EP2026905A1

EP2026905A1 - Method for producing chlorine by gas phase oxidation

Info

Publication number: EP2026905A1
Application number: EP07725285A
Authority: EP
Inventors: Aurel Wolf; Leslaw Mleczko; Oliver Felix-Karl SCHLÜTER; Stephan Schubert
Original assignee: Bayer MaterialScience AG
Current assignee: Covestro Deutschland AG
Priority date: 2006-05-23
Filing date: 2007-05-16
Publication date: 2009-02-25
Also published as: WO2007134772A1; DE102007020154A1; RU2008150585A; KR20090009896A; BRPI0712011A2; TW200812909A; US20070274897A1; JP2009537449A

Abstract

The invention relates to a method for producing chlorine by the catalytic gas phase oxidation of hydrogen chloride using oxygen, wherein the catalyst comprises tin dioxide and at least one ruthenium compound containing halogen. The invention also relates to a catalyst composition and the use thereof.

Description

Process for producing chlorine by gas phase oxidation

The present invention relates to a process for the production of chlorine by catalytic gas-phase oxidation of hydrogen chloride with oxygen, wherein the catalyst comprises tin dioxide and at least one halogen-containing ruthenium compound, a catalyst composition and the use thereof.

The process of catalytic hydrogen chloride oxidation with oxygen in an exothermic equilibrium reaction, developed by Deacon in 1868, was at the beginning of technical chlorine chemistry:

4 HCl + O ₂ => 2 Cl ₂ + 2 H ₂ O.

However, the chloroalkali electrolysis strongly suppressed the Deacon process. Nearly all chlorine production was achieved by electrolysis of aqueous saline solutions [Ullmann Encyclopedia of industrial chemistry, seventh release, 2006]. However, the attractiveness of the Deacon process has increased again recently, as the global demand for chlorine is growing faster than the demand for caustic soda. This development is countered by the process for the production of chlorine by oxidation of hydrogen chloride, which is decoupled from the sodium hydroxide production. In addition, hydrogen chloride precipitates in large quantities, for example in phosgenation reactions, such as in isocyanate production, as by-product.

The oxidation of hydrogen chloride to chlorine is an equilibrium reaction. The position of the equilibrium shifts with increasing temperature to the detriment of the desired end product. It is therefore advantageous to use catalysts with the highest possible activity, which allow the reaction to proceed at low temperature.

The first catalysts for the hydrogen chloride oxidation contained as active component copper chloride or oxide and were already described in 1868 by Deacon. However, these showed low activity at low temperature (<400 ⁰ C). Although the activity could be increased by increasing the reaction temperature, it was disadvantageous that the volatility of the active components at high temperatures led to a rapid decrease in the catalyst activity.

EP 0 184 413 describes the oxidation of hydrogen chloride with catalysts based on chromium oxides. However, the process realized thereby had insufficient activity and high reaction temperatures. The first catalysts for the hydrogen chloride oxidation with the catalytically active component ruthenium were already described in 1965 in DE 1 567 788. In this case, starting from RuCl _3, for example, supported on silica and alumina. However, the activity of these RuCl ₃ / SiO ₂ catalysts is very low. Further Ru-based catalysts with the active material ruthenium oxide or ruthenium mixed oxide and as carrier material various oxides, such as, for example, titanium dioxide, zirconium dioxide, etc., have been claimed in DE-A 197 48 299. The content of ruthenium oxide is from 0.1% by weight to 20% by weight and the average particle diameter of ruthenium oxide is from 1.0 nm to 10.0 nm. Further Ru catalysts supported on titanium dioxide or zirconium dioxide are known from DE-A 197 34 412 known. For the preparation of the ruthenium chloride and ruthenium oxide catalysts described therein, which contain at least one compound titanium oxide and zirconium oxide, a number of Ru starting compounds have been indicated, such as, for example, ruthenium-carbonyl complexes, ruthenium salts of inorganic acids, ruthenium-nitrosyl complexes, Ruthenium-amine complexes, ruthenium complexes of organic amines or ruthenium-acetylacetonate complexes. In a preferred embodiment, TiO _{2 was} used as a carrier in the form of rutile. The ruthenium oxide catalysts have quite high activity, but their preparation is complicated and requires a series of operations such as precipitation, impregnation followed by precipitation, etc., whose scale-up is technically difficult. In addition, ruthenium oxide catalysts also tend to sinter at high temperatures and thus to deactivate.

