WO2010020346A1

WO2010020346A1 - Catalytic oxidation of hydrogen chloride with ozone

Info

Publication number: WO2010020346A1
Application number: PCT/EP2009/005684
Authority: WO
Inventors: Eberhard Stelter; Frank-Dieter Kopinke; Ulf Roland; Robert Köhler; Frank Holzer; Friedhelm Kämper
Original assignee: Bayer Materialscience Ag
Priority date: 2008-08-16
Filing date: 2009-08-06
Publication date: 2010-02-25
Also published as: DE102008038096A1

Abstract

The invention relates to a method for the heterogeneous catalytic oxidation of hydrogen chloride by means of gases comprising oxygen, wherein a gas mixture comprising at least hydrogen chloride, oxygen, ozone and optionally further additional compounds are produced and passed through a fixed catalyst.

Description

Catalytic oxidation of hydrogen chloride with ozone

The invention relates to a process for the production of chlorine by heterogeneously catalyzed oxidation of hydrogen chloride with ozone under conditions which allow efficient utilization of the ozone and the achievement of high levels of HCl conversion.

In the production of many organic compounds as well as in the production of raw materials for the production of polymers, chlorine (Cl ₂ ) is used as a reaction partner in the production chain. The conversion of chlorine-containing intermediates into chlorine-free end products often produces hydrogen chloride (HCl) as a by-product. An example of this reaction chain is the production of polyurethanes via phosgene as an intermediate. The further use of the resulting hydrogen chloride can be carried out, for example, by marketing the aqueous solution (hydrochloric acid) or by using the hydrogen chloride in syntheses of other chemical products. However, the accumulating amounts of hydrogen chloride can not always be fully utilized at the site of his seizure. Transport of hydrogen chloride or hydrochloric acid over long distances is uneconomical. The disposal of hydrogen chloride by neutralization with lye is technically possible, but also unattractive from an economic and environmental point of view. For economic and ecological reasons, a production with a closed chlorine cycle is therefore desirable. This should include the recycling of hydrogen chloride to chlorine. Because of the essential role of chlorine chemistry in the chemical industry and because of the large amounts of hydrogen chloride in the order of> 10 ⁹ kg / a in Germany alone, technologies for HCl recycling have enormous economic importance.

HCl recycling processes are state of the art (compare Ullmann Enzyklopadie der technischen Chemie, Weinheim, 4th edition 1975, Vol. 9, pp. 357 ff. Or Winnacker-Kuchler: Chemical Technology, Processes and Products, Wiley-VCH Verlag, 5 Edition 2005, Vol. 3, pp. 512 ff.): These include in particular the electrolysis of hydrochloric acid and the oxidation of hydrogen chloride with oxygen (Deacon reaction) according to:

4 HCl + O ₂ -> 2 Cl ₂ + 2 H ₂ O

The Deacon reaction can be carried out either at high temperatures (> 700 ° C) purely thermally or in the presence of catalysts at a temperature of 300 to 450 ⁰ C. The purely thermal Deacon reaction is not used for HCl recycling on an industrial scale. Suitable catalysts for the catalyzed variant are described, for example, in DE 1 567 788 A1. Older methods use as the catalytically active component mostly doped copper chloride (eg Shell-Chlorine method, Dow-Hercules method), while more modern methods use ruthenium-based catalysts. The Deacon reaction is exothermic (standard reaction enthalpy -57 kJ / mol chlorine) and reversible. At the required reaction temperature of> 300 ° C for technical processes, the reaction equilibrium is no longer completely on the product side. From the known thermodynamic data of the reaction follows that, for example, at 350 ⁰ C reaction temperature, 0.1 MPa gas pressure and stoichiometric Eduktverhältnissen (HCl: O ₂ = 4: 1 moles / mol) a maximum degree of HCl conversion of about 85% can be achieved. Higher HCl conversion is achievable only by an excess of oxygen, but at the expense of higher costs for the treatment of the reaction products. If it were possible to lower the reaction temperature to 100 ^° C., an equilibrium conversion of 99% would be possible.

