WO2010040468A2

WO2010040468A2 - Uranium catalyst and method for production thereof, and use thereof

Info

Publication number: WO2010040468A2
Application number: PCT/EP2009/007039
Authority: WO
Inventors: Aurel Wolf; Leslaw Mleczko; Oliver Felix-Karl SCHLÜTER; Stephan Schubert
Original assignee: Bayer Technology Services Gmbh
Priority date: 2008-10-09
Filing date: 2009-10-01
Publication date: 2010-04-15
Also published as: WO2010040468A3; DE102008050978A1

Abstract

The present invention relates to a novel uranium catalyst, to a method for the production thereof by precipitating from a solution, and to the use thereof in the course of a method for producing chlorine from hydrogen chloride. The catalyst comprises a uranuate of at least one alkali metal and/or alkaline earth metal.

Description

Uranium catalyst and process for its preparation and its uses

The present invention relates to a novel uranium catalyst, to a process for its preparation by precipitation from a solution and to its use in the course of processes for the production of chlorine from hydrogen chloride. Almost all of the technical production of chlorine today takes place through the electrolysis of aqueous saline solutions.

A major disadvantage of such chloralkali electrolysis, however, is that in addition to the desired reaction product chlorine and sodium hydroxide is obtained in large quantities. Thus, the amount of caustic soda produced is directly coupled to the amount of chlorine produced. However, the demand for caustic soda is not linked to the demand for chlorine, so sales revenues for this by-product have declined sharply, especially in the recent past.

In terms of process technology, this means that in such chloralkali electrolysis process energy is present bound in a product, which is not sufficiently compensated for the expense of this energy.

An alternative to such processes is the "Deacon process" developed by Deacon in 1868 and named after him, in which chlorine is formed by the heterogeneous catalytic oxidation of hydrogen chloride with simultaneous formation of water. The main advantage of this process is that it is decoupled from the caustic soda production. In addition, the precursor hydrogen chloride is easily accessible; it is obtained in large quantities, for example in phosgenation reactions, such as in the production of isocyanates, in which again the chlorine produced via the intermediate phosgene is preferably used.

According to the prior art, preference is given to using catalysts comprising transition metals and / or noble metals for the conversion of hydrogen chloride to chlorine. For example, WO 2007 134771 discloses that catalysts comprising at least one of copper, potassium, sodium, chromium, cerium, gold, bismuth, ruthenium, rhodium, platinum and the elements of VQI. Subgroup of the Periodic Table of the Elements can be used for this purpose. It is further disclosed that the oxides, halides or mixed oxides / halides of the aforementioned elements are preferably used. Particular preference is given to copper chloride, copper oxide, potassium chloride, sodium chloride, chromium oxide, bismuth oxide, ruthenium oxide, ruthenium chloride, ruthenium oxychloride and also rhodium oxide.

According to the disclosure of WO 2007 134771, these catalysts are distinguished by a particularly high activity for the conversion of hydrogen chloride to chlorine. WO 2004 052776 discloses that it is a well-known problem in the field of heterogeneous catalytic oxidation of hydrogen chloride to chlorine that so-called "hot spots" are formed in the processes These hot spots designate places of a disproportionate one Temperature increase, which according to the disclosure of WO 2004 052776 can lead to the destruction of the catalyst material. WO 2004 052776 discloses as a solution to this technical problem, the execution of a cooled process in tube bundles.

The technical solution disclosed in WO 2004 052776 comprises the cooling of the contact tubes. The alternative technical solution disclosed in WO 2007 134771 comprises the multistage adiabatic exports of the process with interstage cooling.

Both technical solutions are procedurally and technically complex and therefore at least economically unfavorable, since in any case the investment costs in the apparatus either due to a complicated embodiment in the case of WO 2004 052776 or due to a multiple execution simpler embodiment in the case of WO 2007 134771 are considerable. In addition, in both cases there is the technically unfavorable effect that destruction of the same can not be ruled out when using the catalysts disclosed therein.

