阅读说明：本技术 用于通过气相氧化制备氯的催化剂和方法 (Catalyst and process for the production of chlorine by gas phase oxidation ) 是由 A.沃尔夫 L.姆莱齐科 O.F-K.施吕特 于 2011-08-22 设计创作，主要内容包括：本发明涉及用于通过气相氧化制备氯的催化剂和方法。具体地,本发明涉及一种通过用氧对氯化氢进行催化气相氧化制备氯的催化剂,和所述催化剂的用途,其中所述催化剂包括煅烧的二氧化锡作为载体材料和至少一种含卤素的钌化合物。(The present invention relates to a catalyst and a process for the production of chlorine by gas phase oxidation. In particular, the invention relates to a catalyst for the production of chlorine by catalytic gas phase oxidation of hydrogen chloride with oxygen, wherein the catalyst comprises calcined tin dioxide as support material and at least one halogen-containing ruthenium compound, and to the use of the catalyst.)

1. catalyst composition comprising at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active substance, characterized in that the support material is calcined in the presence of an oxidizing gas, in particular in the presence of air, at a temperature of at least 450 ℃ before the catalytically active substance is applied, and that the support material comprises a further binder, wherein the proportion of binder is 1 to 30% by weight, based on the finished catalyst, wherein more than 90% of the tin dioxide is of the cassiterite structure.

2. Composition according to claim 1, characterized in that the ruthenium compound is a halogen-and/or oxygen-containing ruthenium compound.

3. The composition as claimed in claim 2, wherein the halogen of the ruthenium compound is selected from the group consisting of: chlorine, bromine and iodine, especially chlorine.

4. Composition as claimed in any one of claims 1 to 3, characterized in that the catalytically active ruthenium compound is selected from: ruthenium chloride, ruthenium oxychloride and mixtures of ruthenium chloride and ruthenium oxide, especially ruthenium oxychloride compounds.

5. Composition as claimed in claim 4, characterized in that the catalytically active ruthenium compound is a mixed compound corresponding to the general formula RuCl _x O _y, where x is from 0.8 to 1.5 and y is from 0.7 to 1.6.

6. The composition as claimed in any of claims 1 to 5, characterized in that the temperature at which the support material is calcined before the catalytically active substance is applied is at least 500 ℃, preferably at least 700 ℃, particularly preferably from 700 ℃ to 1100 ℃.

7. The composition as claimed in any of claims 1 to 6, characterized in that the support material is calcined for a duration of 0.5 hours to 10 hours, preferably 1 hour to 6 hours, before the catalytically active substance is applied.

8. Composition as claimed in any of claims 1 to 7, characterized in that the oxidizing gas when calcining the support material before applying the catalytically active substance has an oxygen content of 10% by volume to 50% by volume, preferably 15 to 25% by volume.

9. The composition as claimed in any of claims 1 to 8, characterized in that the catalyst is obtainable by a process in which the removal of the solvent comprises drying at least 80 ℃, preferably at least 100 ℃.

10. Composition as claimed in any of claims 1 to 9, characterized in that the catalyst composition is obtainable by calcining a support material carrying a halogen-containing ruthenium compound at a temperature of at least 200 ℃, preferably at least 240 ℃, particularly preferably at least 250 ℃ and 650 ℃, in particular in an oxygen-containing atmosphere, particularly preferably under air conditions.

11. Composition as claimed in any of claims 1 to 10, characterized in that the proportion of ruthenium from the halogen-containing ruthenium compound relative to the total catalyst composition, in particular after calcination, is from 0.5 to 5% by weight, preferably from 1.0 to 4% by weight, particularly preferably from 1.5 to 3% by weight.

12. Composition as claimed in any one of claims 1 to 11, characterized in that the tin dioxide is entirely of the cassiterite structure.

13. A process for preparing chlorine by catalytic gas phase oxidation of hydrogen chloride with oxygen over a solid catalyst, wherein the catalyst comprises at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active substance, characterized in that the catalyst used is a composition as claimed in any of claims 1 to 12.

14. The process as claimed in claim 13, characterized in that the gas-phase oxidation of hydrogen chloride comprises passing a gas comprising hydrogen chloride and oxygen at a temperature of 180-500 ℃, preferably 200-450 ℃, particularly preferably 250-420 ℃, and separating the chlorine formed from the water of reaction and optionally unconverted oxygen and hydrogen chloride.

