DE102008050977A1 - Integrated process for the production of chlorine - Google Patents

Abstract

The invention relates to a process for the production of chlorine in three process steps, wherein in a first process step, a catalytic oxidation of hydrogen chloride to chlorine on a uranium oxide catalyst is carried out in a second step, the resulting chlorine at least partially separated and in a third process step, an electrochemical oxidation of Hydrogen chloride to chlorine is carried out.

Description

The The invention relates to a process for the production of chlorine in three Process steps, wherein in a first process step a catalytic oxidation of hydrogen chloride to chlorine on a uranium oxide catalyst is executed, in a second step, the resulting Chlorine at least partially separated and in a third step an electrochemical oxidation of hydrogen chloride to chlorine is carried out.

A Reaction of great industrial interest is that of Deacon 1868 developed processes of catalytic hydrogen chloride oxidation with oxygen.

By Chloralkali electrolysis has been the Deacon process in the past strongly pushed into the background. Almost the entire production Chlorine was obtained by electrolysis of aqueous saline solutions.

The o. g. Deacon procedure is however in particular with regard to worldwide growing chlorine demand in view of less strong growing Demand for caustic soda, which is the essential by - product of Chloralkali electrolysis forms, of high economic interest.

This Development comes through the process for the production of chlorine catalytic oxidation of hydrogen chloride, which is derived from the Sodium hydroxide production is decoupled. Furthermore Falls hydrogen chloride in large quantities, for example in phosgenation reactions, for example in isocyanate production, as by-product.

The Catalytic 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 chlorine.

The currently used for the catalytic oxidation of chlorine Catalysts in the context of processes that are compatible with the o. G. Deacon process are therefore based on catalyst components already high activity at low temperatures Have conversion of hydrogen chloride to chlorine.

So revealed the WO 2007/134726 in that catalysts based on ruthenium, palladium, platinum, osmium, iridium, silver, copper or rhenium are suitable for this purpose. The WO 2007/134726 also discloses that from this first process step according to the prior art always still a product stream is obtained, the still shares of hydrogen chloride, water, oxygen, and other secondary components, such as. B. contains carbon dioxide. This results according to the WO 2007/134726 in the prior art, the need for further treatment of the product stream z. B. by more or less complex process of adsorption and desorption.

The WO 2007/134726 discloses therefore that a process comprising a further process step in the sense of an electrochemical oxidation after prior separation of the hydrogen chloride by condensation from the remaining product stream is advantageous. It is disclosed that purification of the hydrogen chloride is preferred, as minor constituents contained in the product stream are no longer capable of adversely affecting electrochemical oxidation, e.g. B. no longer prove the necessary for electrochemical oxidation electrolytic cell.

The WO 2007/134726 does not disclose that another side effect, resulting in particular from the use of ruthenium-based catalyst components, does not occur. This refers to the well-known property of such transition metals, such as ruthenium, to form complexes with minor constituents of the process gases at elevated temperatures or to be itself converted by oxidation into a volatile form. Such complexes are about those with carbon monoxide, as it also according to the WO 2007/134726 may be included in the process gases from the operation of the disclosed process in association with phosgenation processes. The formation and the volatility of such compounds describe approximately Goodwin et al. in "Reactive Metallization from Ru / Al2O3 as a Result of Ruthenium Carbonyl Formation" (Appl. Catalysis, 1986 24: 199-209) , It is also disclosed herein that such volatilization of ruthenium occurs noticeably even at temperatures above 100 ° C.