A further alternative to the complicated apparatus of solving the above-mentioned problems with respect to the catalysts is disclosed in EP 1 170 250. According to the disclosure of EP 1 170 250, the excessively high temperatures in the region of the reaction zones are counteracted by reduced catalyst beds with reduced reaction times Activity of the catalyst can be used. Such adapted catalyst beds are achieved, for example, by "diluting" the catalyst beds with inert material, or simply by providing reaction zones with a lower proportion of catalyst, but the process disclosed in EP 1 170 250 is disadvantageous because such "dilution" reaction zones with a desired low space-time yield can be created. However, this is at the expense of the economic operation of the process, since the reaction zones, which are particularly diluted at the beginning of the process strongly with inert material, must first be heated to the operating temperatures. For this purpose, energy is expended in order to heat up the inert material that is actually not required for carrying out the reaction. Not least, according to the disclosure of EP 1 170 250 destruction of the catalysts in case of failure can not be excluded.

It is disclosed in DE 1 078 100 that catalysts comprising uranium can also be used for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine. DE 1 078 100 further discloses that such catalysts even at higher temperatures up to 480 ⁰ C without

Danger of destruction are usable. The catalysts disclosed in DE 1 078 100 include support materials such as kaolin, silica gel, kieselguhr, pumice, etc. In DE 1 078 100, the catalysts are prepared by applying the uranium from the solution to the support. It is not disclosed that the catalysts can be obtained by precipitation. Further, the disclosed catalysts do not comprise uraniumates comprising sodium and uranium. The maximum achievable conversion which can be achieved in DE 1 078 100 with the catalysts is 62%, which is small and thus disadvantageous in comparison with the conversions possible according to the disclosures set out above. This is especially true since 600 cm ^{3 of} the reactor are filled with the catalyst in the specific embodiment in which said 62% conversion is achieved. This in turn means that in the further information, the activity of the catalyst seems to be quite low.

In the patent application with the international application number PCT / EP2008 / 005183, uranium oxide catalysts are disclosed, which consist in a preferred development only of uranium oxide, or which consist in the general case of a support of uranium oxide and another catalytic component. Such further catalytically active components may be substances already disclosed in WO 2007 134771, for example. The catalysts comprising the support of uranium oxide and a further catalytically active component can be obtained according to PCT / EP2008 / 005183 by impregnating the further catalytically active component on the support of uranium oxide. It is also disclosed that the catalysts may comprise promoters, wherein these alkali, alkaline earth and rare earth metals may be especially sodium, cesium, strontium, barium and / or cerium. However, according to PCT / EP2008 / 005183, these promoters are subsequently applied to the catalyst.

The catalysts disclosed in PCT / EP2008 / 005183 are disclosed as being particularly stable, so that they are advantageous over the catalysts used according to the disclosures of WO 2004 052776, WO 2007 134771 and EP 1 170 250. The catalysts have quite high productivity at temperatures of 540 ⁰ C and 600 ⁰ C according to the embodiments of PCT / EP2008 / 005183. However, these still remain behind the possible productivities, such as would be achievable with other catalysts according to the disclosures of WO 2004 052776, WO 2007 134771 and EP 1 170 250 at lower temperatures. It was therefore omitted in favor of stability to a certain activity of the catalysts for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine, which is disadvantageous.

Starting from the prior art, therefore, there is still the need to provide a catalyst for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine, which can be used in a higher temperature range, without the risk of sustained damage, and the other Catalysts which can be used in these temperature ranges have an increased activity. - A -

It has now surprisingly been found that a catalyst for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine, characterized in that the catalyst comprises a uranate of at least one alkali and / or alkaline earth metal, can achieve this object.

Uranates in the context of the present invention refer to materials containing uranium and oxygen in any stoichiometric or non-stoichiometric composition having negative charges.

Uranates are preferably negatively charged substances having a composition of UOχ, where X is a real number greater than 1 but less than or equal to 5.

The at least one alkali and / or alkaline earth metal contained in the catalyst according to the invention, in the context of the present invention, denotes any substance of the first or second main group of the Periodic Table of the Elements.

Preferred alkali and / or alkaline earth metals are those selected from the list containing barium, calcium, cesium, potassium, lithium, magnesium, sodium, rubidium and strontium.

Particularly preferred are those selected from the list containing barium, calcium, potassium, magnesium and sodium.

The uranium rates of the at least one alkali and / or alkaline earth metal usually have a general composition [M ^q ] _{2m / q} [U "θ _{3n + m} ] with n = 1, 2, 3, 6, 7, 13, 16 and m = 1, 2 or 3 and q = 1 or 2. Here, q represents the number of positive charges that the alkali or alkaline earth metal has. Preferred uraniumates of alkali or alkaline earth metals are Na ₆ U ₇ Oa ₄ or Ba ₃ U ₇ O _24. The sodiumuranate Na ₆ U ₇ O ₂₄ is particularly preferred.