EP 0 936 184 A2 describes a process for catalytic hydrogen chloride oxidation wherein the catalyst is selected from an extensive list of possible catalysts. Among the catalysts is the variant designated by number (6), which consists of the active component (A) and a component (B). The component (B) is a compound component having a certain thermal conductivity. As an example, mention is made, among other things, of tin dioxide. In addition, the component (A) can be mounted on a support. However, possible carriers do not include tin dioxide. There is not a single example in which tin dioxide was used. Furthermore, this patent exclusively describes the use of ruthenium oxide as a catalyst component. This is produced in particular by impregnating the support with a ruthenium chloride solution, precipitating the ruthenium hydroxide on the support and then calcining. Thus, said document does not disclose the use of tin dioxide as catalyst support in the catalytic gas-phase oxidation of hydrogen chloride with oxygen nor the use of a halogen-containing ruthenium compound as a catalyst component.

The previously developed catalysts for the Deacon process have a number of shortcomings. At low temperatures their activity is insufficient. By a Increasing the reaction temperature, although the activity could be increased, but this led to sintering / deactivation or loss of the catalytic component.

The object of the present invention was to provide a catalytic system which accomplishes the oxidation of hydrogen chloride at low temperatures and with high activities. The task is solved by the development of a very specific combination of catalytically active components and a specific carrier material.

Surprisingly, it has been found that by the targeted support of a halogen-containing ruthenium compound on tin dioxide, due to a special interaction between catalytically active component and support, new highly active catalysts are provided, especially at temperatures of <350 ⁰ C in the hydrogen chloride oxidation still have a high catalytic activity. A further advantage of the catalyst system according to the invention is the simple and easily scalable application of the catalytically active component to the support. Furthermore, a conversion of the catalytically active halogen-containing species into the oxide is eliminated.

The present invention thus provides a process for producing chlorine by catalytic gas-phase oxidation of hydrogen chloride with oxygen, wherein the catalyst comprises at least tin dioxide and at least one halogen-containing ruthenium compound.

In a preferred embodiment, tin (IV) oxide is used as a carrier of the catalytically active component, particularly preferably tin dioxide in rutile structure.

According to the invention, a halogen-containing ruthenium compound is used as the catalytically active component. It is a compound in which halogen ionic to polarized is covalently bonded to a ruthenium atom.

The halogen in the halogen-containing ruthenium compound is preferably selected from the group consisting of chlorine, bromine and iodine. Particularly preferred is chlorine.

The halogen-containing ruthenium compound includes those consisting solely of halogen and ruthenium. However, preference is given to those which contain both oxygen and halogen, in particular chlorine or chloride. At least one ruthenium oxychloride compound is particularly preferably used as the catalytically active species. A ruthenium oxychloride compound in the context of the invention is a compound in which both oxygen and chlorine are present ionically to polarized covalently bonded to ruthenium. Such a compound thus has the general composition RuO _x CI _y . According to the invention, various such ruthenium oxychloride compounds can be present side by side in the catalyst. Examples of defined Ruthenium oxychloride compounds include in particular the following compositions: Ru ₂ OCl ₄ , RuOCl ₂ , Ru ₂ OCl ₅ and Ru ₂ OCl ₆ .

In a particularly preferred process, the halogen-containing ruthenium compound is a mixed compound corresponding to the general formula RuCl _x Oy, wherein x is a number from 0.8 to 1.5 and y is a number from 0.7 to 1.6.

The catalytically active ruthenium oxychloride compound according to the invention is preferably obtainable by a process which comprises first applying a particular aqueous solution or suspension of at least one halogen-containing ruthenium compound to tin dioxide and removing the solvent.

Other conceivable methods include the chlorination of non-chlorinated ruthenium compounds, such as ruthenium hydroxides, before or after coating on the support.

A preferred method involves applying an aqueous solution of RuCl ₃ to the tin dioxide.

The application includes in particular the impregnation of the optionally freshly precipitated tin dioxide with the solution of the halogen-containing ruthenium compound.

After the application of the halogen-containing ruthenium compound is generally carried out a drying step, which is conveniently carried out in the presence of oxygen or air to at least partially to allow conversion to the preferred ruthenium oxychloride compounds. To avoid conversion of the preferred ruthenium oxychloride compounds in ruthenium oxides, the drying should preferably be less than 280 ° C carried out, in particular at least 80 ⁰ C, more preferably at least 100 ⁰ C.

