of chlorine by catalytic gas phase oxidation of hydrogen chloride with oxygen, in which the catalyst contains at least a compound doped with an element selected from the group consisting of: nb, V, Ta, Cr, Mo, Au, In, Sc, Y and lanthanides, In particular La and Ce, and ruthenium compounds.

In a preferred embodiment, doped tin dioxide is used as support for the catalytically active component, wherein the tin dioxide is present in the cassiterite structure.

The doped tin dioxide contains, in addition to tin, at least one compound of an element selected from the group consisting of: nb, Ce, La, Y, Sc, V, Mo, Cr, Au, preferably Nb. The proportion of doping is in the range from 0.01 to 30% by weight, preferably from 0.05 to 20% by weight, and very preferably from 0.1 to 10% by weight, based on the total weight of tin dioxide and minor constituents.

Without being limited thereto, the doped tin dioxide may be prepared by co-precipitation of a suitable soluble tin salt and a salt of the doping element, by high heat treatment of the salt, by Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), spray pyrolysis, etc. of a suitable solution, wherein the preparation may preferably be carried out by co-precipitation.

The co-precipitation can be carried out batchwise, semi-continuously or continuously. The precipitation can be caused, for example, by a change in temperature or concentration (also by evaporation of the solvent), by a change in pH and/or by the addition of a precipitating agent or a combination thereof. The co-precipitation may preferably be performed by adding a precipitation reagent. Conventional apparatuses for this are stirred tanks, static mixers, valve mixers, micromixers, nozzle apparatuses, which ensure intensive mixing of the salt solution and the precipitating reagent.

Various starting compounds can be used as long as the Sn precursor and the salt of the doping element are soluble in the solvent used, i.e. in the case of co-precipitation, co-precipitation is also possible. Examples of these starting compounds are acetates, nitrates, chlorides and other soluble compounds.

Preferred solvents are short chains (C)₁-C₆) Alcohols, such as methanol, ethanol, n-propanol, isopropanol or butanol and water and mixtures thereof. Particularly preferred are short chain alcohols.

Examples of suitable precipitating agents are ammonium carbonate, ammonium hydroxide, ammonia, urea, solutions of alkali metal-or alkaline earth metal carbonates and alkali metal-or alkaline earth metal hydroxides in the abovementioned solvents.

The precipitation is preferably carried out continuously. The metal salt solution and optionally the precipitation reagent and the further doping components are mixed in the mixing device with high mixing intensity by means of a conveying device. Preference is given to using static mixers, Y-mixers, multi-layer mixers (Multilaminationsmischer), valve mixers, micromixers, (twin-feed (Zweistoff)) nozzle mixers and further similar mixers known to the person skilled in the art.

To improve the precipitation characteristics and to surface modify the manufactured solid, surface-active substances (e.g. ionic or non-ionic surfactants or carboxylic acids) may be added.

It is advantageous and therefore preferred to coprecipitate the components forming the doped carrier, in particular from an alcoholic solution, for example by adding ammonia solution, ammonium carbonate, ammonium hydroxide, urea, alkali metal carbonates and alkali metal hydroxides as precipitating agents.

The doped support obtained in solid form can be separated from the reactant solution according to methods known to the person skilled in the art, such as settling, filtration, centrifugation, evaporation and concentration. Sedimentation and evaporation are preferred. The solid obtained can be further washed or used further as obtained. To improve the operability of the resulting catalyst, it may be dried. As is known in heterogeneous catalysts, it can be advantageous to further adjust the supported tin dioxide as support. Such adjustments may be calcination and heat treatment, as well as treatment with a reactive atmosphere or, for example, steam, in order to improve catalyst performance. Preference is given to thermal pretreatment in an oxidizing atmosphere, in particular air, preferably at 1500 ℃ under 250-. The adjustment can be carried out upstream or downstream of the shaping and/or classification.

According to the invention, at least one ruthenium-containing compound is used as catalytically active component. The catalytically active component is in particular ruthenium halide, ruthenium hydroxide, ruthenium oxide, ruthenium oxyhalide and/or ruthenium in metallic form.

Preferred are catalyst compositions in which the ruthenium compound is a halogen-and/or oxygen-containing ruthenium compound.

As catalytically active components, preference is given to using halogen-containing ruthenium compounds. The catalytically active component is, for example, a compound in which the halogen is ionically bonded to the polar covalent bond on the ruthenium atom.