15. The process as claimed in either of claims 13 and 14, characterized in that the gas-phase oxidation is carried out at a pressure of from 1 to 25bar, preferably from 1.2 to 20bar, particularly preferably from 1.5 to 17bar and particularly preferably from 2.0 to 15 bar.

16. The process as claimed in any of claims 13 to 15, characterized in that the gas-phase oxidation is carried out adiabatically or isothermally, in particular adiabatically.

17. Use of a calcined catalyst support comprising tin dioxide, wherein the material of the support comprises a further binder, wherein the proportion of binder is 1 to 30% by weight, based on the finished catalyst, wherein more than 90% of the tin dioxide is of the cassiterite structure, for a catalyst in the catalytic gas phase oxidation of hydrogen chloride with oxygen.

Technical Field

The invention results from a known process for preparing chlorine by catalytic gas phase oxidation of hydrogen chloride with oxygen, wherein the catalyst comprises tin dioxide as support and at least one halogen-and/or oxygen-containing ruthenium compound. The invention relates to the calcination of tin dioxide before the application of a catalytically active substance, to a catalyst composition and to the use thereof.

Background

The oxygen-catalyzed hydrogen chloride oxidation process developed by Deacon in 1868 with an exothermic equilibrium reaction was the beginning of industrial chlorine chemistry:

4HCl+O₂→2Cl₂+2H₂O

However, chlor-alkali electrolysis forces the Deacon process to a large extent to fall short. Almost all chlorine is produced by electrolysis of aqueous sodium chloride solution [ Ullmann Encyclopedia of industrial chemistry, seventhhrease, 2006 ]. However, as the global demand for chlorine has grown faster than the demand for sodium hydroxide solution, the attractiveness of the Deacon process has increased again in recent times. This development caters for a process for the preparation of chlorine by oxidation of hydrogen chloride, which process is free from the production of sodium hydroxide solution. Furthermore, in phosgenation reactions, for example in the preparation of isocyanates, hydrogen chloride is obtained in large amounts as a coproduct.

The oxidation of hydrogen chloride to chlorine is an equilibrium reaction. As the temperature increases, the equilibrium position shifts in a direction that is detrimental to the desired end product. It is therefore advantageous to use the catalyst with as high an activity as possible, which allows the reaction to proceed at low temperatures.

DE 1567788 has already described in 1965 a first catalyst for hydrogen chloride oxidation having ruthenium as catalytically active component, in this case starting from RuCl ₃, for example supported on silica and alumina, furthermore, DE-A19748299, DE-A19734412 and EP 0936184A 2 describe other Ru-based catalysts having ruthenium oxide as active component or mixed ruthenium oxide as active component and various oxides, such as titanium dioxide, zirconium dioxide, etc., as support materials.

Furthermore, documents WO2007/134772 a1 and WO2007/134721 a1 disclose ruthenium-based catalyst systems supported on tin dioxide, the activity of which is clearly more prominent than in the prior art.

However, a disadvantage of the catalyst systems claimed in WO 2007/134772A 1 and WO 2007/134721A 1 is that under the reaction conditions of HCl gas-phase oxidation, tin can be liberated from the support material in the form of volatile compounds SnCl ₄ (austeragen). this is particularly disadvantageous for the lifetime of the catalyst, since premature loss of tin gradually reduces the mechanical stability.

Disclosure of Invention

It is therefore an object of the present invention to increase the chemical stability of the catalysts known from WO2007/134772 a1 and WO2007/134721 a1 with respect to tin stripping without impairing their advantageous activity. This object is achieved by calcining the tin dioxide-containing support component before applying the catalytically active substance.

It has now been found that, surprisingly, the controlled calcination of a tin dioxide-containing support before application of a catalytically active substance can improve the chemical stability, and the activity, of the catalyst under the reaction conditions of the gas-phase oxidation of HCl.

The invention provides a catalyst composition comprising at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active substance, characterized in that the support material is calcined at a temperature of at least 450 ℃ in the presence of an oxidizing gas, in particular in the presence of air, before the catalytically active substance is applied.

In a preferred embodiment, tin dioxide is used as a support for the catalytically active component, wherein the tin dioxide is of the cassiterite structure.