The possibility of further oxidation of ruthenium to the volatile compound describe approximately Backmann et al. in "On the transport and speciation of ruthenium in high temperature oxidizing conditions" (Radochim, Acta, 2005 93: 297-304) , It is also disclosed herein that in addition to the Ru and RuO ₂ phases, all oxides of ruthenium are volatile compounds which are formed in large quantities within minutes at temperatures above 800 ° C. At temperatures of up to 500 ° C, as in the WO 2007/134726 It can therefore be assumed that the formation of the volatile ruthenium species also occurs, albeit not in speed. In industrial processes in which such processes are operated, however, operating times of months to years are quite common, so that a noticeable effect can be assumed.

hereby would increase the catalytic oxidation of hydrogen chloride Chlorine after a short time due to the loss of catalyst no longer be able to achieve a sufficient level of sales. Further, such complexes can be found in the following electrochemical oxidation on the electrode surfaces by reduction of the transition metal contained in them deposition, whereby this process step adversely affected becomes.

According to the WO 2007/134726 Therefore, it is also preferable to carry out the catalytic oxidation isothermally. In any case, the catalytic oxidation should be carried out within the temperatures of 180 ° C to 500 ° C. However, particularly preferred are lower temperatures of 220 ° C to 350 ° C.

That in the WO 2007/134726 Thus, the disclosed process is disadvantageous because it can not be operated at higher temperatures without fear of loss of the catalyst from the catalytic oxidation of hydrogen chloride to chlorine.

There the catalytic oxidation of hydrogen chloride to chlorine but one is exothermic reaction, is such a temperature increase always costly to prevent or leads process technically in case of failure, if necessary, the need for renewal after that destroyed catalysts of catalytic Oxidation of hydrogen chloride to chlorine.

Moreover, the procedure is the WO 2007/134726 disadvantageous because it still requires a purification step between the catalytic oxidation and the electrochemical oxidation in order to prevent, for example, a coating of the electrolysis cell necessary for electrochemical oxidation.

From the DE 1 078 100 It is known that salts or oxides of rare earths, of silver and of uranium can also be used as catalysts for the catalytic oxidation of hydrogen chloride to chlorine. It is further disclosed that at a temperature of 480 ° C, a catalyst comprising uranium oxide, a conversion of 62% of the hydrogen chloride to chlorine allows.

That in the DE 1 078 100 The disclosed process is disadvantageous since it allows a maximum of 62% conversion. This is partly due to the equilibrium position at elevated temperatures.

outgoing The prior art still has the task of a method to make available that it allows a turnover of Hydrogen chloride to allow chlorine without the restrictions according to the methods of the prior art regarding the necessary cleaning the gas stream or regarding lower recoverable sales to be subject.

• a) Oxidation von Chlorwasserstoff mit Sauerstoff zu Chlor in mindestens einer ersten Reaktionszone in Gegenwart eines Katalysators erhaltend einen Produktstrom P₁,
• b) mindestens teilweises Abtrennen des im Produktstrom P₁ aus a) enthaltenen Chlor, erhaltend einen Produktstrom P₃,
• c) elektrochemische Oxidation des im Produktstrom P₃ aus b) enthaltenen Chlorwasserstoffs in einer zweiten Reaktionszone, wobei der Produktstrom P₃ auch Wasser, sowie gegebenenfalls auch Chlor umfasst,

dadurch gekennzeichnet, dass der Produktstrom P₃ aus b) der Reaktionszone gemäß c) direkt zugeleitet wird und dass der Katalysator gemäß a) eine Uranverbindung umfasst, diese Aufgabe zu lösen vermag.It has now surprisingly been found that a process for the production of chlorine from a reaction mixture A, which contains at least hydrogen chloride, comprising the steps

• a) oxidation of hydrogen chloride with oxygen to chlorine in at least one first reaction zone in the presence of a catalyst, obtaining a product stream P ₁ ,
• b) at least partially separating off the chlorine contained in the product stream P ₁ from a), obtaining a product stream P ₃ ,
• c) electrochemical oxidation of the hydrogen chloride present in the product stream P ₃ from b) in a second reaction zone, the product stream P ₃ also comprising water, and optionally also chlorine,

characterized in that the product stream P ₃ from b) is fed directly to the reaction zone according to c) and that the catalyst according to a) comprises a uranium compound, to be able to achieve this object.

