EP2150497A2

EP2150497A2 - Method for the recovery of ruthenium from a supported catalyst material containing ruthenium

Info

Publication number: EP2150497A2
Application number: EP08735260A
Authority: EP
Inventors: Michel Haas; Peter Weuta; Aurel Wolf; Oliver Felix-Karl SCHLÜTER
Original assignee: Bayer MaterialScience AG
Current assignee: Covestro Deutschland AG
Priority date: 2007-04-26
Filing date: 2008-04-16
Publication date: 2010-02-10
Also published as: WO2008131856A2; KR20100015859A; JP2010524672A; TW200906731A; US20080287282A1; CN101663242A; WO2008131856A3; DE102007020142A1

Abstract

The invention relates to a method for the recovery of ruthenium in the form of ruthenium halide, in particular ruthenium chloride from a supported catalyst material containing ruthenium, comprising at least the following steps: a) chemical decomposition of the catalyst material, b) production of a crude ruthenium salt solution, c) purification of the crude ruthenium salt solution and optional expulsion of gaseous ruthenium tetraoxide from said solution, d) subsequent treatment of the purified ruthenium compound contained in c), in particular the ruthenium tetraoxide with hydrogen halide or hydrohalic acid to obtain ruthenium halide, or in particular with hydrogen chloride or hydrochloric acid to obtain ruthenium chloride.

Description

Process for the recovery of ruthenium from a ruthenium-containing supported catalyst material

Ruthenium and ruthenium compounds are often components of catalysts, but are not limited to this application. In particular, ruthenium oxide, ruthenium mixed oxide, ruthenium chloride, ruthenium oxide chlorides and metallic ruthenium, supported or unsupported, are used in many applications, i.a. a. Catalysis, used. Ruthenium compounds are also often used in electrocatalytic processes or in heterogeneous catalysis.

The ruthenium component may in particular be metallic ruthenium and also ruthenium chloride, ruthenium oxide or a chlorine-containing ruthenium oxide species.

In view of the rarity of ruthenium, recovery of this precious metal and its compounds is an interesting alternative to re-buying the precious metal. Especially for industrially applied catalysts and electrodes, this approach is of very particular economic advantage, since catalysts and electrodes for these applications have appreciable amounts of ruthenium can contain.

Some patent and published patent applications describe well-known approaches to the purification of ruthenium compounds. However, these are generally insufficiently efficient or industrially unworkable.

EP 424 776 B1 describes a method in which the purification of an aqueous ruthenium-containing solution, in the form of alkali ruthenate, is carried out by oxidation with ozone at a pH above 8 to ruthenium tetroxide. A particular disadvantage is the associated considerable procedural expense of an at least two-stage process (first transfer of the Ru-containing starting compound in an alkali ruthenate, then conversion of this ruthenate in RuO ₄ ).

EP 1 026 283 A1 describes a method for the purification of metallic ruthenium powder in order to produce highly pure metallic ruthenium sputtering targets. The ruthenium is placed in a sodium hydroxide solution and then reacts with addition of ozone or chlorine-containing gas to Rutheniumtetroxid. Ruthenium tetroxide is absorbed in the next step in HCl or HCl / ammonium chloride and dried under a hydrogen atmosphere. The metallic ruthenium powder thus obtained can then be pressed to a target. A particular disadvantage is the high chlorine consumption typical for the implementation of the process. EP 1 072 690 describes a method for ruthenium work-up in the gas phase in the HCl stream and JP 01 142040 represents a procedure in which ruthenium is expelled with chlorine in a reducing atmosphere at 600 ⁰ C - 1200 ⁰ C.

In a variant, the invention utilizes the effect that ruthenium compounds which are not in solution form volatile ruthenium tetroxide (RUCM) at elevated temperature in an oxygen-containing atmosphere. Such a method would have the considerable advantage that the ruthenium would not have to be dissolved first. However, this reaction takes place only very slowly in the presence of oxygen and does not allow economic feasibility by the much too long evaporation times at very high temperatures.