The invention still further provides a process for preparing chlorine by catalytic gas-phase oxidation of hydrogen chloride with oxygen over a solid catalyst, wherein the catalyst comprises at least tin dioxide as support material and at least one ruthenium-containing compound as catalytically active substance, characterized in that the support material is calcined at a temperature of at least 450 ℃ in the presence of an oxidizing gas, in particular in the presence of air, before the catalytically active substance is applied.

According to the invention, the catalytically active component used is at least one ruthenium-containing compound. It is in particular ruthenium halide, ruthenium hydroxide, ruthenium oxide, ruthenium oxyhalide and/or ruthenium in metallic form.

Preferred are catalyst compositions wherein the ruthenium compound is a halogen-and/or oxygen-containing ruthenium compound.

The catalytically active components used are preferably halogen-containing ruthenium compounds. This is, for example, a compound in which the halogen is present in the form of an ionic to polar covalent bond to the ruthenium atom.

The halogen in the preferred halogen-containing ruthenium compounds is preferably selected from chlorine, bromine and iodine. Chlorine is particularly preferred.

The halogen-containing ruthenium compound includes those composed of only halogen and ruthenium. However, preference is given to those which contain both oxygen and halogen, especially chlorine or chloride. Particularly preferred catalyst compositions are those in which the catalytically active ruthenium compound is selected from: ruthenium chloride, ruthenium oxychloride and mixtures of ruthenium chloride and ruthenium oxide, especially ruthenium oxychloride compounds.

Ruthenium oxychloride in the context of the present invention is a compound in which oxygen and chlorine are simultaneously present in an ionically to polarizable covalently bonded to the ruthenium, such a compound having the general formula RuO _x Cl _y preferably a plurality of ruthenium oxychloride compounds of this class may be present simultaneously with one another in the catalyst examples of particularly preferred ruthenium oxychloride compounds defined also include inter alia the following compositions Ru ₂ Cl _{4 2}, Ru ₂ OCl ₅ and Ru ₂ OCl ₆.

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

The catalytically active ruthenium oxychloride compound in the context of the present invention is preferably obtainable by a process which comprises: a solution or suspension, in particular an aqueous solution or suspension, of at least one halogen-containing ruthenium compound is first applied to the calcined tin dioxide-containing support, and the solvent is then removed.

Other conceivable methods include chlorinating a non-chlorine-containing ruthenium compound, such as ruthenium hydroxide, either before or after applying the ruthenium compound to the support.

A preferred method comprises applying an aqueous solution of RuCl ₃ to a support.

The temperature during calcination of the support material before application of the catalytically active species is preferably at least 700 c, more preferably from 700 c to 1100 c. The duration of the calcination of the support material before the application of the catalytically active substance is preferably from 0.5 hour to 10 hours, particularly preferably from 1 hour to 6 hours. The oxidizing gas used in calcining the support material before the application of the catalytically active substance preferably contains from 10% to 50% by volume, particularly preferably from 15 to 25% by volume, of oxygen.

If the calcination of the support material is carried out at too high a temperature (for example >1500 ℃) or at a suitable temperature for too long a time before the application of the catalytically active substance, although the chemical stability is likewise increased, a gradual reduction in the BET surface area and consequently in some cases in the activity of the catalyst formed therefrom also results as a result of the sintering.

The application of the ruthenium compound is generally followed by a drying step, which is schematically carried out in the presence of oxygen or air, so as to be able to be converted, at least in part, into the preferred ruthenium oxychloride compound. In order to prevent the preferred ruthenium oxychloride compounds from being converted to ruthenium oxide, the drying should preferably be carried out at a temperature of less than 280 ℃, in particular at least 80 ℃, particularly preferably at least 100 ℃. The drying time is preferably 10 minutes to 6 hours. The catalyst may be dried under standard pressure or, preferably, under reduced pressure.

A preferred process is characterized in that the catalyst is obtainable by supporting a halogen-containing ruthenium compound on a tin dioxide-containing support which has been calcined before application of the active material and calcining it at a temperature of at least 200 ℃, preferably at least 240 ℃, particularly preferably from at least 250 to 650 ℃, in particular in an oxygen-containing atmosphere, more preferably under air conditions. The calcination time is preferably 30 minutes to 24 hours.

In a particularly preferred process, the proportion of ruthenium from the catalytically active ruthenium compound relative to the total catalyst composition, especially after calcination, is from 0.5 to 5% by weight, preferably from 1.0 to 4% by weight, particularly preferably from 1.5 to 3% by weight.