The inventive method is particularly advantageous because it was surprisingly found that the inventive method allows the direct supply of the product stream P ₃ in the electrochemical oxidation of hydrogen chloride to chlorine, without any need for further treatment except that Separation of chlorine is necessary so that the reaction mixture fed to step a) of the process may also comprise minor constituents which need not be separated in step b) of the process.

This is due to the catalyst comprising a uranium compound, which can be operated at higher temperatures, without that its catalytic properties are significantly influenced and because at these higher temperatures, those in the reaction mixture A optionally contained minor constituents can be oxidized.

Minor ingredients denote fabrics in the context of the present invention which include carbon and in which the carbon at least partially present in an oxidation number less than or equal to two.

Examples for minor constituents in whose presence the invention Process proves to be particularly advantageous are therefore approximately halogenated or non-halogenated aromatic hydrocarbons, such as chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, trichlorobenzenes, the corresponding Chlorotoluenes or chloroxylenes, chloroethylbenzene, toluene, or xylene. Such minor constituents usually come from phosgenation processes, with which the inventive method thus can also be operated in an advantageous manner in combination.

One Another example of a minor component in whose Are the method of the invention present is particularly advantageous is carbon monoxide.

While in method z. B. after the disclosure of WO 2007/134726 be expected that the presence of z. As carbon monoxide to form transition metal complexes in the catalytic oxidation of hydrogen chloride to chlorine and thus after a short time to poor conversion of the catalytic oxidation, and subsequently also leads to poor sales in the course of electrochemical oxidation by deposition of elemental transition metal on the electrode of the electrochemical oxidation Surprisingly, the process according to the invention proves to be unaffected by such problems, since the catalyst comprising a uranium compound does not tend to form such complexes.

It So it was surprisingly found that in the step a) used the method according to the invention A catalyst comprising a uranium compound, in no way, e.g. B. in terms of volatile compounds with minor components, from the reaction zone of step a) of the invention Procedure is carried out so that a permanent operation of a method according to the invention also sichergesteilt can be.

Furthermore, it is thus ensured that there can be no metal or transition metal residues in the product stream P _{3 which} can precipitate on the surface of the electrodes of the electrochemical oxidation according to step c) of the method according to the invention.

catalysts comprising a uranium compound, can according to the Covering invention comprise a carrier material or Not.

Becomes a catalyst comprising a uranium compound in step a) of used according to the invention, the one Carrier material comprises, so are usable carrier materials those selected from the list containing silicon dioxide, Alumina, titania, tin dioxide, zirconia, ceria, Carbon nanotubes or mixtures thereof.

Usually the proportion of uranium compound on the catalyst, if in addition a carrier material, in the range of 0.1 to 90% by weight, preferably in the range of 1 to 60 wt .-%, particularly preferably in Range of 1 to 50 wt .-% based on the total mass of uranium compound and carrier material.

The use of catalysts comprising a support material is generally advantageous, in particular to obtain the structured beds described below. However, the carrier materials according to the list above, similar to the catalysts used in the prior art, may optionally be recovered in the product stream P ₁ and / or P ₃ , so that their use may be disadvantageous to the preferred further development described below. In general, the support materials have a lower tendency to deposit on the electrodes of step c) of the method according to the invention, so that they are nevertheless usable in principle.

Suitable uranium compounds of the catalyst are uranium oxides, uranium chlorides and / or uranium oxychlorides. Suitable uranium oxides are either UO ₃ , UO ₂ , UO, or uranium oxides of a non-stoichiometric composition. Preferred uranium oxides of non-stoichiometric composition are those having a uranium to oxygen ratio according to the formula UO _x of UO _2.1 to UO ₅ . Particularly preferred are those uranium oxides selected from the list containing U ₃ O ₅ , U ₂ O ₅ , U ₃ O ₇ , U ₃ O ₈ and U ₄ O ₉ . Uranium oxychlorides in the context of the present invention designate substances of the general composition UO _x Cl _y , where x and y are each natural numbers greater than zero. Thus, uranium oxychlorides also do not refer to stoichiometric compositions containing chlorine, oxygen and uranium.