Another major disadvantage of the catalyzed HCl oxidation is that the catalyst used for the reaction is sensitive to impurities in the hydrogen chloride. As a result of a catalyst activity loss, the recycling capacity of the plant may drop rapidly and drastically. At the same time, the workup of the reaction gases leaving the reactor (oxygen, hydrogen chloride, chlorine, water) becomes even more complicated due to the incomplete conversion of the HCl oxidation. Overall, this significantly reduces the cost-effectiveness of the process.

In order to achieve a high HCl conversion even at a thermodynamically favorable, low reaction temperature, so-called non-thermal excitation sources were investigated for the Deacon reaction. Methods in which chemical reactions are not thermally activated are described, for example, in Stiller (W. Stiller: Non-thermally Activated Chemistry, Birkhäuser Verlag, Basel, Boston, 1987, pp. 33-34, pp. 45-49, pp. 122-124, p. 138-145.). Non-thermally activated HCl oxidation processes are described, for example, in the specifications JP 5 907 3405A, RU 2253 607 A, DD 88 309, SU 180 1943 A, Cooper et al. Eng. Chem. Fundam., 7 (3), 400-409 (1968)), van Drumpt (JD van Drumpt: Oxidation of Hydrogen. (WW Cooper, HS Mickley, RF Baddour: Oxidation of hydrogen chloride in a microwave discharge Chloride with Molecular Oxygen in a Silent Electrical Discharge, Ind. Eng. Chem., Fundam., 22 (4), 594-595 (1972)) and DE 10200602 276 A1.

JP 59-73 405A describes the photoxidation of gaseous hydrogen chloride using pulsed laser radiation or a high-pressure mercury-vapor lamp or a combination of the two photon sources mentioned in order to excite the reactants. RU 2 253 607 also describes a photochemical process for the production of chlorine in which an HCl-air mixture flows through a tubular reactor and the activation of the reactants in a reaction zone by a mercury vapor radiator. EP1914199 describes a process for producing chlorine from a gaseous hydrogen chloride and oxygen-containing Mixture under the action of ultraviolet radiation, at a wavelength in the range of 165 nm to 270 nm at a density of ultraviolet radiation of (10-40) 10 -4 W / cm 3 and a pressure of not more than 0.1 MPa. Alternatively, the oxygen may be activated upon exposure to a current of accelerated electrons having an energy of 100 keV to 2 MeV. The oxidation of the hydrogen chloride is carried out by the activated oxygen to form the target product. Almost quantitative degrees of implementation are asserted without there being any heating of the product mixture. It is not mentioned which energy expenditure is necessary for the excitation sources (UV or electrons) to achieve the stated degrees of conversion. Furthermore, there is no information on the residence time of the reactants or the size of the reaction apparatus used. According to the application, the main reaction path is via excited (individual) oxygen atoms, ozone is only mentioned as a by-product of the oxygen excitation.

WO2008002197 describes a method for the production of chlorine, in which a gaseous hydrogen chloride and oxygen mixture is transferred at a pressure of 1.1 to 5.0 bar under the action of electrical pulse discharge in a low-temperature plasma, in which hydrogen chloride is oxidized by oxygen. The oxidation product is separated after condensation of the water contained.

DD 88 309 A describes a catalyzed HCl oxidation at 150 ° -250 ° C, which is additionally supported by the use of UV radiation.

The person skilled in the art is generally familiar with the fact that mercury vapor lamps emit UV radiation in different wavelength ranges depending on the filling pressure and this radiation can be used to initiate photochemical reactions if at least one reactant absorbs photons in the relevant spectral range.

The document SU 1 801 943 A describes a process for HCl oxidation with air in an electrical pulse discharge (10 to 40 kV) at 20 to 30 ^° C. With a residence time of up to 140 s in the discharge zone, only an HCl conversion rate of up to 74% is achieved. The patent contains no information on the discharge arrangement used. Van Drumpt et al. (1972) describe the HCl oxidation in cold plasma of a modified Siemens tube at atmospheric pressure. It was possible to convert up to 6% of hydrogen chloride into chlorine. Cooper et al. (1968) describe the HCl oxidation in a high-energy microwave plasma. A reaction temperature of 500 to 700 ⁰ C and low gas pressures in the range of 13 to 27 mbar make these conditions for a technical implementation on a production scale seem less useful. - A -

The document DE 10200 602 276 A1 describes an integrated process for the preparation of isocyanates from phosgene and at least one amine and oxidation of the resulting hydrogen chloride with oxygen to chlorine, the chlorine being recycled to produce the phosgene. The document is particularly based on processes for the preparation of chlorine by non-thermally activated reaction of hydrogen chloride with oxygen, in which from the resulting gas mixture in the reaction consisting at least of the target products of chlorine and water, unreacted hydrogen chloride and oxygen and optionally other minor components such Carbon dioxide and nitrogen chlorine is removed and recycled into the phosgene production.