It has now surprisingly been found that the catalysts according to the invention have the same preferred and high stabilities as already disclosed in PCT / EP2008 / 005183, but at the same time have a drastically increased activity for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine ,

The catalyst according to the invention may also comprise further substances in addition to the uranate of at least one alkali and / or alkaline earth metal.

In alternative embodiments, in addition to the uranate of at least one alkali and / or alkaline earth metal, the catalyst also comprises uranium oxide. Uranium oxide in the context of the present invention refers to stoichiometric and nonstoichiometric substances containing uranium and oxygen. Examples of stoichiometric substances are about UO ₃ , UO ₂ and UO. Possible non-stoichiometric substances resulting from mixtures of these species in the sense of this invention are, for example, U ₃ O ₅ , U ₂ O ₅ , U ₃ O ₇ , U ₃ O ₈ , U ₄ O ₉ and Ui ₃ O ₃₄ . Preferred uranium oxides have a general composition of more than UO ₂ to Uθ _2.9 , these uranium oxides are understood according to the general formula UOχ with 2 <X <2.9 as uranium oxides or mixtures thereof and X indicates only the stoichiometric ratio between uranium and oxygen in the compound.

In other alternative embodiments, the catalyst in addition to the uranium of at least one alkali and / or alkaline earth metal also salts and / or oxides of alkali and / or alkaline earth metals.

Another object of the present invention is a process for the preparation of the inventive catalysts, characterized in that a) a uranium salt is precipitated by adding a strong alkali and / or alkaline earth liquor from a homogeneous, aqueous solution containing a precipitate A, and b) the Precipitate A is subsequently separated from the aqueous solution and dried.

Uranium salt in the context of the present invention means any compound comprising at least one ion of the element uranium with at least one counter-ion, wherein the total of optionally a plurality of counter-ions in total carries as many opposite charges as the totality of the optionally contained more uranium ions ,

The uranium ions in the uranium salt according to the invention may be charged twice, three times, four times, five times or six times positively. Preferably, the uranium ions in the uranium salt are four, five or six times positively charged. Particularly preferably, the uranium ions of the uranium salt are six times positively charged. Preferred uranium salts are uranyl oxide acetate UO ₂ Ac ₂ and uranium oxide nitrate UO ₂ (NO ₃ ) ₂ .

These uranium salts are particularly advantageous because they can be dissolved in aqueous solutions in high proportions and at the same time the acetate and nitrate radicals with the alkali and / or alkaline earth metal ions of the alkali and / or alkaline earth liquors are completely dissociated in water, so they are not together with the precipitate A precipitate and contaminate the precipitate. In addition, these uranium salts are particularly advantageous because they are reacted in drying at step b), at the preferred temperatures in gaseous nitrogen oxides or gaseous carbon oxides, such as carbon monoxide or carbon dioxide and thus can no longer contaminate the catalyst obtained.

Strong alkali and / or alkaline earth liquors in the context of the present invention designate lyes comprising at least one ion of an alkali and / or alkaline earth metal.

Preferred strong alkali and / or alkaline earth liquors are those having a pKa of 9.25 or greater. Preference is given to bases having a pKa value of 15 or more. Particularly preferred alkali and / or alkaline-earth liquors are sodium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide and / or sodium aluminates, such as NaAl (OH) ₄ .

The homogeneous aqueous solution present in the process according to step a) denotes solutions in which all substances are present in molecular solution.

In order for the uranium salt to be molecularly dissolved in the aqueous solution, it is therefore expedient that the aqueous solution of step a) before addition of the strong liquor has a pH which is less than or equal to 7. The person skilled in the art will have suitable means for achieving this.

By the process according to the invention, precursors of the advantageous catalysts according to the invention comprising a uranate of at least one alkali and / or alkaline earth metal are obtained in step a) by mixing the precipitate A at this time as a mixed form between uranium oxide, uranium hydroxide, alkali and / or alkaline earth lanthanate, alkali metal and / or alkaline earth metal hydroxide and / or one of the hydrates of the aforementioned, is present in the aqueous solution as a solid.