A preferred method is characterized in that the catalyst is obtainable in that a containing a halogen-containing ruthenium compound tin dioxide at a temperature of at least 200 ⁰ C, preferably at least 22O ⁰ C, more preferably at least 25O ⁰ C to 500 ⁰ C, in particular is calcined in an oxygen-containing atmosphere, more preferably under air.

In a particularly preferred process, the proportion of ruthenium from the halogen-containing ruthenium compound in relation to the total catalyst composition, in particular after calcining, is 0.5 to 5% by weight, preferably 1.0 to 3% by weight, more preferably 1.5 to 3% by weight. If, as a catalytically active species, halogen-ruthenium compounds which contain no oxygen are to be absorbed, drying is also possible at elevated temperatures, with exclusion of oxygen.

The substantial conversion of the halogen-ruthenium compound into the preferred ruthenium oxyhalogen compounds is preferably carried out in the reactor under the conditions of the oxidation process. Thus, the evaluation of the interplanar spacings in HR-TEM (High Resolution - Transmission Electron Microscopy) of a ruthenium chloride SnO ₂ catalyst shows that it converts from hydrogen chloride to ruthenium oxychloride under the conditions of gas-phase oxidation.

Preferably, the catalyst is obtainable by a process which comprises applying an aqueous solution or suspension of at least one halogen-containing ruthenium compound to tin dioxide and then drying at less than 280 ^° C., and then activating under the conditions of gas-phase oxidation of hydrogen chloride, in which a substantial conversion takes place in the Rutheniumoxychloride. The longer the drying takes place in the presence of oxygen, the more oxychloride forms.

Usually, the loading of the catalytically active component, i. of the halogen-containing ruthenium compound, in the range of 0.1-80% by weight, preferably in the range of 1-50% by weight, particularly preferably in the range of 1-20% by weight, based on the total weight of the catalyst ( Catalyst component and carrier).

Most preferably, the catalytic component, i. the halogen-containing ruthenium compound, for example, by wet and wet impregnation of a carrier with suitable present in solution starting compounds or starting compounds in liquid or colloidal form, up and co-Auffällverfahren, and ion exchange and gas phase coating (CVD, PVD) are applied to the support.

Suitable promoters are in particular basic metals - e.g. Alkali, alkaline earth and rare earth metals -, alkali metals are particularly preferred Na and Cs and alkaline earth metals, particularly preferred are alkaline earth metals, in particular Sr and Ba.

The promoters may, but are not limited to, be applied to the catalyst by impregnation and CVD processes; preference is given to impregnation, particularly preferably after application of the main catalytic component.

To stabilize the dispersion of the main catalytic component on the support, for example, but not limited to, various dispersion stabilizers such as For example, scandium oxides, manganese oxides and lanthanum oxides, etc. are used. The stabilizers are preferably applied together with the main catalytic component by impregnation and / or precipitation.

The tin dioxide used according to the invention is commercially available (eg from Chempur, Alfa Aesar) or obtainable, for example, by alkaline precipitation of tin (TV) chloride and subsequent drying. It has in particular BET surface areas of about 1 to 300 m ² / g.

The tin dioxide used as the carrier according to the invention may under thermal stress (such as at temperatures greater than 250 ⁰ C) undergo a reduction in the specific surface area, which may be accompanied by a reduction in the catalyst activity. The pretreatment of the Vicinal carrier can be done by calcination, for example at 250-1500 ° C, but more preferably at 300-1200 ⁰ C. The above-mentioned dispersion stabilizers may also serve to stabilize the surface of the tin dioxide at high temperatures.

A further preferred method is namely characterized in that the reaction temperature in the catalytic gas phase oxidation up to 450 ⁰ C, preferably at most 420 ⁰ C.

The catalysts can be dried under normal pressure or preferably at reduced pressure, preferably at 40 to 200 ^° C. The drying time is preferably 10 minutes to 6 hours.

The catalysts according to the invention for the hydrogen chloride oxidation are characterized by a high activity at low temperatures.