The main disadvantage of the previously described non-thermal HCl oxidation processes is their unsatisfactory energy efficiency. In no case has a sufficiently high degree of HCl conversion (> 90%) been described, as it is sought with the present invention.

The object of the present invention is therefore to provide a method for recycling hydrogen chloride to chlorine, which can be operated simply, safely and energy-efficiently. In particular, a very high degree of hydrogen chloride conversion (in particular at least 70%) should be achieved even with decreasing activity of an oxidation catalyst in order to simplify the workup of the reaction products and to keep the plant capacity high over long periods of operation.

The above object is achieved by a heterogeneously catalyzed oxidation of hydrogen chloride with ozone, especially at low catalyst temperature.

The invention relates to a process for the heterogeneously catalyzed oxidation of hydrogen chloride by means of oxygen-containing gases, characterized in that a gas mixture consisting at least of hydrogen chloride, oxygen, ozone and optionally other secondary components is generated and passed over a solid catalyst.

In a preferred method, a catalyst is used, as the catalytic active components of metals of the 1st, 7th or 8th subgroup of the Periodic Table of the Elements or oxides, oxide chlorides or chlorides of the metals of the 1st, 7th or 8th subgroup, or mixtures thereof Has metals or metal compounds.

The process is preferably conducted in such a way that more than one oxygen atom per consumed ozone molecule is converted during the reaction for the HCl oxidation.

The reaction temperature of the HCl oxidation with ozone is adjusted by a preferred process in a range up to 250 ^° C., preferably from 20 to 250 ^° C., preferably from 50 to 150 ^° C. Advantageously, HCl oxidation is carried out with ozone at elevated pressure, in particular a pressure of up to 25 bar, preferably 5 to 25 bar in a particularly preferred method. This facilitates, for example, coupling to previous other HCl oxidation states, which are merely catalyzed oxidation reactions of hydrogen chloride with oxygen-containing gases.

Preferably, the new HCl oxidation is carried out with ozone at an ozone concentration of 2 to 15 wt .-%, preferably 4 to 13 wt .-% based on the amount of oxygen and ozone.

Particularly advantageous is an extension of the new process, characterized in that the HCl oxidation is combined with ozone with one or more other HCl oxidation reactions and performed downstream as a further step, one or more other HCl oxidation reactions.

The other HCl oxidation reactions are catalyzed oxidation reactions of hydrogen chloride with oxygen-containing gases.

The abovementioned combined methods are preferably operated so that first the main portion of the HCl oxidation, in particular up to an HCl conversion of at least 70%, preferably at least 80%, is achieved in another catalyzed oxidation process, after which the HCl oxidation is followed by ozone ,

A preferred embodiment consists of a combination of a catalyzed Deacon reaction, which is operated at elevated temperature, in particular at least 300 ⁰ C, with a downstream ozone oxidation at low temperature, in particular <300 ° C, wherein in the oxidation state with ozone only as much ozone is fed as is necessary to achieve the desired degree of HCl conversion.

While the HCl oxidation with molecular oxygen (O ₂ ) to the usual Deacon catalysts (CuCl ₂ , FeCl ₃ , RuO _2, etc.) requires a reaction temperature of typically 300 ⁰ C and more, it was surprisingly found that on some catalysts with Ozone (O ₃ ) a rapid and smooth oxidation of hydrogen chloride to chlorine even at much lower temperature, more preferably 50 to 150 ⁰ C, is possible.

It has been found that a large number of heterogeneous catalysts, which in particular contain metals of groups 1, 7 and 8 of the periodic table, support this reaction. A particularly preferred catalyst for HCl oxidation with ozone consists of ruthenium oxide Titanium dioxide. This catalyst can be identical to the Deacon catalyst, which is also effective at high temperatures, for the possibly preceding other HCl oxidation.