The known methods have the disadvantage that they are difficult to apply to oxide-based catalysts. In order to obtain purified ruthenium compounds from supported catalyst material or electrode material (i.e., supported ruthenium compounds), additional digestion would have to occur. This can be done after partially known often carried out in aggressive media such as nitrate or chlorate melt at high temperatures digestion process, which materially means a major challenge. The disadvantages of known digestion methods can be partially avoided in particular by pretreatment by means of reducing agents.

It has also surprisingly been found that the digestion of supported catalyst material can be simplified if, for example, volatilization of the solid ruthenium component into the gas phase under elevated temperature is considerably accelerated by the fact that ozone and / or chlorine and / or oxygen continue to be present in an oxygen-containing gas stream Hydrogen chloride, for example under the form of CI ₂ or HCl are present.

The invention relates, on the one hand, to a process for the recovery of ruthenium in the form of ruthenium halide, in particular ruthenium chloride, from a ruthenium-containing supported catalyst material having at least the following steps:

a) chemical decomposition of the catalyst material

b) preparing a crude ruthenium salt solution,

c) purification of the crude ruthenium salt solution and, if appropriate, expulsion of gaseous ruthenium tetraoxide from the solution,

d) subsequent treatment of the purified ruthenium compound obtained in c), in particular of the ruthenium tetraoxide with hydrogen halide or hydrogen halide to obtain Rutheniumhalogenid, in particular with hydrogen chloride or hydrochloric acid for the production of ruthenium chloride.

Preferred is an embodiment of the method in which the digestion a) is carried out by

al) melting a mixture of catalyst material and oxidizing agent, and optionally additionally alkali metal hydroxide and / or alkali metal carbonate, preferably

Sodium hydroxide and / or sodium carbonate,

a2) reacting the mixture at a temperature of from 250 to 750 ^° C., in particular from 350 to 700 ^° C.,

a3) cooling the melt and dissolving the melt in mineral acid, in particular in hydrochloric acid and / or sulfuric acid, particularly preferably in hydrochloric acid,

a4) if appropriate, removal of any undissolved carrier material or other insoluble constituents from the solution and subsequent washing out of the optionally undissolved carrier material or other insoluble constituents with aqueous solvent or mineral acid, especially in hydrochloric acid and / or sulfuric acid, more preferably in hydrochloric acid, and combination of washing liquid loaded with ruthenium with the separated crude ruthenium solution,

a5) adjusting the crude ruthenium solution before and / or after the separation a4) of solids to a pH of at most 5,

and providing the crude ruthenium solution.

Melt digestion with oxidant per se is e.g. particularly described in US-A-4132569 or US-A-4002470, the contents of which are incorporated herein by reference.

Suitable oxidizing agents are preferably oxygen-containing mineral salts, in particular nitrates, chlorates, perchlorates, peroxodisulfates, permanganates, peroxides, chromates, dichromates of alkali metals or alkaline earth metals, in particular of alkali metals. The oxidizing agents may also be present in any mixtures / combinations.

By the preferred dilution of the substances used for the oxidation of the ruthenium compounds, in particular chlorates, nitrates, peroxides, peroxodisulfates or mixtures thereof by appropriate amounts of alkali metal hydroxide or alkali metal carbonate or mixtures thereof, commercially available materials such as steel or nickel can be used as the construction material for the reactors for the digestion become. Due to the relatively simple construction the reactors ('tanks') is a possible replacement after appropriate operating time associated with acceptable cost. Crucial for the economy of this digestion process is the preferred use of oxidants, which can be disposed of relatively easily after completion of the melt digestion from an ecological point of view. For example, it is preferable to use chlorates, peroxides or peroxodisulfates - these substances are finally converted into chlorides, hydroxides or sulfates as part of the melt digestion process.