Preferably, as described above, the new catalyst composition is used in the catalytic process known as the Deacon process. Here, hydrogen chloride is oxidized with oxygen in an exothermic equilibrium reaction to chlorine, whereby water vapor is obtained. The reaction temperature is usually from 180 to 500 ⁰ C, particularly preferably 200 to 400 ⁰ C, particularly preferably 220 to 350 ⁰ C, the reaction pressure can be 1 to 25 bar, preferably 1, 2 to 20 bar, particularly preferably 1.5 to 17 bar, most preferably 2 to 15 bar. Since it is an equilibrium reaction, it is expedient to work at the lowest possible temperatures at which the catalyst still has sufficient activity. Furthermore, it is expedient to use oxygen in excess of stoichiometric amounts of hydrogen chloride. For example, a two- to four-fold excess of oxygen is customary. Since no loss of selectivity is to be feared, it may be economically advantageous to work at relatively high pressure and, accordingly, longer residence time than normal pressure. Suitable preferred catalysts for the Deacon process which may be combined with the novel catalyst support include ruthenium oxide, ruthenium chloride or other ruthenium compounds supported on silica, alumina, titania or zirconia.

In addition to the ruthenium compound, suitable catalysts may also contain compounds of other noble metals, for example gold, palladium, platinum, osmium, iridium, silver, copper or rhenium. Suitable catalysts may further contain chromium oxide.

The catalytic hydrogen chloride oxidation may preferably be adiabatic or isothermal or approximately isothermal, batchwise, but preferably continuously or as a fixed bed process, preferably as a fixed bed process, particularly preferably in tube bundle reactors to heterogeneous catalysts at a reactor temperature of 180 to 500 ⁰ C, preferably 200 to 400 ^0th C, more preferably 220 to 35O ⁰ C and a pressure of 1 to 25 bar (1000 to 25000 hPa), preferably 1.2 to 20 bar, more preferably 1.5 to 17 bar and particularly preferably carried out 2.0 to 15 bar become.

Typical reactors in which the catalytic hydrogen chloride oxidation is carried out are fixed bed or fluidized bed reactors. The catalytic hydrogen chloride oxidation can preferably also be carried out in several stages.

In the case of the adiabatic, isothermal or approximately isothermal mode of operation, it is also possible to use a plurality of reactors with intermediate cooling, that is to say 2 to 10, preferably 2 to 6, particularly preferably 2 to 5, in particular 2 to 3, connected in series. The oxygen can be added either completely together with the hydrogen chloride before the first reactor or distributed over the various reactors. This series connection of individual reactors can also be combined in one apparatus.

Another preferred embodiment of a suitable device for the method is that one uses a structured catalyst bed, in which the catalyst activity in

Flow direction increases. Such structuring of the catalyst bed can be achieved by different impregnation of the catalyst support with active material or by different

Dilution of the catalyst with an inert material. As an inert material, for example, rings, cylinders or balls of tin dioxide, titanium dioxide, zirconium dioxide or mixtures thereof, alumina, steatite, ceramic, glass, graphite or stainless steel can be used. In the preferred use of shaped catalyst bodies, the inert material should preferably similar outer

Have dimensions. Ais shaped catalyst bodies are molded body with arbitrary shapes, preferably are tablets, rings, cylinders, stars, wagon wheels or balls, particularly preferred are rings, cylinders, balls or star strands as a form. The spherical shape is preferred. The size of the shaped catalyst body, bsp. On average, the diameter of spheres or the maximum cross-sectional width is 0.3 to 7 mm, more preferably 0.8 to 5 mm.

Alternatively to the finely divided catalyst (fOrm) bodies described above, the support may also be a monolith of support material, e.g. not only a "classical" carrier body with parallel, radially non-interconnected channels, it also includes foams, sponges or the like with three-dimensional connections within the carrier body to the monoliths and carrier body with cross-flow channels.

The monolithic carrier may have a honeycomb structure, but also an open or closed cross-channel structure. The monolithic carrier has a preferred cell density of 100 to 900 cpsi (cells per square inch), more preferably 200 to 600 cpsi.

A monolith according to the present invention is e.g. in "Monoliths in multiphase catalytic processes - aspects and prospects" by F. Kapteijn, J.J. Heiszwolf T.A. Nijhuis and J.A. Moulijn, Cattech 3, 1999, p24.

Silica, graphite, rutile or anatase titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, preferably titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably γ- or δ-aluminum oxide, are particularly suitable as additional carrier materials or binders for the carrier or their mixtures. Preferred binder is alumina or zirconia. The proportion of binder, based on the finished catalyst, can be 1 to 70% by weight, preferably 2 to 50% by weight and very preferably 5 to 30% by weight. The binder increases the mechanical stability (strength) of the shaped catalyst bodies.

In a particularly preferred variant of the invention, the catalytically active component is substantially on the surface of the actual support material, e.g. of the tin oxide, but not present on the surface of the binder.

