EP2178636A1

EP2178636A1 - Thermally stable catalyst for hydrogen chloride gas phase oxidation

Info

Publication number: EP2178636A1
Application number: EP08773671A
Authority: EP
Inventors: Aurel Wolf; Leslaw Mleczko; Oliver Felix-Karl SCHLÜTER; Stephan Schubert
Original assignee: Bayer Technology Services GmbH
Current assignee: Bayer Intellectual Property GmbH
Priority date: 2007-07-13
Filing date: 2008-06-26
Publication date: 2010-04-28
Also published as: RU2010104937A; JP5225377B2; CN101743059A; RU2469790C2; RU2486006C2; CN101687178A; US20100202959A1; WO2009010167A1; EP2178637A1; RU2010104936A; JP2010533059A; WO2009010182A1; JP2010533058A; US20100183498A1; JP5269075B2; US7985395B2

Abstract

The present invention relates to a catalyst for oxidation reactions, said catalyst comprising at least one constituent which is active in the catalysis of hydrogen chloride oxidation and a support therefor, wherein the support is based on uranium oxide. The catalyst is notable for a high stability and activity.

Description

Temperature stable catalyst for the hydrogen chloride gas phase oxidation

The present invention relates to a catalyst for oxidation reactions comprising at least one active ingredient in the oxidation reaction catalysis and a carrier therefor, characterized in that the carrier comprises uranium oxides. The catalyst is characterized by higher stability and activity compared to prior art catalysts.

It is known that uranium oxides are suitable as oxidation catalysts for a number of complete or selective oxidations. A typical example of the use of uranium-based catalysts is CO oxidation to CO 2, as described, for example, by Campbell et al in J. Molec. Cat. A: Chem., (2006), 245 (1-2), 62-68. Further oxidations catalysed by uranium-containing mixed oxides are, for example, those of isobutene to acrolein (Corberan et al., Ind. Eng. Chem. Prod. Res. Dev., (1984), 24, 546, and 1985, 24, 62) and that of propylene to acrolein and acrylonitrile (US Pat. Nos. 3,308,151 and 3,198,750). Furthermore, there is the total oxidation of VOC (volatile organic compounds) to U ₃ O ₈ , in particular by Hutchings et. al. (Nature, (1996), 384, p341). Uranium oxide as a carrier for nanoscale gold particles is described, for example, in Green Chemistry (2005), 7 (11), 768-770 and (2007) 9 (3), 267-272. Applications in the field of hydrogen chloride oxidation are not disclosed in this context.

Ruthenium is, as is well known, in particular as a reduction catalyst or as an oxidation catalyst application (Handbook of Heterogeneous Catalysis, 1997, S2160 and S2181).

Oxidation under more severe conditions in terms of temperature and oxygen partial pressure is the method of catalytic hydrogen chloride oxidation with oxygen developed by Deacon in 1868:

4 HCl + O ₂ => 2 Cl ₂ + 2 H ₂ O.

The 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. It is therefore advantageous to use catalysts with the highest possible activity, which allow the reaction to proceed at low temperature. The first catalysts for the oxidation of hydrogen chloride with the catalytically active ingredient ruthenium were described as early as 1965 in DE 1 567 788, in this case starting from RuCl ₃ . As supports Al ₂ O ₃ and SiO _{2 were} claimed. The activity of this combination is relatively low, as these carriers can not provide lattice oxygen atoms for the oxidation process.

Other Ru-based catalysts with ruthenium oxide or ruthenium mixed oxide as the active ingredient were claimed in DE-A 197 48 299. In this case, the content of ruthenium oxide is from 0.1% by weight to 20% by weight and the average particle diameter of ruthenium oxide is from 1.0 nm to 10.0 nm.

Other supported on titanium oxide or zirconium Ru catalysts are known from DE-A 197 34 412. For the preparation of the ruthenium chloride catalysts described therein, which contain at least one compound titanium dioxide and zirconium dioxide, a number of Ru starting compounds have been indicated, such as, for example, ruthenium-carbonyl complexes, ruthenium salts of inorganic acids, ruthenium-nitrosyl complexes, ruthenium-amine. Complex, ruthenium complexes of organic amines or ruthenium-acetylacetonate complexes. In a preferred embodiment, titanium dioxide in the form of rutile was used as carrier. Although Ru catalysts have a fairly high activity, they tend to sinter and thus deactivate at higher temperatures. To increase the economy, however, a further increase in activity with good long-term stability is necessary.