The proportions of the alkali metal and / or alkaline earth metal hydroxides in this mixed form result from the fact that precipitation from the solution entrains them at least partially and thus includes them in the precipitate A. As a result, it may also happen that uranium oxide and / or uranium hydroxide is included in the precipitate, which has not been rearranged with the alkali and / or alkaline earth metal ions to the uranium. In a preferred embodiment of the process according to the invention, step a) is carried out so that the strong alkali and / or alkaline earth liquor is simultaneously supplied with a homogeneous aqueous solution of a uranium salt in a container so that the uranium salt is precipitated from this solution as precipitate A. ,

The precipitation according to the inventive step a) as well as according to the step a) according to the preferred embodiment of the method can be carried out continuously or discontinuously.

The precipitation according to step a) of the process can be carried out in devices generally known to those skilled in the art for achieving a high mixing intensity between the homogeneous aqueous solution of a uranium salt and the strong alkali and / or alkaline earth liquor. An overview of advantageous devices and modes of operation, in particular for continuous methods for precipitation, is given for example by WO 2007 093337.

Preferred devices in which such failure is carried out are nozzles and / or micromixers.

The preferred devices are particularly advantageous because they can be integrated in an advantageous manner in continuous processes for the preparation of the catalysts of the invention. Alternatively, the precipitation can also be carried out in stirred containers.

In the erfϊndungsgemäßen step b) of the process, the precipitate A is separated from the water and by drying the optionally still present mixed form between uranium oxide, uranium hydroxide, alkali and / or alkaline earth metal, alkali and / or alkaline earth metal hydroxide and / or one of the hydrates of the aforementioned in the uraniumate according to the invention is converted at least one alkali and / or alkaline earth metal, or optionally further converted uranium hydroxides and / or Uranoxidhydrate converted into uranium oxide.

Step b) of the method according to the invention can be carried out according to embodiments generally known to the person skilled in the art. The separation of water according to step b) of the process according to the invention can be carried out, for example, by centrifugation, filtration, freeze-drying or other generally known processes using devices likewise generally known to the person skilled in the art.

The drying according to step b) of the process according to the invention can be carried out under atmospheric pressure (1013 hPa) or under reduced atmospheric pressure, it being preferred to carry out drying under reduced pressure to atmospheric pressure.

At the same time, the drying can be carried out at room temperature (23 ° C.) or at a temperature which is elevated relative to room temperature, it being preferred to carry out the drying at a temperature which is higher than room temperature. It is particularly preferred to carry out the drying at temperatures of 500 ^° C. to 1500 ^° C.

The drying can also be carried out in several stages in alternative embodiments of step b) of the process according to the invention. Preference is given in such alternative embodiments predrying at room temperature to 250 ⁰ C and a subsequent drying at temperatures of 500 ⁰ C to 1500 ⁰ C. Such temperatures of 500 ⁰ C to 1500 ⁰ C are particularly advantageous because this certainly all possibly still in Preciproduct A contained hydroxides and hydrates are thus converted to oxides and / or salts, and thus the erfϊndungsgemäßen uranium of at least one alkali and / or alkaline earth metal are preferably formed.

The erfϊndungsgemäße drying or post-drying according to the alternative embodiment of the erfϊndungsgemäßen method at 500 ⁰ C to 1500 ⁰ C may in this respect also under the well-known to those skilled in the term of "calcining" summarized.

In a further preferred development of the process according to the invention, washing of the precipitate A is provided between step a) and step b) of the process. This washing is preferably carried out with water. Such a washing is advantageous because it allows residues of alkali and / or alkaline earth liquor or uranium salt, which may have been deposited on the surface of the precipitated product A, to be washed off, so that the catalysts obtained after step b) of the process according to the invention are present on the surface have the desired composition. Another object of the present invention are processes for the preparation of chlorine, characterized in that in a reaction zone hydrogen chloride in the presence of uranium of at least one alkali and / or alkaline earth metal is oxidized to chlorine.

Such processes are preferably operated at temperatures above 400 ⁰ C in a reaction zone. Operation at such temperatures is particularly advantageous because the uranates of at least one alkali and / or alkaline earth metal are particularly active, but at the same time stable, especially at these temperatures.