If the catalytically active substance applied is an oxygen-free halogen-ruthenium compound, it can also be dried at higher temperatures in the absence of oxygen.

Preferably, the catalyst is obtainable by a process comprising: an aqueous solution or suspension of at least one halogen-containing ruthenium compound is applied to the calcined tin dioxide-containing support component, followed by drying at a temperature below 280 ℃ and then activation under gas-phase oxidation conditions of hydrogen chloride, during which substantial conversion to ruthenium oxychloride takes place. The longer the drying time in the presence of oxygen, the more oxychloride is formed.

In a particularly preferred variant, the oxygen-containing ruthenium compound is applied to the support. This is a compound in which oxygen is bonded to the ruthenium atom in an ion-to-polar covalent form. The compound is prepared by the following steps: an aqueous solution or suspension of at least one halogen-containing ruthenium compound is applied to the calcined tin dioxide, followed by precipitation with a basic compound to give ruthenium hydroxide, and optionally the precipitated product is calcined.

The precipitation can be carried out under alkaline conditions, directly forming the ruthenium compound containing oxygen. It is also possible to carry out the process under reducing conditions, first of all to form metallic ruthenium and then to carry out the calcination under oxygen-supplying conditions, in which an oxygen-containing ruthenium compound is formed.

A preferred method comprises applying an aqueous solution of RuCl ₃ to the calcined tin dioxide-containing support component by impregnation, soaking, or the like.

The application of the halogen-containing ruthenium compound is generally followed by a precipitation step and a drying or calcination step, which is suitably carried out at a temperature of up to 650 ℃ in the presence of oxygen or air.

Particularly preferably, the catalytic component, i.e. the ruthenium-containing compound, can be applied to the support, for example, by impregnation of the support with suitable starting compounds present in solution or in liquid or colloidal form in the moist (Feucht/Nass), precipitation and coprecipitation processes, as well as ion exchange processes and gas-phase coating processes (CVD, PVD).

The catalyst for hydrogen chloride oxidation of the present invention is notable for high activity and high stability at low temperatures.

Preferably, the novel catalyst composition is used in a catalytic process known as the Deacon process, as already described above. In this process, hydrogen chloride is oxidized with oxygen to chlorine in an exothermic equilibrium reaction, with water vapor being formed. The reaction temperature is generally 180-500 ℃, particularly preferably 200-450 ℃, and particularly preferably 250-420 ℃; typical reaction pressures are from 1 to 25bar, preferably from 1.2 to 20bar, particularly preferably from 1.5 to 17bar, very particularly preferably from 2 to 15 bar. Since the reaction is an equilibrium reaction, it is suitably carried out at as low a temperature as possible at which the catalyst still has sufficient activity. It is also suitable to use oxygen in a superstoichiometric amount relative to hydrogen chloride. For example, a 2-4 fold excess of oxygen is typically used. Since there is no selectivity loss concern, it is economically advantageous to operate at relatively high pressures and correspondingly longer residence times compared to standard pressures.

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

The catalytic hydrogen chloride oxidation can be carried out batchwise, preferably adiabatically or isothermally or almost isothermally, preferably batchwise, but preferably continuously, in a fluidized bed or fixed bed process, preferably in a fixed bed process, particularly preferably adiabatically, at a reactor temperature of 180-500 deg.C, preferably 200-450 deg.C, particularly preferably 250-420 deg.C, and at a pressure of 1-25bar (1000-25000hPa), preferably 1.2-20bar, particularly preferably 1.5-17bar and particularly preferably 2.0-15 bar.

Typical reaction apparatus for carrying out catalytic hydrogen chloride oxidation therein are fixed bed or fluidized bed reactors. The catalytic hydrogen chloride oxidation can also preferably be carried out in a plurality of stages.

In an adiabatic, isothermal or near isothermal process system, but preferably in an adiabatic process system, it is also possible to use a plurality, in particular 2 to 10, preferably 2 to 6, reactors in series with intercooling devices. The hydrogen chloride can be added either completely before the first reactor together with the oxygen or distributed over the different reactors. Such series of individual reactors may also be combined in one apparatus.