For additional doping of the catalysts are suitable as promoters alkali metals such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, more preferably potassium, alkaline earth metals such as magnesium, calcium, strontium and barium, preferably magnesium and calcium, more preferably magnesium , Rare earth metals such as scandium, yttrium, lanthanum, cerium, praseodymium and neodymium, preferably scandium, yttrium, lanthanum and cerium, more preferably lanthanum and cerium, or mixtures thereof. The conversion of hydrogen chloride in a single pass may preferably be limited to 15 to 90%, preferably 40 to 85%, particularly preferably 50 to 70%. After conversion, unreacted hydrogen chloride can be partly or completely recycled to the catalytic hydrogen chloride oxidation. The volume ratio of hydrogen chloride to oxygen at the reactor inlet is preferably 1: 1 to 20: 1, preferably 2: 1 to 8: 1, particularly preferably 2: 1 to 5: 1.

The heat of reaction of the catalytic hydrogen chloride oxidation can be used advantageously for the production of high-pressure steam. This can be used to operate a phosgenation reactor and / or distillation columns, in particular of isocyanate distillation columns.

In a further step, the chlorine formed is separated off. The separation step usually comprises several stages, namely the separation and optionally recycling of unreacted hydrogen chloride from the product gas stream of the catalytic hydrogen chloride oxidation, the drying of the obtained, substantially chlorine and oxygen-containing stream and the separation of chlorine from the dried stream.

The separation of unreacted hydrogen chloride and water vapor formed can be carried out by condensation of aqueous hydrochloric acid from the product gas stream of hydrogen chloride oxidation by cooling. Hydrogen chloride can also be absorbed in dilute hydrochloric acid or water.

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

The invention further provides a catalyst composition comprising tin dioxide and at least one halogen-containing ruthenium compound.

Preferred is a composition characterized in that the halogen is selected from the group: chlorine, bromine and iodine.

The halogen-containing ruthenium compound particularly preferably comprises a ruthenium oxychloride compound.

Most preferably, the halogen-containing ruthenium compound is a mixed compound corresponding to the general formula RuCl _x Oy, wherein x is a number from 0.8 to 1.5 and y is a number from 0.7 to 1.6. The catalyst composition is preferably obtainable by a process which comprises applying a particular aqueous solution or suspension of at least one halogen-containing ruthenium compound to tin dioxide and removing the solvent.

In this case, the halogen-containing ruthenium compound RuCl ₃ is particularly preferred.

The catalyst composition is obtainable, in particular, by a process which comprises applying an aqueous solution or suspension of at least one halogen-containing ruthenium compound to tin dioxide and subsequently drying it at at least 80 ^° C., preferably at least 100 ^° C.

The catalyst composition is particularly preferably obtainable by a method that a loaded with a halogen-containing ruthenium compound Zinndioxidträger at a temperature of at least 200 ⁰ C, preferably at least 240 ⁰ C, particularly preferably at least 27O ⁰ C to 500 ⁰ C, in particular in an oxygen-containing Atmosphere, particularly preferably calcined under air.

The proportion of the halogen-containing ruthenium compound in relation to the total catalyst composition is, in particular after calcining, 0.5 to 5% by weight, preferably 1.0 to 3% by weight.

Another object of the invention is the use of the catalyst composition as a catalyst, in particular for oxidation reactions, particularly preferably as a catalyst in the catalytic gas phase oxidation of hydrogen chloride with oxygen.

The following examples illustrate the present invention:

Examples

Example 1 (Invention)

Support of ruthenium chloride on SnO ₂

In a round bottom flask with dropping funnel and reflux condenser, 20 g of commercially available stannic oxide (Chempur, having a BET surface area of 4.4 m ² / g) in a solution of commercially available 2.35 g of ruthenium chloride n-hydrate suspended in 50 ml of water and 180 min at

Room temperature and then stirred at 65 ⁰ C for 120 min. The excess solution was filtered off and the moist solid dried at 120 ° C in a vacuum oven for 4 h and each

5 g then dried for 3 h at 250 ⁰ C in a stream of air, whereby a ruthenium chloride catalyst supported on tin (IV) oxide was obtained. The amount determined by elemental analysis (ICP-OES)

Ru was 4.1% by weight of Cl 1.1% by weight.