In a preferred development of the invention Method, the catalyst used contains only one Support from a uranium link D. h. the catalyst contains only one uranium connection.

The Use of such catalysts is particularly advantageous because on the use of transition metals and precious metals can be completely dispensed with and thus the above Disadvantages of the methods of the prior art regarding the used Catalysts can be excluded. Furthermore In this case, too, may be disturbing Influences of carrier materials on the electrochemical Oxidation according to step c) excluded become. Such disturbing influences are about the least Partial entrainment of these substrates in the product stream A, which then in turn on the surfaces the electrodes of the electrochemical oxidation according to the Precipitate step c) of the method according to the invention can.

Consequently can the inventive method via be operated for a long time, without a renewal of the catalyst of step a) or the electrodes of step c) becomes necessary. This is particularly economically advantageous.

Of the used catalyst can be used as a bed of particles or in the form of shaped bodies.

Lies the catalyst before as a bed of particles, so is he prefers as a structured bed, the by characterized in that the catalyst activity in the Main flow direction of the reaction zone of step a) increases.

These structured bedding is particularly advantageous because thereby in the main flow direction of the reaction zone of step a) achieved the same sales per unit room become. While at the entrance of the reaction zone through the high concentration of hydrogen chloride and oxygen already high Reaction rates can be achieved this against exit of the reaction zone by the increased catalyst activity continue to maintain. This requires a particularly efficient Use of the catalyst.

A such structuring of the catalyst bed can by different ratios of uranium compound to carrier material or by different dilution of a catalyst done with an inert material.

Lies the catalyst is in the form of a shaped article, shaped articles are suitable with any shapes, preferred are tablets, rings, cylinders, Stars, wagon wheels or balls are particularly preferred Balls, rings, cylinders or star strands.

The Reaction zone of step a) of the invention Process can take place at temperatures above 350 ° C operated to temperatures of 800 ° C. Prefers it is operated at temperatures of 400 to 600 ° C.

In contrast to the methods of the prior art, as in the WO 2007/134726 In this case, the upper temperature is not a limit at which the method according to the invention is no longer sufficiently practicable, but merely represents a limitation in that the surprising positive effect of the possibility of oxidation of secondary constituents has already almost completely occurred, so that a further increase in temperature appears economically unfavorable.

The lower temperature limit is particularly advantageous because in this Temperature a variety of minor constituents in the reaction zone of step a) of the method according to the invention already oxidized to other gaseous compounds.

in the Case of minor constituents comprising only hydrocarbons, Such other gaseous compounds are, for example, carbon monoxide and / or carbon dioxide. In the case of minor constituents comprising chlorine, are such other gaseous compounds such as hydrogen chloride and / or chlorine, which in turn is part of the invention Procedure are. The method thus has a particularly advantageous effect, if the secondary constituents halogenated, in particular chlorinated Hydrocarbons, or carbon monoxide are.

Further, the catalyst comprising a uranium compound is surprisingly more active at these temperatures than at lower temperatures, contrary to e.g. As the ruthenium catalysts of the prior art, which tend to be entrained with the product stream P ₁ with increasing temperature, and thus lose activity in the course of operation of such methods. This is not the case in the method according to the invention.

Of the Step a) of the process according to the invention is customary at pressures between 1 and 30 bar. Preferably at pressures of 5 to 10 bar.

These Pressures are in comparison to those disclosed above, preferred temperature ranges are not essential for the particularly advantageous feasibility of the invention Process.

Much more For example, the pressures disclosed herein are the areas in which the general embodiment of erfindungemäßen Method has proven to be economical. It can be but also, for. B. by the interconnection of the invention Method with further methods in the sense of a process network, lower or higher pressures than beneficial prove, without thereby the inventive Process lose its special advantage would.