Further preferred is another embodiment of the method in which the digestion a) is carried out by:

a6) dissolving the catalyst material in more concentrated mineral acid, in particular in hydrochloric acid and / or sulfuric acid, more preferably in hydrochloric acid, preferably at a concentration of at least 20%,

^a 7) optionally removing any undissolved carrier or other insoluble matter from the solution and then washing away the undissolved carrier or other insoluble matter with aqueous solvent or

Mineral acid, in particular in hydrochloric acid and / or sulfuric acid, more preferably in hydrochloric acid, and combining the washing liquid loaded with ruthenium with the separated crude ruthenium iumlösung,

a8) adjusting the crude ruthenium solution before and / or after the separation a7) of solids to a pH of at most 5,

and providing the crude ruthenium solution.

However, due to the relatively high chemical inertness of the optionally present oxidic ruthenium compounds towards acid digestion as described above, a previous reduction of the oxides to the metal or at least a lower oxidation state than + IV (RUO ₂ ) may be helpful. The reduction step will be described below. After the reduction, the ruthenium can be dissolved with acid with addition of an oxidizing agent and separated in a further process stage as RuO ₄ .

The invention further provides a process for the recovery of ruthenium in the form of ruthenium halide, in particular ruthenium chloride, from a ruthenium-containing supported catalyst material having at least the following steps:

a ') digestion of the catalyst material by treating the material at a temperature above 600 ⁰ C in an oxygen-containing atmosphere with the addition of ozone and / or Chlorine and / or hydrogen chloride to expel the ruthenium as volatile purified ruthenium compound,

b ') subsequent treatment of the purified ruthenium compound obtained in a'), in particular a ruthenium tetraoxide with hydrogen halide or hydrohalic acid, to obtain ruthenium halide, in particular with hydrogen chloride or hydrochloric acid, to obtain ruthenium chloride.

By the aforementioned higher temperature digestion process, when the crude ruthenium oxide is expelled, which could be further processed for reuse as a catalyst, a material is first obtained which is not pure enough. In a preferred method, therefore, the digestion is carried out with a further purification step c) to improve the content of e.g. to reach Fe, Cu or Pt. Preference is given to a process which is characterized in that the proportion of oxygen in the digestion gas during digestion a ') is 1 to 30% by volume, in particular 2 to 20% by volume, and the content of chlorine is up to 95% by volume. , the content of hydrogen chloride is up to 95% by volume and the content of ozone is up to 20% by volume.

Also preferred is a modification of both processes, which is characterized in that the catalyst material is exposed to a hydrogen-containing atmosphere for the reduction of the ruthenium compound prior to digestion a) or a ').

Also preferred is a modification of both methods, which is characterized in that the catalyst material before the digestion a) or a '), in particular by exposure to an atmosphere containing oxygen, is purified from sulfur compounds.

Also preferred is a modification of both methods, which is characterized in that the catalyst material originates from a used catalyst for the gas phase oxidation of hydrogen chloride with oxygen or a used electrode material for the electrolysis.

Also preferred is a modification of both processes, which is characterized in that the catalyst material as support material is a material from the series: tin dioxide, silica, graphite, titanium, titanium dioxide with rutile or anatase structure, zirconium dioxide, alumina, silica, carbon nanotubes, nickel , Nickel oxide, silicon carbide and tungsten carbide or mixtures thereof, preferably tin dioxide, titanium dioxide, zirconium dioxide, aluminum oxide.

Also preferred is a modification of both processes, which is characterized in that the catalyst material contains ruthenium as metal or in the form of a ruthenium compound selected from the series: ruthenium oxide, ruthenium chloride and ruthenium oxychloride. Preferably, the purification c) in both aforementioned methods, characterized in that the crude solution of a purification by means of ion exchange, recrystallization and in particular by expelling gaseous Rutheniumtetraoxid.

Preference is also given to a process which is characterized in that the ruthenium halide recovered in step d), in particular ruthenium chloride, is reused for the preparation of new catalyst or electrode material, in particular as ruthenium, ruthenium oxide, ruthenium chloride or ruthenium oxychloride catalyst on one Carrier or as electrode coating.