The halogen in the preferred halogen-containing ruthenium compounds is preferably selected from chlorine, bromine and iodine. Chlorine is particularly preferred.

The halogen-containing ruthenium compounds include those consisting of only halogen and ruthenium. However, those containing oxygen and halogen, especially chlorine or chloride, are preferred. Particularly preferred are catalyst compositions in which the catalytically active ruthenium compound is selected from the following: ruthenium chloride, ruthenium oxychloride and mixtures of ruthenium chloride with ruthenium oxide and especially ruthenium oxychloride compounds.

Particular preference is given to using at least one ruthenium oxychloride compound as catalytically active substance. Ruthenium oxychloride compounds within the scope of the invention are compounds in which oxygen and chlorine are present on the ruthenium atom in ionic bonds to polar covalent bonds. Such compounds therefore have the general composition RuO_xCl_y. Preferably, a plurality of ruthenium oxychloride compounds of this type can be present simultaneously in the catalyst. Examples of particularly preferred ruthenium oxychloride compounds defined include in particular the following compositions: ru₂Cl₄、RuOCl₂、Ru₂OCl₅And Ru₂OCl₆。

In a particularly preferred process, the halogen-containing ruthenium compound corresponds to the general formula RuCl_xO_yWherein x represents a number of 0.8 to 1.5 and y represents a number of 0.7 to 1.6.

The catalytically active ruthenium oxychloride compounds within the scope of the invention can preferably be obtained by a process which comprises firstly applying, in particular an aqueous solution or suspension, of at least one halogen-containing ruthenium compound to the doped tin dioxide and removing the solvent.

Other conceivable methods include chlorinating a non-ruthenium chloride compound, such as ruthenium hydroxide, either before or after the ruthenium compound is absorbed on the support.

A preferred method involves combining RuCl₃Is applied to the doped tin dioxide.

The application of the ruthenium compound is generally followed by a drying step, which is suitably carried out in the presence of oxygen or air, so that it can be converted at least partially into the preferred ruthenium oxychloride compound. In order to prevent the preferred ruthenium oxychloride compounds from being converted into ruthenium oxide, the drying should preferably be carried out at temperatures below 280 ℃, in particular at temperatures of at least 80 ℃, particularly preferably at temperatures of at least 100 ℃. The drying time is preferably 10 minutes to 6 hours. The catalyst may be dried at normal pressure or, preferably, at reduced pressure.

A preferred process is characterized in that the catalyst is obtainable by: the doped tin dioxide support loaded with the halogen-containing ruthenium compound is calcined at a temperature of at least 200 ℃, preferably at least 240 ℃, particularly preferably at least 250-500 ℃, in particular in an oxygen-containing atmosphere, particularly preferably in air. The duration of calcination is preferably from 30 minutes to 24 hours.

In a particularly preferred process, the proportion of ruthenium of the catalytically active ruthenium compound, in particular after calcination, is from 0.5 to 5% by weight, preferably from 1.0 to 4% by weight, particularly preferably from 1.5 to 3% by weight, relative to the entire catalyst composition.

If the catalytically active substance applied is to be an oxygen-free halogen-ruthenium compound, it can also be dried at higher temperatures with exclusion of oxygen.

The catalyst is preferably obtainable by a process which comprises applying an aqueous solution or suspension of at least one halogen-containing ruthenium compound to doped tin dioxide and subsequent drying at below 280 ℃ and subsequent activation under gas-phase oxidation conditions of hydrogen chloride, in the course of which it is largely converted to ruthenium oxychloride. The longer the drying is carried out in the presence of oxygen, the more oxychloride is formed.

In a particularly preferred embodiment, the oxygen-containing ruthenium compound is applied to the support. Which is a compound in which oxygen is ionically bonded to a polar covalent bond on the ruthenium atom. The compounds are prepared by applying an aqueous solution or suspension of at least one halogen-containing ruthenium compound to doped tin dioxide and subsequently precipitating to ruthenium hydroxide with the aid of a basic compound and optionally calcining the precipitated product.

The precipitation can be carried out under alkaline conditions, directly forming the oxygen-containing ruthenium compound. It is also possible to carry out the reaction under reducing conditions, first forming metallic ruthenium and then introducing oxygen for calcination, thereby forming the oxygen-containing ruthenium compound.

One preferred method includes impregnating, soaking, etc. RuCl₃The aqueous solution is applied to the doped tin dioxide.

The application of the halogen-containing ruthenium compound is generally followed by a precipitation and drying or calcination step, which is suitably carried out in the presence of oxygen or air at temperatures of up to 650 ℃.