Of the Step a) of the method according to the invention can in one or more reaction zones connected in parallel or in series be executed. Here are the individual Reaction zones are in a device or split present in different devices.

Of the Oxygen can either be completely together with the hydrogen chloride before the first reaction zone or over the different ones Reaction zones are added distributed.

Further can step a) of the method according to the invention independent of step b) of the erfindungemäßen Process carried out continuously or discontinuously become. Preferably, the step a) of the invention Process but carried out continuously.

devices, in which the step a) of the invention Method can be carried out are about fixed bed, Fluid bed or fluidized bed reactors, as known to those skilled in the art in their embodiments are well known. Prefers are fixed bed reactors, as in these the above structured Leakage of the catalyst achieved in an advantageous manner can be.

In a preferred further development of step a) of the process according to the invention, the heat generated in the reaction zone by the exothermic formation of chlorine from hydrogen chloride from the reaction zone or after the reaction zone is removed from the product stream P ₁ and used to heat the reaction mixture A in or before the reaction zone of the reaction mixture Step a) used. If appropriate, this can take place together with the at least partial transfer of the product stream P ₁ from step a) into a liquid phase, as will be described below.

A such removal of heat is particularly advantageous because it makes the process more economical.

The Separating according to step b) of the invention The process is usually carried out according to the expert in general known principles for separating chlorine or hydrogen chloride from gas streams. Non-conclusive examples this is about the fractional or unfractionated Condensation of at least hydrogen chloride, or adsorption and subsequent desorption of chlorine or hydrogen chloride.

It is essential that at least portions, preferably more than 50 wt .-%, more preferably over 80 wt.% Of the chlorine contained in the product P ₁ containing a product stream P _{2 are} separated, since this in the presence of water in the sense of an equilibrium reaction for the formation of hydrochloric tends to be well known to those skilled in the art. Since chlorine is to be formed with the process according to the invention, such formation of hydrogen chloride is disadvantageous.

In the sense of the step c) of the process according to the invention, which is preferably to be carried out in a liquid phase, it is preferred if the hydrogen chloride present in the product stream P _{1 is} fractionated in step b), ie essentially only the hydrogen chloride and optionally water by condensation from the product stream P _{1 is} separated and this condensate forms the product stream P ₃ , while the remaining chlorine in the sense of a second product stream P ₂ is essentially led out of the process.

The electrochemical oxidation of hydrogen chloride to chlorine in accordance with Step c) of the method according to the invention according to well-known diaphragm method or by means of a Oxygen consumption cathode are performed.

Possible embodiments of diaphragm methods are disclosed in US Pat WO 2007/134726 described.

In a preferred embodiment of the invention Method is the step c) of the method with an oxygen-consuming cathode executed.

For this purpose, the product stream P ₃ from step b) of the process according to the invention is preferably first converted into a liquid phase.

In this preferred embodiment of the method using an oxygen-consuming cathode is in the reaction zone of step c), a first electrode space E ₁ to which from step b) of the inventive method resulting product stream P ₃ , comprising hydrogen chloride, is fed, and it is located in the reaction zone, a further electrode space E ₂ , also containing an electrode into which an electrolyte solution comprising dissolved oxygen or a gas comprising oxygen, is introduced, wherein electrode space E ₁ and electrode space E _{2 are} separated by a membrane and the electrodes via a power supply S. electrically conductively connected to each other.

The electrode of the electrode space E ₁ can in this case be used in the form of a rod, a plate, a net or a fabric and can consist of a material selected from the list containing carbon black, graphite or metal. As metals, for example, titanium or titanium alloys or the special metal alloys, which are known to the skilled worker under the name Hastelloy and Incolloy, can be used.

Especially preferred are materials selected from the list containing Graphite, titanium, titanium alloy, or the special metal alloys Hastelloy and Incolloy.