The content of ruthenium in the catalyst material is typically up to 10 wt .-%, in particular 1 to 5 wt .-%, particularly preferably 1.5 to 4 wt .-%.

The content of ruthenium in the coating of the electrode material is typically up to 50 wt .-%, in particular 30 to 45 wt .-%, particularly preferably 35 to 40 wt .-%.

It may be advantageous in some ruthenium compounds to first reduce the noble metal in a hydrogen atmosphere to subsequently carry out the expulsion of the ruthenium component.

The expelled ruthenium can then be absorbed in a solution and processed further. For this purpose, preferably a hydrochloric acid solution in which the ruthenium compound can be converted to ruthenium chloride is suitable. Ruthenium chloride is a type of compound that is particularly preferred for the preparation of catalysts.

As a particular advantage of the invention, it has been found that the ruthenium salt (in particular RuCh) formed by absorption of RuO ₄ in mineral acid has a very high purity, which is necessary for the use of RuCb as starting material for catalyst preparation, in particular for the deacon process or electrolysis. having. The ruthenium salt, in particular ruthenium chloride, obtainable by the preferred processes has as traces in total a content of Si, Ca, Mg and Al of at most 220 ppm, more preferably of at most 150 ppm, a content of Rh, Ir, Pt and Pd in the Sum of at most 250 ppm, more preferably of at most 150 ppm, a content of Cu of at most 25 ppm, more preferably of at most 15 ppm and a content of K, Na, Fe of in each case at most 125 ppm, more preferably of at most 100 ppm ,

This high degree of purity is by conventional known methods, such. B. recrystallization of salts alone achievable only with considerable effort. An oxidation or reduction step, which is carried out first at lower temperatures than the actual volatilization, can also have the considerable advantage over the used catalyst of carrying out a first purification step. Secondary components such as deposited carbon, sulfur compounds, etc. can then be separated from the surface of the catalyst.

But other previous purification steps such as washing out, possibly with acids, the supported ruthenium compound can be used here. This pre-cleaning then allows a more efficient expulsion of the ruthenium compound in that the precious metal is made more accessible, and in the subsequent step a simplified purification of the precious metal.

Such a method provides a significant advantage, since the ejection times of ruthenium are significantly reduced. In addition, the ruthenium does not need to be solubilized in a previous step, an expense which is not negligible. Furthermore, it is a very environmentally friendly and economical method, since no melting salts are used by dispensing with the carrier digestion. The costs of these molten salts are not insignificant because they must then be disposed of costly and expensive.

Ruthenium-containing electrode material can be used without prior separation of the ruthenium-containing component in the process according to the invention or, after separation, ruthenium-containing component. For this purpose, both mechanical methods such as sandblasting with aluminates or silicates, etc., as well as chemical methods can be used.

The separated from the electrode coating remains and it requires further purification because of foreign bodies from the previous sandblasting.

The ruthenium recovered by the process according to the invention can subsequently be used again in the preparation of catalysts or electrodes.

The invention therefore furthermore relates to the use of the recovered ruthenium compound obtained as a catalyst or electrode material, in particular as a ruthenium, ruthenium oxide, ruthenium chloride or ruthenium oxide chloride catalyst, on a support or as an electrode coating.

The ruthenium compound recovered by the process according to the invention is particularly preferably reused in the catalytic process known as the Deacon process. Here, hydrogen chloride is oxidized with oxygen in an exothermic equilibrium reaction to chlorine, whereby water vapor is obtained. The reaction temperature is usually 150 to 50O 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 usually include ruthenium oxide, ruthenium chloride, ruthenium oxide chloride or other ruthenium compounds supported on silica, alumina, titania or zirconia. Suitable catalysts can be obtained, for example, by applying ruthenium chloride to the support and then drying or drying and calcining. In addition to the ruthenium compound, suitable catalysts may also contain compounds of other noble metals, for example gold, palladium, platinum, osmium, iridium, silver, copper or rhenium. Suitable catalysts may additionally contain chromium oxide.