Particularly preferably, the catalytically active component, i.e. the ruthenium-containing compound, can be applied to the support, for example by means of the wet- (Feucht-) and wet-impregnation, precipitation-and coprecipitation processes, and ion exchange and gas phase coating (CVD, PVD) with suitable starting compounds present in solution or supports of starting compounds in liquid or colloidal form.

The catalyst for hydrogen chloride oxidation according to the present invention is superior in high activity and high stability at low temperature.

Preferably, the novel catalyst composition is used in a catalytic process known as the Deacon process or the HCl gas phase oxidation, as already described above. In this process, hydrogen chloride is oxidized to chlorine with oxygen in an exothermic equilibrium reaction, with the formation of water vapor. The reaction temperature is generally 180-500 ℃, particularly preferably 200-450 ℃, and particularly preferably 250-420 ℃; the customary reaction pressures are from 1 to 25 bar, preferably from 1.2 to 20 bar, particularly preferably from 1.5 to 17 bar, very particularly preferably from 2 to 15 bar. Since the reaction is an equilibrium reaction, it is suitable to operate at temperatures at which the lowest possible catalyst still has sufficient activity. It is also suitable to use oxygen in a stoichiometric excess with respect to the hydrogen chloride. For example, oxygen is usually in excess of 2-4 times. Since no loss of selectivity has to be feared, it can be economically advantageous to use relatively high pressures and correspondingly longer residence times than at standard pressures.

In addition to the ruthenium compounds, suitable catalysts may also contain other compounds of the following metals or noble metals: such as gold, palladium, platinum, osmium, iridium, silver, copper, cerium, chromium, or rhenium.

The catalytic hydrogen chloride oxidation can preferably be carried out adiabatically or isothermally or approximately isothermally, batchwise but preferably continuously, as a fluidized-bed or fixed-bed process, preferably as a fixed-bed process, particularly preferably adiabatically, at a reactor temperature of from 180-.

Typical reaction apparatuses for carrying out catalytic hydrogen chloride oxidation are fixed-bed or fluidized-bed reactors. The catalytic hydrogen chloride oxidation can also preferably be carried out in a plurality of stages.

However, in an adiabatic, isothermal or approximately isothermal process variant, preferably an adiabatic process variant, it is also possible to use a plurality, in particular 2 to 10, preferably 2 to 6, cascade reactors with intermediate cooling. The hydrogen chloride can either be added completely with the oxygen before the first reactor or be added via a separate reactor partition. The series connection of the reactors can also be combined in one apparatus.

A further preferred embodiment of the apparatus suitable for the process consists in using a structured catalyst bed in which the catalyst activity increases in the flow direction. The structuring of such catalyst beds may be achieved by impregnation of the catalyst support with a plurality of active materials or by dilution of the catalyst with a plurality of inert materials. As inert material, for example, titanium dioxide, zirconium dioxide or mixtures thereof, aluminum oxide, talc, ceramics, glass, graphite or stainless steel rings, cylinders or spheres can be used. In the catalyst shaped bodies preferably used, the inert material should preferably have similar external dimensions.

The catalyst molded body is preferably a molded body having an arbitrary shape, preferably a sheet, a ring, a cylinder, a star, a wheel or a sphere, and particularly preferably a ring, a cylinder, a sphere or a star strand. Preferably spherical. The catalyst shaped bodies have a size, for example a diameter or a maximum cross-sectional width in the case of spheres, of, on average, in particular from 0.3 to 7 mm, very preferably from 0.8 to 5 mm.

Instead of the aforementioned finely divided catalyst (shaped) bodies, the support may also be a monolith of support material, for example not only a "conventional" support having parallel, radially unconnected channels; also included are foams, sponges and the like having three-dimensional connections within the support to form monoliths, and supports having cross-flow channels.

The monolithic support may have a honeycomb structure, but may also have an open or closed cross channel structure. The monolith support has a cell density of preferably 100-.

Monoliths within the scope of the present invention are disclosed, for example, in F.Kapteijn, J.J.Heiszwolf, T.A. Nijhuis and J.A Moulijn in "Monooliths in multiple phase catalytic processes-aspects and processes", Cattech 3, 1999, page 24.