The electrode of the electrode space E ₂ may have the same shapes as the electrode of the electrode space E ₁ and may be made of titanium or titanium alloys such as titanium-palladium and may be coated. If the electrode is coated, it is preferably coated with a mixed oxide comprising one or more of the metals ruthenium, iridium and titanium. Particularly preferred is a coating comprising a mixed oxide of ruthenium oxide and titanium oxide or a mixture of ruthenium oxide, iridium oxide and titanium oxide.

The electrode of the electrode space E ₂ may also be made of graphite and other carbon materials such as diamond.

The aforementioned materials of the electrodes of the electrode spaces E ₁ and E ₂ are particularly advantageous because they are particularly resistant to the chemically aggressive substances hydrogen chloride and chlorine. This means that these materials do not tend to corrode upon contact with the product stream P ₃ , so that the advantageousness of the method according to the invention is particularly pronounced, since the need for renewal of catalyst and / or electrodes is not necessary for a long time and the entire process thus can be operated for a long time without necessary maintenance.

The membrane located between the electrode spaces E ₁ and E _{2 of} the reaction zone of step c) is usually a polymer membrane. Preferred polymer membranes are all polymer membranes, which the person skilled in the art generally knows under the generic term of the cation exchange membrane. Preferred membranes include polymeric perfluorosulfonic acids. The membranes can also reinforcing fabric of other materials, preferably fluorinated polymers, and more preferably polytetrafluoroethylene.

The Thickness of the membrane is usually less than 1 mm. The thickness of the membrane is preferably less than 500 μm, more preferably less than 400 microns, most preferably less than 250 μm.

The step c) according to the preferred embodiment is usually operated by applying a current density of 4-7 kA / m ² .

Of the Step c) of the method according to the invention can be executed at any pressure. It is preferred but at a lower pressure than that of step a) of the invention Process executed. Particularly preferred is the step c) carried out at about ambient pressure (1013 hPa).

Of the Step c) of the method according to the invention can also be carried out at any temperatures. However, it is preferably at temperatures from room temperature to 100 ° C executed.

The Temperatures are particularly advantageous because of the energy content of the material stream obtained from step c) of the process with it is reduced, so that this energy the inventive Procedure is available. This energy was preferred according to the preferred further development described above of step a) of the process recovered in the form of heat and for the heating of the reaction mixture A of step a) of the method according to the invention used.

The Invention will be explained below with reference to examples and figures, without thereby restricting them to this.

1 in this case shows an embodiment of the method according to the invention, in which a reaction mixture (A) containing hydrogen chloride, oxygen and minor constituents comprising carbon monoxide and chlorobenzene or other partially halogenated aromatics such as dichlorobenzene or the like, having a temperature T ₂ in a first reaction zone (R ₁ ) containing a catalyst (K) from uranium oxide, is introduced after the reaction mixture A in a first heat exchanger (W ₁ ) from a temperature T ₁ to T ₂ > T _{1 was} heated. In the reaction zone R ₁ , the reaction mixture is heated to a temperature T ₃ > T ₂ and exits as the first product stream P ₁ containing residues of hydrogen chloride, and chlorine and carbon dioxide. In a second heat exchanger (W ₂ ), the first product stream P _{1 is} cooled to a temperature T ₄ <T ₃ . The heat obtained in this way is supplied to the first heat exchanger W ₁ by means of a heat transfer fluid connection (L). The first product stream P ₁ is in this case partially condensed in the second heat exchanger W ₂ , so that a second product stream in the form of a gas stream (P ₂ ), comprising essentially chlorine and carbon dioxide, can be led out of the process. The condensed third product stream (P ₃ ) is then fed to a first electrode space (E ₁ ) in a second reaction zone (R ₂ ), wherein the first electrode space E _{1 is} connected to a second electrode space (E ₂ ) via a membrane (M). In the electrode spaces E ₁ and E ₂ are each graphite electrodes in rod form (1, 2), which are connected to a power source (S). In the second reaction zone R ₂ , chlorine is formed in the electrode space E ₁ by means of electrochemical oxidation from the remainder of hydrogen chloride in P ₃ , while at the same time oxygen is reduced to water in the second electrode space E ₂ . A fourth product stream P _{4 is obtained} from the electrode space E _{1 of} the second reaction zone R ₂ , which contains only chlorine.