It is well known to those skilled in the art that the rate of reaction of a chemical reaction generally increases with the temperature at which it is carried out. Thus, the present invention disclosed methods for the oxidation of hydrogen chloride to chlorine are particularly advantageous because for the first time the increased reaction rates for the industrial production of chlorine from hydrogen chloride can be achieved without the catalysts would be destroyed.

The catalysts according to the invention, which are preferably prepared by the process presented here, are preferably used in the abovementioned processes for preparing chlorine, since it has surprisingly been found that they are temperature-stable but at the same time substantially more active than catalysts for the abovementioned oxidation of hydrogen chloride to chlorine, as comparably stable catalysts.

Another object of the present invention is therefore the use of uraniumates of at least one alkali and / or alkaline earth metal as a catalyst for the oxidation of hydrogen chloride to chlorine.

In the following, the invention will be explained in more detail by means of examples, without, however, limiting it thereto.

An embodiment of a preferred variant of this invention is shown in Fig. 1, without the invention being limited thereto. Not erfϊndungsgemäße variants are shown in Figs. 2 to 3.

Fig. 1 shows a powder X-ray diffractogram a) of a catalyst according to the invention comprising Na ₆ U ₇ O ₂ ^ prepared according to Example 1, and hereunder idealized spectra used to identify the phases U ₃ O ₈ b), as well as Na ₆ U ₇ O ₂₄ c) according to Example 1 were used. The intensity of the X-ray signal (I) is shown in each case over the angle 2Θ.

Fig. 2 shows a powder X-ray diffractogram a) of a catalyst not according to the invention, which was prepared according to the Comparative Example 1, and below an idealized spectrum, which was used to identify the phase U ₃ O ₈ b). Shown is the intensity of the X-ray signal (I) over the angle 2Θ.

3 shows a powder X-ray diffractogram a) of a further catalyst not according to the invention, which was prepared according to the counter-example 2, and below an idealized spectrum which was used for the identification of the phase U ₃ Og b). Shown again is the intensity of the X-ray signal (I) over the angle 2Θ.

Examples

Example 1: Preparation of a catalyst according to the invention

In a three-necked flask equipped with magnetic stirrer, pH measuring device and dropping funnel, 60 ml of distilled water were introduced. In a first beaker, a solution of 2 g of uranyl acetate dihydrate (Riedel-Haen) in 35 ml of distilled water was first prepared by weighing.

In another beaker, 50 ml of a 0.5 molar NaOH solution were kept ready.

The contents of the beaker and further beaker were then added via dropping funnel into the three-necked flask by adding dropwise. Here, in particular, the contents of the other beaker were added so that a pH of 10.5, measured by the pH measuring device, was maintained constant. Within a short time, a cloudy precipitate formed in the three-necked flask.

The resulting solid was filtered through a suction filter and washed with distilled water until the washings were neutral (pH ~ 7). Subsequently, the solid was predried under air and ambient pressure for 2 h at 90 ⁰ C and subsequently dried at 800 ⁰ C for 4 h.

There were then obtained about 1.3 g of a white solid, which was subsequently subjected to a powder X-ray diffractometric measurement (D5000 reflection diffractometer with automatic aperture stop, Bruker AXS, analysis according to the method of the manufacturer), one phase containing Na ₆ U ₇ C ^ was identified next to a UsOg phase (see Fig. 1).

Example 2 (comparative example): Preparation of a first catalyst not according to the invention by pyrolysis

1 g uranyl acetate dihydrate (Riedel-de-Haen) were pre-dried for 2 h at 300 ⁰ C and then treated for 4 h at 800 ⁰ C in a muffle furnace under air. There was obtained 0.7 g of a black powder. The powder thus prepared was examined by X-ray diffractometric analysis analogously to Example 1, with only one U ₃ O ₈ phase being identified (compare FIG. 2).

Example 3 (comparative example): forming a further catalyst not according to the invention 2 g of powdered uranium (V / VI) oxide (from Strem Chemicals.) Were pre-dried overnight at 150 ⁰ C in a drying oven at ambient pressure and then for 2 h in air at 800 ⁰ C treated. The powder was investigated analogously to Example 1 powder X-ray diffractometry, with only one

was identified (see Fig. 3).