Ozone is a well-known, technically used oxidizing agent that is usually produced by silent electrical discharge in a Siemens tube. Ozone can be decomposed catalytically according to 2 O ₃ -> 3 O ₂ easily into molecular oxygen. As a rule, however, only a maximum of one of the three oxygen atoms of the ozone can be utilized for the desired oxidation reactions. The remaining two oxygen atoms are lost as much less reactive molecular oxygen. They must be activated by renewed energy input, eg by increased reaction temperatures. In the heterogeneously catalyzed HCl oxidation according to the invention, it was surprisingly found that up to three oxygen atoms per ozone molecule can be utilized for the HCl oxidation, so that an advantageous reaction stoichiometry according to 6 HCl + O ₃ → 3 H ₂ O + 3 Cl _{2 is} achieved can be. Since the cost of ozone generation significantly affects the overall cost of an ozone-based process, the efficiency of ozone utilization is essential to the success of the process of the present invention.

The new heterogeneously catalyzed HCl oxidation with ozone proceeds even rapidly and completely even if unconverted hydrogen chloride in low concentration is present in addition to chlorine in high concentration in the product of a Deacon reactor. This preferred combination allows ozone feed to be minimized and matched precisely to the need to achieve high total hydrogen chloride conversions. It also provides a high degree of flexibility for controlling the overall process: a decrease in the activity of the catalyst in the primary stage (oxidation at> 300 ° C with air or technical oxygen), e.g. due to aging or partial poisoning, can be compensated by increased supply of ozone in the secondary stage. Heterogeneously catalyzed HCl oxidation with ozone is much more robust than the catalyzed Deacon reaction with molecular oxygen.

The new one- or two-stage HCl oxidation at low reaction temperatures allows the thermodynamic equilibrium of the HCl oxidation reaction to be shifted far to the side of the reaction products chlorine and water. The remaining at high HCl conversion in the product stream small amounts of hydrogen chloride require no complex recovery. They can be removed by a simple wash of water. This additionally simplifies product processing and thus improves the economic efficiency of the process.

Particularly preferred is the new heterogeneously catalyzed HCl oxidation with ozone as described above in combination with the known as Deacon process, catalyzed Deacon reaction with molecular oxygen. Here, hydrogen chloride is oxidized with oxygen in an exothermic equilibrium reaction to chlorine, wherein water vapor accrues. The reaction temperature is usually 150 to 500 ⁰ C, the usual reaction pressure is 1 to 25 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 include ruthenium oxide, ruthenium chloride or other ruthenium compounds on silica, alumina,

Titanium dioxide or zirconium dioxide as carrier. Suitable catalysts may for example by

Applying ruthenium chloride to the support and then drying or drying and calcination are obtained. Suitable catalysts may, in addition to or instead of a ruthenium compound, also contain compounds of other noble metals, for example gold, palladium, platinum, osmium, iridium, silver, copper or rhenium. suitable

Catalysts may also contain chromium (πi) oxide.

The catalyzed hydrogen chloride oxidation may be adiabatic or preferably isothermal or approximately isothermal, batchwise, but preferably continuously or as a fixed bed process, preferably as a fixed bed process, more 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 350 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 in particular 2.0 to 15 bar are performed ,

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

In the isothermal or approximately isothermal mode of operation, it is also possible to use a plurality of reactors, that is to say 2 to 10, preferably 2 to 6, particularly preferably 2 to 5, in particular 2 to 3, series-connected reactors with additional intermediate cooling. The hydrogen chloride can be added either completely together with the oxygen before the first reactor or distributed over the various reactors. This series connection of individual reactors can also be combined in one apparatus. A further preferred embodiment of a device suitable for the method consists in using a structured catalyst bed in which the catalyst activity increases in the flow direction. Such structuring of the catalyst bed can be done 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 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 have similar external dimensions.

Suitable shaped catalyst bodies are shaped bodies with any desired shapes, preference being given to tablets, rings, cylinders, stars, carriage wheels or spheres, particular preference being given to rings, cylinders or star strands as molds.