Example 2 (Invention)

In a round bottom flask with dropping funnel and reflux condenser, 20 g of commercially available stannic oxide (Sigma-Aldrich, having a BET surface area of 15 m ² / g) in a solution of commercially available 2.35 g of ruthenium chloride n-hydrate in Suspended 50 ml of water and stirred for 60 min at room temperature. Subsequently, the water is separated in an air stream at 60 ⁰ C. Calcination was carried out for 16 h at 250 ⁰ C in the air stream, whereby a ruthenium chloride catalyst supported on tin (IV) oxide was obtained. The amount of Ru determined by elemental analysis (ICP-OES) was 3.8% by weight and that of Cl was 1.6% by weight.

Example 3 (comparison)

Support of ruthenium chloride on silica gel (SiO ₂ )

According to the procedure in Example 1, a catalyst ruthenium chloride was prepared on silica (silica gel 100, Merck) and calcined for 3 h at 250 ⁰ C in an air stream. The amount of Ru determined by elemental analysis (ICP-OES) was 4.1% by weight, of Cl 0.8% by weight.

Example 4 (comparison)

Support of ruthenium oxide on titanium dioxide (TiO ₂ )

20 g of support (titanium oxide, manufacturer Sachtleben, with a BET surface area of 90 m ² / g) were suspended at room temperature in a 1 L three-necked flask and stirred with a magnetic stirrer. 1.93 g Ruthenium chloride n-hydrate was dissolved in 50 ml of water and added to the suspension. Subsequently, the suspension was stirred for 30 minutes. Then, within 15 minutes, 24 g of 10% sodium hydroxide solution were added dropwise and the mixture was stirred for a further 30 minutes. Thereafter, a further 12 g of 10% sodium hydroxide solution were added dropwise in 10 minutes. The reaction mixture was then heated to 65 ° C and kept for 1 h at this temperature and cooled with stirring to 40 ⁰ C. Thereafter, the suspension was filtered off and the solid was washed five times with 50 ml of water. The moist solid was dried at 120 ^° C. in a vacuum drying oven for 4 hours and then calcined in a muffle furnace for 2 hours at 300 ^° C. The amount of Ru determined by elemental analysis (ICP-OES) was 4.0% by weight of that of Cl <0.2% by weight.

Example 5 (reference)

Blank test with tin dioxide

As a blank, tin dioxide was used instead of a catalyst and tested as described below. The small amount of chlorine produced is due to the gas phase reaction.

Catalyst Tests Examples 1-5

Use of the catalysts in HCl oxidation

The catalysts from Examples 1 to 5 were in a fixed bed in a quartz reaction tube (internal diameter 10 mm) at 300 ⁰ C with a gas mixture of 80 ml / min

(STP) Hydrogen chloride and 80 ml / min (STP) oxygen flows through. The quartz reaction tube was heated by an electrically heated sand fluid bed. After 30 minutes, the product gas flow for

Passed for 10 min in 16% potassium iodide solution. The resulting iodine was then treated with 0.1 N

Titrated back thiosulfate solution to determine the amount of chlorine introduced. Table 1 shows the results. Table 1: Activity in HCl oxidation

Example Compound Ru Cl Chlorination Chlorination

% By weight% mmol / min.g mmol / min.g

(Cat) (Ru)

1 RuCl ₃ / SnO ₂ 4.1 1.1 0.35 8.5

2 RuCl ₃ / SnO ₂ 3.8 3.8 1.6 0.89 23.4

3 (Cf.) RuCl ₃ / Si0 ₂ 4.1 0.8 0.15 3.8

4 (VgI) RuO ₂ / TiO ₂ 4.0 <0.2 0.55 13.7

5 (Ref.) SnO ₂ - - (0.08) -

Long-term test: Long-term stability of tin oxide-supported catalyst

The catalyst of Example 1 was tested as described above, but the experimental time was extended and several samples were taken by bubbling into 16% potassium iodide solution for 10 minutes. This results in the chlorine quantities listed in FIG.

Example 6

4.994 g of commercial ruthenium chloride n-hydrate was dissolved in 16.62 g of H2O. 100 g spherical SnO2 moldings having an average diameter of 1.9 mm, a BET of 45.1 mVg and 15 wt% A12O3 as binder were added to the solution and mixed until the solution was completely absorbed by the carrier. After a service life of 1 h, the solid was dried in an air stream at 60 ⁰ C overnight. Subsequently, the catalyst was calcined at 250 ^° C. for 16 h. The amount of Ru determined by elemental analysis (ICP-OES) was 1.9% by weight, of Cl 0.5% by weight.