Examples 4-6: Use of the Catalysts of Examples 1-3 for the Heterogeneous Catalytic Oxidation of Hydrogen Chloride to Chlorine at 400 ^° C. 0.2 g of the substances obtained according to Examples 1 to 3 were ground by hand in a mortar and mixed with 1 quartz sand (100-200 μm) was introduced into a quartz reaction tube (diameter ~ 10 mm).

The quartz reaction tube was heated to 400 ⁰ C and operated in the following at this temperature. A gas mixture of 80 ml / min of hydrogen chloride and 80 ml / min of oxygen was passed through the quartz reaction tube.

After 30 minutes, the product gas stream was passed into a 16% by weight potassium iodide solution for 10 minutes and the resulting iodine was back titrated with a 0.1 N thiosulfate solution to determine the amount of chlorine introduced. From this, the activities shown in Table 1 of the substances according to Examples 1 to 3 at 400 ⁰ C were calculated.

The activity was in all cases according to the general formula vJLL - "^{> n} _ermι helled.

Catalyst measuring time

Examples 7-9: Use of the catalysts of Examples 1-3 for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine at 500 ⁰ C Experiments were analogous to those of Examples 4-6 performed, where the only difference is now the quartz reaction tube to 500 ⁰ C was heated and subsequently operated at this temperature.

From this, analogously to Examples 4-6, the activities of the substances according to Examples 1 to 3 shown in Table 1 were calculated at 500 ^° C. Examples 10-12: Use of the catalysts from Examples 1-3 for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine at 540 ^° C.

Were carried out analogous to those of Examples 4-6 Attempts were then heated with the only difference, the quartz reaction tube to 540 ⁰ C and operated in the following at this temperature. From this, analogously to Examples 4-6, the activities of the substances according to Examples 1 to 3 shown in Table 1 were calculated at 540 ^° C. Examples 13-15: Use of the catalysts from Examples 1-3 for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine at 600 ^° C.

Were carried out analogous to those of Examples 4-6 Attempts were then heated with the only difference, the quartz reaction tube to 600 ⁰ C and operated in the following at this temperature.

From this, the activities of the substances according to Examples 1 to 3 at 600 ^° C. shown in Table 1 were calculated analogously to Examples 4-6.

Table 1: Results of Examples 4 to 15 for the substances in accordance with Examples 1 to 3

From Table 1 shows that the inventive catalyst according to Example 1, especially at temperatures above 500 ⁰ C significantly higher activity for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine, as the catalysts, as obtained similarly from the prior art ,

Claims

claims:

I. Catalyst for the heterogeneous catalytic oxidation of hydrogen chloride to chlorine, characterized in that the catalyst comprises a uranate of at least one alkali and / or alkaline earth metal.

2. A catalyst according to claim 1, characterized in that the alkali and / or alkaline earth metal is selected from the list containing barium, calcium, potassium, magnesium and sodium.

3. A catalyst according to claim 1 or 2, characterized in that it Na _ö U ₇ O ₂₄ or Ba ₃ U ₇ O ₂₄ comprises.

4. A process for the preparation of a catalyst according to any one of the preceding claims, characterized in that a) a uranium salt is obtained by adding a strong alkali and / or alkaline earth liquor from a homogeneous, aqueous solution containing a precipitated product A, and b) the precipitate A subsequently separated from the aqueous solution and dried.

5. The method according to claim 4, characterized in that the uranium salt Uranyloxideacetat UO ₂ Ac ₂ or Uranyloxidnitrat UO ₂ (NOa) ₂ is.

6. The method according to claim 4 or 5, characterized in that the drying according to step b) is carried out at temperatures of 500 ⁰ C to 1500 ⁰ C.

7. The method according to claim 4 or 5, characterized in that the drying according to step b) is carried out in several stages, wherein a predrying at room temperature to 250 ⁰ C and a post-drying at temperatures of 500 ⁰ C to 1500 ⁰ C is provided.

8. The method according to any one of claims 4 to 7, characterized in that between the step a) and the step b) of the method, a washing of the precipitate A is provided.

9. A catalyst according to claim 1, characterized in that it has been prepared by a process according to claims 4 to 8.

10. A process for the preparation of chlorine, characterized in that in a reaction zone hydrogen chloride in the presence of uranium at least one alkali and / or

Alkaline earth metal is oxidized to chlorine.

I I. Use of uraniumates of at least one alkali and / or alkaline earth metal as a catalyst for the oxidation of hydrogen chloride to chlorine.