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

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

In the case of the adiabatic, isothermal or approximately isothermal mode of operation, it is also possible to use a plurality of reactors with intermediate cooling, that is to say 2 to 10, preferably 2 to 6, particularly preferably 2 to 5, in particular 2 to 3, connected in series. The 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 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 novel carrier materials are tin dioxide, silicon dioxide, graphite, rutile or anatase titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, preferably tin dioxide, titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably γ- or δ-aluminum oxide or their mixtures mixtures.

The copper or ruthenium catalysts can be preferably obtained in the form of their chlorides for example by impregnating the support material with aqueous solutions of CuCl or RuCl ^ ₃ and optionally a promoter for doping. 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%. Unreacted hydrogen chloride can be partially or completely separated into the catalytic after separation Hydrogen chloride oxidation can be attributed. The volume ratio of hydrogen chloride to oxygen at the reactor inlet is preferably 1: 1 to 20: 1, preferably 2: 1 to 8: 1, particularly preferably 2: 1 to 5: 1.

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

Examples

example 1

In a sand-bed heated quartz glass reactor (ID 10 mm), 4.5 g of catalyst spheres (RuC13 / SnO2, A12O3, 2% by weight Ru, 1.5 mm) were mixed with 2.9 g SiO ₂ spheres (SS62138, US Pat.

Saint-Gobain, 1.5 mm). The catalyst bed was heated constantly at 682 ° C, the silicon dioxide particles subject to a temperature gradient of> 532 ⁰ C between

Catalyst bed and reactor outlet. The reactor was treated with 20 ml / min (STP) HCl for 8 h

Flows through 80 ml / min (STP) O ₂ . The hydrogen chloride was partially reacted with the oxygen to form chlorine and water. The reaction gas was passed into 15% HCl and absorbed. The

Analysis showed a recovery of Ru as RuCb of 76%.

Example 2

In a sand-vitrified quartz glass reactor (ID 10 mm), 5.3 g of catalyst spheres (RuCl ₃ ZSnO ₂₁ Al ₂ O ₃ , 2% by weight Ru, 1.5 mm) were mixed with 1.7 g of SiO ₂ spheres (SS62138,

Saint-Gobain, 1.5 mm). The catalyst bed was heated constantly at 687 ° C, the silicon dioxide particles were subject to a temperature gradient of> 537 ⁰ C between

Catalyst bed and reactor exit. The reactor was bubbled with 160 ml / min (STP) N ₂ and 80 ml / min (STP) O _{2 for} 8 h. The reaction gas was passed into 15% HCl and absorbed. The analysis showed a recovery of Ru as RuCl ₃ of only 7.2%.

Compared to Example 1 shows that optionally O ₂ should be used together with HCl. Hereby, the chlorine-containing atmosphere (Cl ₂ and / or HCl) promotes a significantly stronger downforce of the RuO ₄ .

Example 3

Digestion of ruthenium oxide chloride catalyst

In a three-necked flask with reflux condenser; Dropping funnel, N ₂ feed (0.25 l / min), 2 - 2.5 g of ruthenium oxide chloride catalyst, ie a calcined under air, used ruthenium chloride catalyst, which was used in a Deacon process, and a magnetic stirrer presented (It was independently used both a SnO ₂ - or TiO ₂ - supported catalyst). The output of the three-necked flask was with two wash bottles connected - the applied N ₂ purge was passed through the wash bottles. The first was filled with 15 wt .-% hydrochloric acid, the second with 15 wt .-% sodium hydroxide solution.

About 100 ml of HCl (conc.) Was added and heated to boiling while stirring.

After refluxing for about 2 hours, 20 g of NaClO ₃ in the form of a solution were slowly added via dropping funnel under N ₂ purge. The addition time was about 30 min

The contents of the three neck flask were h under N ₂ then 2 -Spühlung boiled under reflux, then cooled under N ₂ purge and drawn a sample of the clear supernatant.