Suitable further support materials or binders for the support are, for example, silicon dioxide, graphite, titanium dioxide having a rutile or anatase structure, zirconium dioxide, aluminum oxide or mixtures thereof, preferably titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably gamma-or delta-aluminum oxide or mixtures thereof. Preferred binders are alumina or zirconia. The proportion of binder may be from 1 to 30% by weight, preferably from 2 to 25% by weight and very preferably from 5 to 20% by weight, based on the finished catalyst. The binder improves the mechanical stability (strength) of the catalyst shaped body.

In a particularly preferred embodiment of the invention, the catalytically active component is present essentially on the surface of the actual support material, for example on the surface of the doped tin dioxide, but not on the surface of the binder.

The following are suitable as promoters for the doping of the further catalyst: alkali metals or metal compounds such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, particularly preferably potassium, alkaline earth metals such as magnesium, calcium, strontium and barium, preferably magnesium and calcium, particularly preferably magnesium, rare earth metals such as scandium, yttrium, lanthanum, cerium, praseodymium and neodymium, preferably scandium, yttrium, lanthanum and cerium, particularly preferably lanthanum and cerium or mixtures thereof.

Without being limited thereto, the promoter may be applied to the catalyst by impregnation and CVD methods, preferably for example impregnation of metal compounds, in particular nitrates, particularly preferably together with the main components of the catalyst.

The conversion of hydrogen chloride in the single-pass HCl oxidation can preferably be limited to 15 to 90%, preferably 40 to 90%, particularly preferably 70 to 90%. The unconverted hydrogen chloride can be returned after separation, partially or completely, to the catalytic hydrogen chloride oxidation. The volume ratio of oxygen to hydrogen chloride at the reactor inlet is preferably from 1: 2 to 20: 1, preferably from 2: 1 to 8: 1, particularly preferably from 2: 1 to 5: 1.

The heat of reaction of the catalytic hydrogen chloride oxidation can be used in an advantageous manner for generating high-pressure steam. Such high-pressure steam can be used for the operation of the phosgenation reactor and/or the distillation column, in particular the isocyanate distillation column.

In a further step, the chlorine formed is separated off. This separation step generally comprises a plurality of stages, namely the separation of unconverted hydrogen chloride from the product gas stream of the catalytic hydrogen chloride oxidation and optionally recycling, the drying of the resulting stream comprising predominantly chlorine and oxygen and the separation of chlorine from the dried stream.

Unconverted hydrogen chloride and the steam formed can be separated by cooling to condense the aqueous hydrochloric acid solution to discharge a product gas stream of hydrogen chloride oxidation. The hydrogen chloride can also be absorbed in dilute hydrochloric acid or water.

The invention further relates to the use of doped tin dioxide as a catalyst support for the catalytic gas phase oxidation of hydrogen chloride with oxygen.

A further subject of the invention is the use of the novel catalyst compositions as catalysts, in particular for oxidation reactions, particularly preferably as catalysts in the catalytic gas-phase oxidation of hydrogen chloride with oxygen.

The following examples illustrate the invention:

examples

Example 1 (according to the invention)

Manufacture of Nb-doped SnO by coprecipitation₂

At room temperature, SnCl with a concentration of 0.2 mol/l is pumped₄Or 8.1 mmoles/l NbCl₅And 0.1 mol/l NH₃The deionized water solution of (a) was transported through a valve mixer (from Ehrfeld) ensuring intensive continuous mixing. The suspension formed was collected with stirring in a beaker, during which the pH was maintained at 9.2. The volumetric flow rate of solution A was 250 ml/h. The volumetric flow rate of solution B was first 500 ml/h and was continuously adjusted to ensure a constant pH. The solid thus obtained is centrifuged and then washed free of NH by deionized water₃. The filter cake was dried under air at 120 ℃ overnight and then calcined under air at 1000 ℃ for 2 hours. SnO thus produced₂The theoretical content of Nb in the steel is 2.5 wt.%. With the aid of TEM-EDX (measured according to the manufacturer's instructions, Fei Corp., model number TECNA)I20 EDX Detector from EDAX, model PV9760/98GE), Nb in SnO₂Homogeneous distribution in the matrix.

Example 2 (according to the invention)

SnO doped with Nb by ruthenium chloride₂On the load

In a round bottom flask, 1.68 grams of doped SnO prepared in example 1₂Suspended in a commercially available solution of 0.0865 g of ruthenium chloride-n-hydrate in 5 ml of water and stirred at room temperature for 180 minutes. The excess solution was concentrated by evaporation at 60 ℃ overnight. The solid obtained is subsequently calcined at 250 ℃ for 16 hours in an air stream, thus obtaining the doped SnO supported₂Ruthenium chloride catalyst. The amount of ruthenium supported corresponds to a proportion of 2.01% by weight.