The previously developed supported ruthenium oxidation catalyst systems have insufficient activity or stability for the hydrogen chloride oxidation. Although the activity can be increased by increasing the reaction temperature, this leads to sintering / deactivation or to the loss of the catalytically active ingredient.

DE 1 078 100 discloses catalysts comprising salts or oxides of silver, uranium or thorium which are located on inert carriers of kaolin, silica gel, diatomaceous earth or pumice. It is not disclosed that the resulting catalysts are calcined, which results in low stability of the disclosed catalysts. In addition, it is not disclosed that the carrier alone may have a catalytic activity and may consist of uranium oxide. There is always disclosed a composition which detects the presence of silver and salts or oxides of rare earths. Accordingly, in the absence of further disclosure, it can be assumed that the technical teaching aims at a co-catalytic effect, which enables the conversion of the individual catalytically active constituents only a conversion.

This is disadvantageous because both the use of silver and the rare earth salts or oxides cause the catalyst to be economically unfavorable to alternatives without these ingredients. In particular, the use of silver may be considered particularly disadvantageous in view of the continuously increasing prices of this precious metal.

The object of the present invention was thus to provide a catalyst which accomplishes the oxidation of hydrogen chloride with high activity and / or stability and thereby can be obtained economically advantageous over the prior art.

Surprisingly, it has been found that the targeted support of catalytically active in the oxidation of metals, such as ruthenium, on uranium oxides, due to a special interaction between catalytically active ingredient and carrier, a number of new highly active catalysts can be produced which have a high catalytic activity exhibit.

In addition, it has surprisingly been found that the fiction, modern based on uranium oxides catalysts have a special stability in oxygen and hydrogen chloride atmosphere even at high temperatures and that can be optionally dispensed with additional catalytically active ingredients in particular catalysts based on uranium oxides, as these themselves already a Have activity and / or stability in the oxidation of hydrogen chloride.

The present invention thus relates to a catalyst for oxidation reactions which comprises at least one active ingredient in the catalysis of oxidation reactions and a carrier therefor, characterized in that the carrier is based on a uranium-containing compound, in particular uranium oxide.

Preferred is a catalyst in which the carrier comprises a uranium oxide. Preference is given to uranium oxides such as UO ₃ , UO ₂ , UO or from mixtures of these Species resulting non-stoichiometric phases such as U ₃ O ₅ , U ₂ O _5> U ₃ O ₇ , U ₃ Og, U ₄ θ ₉ , U] ₃ O ₃₄ . Particularly preferred are uranium oxides or mixtures of these with a stoichiometric composition of UO ₂ ] to UO _2.9 .

Examples of suitable carrier materials which can be combined with uranium oxide are silicon dioxide, rutile or anatase titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, preferably titanium dioxide, zirconium dioxide, aluminum oxide or mixtures thereof, particularly preferably γ- or δ-aluminum oxide or mixtures thereof.

In a preferred development of the present invention, the catalyst consists only of a carrier comprising uranium oxide.

Thus, in the preferred development, the at least one active ingredient in the oxidation reaction catalysis is identical to at least one constituent of the carrier and is a uranium oxide or a mixture of uranium oxides.

This is particularly advantageous because it can be dispensed with the further use of expensive precious metals or semimetals as further active ingredients of the catalyst.

In this development, preference is given to using a support as catalyst comprising uranium oxides or mixtures thereof with a stoichiometric composition of Uθ _2, i to UO _2i9 . In particular, these stoichiometries show a particularly high activity and stability.

The uranium oxides can also be combined with the other support materials just described.

These preferred catalysts in the form of excipients comprising uranium oxide or mixtures of uranium oxide as catalysts are particularly advantageous because they surprisingly have an extremely high activity and stability for oxidation reactions.

Also preferably, the catalyst consists only of a carrier comprising uranium oxide and subjected to pretreatment.

The pretreatment is usually a pretreatment under the process conditions of use of the catalyst. Since the catalysts disclosed herein are preferred in the Oxidation of HCl with oxygen is used, pretreatment with a stoichiometric mixture of oxygen and HCl is preferred. Preference is given to pretreating with a stoichiometric mixture of HCl and oxygen at at least 400 ° C., preferably at least 500 ° C. The pretreatment is usually at least for 10 h. Preferably at least for 50 h, more preferably at least for 100 h.

The pretreatment can be carried out as long as desired at any temperatures. It has been shown that a longer and hotter pretreatment is better than a shorter and colder one. There are also shorter and colder pretreatments conceivable. It is a question of weighing how much additional work in pretreatment, which is reflected in increased activity, can be compensated for by this gain in activity. Therefore, the temperature ranges and periods just given are to be understood as meaningful recommendations, but not as technical limitations.