Ruthenium compounds or copper compounds on support materials, which may also be doped, are particularly suitable as heterogeneous catalysts, preference being given to optionally doped ruthenium catalysts. Examples of suitable carrier materials are silicon dioxide, 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 or mixtures thereof.

The copper or ruthenium-supported catalysts can be obtained, for example, by impregnation of the support material with aqueous solutions of CuCl ₂ or RuCl ₃ and optionally a promoter for doping, preferably in the form of their chlorides. The shaping of the catalyst can take place after or preferably before the impregnation of the support material.

For doping 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, particularly 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 moldings can then be dried at a temperature of 100 to 400 ⁰ C, preferably 100 to 300 ⁰ C, for example, under a nitrogen, argon or air atmosphere and optionally calcined. Preferably, the moldings are first dried at 100 to 150 ⁰ C and then calcined at 200 to 400 ⁰ C. 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 partially or completely recycled to the catalyzed hydrogen chloride oxidation. The volume ratio of hydrogen chloride to oxygen at the reactor inlet is preferably 1: 1 to 20: 1, preferably 1: 1 to 8: 1, more preferably 1: 1 to 5: 1.

The chlorine produced by the new process is further used in production processes for the production of polymers such as polyurethanes and PVC, which as a by-product provide the hydrogen chloride for the new oxidation process.

The invention is explained in more detail below by the examples, which, however, do not represent a limitation of the invention.

Examples

Example 1: (reaction between hydrogen chloride and ozone without catalyst)

Technical oxygen (100 ml / min) was passed through a commercial ozone generator which can generate ozone by silent discharge. At the outlet of the ozone generator, dry hydrogen chloride (100 ml / min) was added to the ozone / oxygen mixture. The mixed gas streams passed through an empty glass tube at 25 ° C (d _outside xd _Wan dx L = 22 x 1 x 110 mm). The residence time in the glass tube was about 10 s. Gas samples were taken at the inlet and outlet of the glass tube and analyzed photometrically for their chlorine and ozone content by means of a gas cuvette in a UV-vis spectrometer. Ozone has an absorption maximum at 254 nm, chlorine at 330 nm, so that both components can be determined side by side photometrically. 20 minutes after the ozone generator was switched on, the following concentrations were measured: at the entrance of the glass tube 3.0 ± 0.2% by volume of ozone and 0% by volume of chlorine; 2.8 ± 0.2 vol.% ozone and <0..1 vol.% chlorine at the outlet of the glass tube.

The example shows that without a catalyst, there is no rapid HCl oxidation by ozone in a homogeneous gas phase.

Example 2: (Heterogeneously catalyzed HCl oxidation with ozone at low temperature)

The experimental setup described in Example 1 was modified such that the glass tube was filled with a packed bed of catalyst pellets (about 30 cm ³ , 1 mol% RuO ₂ on TiO ₂ as support) and enclosed by a heating jacket. After adjusting the gas flows given in Example 1 and a reactor temperature of 50 ⁰ C, the ozone generator was turned on. For this experiment, its performance was adjusted so that the oxygen flow contained about 5% ozone by volume. The gas stream leaving the glass tube was analyzed for the first time after about 20 minutes. It contained in addition to traces of ozone (about 0.1 vol .-%) 7 vol .-% chlorine. This chlorine concentration corresponds to an HCl conversion of about 25%. From this, a reaction stoichiometry of the chlorine formation of Cl ₂ : O ₃ «2.8 moles per mole is calculated. At the outlet of the glass tube, the formation of hydrochloric acid condensate droplets was observed. This reaction regime could be maintained for several days without measurable decrease in the chlorine yield. The example shows that ozone can be almost completely reacted at low reaction temperature over a catalyst and efficiently utilized for HCl oxidation.

Example 3: (Heterogeneously catalyzed HCl oxidation with ozone at elevated temperature)

The experimental conditions described in Example 2 were changed so that the reactor temperature was raised to 180 ⁰ C. First, the experimental setup was operated with the ozone generator switched off. The product gas stream leaving the reactor was analyzed for the first time after about 20 minutes. It contained no ozone and only traces (<0.2 vol.%) Of chlorine. Thereafter, the ozone generator was turned on and set to the conditions described in Example 2. In the product stream 4.5 Vol .-% chlorine, but no ozone was measured. The chlorine concentration corresponds to an HCl conversion of about 18%. This results in a stoichiometric ratio of 1.8 moles of chlorine formed per mole of spent ozone.