Examples:

Example 1: Preparation of a uranium oxide catalyst on an alumina carrier

40 g of gamma-Al ₂ O ₃ shaped bodies (BET of 200 m ² / g, from Saint Gobain) were impregnated in a glass beaker with a 10% by weight aqueous solution of uranyl acetate dihydrate (Riedel de Haen) by spraying.

To an exposure time of 1 h, the solid was in an air stream dried at 80 ° C for 2 h. The entire experiment was repeated as many times, up to 12 wt .-% uranium on the moldings available.

Example 2: Preparation of a catalyst containing only uranium oxide

2 g of a powdered uranium (V / VI) oxide (from Strem Chemicals) were placed overnight at 150 ° C in a drying oven dried at ambient pressure and then 2 h below Air calcined at 500 ° C.

Example 3 (Comparative Example): Preparation a ruthenium catalyst on an alumina carrier

5 g of spherical gamma-Al ₂ O ₃ shaped articles (Saint-Gobain) having an average diameter of 1.5 mm and a BET surface area of 200 m ² / g were mixed with a solution of 0.258 g of commercial ruthenium chloride n-hydrate (Riedel de Haen) in 6.5 g H ₂ O analogously to Example 1 impregnated.

To an exposure time of 1 h, the solid was in the air stream at 60 ° C. dried for 5 h. Subsequently, the catalyst became Calcined at 250 ° C for 16 h. This results in a catalyst with converted 2 wt .-% of ruthenium.

Example 4: Implementation of Step a) of the process with catalyst according to Example 1

25 g of the catalyst from Example 1 were introduced into a Ni fixed bed reactor (diameter 10 mm, length 800 mm) together with 25 g of TiO ₂ inert material.

there a fixed bed of about 150 mm was obtained. The Fixed Bed was using an electric heater so heated, that has a radial temperature gradient of 400-600 ° C. formed. The fixed bed reactor was at a pressure of 4 bar with a gas mixture of 100 Nl / h of hydrogen chloride, 100 Nl / h of oxygen and 60 Nl / h nitrogen flows through.

The product stream was passed over two condensation vessels, so that the water formed and the remaining hydrogen chloride were condensed out, while the chlorine was separated as a gas stream. After an operating time of 6 hours, the condensate formed was measured for the content of aluminum and titanium by means of ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry, device: Varian Vista-PRO, method according to manufacturer's instructions) and the content of uranium by means of ICP- MS (Inductively Coupled Plasma-Mass Spectrometry, device: HP Agilent 4500, method according to manufacturer's instructions). From the analysis, the concentrations of aluminum, titanium and uranium in the condensate shown in Table 1 were determined. Table 1: Content of metal in the condensate according to Example 4 metal Concentration [mg / l] aluminum 1.6 titanium 7.9 uranium <0.001

you recognizes that the backing materials facing the catalysts of the prior art already a clear reduced tendency to form volatile compounds have, since these already at least a factor of 1,000 higher concentrated in the condensate are to be found, as the uranium compounds. From this follow both the opposite to the prior art advantageous mode of operation of the invention Process, as well as in particular the advantageousness of his preferred Embodiments.

Example 5: Implementation of the Step a) of the process with catalyst according to Example 2

0.2 g of the catalyst obtained in Example 2 were ground and mixed with 1 g of silica sand (100-200 μm) placed in a quartz reaction tube (diameter - 10 mm).

The Quartz reaction tube was heated to 600 ° C and operated at this temperature below.

It was a gas mixture of 80 ml / min of hydrogen chloride and 80 ml / min Oxygen passed through the quartz reaction tube.