An electron micrograph / analysis (EDX) showed that the catalytically active species (ruthenium oxide chloride) is only on the tin oxide but not on the surface of the alumina (binder). Catalyst Test Example 6

Use of the catalysts in HCl oxidation

25 g of the catalyst from example 6 were installed in a Ni fixed bed reactor (diameter 10 mm, length 800 mm) together with 75 g of uncoated support. In this case, a fixed bed of about 150 mm was obtained. The fixed bed was at 300 ⁰ C and a pressure of 4 bar with a gas mixture of 56 L / h (STP) hydrogen chloride and 28 L / h (STP) oxygen flowed through. Of the

Ni reactor was heated by means of a heat transfer medium. After 30 min was the

Product gas stream passed for 5 min in 16% potassium iodide solution. The resulting iodine was then back titrated with 0.1 N thiosulfate standard solution to determine the amount of chlorine introduced. The catalyst activity was calculated therefrom 0.40 kg _α2 / kgic _A τ "h.

In addition, the addition of aluminum oxide as a binder apparently caused a higher strength of the spherical catalyst than comparable moldings which consist only of tin oxide as a carrier material.

Example 7

Sn coating

20 g of alumina shaped bodies (high-extrudate, 4x9 mm, Sasol) were placed in an iced-water Erlenmeyer flask and covered with 93.34 g of SnCl ₄ and allowed to stand for 30 minutes. Subsequently, the SnCl ₄ was decanted off into a second Erlenmeyer flask. The shaped bodies were covered with 150 ml of water via a dropping funnel and allowed to stand for 30 minutes. The thus coated moldings were washed neutral with water and then dried at 60 ⁰ C / 10 mbar in a drying oven to constant weight (21.51 g). This process was repeated once more. Subsequently, 5 g of the molding were calcined for 4 h at 750 ⁰ C in a muffle furnace. Example 8

Ru-impregnation

0.078 g of ruthenium chloride n-hydrate (Heraeus) were dissolved in 0.39 ml of water and added to 2.5 g of the carrier prepared in Example 7 and mixed until the solution was taken up by the carrier. The impregnation time was 1.5 h. The moist solid was then dried at 60 ^° C. in the oven (air) for about 5 hours. The yield was 2.615 g. The thus prepared ruthenium-containing catalyst was finally calcined for 16 h at 250 ⁰ C in a muffle furnace. The ruthenium content was 1, lWew .-% based on the catalyst material.

FIG. 2 shows a scanning electron micrograph of the extrudate cross section. Figures 3 and 4 show the tin and the ruthenium distribution of this section. Taking into account the carrier-free image sections, the uniform distribution of ruthenium in the carrier extrudate can be seen.

Catalyst Test Example 8

Use of the catalysts in HCl oxidation

Catalytic tests

The catalyst from Example 8 was in a solid bed in a quartz reaction tube (diameter 10 mm) at 300 ⁰ C with a gas mixture of 80 ml / min (STP) of hydrogen chloride and 80 ml / min (STP) oxygen flowed through. The quartz reaction tube was heated by an electrically heated sand fluid bed. After 30 minutes, the product gas stream was passed into 16% potassium iodide solution for 10 minutes. The resulting iodine was then back titrated with 0.1 N thiosulfate standard solution to determine the amount of chlorine introduced. The result was a space-time yield of 1.46 kg ca / kg _K a _f h.

Claims

claims

A process for the production of chlorine by catalytic gas-phase oxidation of hydrogen chloride with oxygen, characterized in that the catalyst comprises at least tin dioxide and at least one halogen-containing ruthenium compound.

2. The method according to claim 1, characterized in that as halogen a halogen from the series: chlorine, bromine and iodine is selected.

3. The method according to claim 1 or 2, characterized in that the halogen-containing ruthenium compound comprises a Rutheniumoxychlorid compound.

4. The method according to claim 3, characterized in that the halogen-containing ruthenium compound is a compound corresponding to the general formula RuCl _x O _y , wherein x is a number from 0.8 to 1, 5 and y is a number from 0.7 to 1, 6 means.

5. The method according to any one of claims 1 to 4, characterized in that the catalyst is obtainable by a method which comprises applying a particular aqueous solution or suspension of at least one halogen-containing ruthenium compound on tin dioxide and removing the solvent.