Example 3 demonstrates that at a catalyst temperature of 180 ^° C., as expected, the catalyzed Deacon reaction with molecular oxygen does not proceed with sufficient speed. A comparison of the results in Examples 2 and 3 shows that with increasing catalyst temperature, the proportion of parasitic ozone decomposition increases over the HCl oxidation. Low reaction temperatures are therefore favorable.

Example 4: (series connection of Deacon reactor and HCl oxidation with ozone)

The experimental setup described in Example 2 was extended by a second heatable catalytic reactor. The first reactor was adjusted to a catalyst temperature of 360 ^° C. and passed through 200 ml / min of a gas mixture consisting of 80% by volume of HCl and 20% by volume of O ₂ (stoichiometric reaction mixture of the Deacon reaction). At the outlet of the first reactor was a condensate trap in which the water of reaction condensing out was collected. After the condensate separator, about 70% by volume of chlorine was measured in the gas stream. The chlorine concentration corresponds to an HCl conversion of about 85%. This value is close to the thermodynamically determined equilibrium conversion.

The resulting product cooled to about 50 ⁰ C product gas was at 100 ml / min of a fresh

Oxygen stream containing 6 vol .-% ozone, mixed and passed over the second catalytic reactor at a catalyst temperature of 50 ⁰ C. The product gas leaving the second reactor had a chlorine concentration of about 44% by volume. In addition, could only measure Traces of HCl (<1 vol .-%) are detected. 1% by volume of unreacted HCl would correspond to a residual HCl content of 1.1%, based on the amount of HCl used. The degree of HCl conversion at the outlet of the series connection of both reactors was therefore more than 98.9%. No ozone could be detected in the product gas. The degree of utilization of the ozone fed in for the oxidation of the HCl was> 63% under these conditions, corresponding to a reaction stoichiometry of 3.8 moles of HCl per mole of O ₃ .

The example shows that HCl can be oxidized heterogeneously catalytically efficiently with ozone even in the presence of a large excess of chlorine and in this way very high overall HCl conversion levels can be achieved.

Claims

Patentansprflche

1. A process for the heterogeneously catalyzed oxidation of hydrogen chloride by means of oxygen-containing gases, characterized in that a gas mixture consisting at least of hydrogen chloride, oxygen, ozone and optionally other secondary components is generated and passed over a solid catalyst.

2. The method according to claim 1, characterized in that the catalyst as catalytic active components metals of the 1st, 7th or 8th subgroup of the Periodic Table of the Elements or oxides, oxide chlorides or chlorides of the metals of the 1st, 7th or 8th subgroup, or mixtures of these metals or metal compounds.

3. The method according to claim 1 or 2, characterized in that in the reaction more than one oxygen atom per consumed ozone molecule for the HCl oxidation is reacted.

4. The method according to any one of claims 1 to 3, characterized in that the reaction temperature of the HCl oxidation with ozone in a range up to 250 ⁰ C preferably from 20 to 250 ⁰ C, preferably 50 to 150 ⁰ C is set.

5. The method according to any one of claims 1 to 4, characterized in that the HCl oxidation at elevated pressure, in particular a pressure of up to 25 bar, preferably 5 to 25 bar is performed.

6. The method according to any one of claims 1 to 5, characterized in that the HCl oxidation with ozone at an ozone concentration of 2 to 15 wt .-%, preferably 4 to

13 wt .-% based on the amount of oxygen and ozone is performed.

7. The method according to any one of claims 1 to 6, characterized in that the HCl oxidation is combined with ozone with one or more other HCl oxidation reactions and performed downstream as a further stage of one or more other HCl oxidation reactions.

8. The method according to claim 7, characterized in that the other HCl oxidation reactions are catalysed oxidation reactions of hydrogen chloride with oxygen-containing gases.

9. The method according to any one of claims 7 or 8, characterized in that initially the main portion of the HCl oxidation, in particular up to a HCl conversion of at least 70%, preferably at least 80% is achieved in another catalyzed oxidation process, the HCl oxidation is followed by ozone.