Example 3 (according to the invention)

SnO doped with Nb by ruthenium chloride₂Load on the shaped body

50 g of spherical Nb-SnO having an average diameter of 1.9 mm and a BET surface area of 47.6 m/g₂Shaped bodies (manufacturer: Saint-Gobain, corresponding to Nb-SnO of example 1)₂) With 2.64 g of commercially available ruthenium chloride-n-hydrate and 0.258 g of CeCl₃A solution in 10 grams of water. After a standing time of 1 hour, the solid was dried in an air stream at about 60 ℃ for 5 hours. The catalyst was then calcined at 250 ℃ for 16 hours. A catalyst with a calculated ruthenium of 2 wt% was obtained.

Example 4 (comparative example)

Ruthenium chloride commercially available SnO₂Load on powder

According to example 2, in commercially available SnO₂(from MEI, BET 8.1 m/g) on a Ru-containing catalyst. The Ru content corresponds to a content of 2 wt%.

Example 5 (comparative example)

Ruthenium chloride commercially available SnO₂Load on the shaped body

50 g of spherical SnO having an average diameter of 1.9 mm and a BET surface area of 47.6 m/g₂Shaped bodies (manufacturer Saint-Gobain, commercially available SnO)₂) With 2.6397 g of commercially available ruthenium chloride-n-hydrate and 0.2582 g of CeCl₃A solution in 8.3 grams of water. After a standing time of 1 hour, the solid was dried in an air stream at about 60 ℃ for 5 hours. The catalyst was then calcined at 250 ℃ for 16 hours. A catalyst with a calculated ruthenium of 2 wt% was obtained.

Catalyst test example 6

Use of the catalyst from example 2 in HCl Oxidation

A gas mixture of 80 ml/min (standard conditions STP) hydrogen chloride and 80 ml/min (STP) oxygen was passed through 0.2 g of the pulverulent catalyst according to example 2 in a fixed bed stack in a quartz reaction tube (internal diameter 10 mm) at 300 ℃. The quartz reaction tube was heated by an electrically heated sand fluidized bed. After 30 minutes, the product gas stream was passed into a 16 wt% potassium iodide solution for 15 minutes. The iodine formed was then back-titrated with a 0.1N thiosulfate standard solution to determine the amount of chlorine introduced. The rate of chlorine formation was found to be 2.79 kg_Cl2Kg/kg_{Catalyst and process for preparing same}Hour.

Catalyst test example 7

Use of the catalyst from example 3 in HCl Oxidation

25 g of the catalyst from example 3 were charged together with 75 g of inert material (glass spheres) into a nickel-fixed-bed reactor (diameter 22 mm, length 800 mm) heated in an oil bath. This gave a fixed bed heap of approximately 150 mm. The fixed bed stack was heated with the aid of heating carriers heated to 350 ℃. A gas mixture of 40.5 liters per hour (STP) hydrogen chloride, 315 liters per hour (STP) oxygen and 94.5 liters per hour (STP) nitrogen was passed through the fixed bed reactor at a pressure of 4 bar. After a given reaction time (e.g. 30 minutes), the product gas stream was passed into a 16% potassium iodide solution for 5 minutes. The iodine formed was then back-titrated with a 0.1N thiosulfate standard solution to determine the amount of chlorine introduced. The conversion thus calculated was 85%. After a running time of 3108 minutes, the condensed reaction samples were analyzed for tin content by means of ICP-OES (inductively coupled plasma-optical emission Spectroscopy, instrument: Varian Vista-PRO, method according to the manufacturer's instructions). The analyzed tin content was 3 ppm.

Catalyst test example 8 (comparative example)

Use of the catalyst from example 4 in HCl Oxidation

Similar to catalyst test example 6, 0.2 grams of the catalyst of example 4 was tested. The rate of chlorine formation was found to be 2.34 kg_Cl2Kg/kg_{Catalyst and process for preparing same}Hour.

Catalyst test example 9 (comparative example)

Use of the catalyst from example 5 in HCl Oxidation

Similar to catalyst test example 7, 25 grams of the catalyst of example 5 was tested. The analysis of the tin in the condensate was carried out by means of ICP-OES (inductively coupled plasma-optical emission Spectroscopy, instrument: Varian Vista-PRO, method according to the manufacturer's instructions). A condensate sample contained 35ppm Sn.