A further preferred embodiment of an apparatus suitable for use in the present process comprises the use of a structured catalyst bed in which the catalyst activity increases gradually in the direction of flow. The configuration of such catalyst beds can be achieved by different soaking of the catalyst support with active material or by different dilution of the catalyst with inert material. For example, the inert material used can be annular, cylindrical or spherical titanium dioxide, zirconium dioxide or mixtures thereof, aluminum oxide, talc, ceramics, glass, graphite or stainless steel. In the preferred use of the catalyst shaped bodies, the inert material should preferably have similar outer dimensions.

Suitable shaped catalyst bodies include shaped bodies having any desired shape, preferably tablet, annular, cylindrical, star, wheel or spherical, particularly preferably annular, cylindrical, spherical or star extrudates, as their shape. Preferably spherical. The size of the shaped catalyst bodies, for example the diameter or the maximum cross-sectional width of the spheres, is in particular from 0.3 to 7mm, very preferably from 0.8 to 5mm, on average.

As an alternative to the finely divided catalyst (shaped) bodies described above, the support may also be a monolith of support material, for example not only a "conventional" support having parallel channels without radial interconnection of the channels; also included are foams, sponges and the like having three-dimensional connections within the support, as well as supports having cross-flow channels.

The monolithic support may have a honeycomb structure, but may also have an open or closed cross-cell structure. The monolithic support has a preferred pore (Zell) density of 100-.

Monoliths in the context of the present invention are disclosed, for example, in "Monooliths in multiple pharmaceutical processes-observations and transcripts" by F.Kapteijn, J.J.Heiszwolf, T.A.Nijhuis and J.A.Moulijn, Cattech 3, 1999, page 24.

Suitable further support materials or binders for the support are, for example, in particular silicon dioxide, graphite, titanium dioxide having a rutile or anatase structure, zirconium dioxide, aluminum oxide or mixtures thereof, preferably titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably gamma-or delta-aluminum oxide or mixtures thereof. Preferred binders are alumina or zirconia. The proportion of binder is from 1 to 30% by weight, more preferably from 2 to 25% by weight, very preferably from 5 to 20% by weight, based on the finished catalyst. The binder improves the mechanical stability (strength) of the catalyst shaped body.

In a particularly preferred variant of the invention, the catalytically active component is present essentially on the surface of the actual support material, for example tin dioxide, and not on the surface of the binder.

For the additional doping of the catalyst, suitable promoters are alkali metals or metal compounds, alkaline earth metals, rare earth metals or mixtures thereof, where alkali metals such as lithium, sodium, potassium, rubidium and cesium, preferably lithium, sodium and potassium, particularly 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, particularly preferably lanthanum and cerium.

The promoters can be, without being restricted thereto, applied to the catalyst by impregnation and CVD methods, preferably by impregnation of, for example, metal compounds, in particular chlorides and/or nitrates, and particularly preferably applied together with the main catalytic component.

In the oxidation of HCl, the hydrogen chloride conversion per pass (Durchgan) can preferably be limited to 15 to 90%, preferably 40 to 90%, particularly preferably 70 to 90%. The unconverted hydrogen chloride can be partly or wholly recycled after separation into the catalytic hydrogen chloride oxidation. The volume ratio of oxygen to hydrogen chloride at the reactor inlet is preferably from 1:2 to 20:1, more preferably from 2:1 to 8:1, particularly preferably from 2:1 to 5: 1.

The heat of reaction of the catalytic hydrogen chloride oxidation can be advantageously used to produce high pressure steam. The steam can be used to operate a phosgenation reactor and/or a distillation column, in particular an isocyanate distillation column.

In a further step, the chlorine formed is separated off. The separation step generally comprises a plurality of stages, in particular the separation of unconverted hydrogen chloride from the product gas stream of the catalytic hydrogen chloride oxidation and optionally its recycling, the drying of the resulting stream, which essentially comprises chlorine and oxygen, and the separation of chlorine from the dried stream.

Unconverted hydrogen chloride and the steam formed can be separated by cooling to condense aqueous hydrochloric acid from the product gas stream of the hydrogen chloride oxidation. The hydrogen chloride can also be absorbed with dilute hydrochloric acid or water.

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

The invention also provides for the use of the novel catalyst composition as a catalyst, in particular for oxidation reactions, particularly preferably as a catalyst for the catalytic gas phase oxidation of hydrogen chloride with oxygen.

Detailed Description

The following examples illustrate the invention.