After an operating time of 140 h, the product gas stream formed was passed through a condensation trap for several hours, so that the resulting H ₂ O and unreacted hydrogen chloride were condensed out. The condensate was analyzed analogously to Example 3 for the content of uranium. There was a concentration of uranium of 0.044 mg / l in the condensate.

Example 6 (Comparative Example): Procedure of step a) of the process with catalyst according to Example 3

One Quartz reaction tube was analogous to Example 5 with 0.2 g of the catalyst from Example 3 and diluted with quartz sand.

The Quartz reaction tube was heated to 540 ° C and operated at this temperature below.

One Gas mixture equal to that in Example 5 was passed through the quartz reaction tube directed.

After an operating time of 37 h, the product stream formed was passed through a condensation trap for several hours, so that the resulting H ₂ O and unreacted hydrogen chloride were condensed out. The condensate was investigated analogously to Example 4 on the content of ruthenium and aluminum. Table 2: Content of metal in the condensate according to Example 6 metal Concentration [mg / l] aluminum 1.5 ruthenium 3.0

you recognizes that the concentration of ruthenium in the product stream already after an operating time of 37 h, at opposite Example 5 reduced temperature that of uranium by a factor exceeds about 68. The amount of aluminum contained is comparable to that of Example 4.

thereto becomes the special advantage of the invention Method and in particular according to the preferred Development very clearly, because now no longer with a deposit of ruthenium in step c) according to the invention of the procedure.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2007/134726 [0008, 0008, 0008, 0009, 0010, 0010, 0011, 0013, 0014, 0016, 0026, 0043, 0060]
• - DE 1078100 [0017, 0018]

Cited non-patent literature

• Goodwin et al. in "Reactive Metallization from Ru / Al 2 O 3 as a Result of Ruthenium Carbonyl Formation" (Appl. Catalysis, 1986 24: 199-209). [0010]
• Backmann et al. in "On the transport and speciation of ruthenium in high temperature oxidizing conditions" (Radochim, Acta, 2005 93: 297-304) [0011]

Claims (10)

A process for the production of chlorine from a reaction mixture A, which contains at least hydrogen chloride, comprising the steps a) oxidation of hydrogen chloride with oxygen to chlorine in at least a first reaction zone in the presence of a catalyst containing a product stream P ₁ , b) at least partially separating the product stream P ₁ from a) containing chlorine, obtaining a product stream P ₃ , c) electrochemical oxidation of the hydrogen chloride contained in the product stream P ₃ from b) in a second reaction zone, the product stream P ₃ also comprising water, and optionally also chlorine, characterized that the product stream P ₃ from b) is fed directly to the reaction zone according to c) and that the catalyst according to a) comprises a uranium compound. Method according to claim 1, characterized in that the catalyst comprises a carrier material. Method according to claim 2, characterized in that the carrier material is also a uranium compound. Method according to one of the preceding claims, characterized in that the uranium compounds uranium oxides, uranium chlorides and / or uranium oxychlorides. A method according to claim 4, characterized in that the uranium oxides are either UO ₃ , UO ₂ , or UO, or uranium oxides of a non-stoichiometric composition. A method according to claim 5, characterized in that the uranium oxides of non-stoichiometric composition are those having a uranium to oxygen ratio according to the formula UO _x of UO _2.1 to UO ₅ . Method according to one of the preceding claims, characterized in that the step a) at temperatures above operated from 350 ° C to temperatures of 800 ° C. becomes. Method according to one of the preceding claims, characterized in that in step b) a fractional condensation is obtained maintaining the product stream P ₃ , from which a product stream P ₂ comprising substantially chlorine is separated. A method according to claim 8, characterized in that the product stream P ₁ extracted heat for heating the reaction mixture A in or before the reaction zone of step a) is used. Method according to one of the preceding claims, characterized in that step c) with an oxygen-consuming cathode is performed.