6. The method according to claim 5, characterized in that the halogen containing ruthenium compound RUCI ₃ is.

7. The method according to claim 5 or 6, characterized in that the catalyst is obtainable by a method which comprises applying an aqueous solution or suspension of at least one halogen-containing ruthenium compound on tin dioxide and the subsequent drying at least 8O ⁰ C, preferably at least 100 comprises ⁰ C.

8. The method according to any one of claims 1 to 7, characterized in that the catalyst is obtainable in that a loaded with a halogen-containing ruthenium tin carrier at a temperature of at least 200 ⁰ C, preferably at least 220 ⁰ C, more preferably at least 25O ⁰ C to 500 ⁰ C, in particular in one

Oxygen-containing atmosphere, particularly preferably calcined under air.

9. The method according to any one of claims 1 to 8, characterized in that the proportion of ruthenium from the halogen-containing ruthenium compound in relation to the total catalyst composition, in particular after calcination 0.5 to 5 wt .-%, preferably 1.0 to 3 % By weight, more preferably 1.5 to 3% by weight.

10. The method according to any one of claims 1 to 9, characterized in that the tin dioxide is present at least partially, preferably completely in the rutile form.

11. The method according to any one of claims 1 to 10, characterized in that the gas phase oxidation of the hydrogen chloride, the passing of a hydrogen chloride and oxygen-containing gas at a temperature of 180 to 500 ⁰ C, preferably 200 to

450 ⁰ C, more preferably 220 to 380 ° C comprises.

12. The method according to any one of claims 1 to 11, characterized in that the gas phase oxidation at a pressure of 1 to 25 bar, preferably 1.2 to 20 bar, more preferably 1, 5 to 17 bar and particularly preferably 2.0 to 15 bar is performed.

13. The method according to any one of claims 1 to 12, characterized in that the gas phase oxidation is performed adiabatically or isothermally, in particular adiabatically.

14. Use of tin dioxide as a catalyst support for a catalyst in the catalytic gas phase oxidation of hydrogen chloride with oxygen.

A catalyst composition comprising tin dioxide and at least one halogen-containing ruthenium compound.

16. The composition according to claim 15, characterized in that the halogen is selected from the series: chlorine, bromine and iodine.

17. The composition of claim 15 or 16, characterized in that the halogen-containing ruthenium compound comprises a ruthenium oxychloride compound.

18. The composition according to claim 17, characterized in that the halogen-containing ruthenium compound is a mixed compound corresponding to the general formula RuCl _x Oy, wherein x is a number from 0.8 to 1, 5 and y is a number from 0.7 to 1 , 6 means.

19. A composition according to any one of claims 15 to 18, characterized in that the catalyst is obtainable by a process which comprises applying a particular aqueous solution or suspension of at least one halogen-containing

Ruthenium compound on tin dioxide and removing the solvent comprises.

20. The composition according to claim 19, characterized in that the halogen-containing ruthenium compound RUCI ₃ is.

21. A composition according to claim 19 or 20, characterized in that the catalyst is obtainable by a process which comprises applying an aqueous solution or Suspension of at least one halogen-containing ruthenium compound on tin dioxide and the subsequent drying at least 8O ⁰ C, preferably at least 100 ⁰ C comprises.

22. The composition according to any one of claims 15 to 21, characterized in that the catalyst is obtainable in that a containing a halogen-containing ruthenium compound tin dioxide carrier at a temperature of at least

200 ⁰ C, preferably at least 220 ⁰ C, more preferably at least 250 ⁰ C to 500 ⁰ C, in particular in an oxygen-containing atmosphere, more preferably calcined under air.

23. A composition according to any one of claims 15 to 22, characterized in that the proportion of the halogen-containing ruthenium compound in relation to the total

Catalyst composition, in particular after calcination 1 to 5 wt .-%, preferably 1.5 to 3 wt .-% is.

24. The composition according to any one of claims 15 to 23, characterized in that it comprises a binder for the carrier which is selected from the series: silica, graphite, titanium dioxide with rutile or anatase structure, zirconium dioxide, alumina or mixtures thereof, preferably Titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, more preferably alumina or zirconia and wherein the proportion of binder based on the finished catalyst is preferably 1 to 70 wt.%, Particularly preferably 2 to 50 wt.% And most preferably 5 to 30 wt. %.

25. Use of the composition according to any one of claims 15 to 24 as a catalyst.

26. Use according to claim 25 as a catalyst for oxidation reactions.

27. Use according to claim 25 or 26 as a catalyst in the catalytic gas phase oxidation of hydrogen chloride with oxygen.