In the clear supernatant of the digestion solution 2 and 1% of the amount of ruthenium contained in the catalyst were recovered (SnO ₂ - or TiO _{2 support} ). 16% or 13% of the amount of ruthenium contained in the catalyst could be recovered (SnO ₂ or TiO ₂ carrier) in the downstream HCl wash bottle.

Ruthenium could not be detected in the NaOH wash bottle.

Example 4

The decomposition method of an oxidic Ru catalyst shown in Example 3 provided a still comparatively small recovery rate. Therefore, an upstream reduction with hydrogen was used, which caused a considerable increase in the recovery rate.

For this purpose, in a reaction tube, 3 g of ruthenium oxide chloride catalyst (SnO ₂ or TiO ₂ - supported) with a gas mixture of 4% H ₂ /96% N ₂ at 550 ⁰ C for 2 h and at least partially reduced to metallic Ru.

The catalyst thus treated was digested with HCl / NaClO ₃ analogously to Example 3. The yield obtained after analysis of the HCl wash bottle gave 74 and 65%, respectively (SnO ₂ and TiO ₂ - supported). The catalyst support had been dissolved only to a small extent and had an almost white color. In the clear supernatant of the digestion solution in each case 1% of the amount of ruthenium contained on the catalyst were found again (SnO ₂ - or TiO ₂ carrier).

Example 5

Digestion of ruthenium oxide chloride catalyst (SnO ₂ or TiO ₂ -supported) - NaOH / KNO ₃ melt In a mortar, 2 g of ruthenium oxide chloride catalyst (SnO ₂ or TiO ₂ -supported) were triturated with 9 g of NaOH (solid) and 4 g of KNO ₃ . The mixture was then reacted in a 50 ml crucible at 500 ^° C. for 2 hours.

After cooling, the melt cake was disrupted as follows:

The melt cake was placed in a three necked flask with reflux condenser; Dropping funnel, N ₂ - feed (0.25 1 / min) transferred. The output of the three-necked flask was connected to two wash bottles - the attached N ₂ purge was passed through the wash bottles. The first was filled with 15 wt .-% hydrochloric acid, the second with 15 wt .-% sodium hydroxide solution.

Approximately 100 ml of HCl (conc.) Were added and heated to boiling with stirring.

The contents of the three-necked flask were refluxed for about 2 hours with N ₂ feed, then cooled with N ₂ purge, and a sample of the clear supernatant was drawn.

In the clear supernatant of the digestion solution 2 and 1% of the amount of ruthenium contained on the catalyst were recovered (SnO ₂ - or TiO ₂ carrier). In the downstream HCl wash bottle 76% and 73% of the amount of ruthenium contained on the catalyst were recovered (SnO ₂ - or TiO ₂ carrier) are.

Ruthenium could not be detected in the NaOH wash bottle.

Example 6

Digestion of ruthenium oxide chloride catalyst (SnO ₂ or TiO ₂ supported) - NaOH / Na ₂ CO ₃ / KNOR melt

Example 5 was repeated with a weight of 5 g NaOH / 4 g Na ₂ CO ₃ instead of 9 g NaOH - The procedure and the work-up were carried out analogously to Example 5.

In the clear supernatant of the digestion solution 1 and 3% of the amount of ruthenium contained on the catalyst were recovered (SnO ₂ - or Tiθ _{2 support} ). In the downstream HCl wash bottle could be recovered 82% and 79% of the amount of ruthenium contained on the catalyst (Snθ ₂ - or Tiθ ₂ carrier).