The results are summarized as follows:

from the test results listed in the above table, it is evident that the stability of the support material is significantly improved, since the tin emission of the catalyst support according to the present invention is reduced to one tenth. It was furthermore found that the activity of the catalyst system according to the invention is increased compared to known catalyst systems.

Claims (16)

1. Catalyst composition comprising at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active material, characterized in that the support material contains a compound selected from the following elements or the following elements as further minor constituents: nb, V, Ta, Cr, Mo, Au, In, Sc, Y and lanthanides, In particular La and Ce, preferably niobium or a niobium compound, particularly preferably niobium oxide.

2. Composition according to claim 1, characterized in that the ruthenium compound is a ruthenium compound containing halogen and/or oxygen.

3. Composition according to claim 2, characterized in that the halogen of the ruthenium compound is selected from the following elements: cl, Br and I, and in particular Cl.

4. Composition according to one of claims 1 to 3, characterized in that the catalytically active ruthenium compound is selected from the following substances: ruthenium chloride, ruthenium oxychloride and mixtures of ruthenium chloride with ruthenium oxide, and in particular comprise ruthenium oxychloride-compounds.

5. Composition according to claim 4, characterized in that the catalytically active ruthenium compound is of the formula RuCl_xO_yWherein x represents a number of 0.8 to 1.5 and y represents a number of 0.7 to 1.6.

6. Composition according to one of claims 1 to 5, characterized in that the proportion of the minor constituents is in the range from 0.01 to 30% by weight, preferably from 0.05 to 20% by weight and very preferably from 0.1 to 10% by weight, based on the total weight of tin dioxide and minor constituents.

7. Composition according to one of claims 1 to 6, characterized in that the catalyst composition is obtainable by a process comprising at least the following steps:

A) preparing an especially aqueous solution or suspension of at least one halogen-containing ruthenium compound,

B) the preparation of soluble tin salts and especially aqueous solutions of the salts of the following elements: nb, V, Ta, Cr, Mo, Au, In, Sc, Y and lanthanides, In particular La and Ce, preferably Nb, and co-precipitating tin with the elements of the minor component,

C) heat treating the precipitated mixture of elemental tin and other elements in the presence of an oxidizing gas to obtain doped tin dioxide, and

D) applying a particularly aqueous solution or suspension of the at least one halogen-containing ruthenium compound of step A) to the doped tin dioxide and removing the solvent.

8. Composition according to claim 7, characterized in that the halogen-containing ruthenium compound used in step A) is RuCl₃。

9. Composition according to claim 7 or 8, characterized in that the catalyst is obtainable by a process in which the removal of the solvent comprises drying at a temperature of at least 80 ℃, preferably at least 100 ℃.

10. Composition according to claims 1-9, characterized in that the catalyst composition is obtainable by: the tin dioxide support loaded with the halogen-containing ruthenium compound is calcined at a temperature of at least 200 ℃, preferably at least 240 ℃, particularly preferably from 250 ℃ to 500 ℃, in particular in an oxygen-containing atmosphere, particularly preferably in air.

11. Composition according to one of claims 1 to 10, characterized in that the proportion of ruthenium of the halogen-containing ruthenium compound is from 0.5 to 5% by weight, preferably from 1.0 to 4% by weight, particularly preferably from 1.5 to 3% by weight, compared with the total catalyst composition, in particular after calcination.

12. Composition according to one of claims 1 to 11, characterized in that the tin dioxide is present at least partially, preferably completely, in the form of cassiterite.

13. Process for the manufacture of chlorine by catalytic gas phase oxidation of hydrogen chloride with oxygen over a solid catalyst, wherein the gas phase oxidation is carried out adiabatically or isothermally, preferably adiabatically, wherein the catalyst comprises at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active material, characterized in that a composition according to one of claims 1 to 12 is used as catalyst.

14. Process according to claim 13, characterized in that the gas phase oxidation of hydrogen chloride comprises introducing a gas comprising hydrogen chloride and oxygen at a temperature of 180-.

15. The process according to any of claims 13 to 14, characterized in that the gas phase oxidation is carried out at a pressure of 1 to 25 bar, preferably 1.2 to 20 bar, particularly preferably 1.5 to 17 bar and especially preferably 2.0 to 15 bar.

16. Use of tin dioxide doped with Nb or niobium compounds as a minor component as a catalyst support for a catalyst in the catalytic gas phase oxidation of hydrogen chloride with oxygen.