Claims

claims

A process for the recovery of ruthenium in the form of ruthenium halide, in particular ruthenium chloride, from a ruthenium-containing supported catalyst material having at least the following steps:

a) chemical decomposition of the catalyst material,

b) preparing a crude ruthenium salt solution,

c) purifying the crude ruthenium salt solution, optionally by expelling gaseous ruthenium tetraoxide from the solution,

d) subsequent treatment of the purified ruthenium compound obtained in c), in particular of the ruthenium tetraoxide with hydrogen halide or

Hydrohalic acid for the recovery of ruthenium halide, in particular with hydrogen chloride or hydrochloric acid for the production of ruthenium chloride.

2. A process for the recovery of ruthenium in the form of ruthenium halide, in particular ruthenium chloride, from a ruthenium-containing supported catalyst material having at least the following steps:

a ') digesting the catalyst material by treating the material at a temperature above 600 ⁰ C in an oxygen-containing atmosphere with the addition of ozone and / or chlorine and / or hydrogen chloride to expel the ruthenium as a volatile purified ruthenium compound,

3. The method according to claim 2, characterized in that the proportion of oxygen in the digestion gas in the digestion a ') 1 to 30 vol .-%, in particular 2 to 20 vol .-%, the

Content of chlorine up to 95 vol .-%, the content of hydrogen chloride up to 95 vol .-% and the content of ozone up to 20 vol .-%.

4. The method according to any one of claims 1 to 3, characterized in that the catalyst material prior to the digestion a) or a ') for the reduction of the ruthenium compound is exposed to a hydrogen-containing atmosphere.

5. The method according to any one of claims 1 to 4, characterized in that the catalyst material before the digestion a) or a ') is purified in particular by exposure to an oxygen-containing atmosphere of sulfur compounds.

6. The method according to any one of claims 1 to 5, characterized in that the catalyst material from a used catalyst for the gas phase oxidation of

Hydrogen chloride comes with oxygen or a used electrode material for electrolysis.

7. The method according to any one of claims 1 to 6, characterized in that the catalyst material as support material, a material from the series: tin dioxide, silica, graphite, titanium, titanium dioxide with rutile or anatase structure, zirconium dioxide,

Alumina, silica, carbon nanotubes, nickel, nickel oxide, silicon carbide and tungsten carbide or mixtures thereof, preferably tin dioxide, titanium dioxide, zirconium dioxide, alumina.

8. The method according to any one of claims 1 to 7, characterized in that the catalyst material contains ruthenium as metal or in the form of a ruthenium compound selected from the series: ruthenium oxide, ruthenium chloride, ruthenium oxide chloride.

9. The method according to one of claims 1 to 8, characterized in that the recovered in step d) ruthenium halide, in particular ruthenium chloride for the production of new catalyst or electrode material is reused, in particular as

Ruthenium, ruthenium oxide, ruthenium chloride or ruthenium oxide chloride catalyst on a support or as an electrode coating.

10. The method according to any one of claims 1 to 9, characterized in that the content of ruthenium in the catalyst material up to 10 wt .-%, in particular 1 to 5 wt .-%, particularly preferably 1.5 to 4 wt .-% is ,

1 1. A method according to any one of claims 1 to 9, characterized in that the content of ruthenium in the electrode coating material used as a catalyst material (coating) up to 50 wt .-%, in particular 30 to 45 wt .-%, particularly preferably 35 to 40 wt .-% based on the coating.

12. Use of the obtained from a method according to any one of claims 1 to 1 1 recovered ruthenium compound as a catalyst or electrode material, in particular as ruthenium, ruthenium, ruthenium or ruthenium on a support or as an electrode coating.

13. Use according to claim 12, characterized in that the ruthenium compound obtained by the process according to any one of claims 1 to 1 1, in particular ruthenium chloride as a trace in the sum of a content of Si, Ca, Mg and Al: of at most 220 ppm, especially preferably of not more than 150 ppm, a content of Rh, Ir, Pt and Pd in the sum of at most 250 ppm, more preferably of at most 150 ppm, a content of Cu of at most 25 ppm, more preferably of at most 15 ppm and a content of K, Na, Fe in each case at most 125 ppm, particularly preferably at most 100 ppm.