It has surprisingly been found, as already described above, that the supports / catalysts of this invention, and in particular the catalysts of the preferred further development, in which the catalyst consists only of a support comprising uranium oxide, under high temperature loading under process conditions Gaining activity as a pretreatment. All known catalysts behave this essentially opposite.

If, in addition to the support comprising uranium oxide, a further catalytically active constituent is used, a catalyst is preferred in which the catalytically active constituent is applied to the support in the form of an aqueous solution or suspension and the solvent is then removed.

Particularly preferred is a catalyst, which is characterized in that the further catalytically active ingredient is applied as an aqueous solution or suspension of ruthenium halides, oxides, hydroxides or oxyhalides each alone or in any mixture on the support and the solvent then Will get removed.

As further catalytically active ingredients in question are all components that catalyze the hydrogen chloride oxidation. For example, the following elements are suitable or compounds thereof: ruthenium, osmium, rhodium, iridium, palladium, platinum, copper, silver, gold, rhenium, bismuth, cobalt, iron, chromium or mixtures thereof. In a preferred embodiment, ruthenium and its compounds are used. In a very preferred embodiment, without being limited thereto, ruthenium is used in oxidic form or as a chloride compound or as an oxychloride compound.

In a further embodiment of the method according to the invention, the further catalytically active ingredient is applied to the carrier in a non-oxidic form and converted into the oxidized form in the course of the reaction.

Typically, the loading with the catalytically active ingredient is in the range of 0.1 to 80 wt .-%, preferably in the range of 1 to 50 wt .-%, particularly preferably in the range of 1 to 25 wt .-% based on the total mass from catalyst and carrier.

The further catalytically active ingredient can be applied by various methods. For example, and without limitation, wet and wet impregnation of a support with suitable starting or starting compounds in liquid or collodial form, up and co-impingement methods, as well as ion exchange and gas phase coating (CVD, PVD) may be employed. Preference is given to a combination of impregnation and subsequent precipitation with reducing (preferably hydrogen, hydrides or hydrazine compounds) or alkaline substances (preferably NaOH, KOH or ammonia).

Suitable promoters are basic-acting metals (for example alkali, alkaline earth and rare earth metals), preference is given to alkali metals, in particular Na and Cs, and alkaline earth metals, particularly preferably alkaline earth metals, in particular Sr and Ba and the rare earth metal Ce.

The promoters optionally present in addition to the further active constituent may, but are not limited thereto, be applied to the catalyst by impregnation and CVD processes, preferably an impregnation, particularly preferably after application of the further catalytically active constituent.

To stabilize the dispersion of the further catalytically active ingredient, for example, without being limited thereto, various dispersion stabilizers such as For example, scandium compounds, manganese oxides and lanthanum oxides are used. The stabilizers are preferably applied together with the further catalytic constituent by impregnation and / or precipitation.

The catalysts can be dried under atmospheric pressure or preferably under reduced pressure under a nitrogen, argon or air atmosphere at 40 to 200 ^° C. The drying time is preferably 10 minutes to 24 hours.

The catalysts can be used uncalcined or calcined. The calcination can be carried out in reducing, oxidizing or inert phase, preference being given to calcination in an air or in nitrogen stream.

This calcination may be applied to the catalyst of the invention comprising a catalytically active ingredient on one based on a uranium containing compound, in particular uranium oxide, but also the catalyst according to the preferred development in which the at least one is active in the oxidation reaction oxidation Constituent at the same time also the carrier is.

The calcining is carried out in the case of a catalyst according to the preferred development of the invention, in the form of carriers comprising uranium oxide or mixtures of uranium oxide as catalysts, in the presence of or in the absence of oxygen in a temperature range of 500 to 1200 ⁰ C, preferably in the range 700 up to 1000 ^° C.

The calcination is carried out in the case of a catalyst comprising carrier and further catalytically active ingredient in the presence of oxidizing gases in a temperature range of 150 to 500 ⁰ C, preferably in the range of 150 ⁰ C to 300 ⁰ C.

For the application of the novel catalysts, the catalytic process known as the Deacon process is preferably used as described above. 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 450 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 oxygen in superstoichiometric amounts of hydrogen chloride use. For example, a two- to four-fold excess of oxygen is customary. Since no loss of selectivity is to be feared, it may be economically advantageous to work at relatively high pressure and, accordingly, longer residence time than normal pressure.

Suitable preferred catalysts for the Deacon process include ruthenium oxide, ruthenium chloride or other ruthenium compounds. Suitable catalysts can be obtained, for example, by applying ruthenium chloride to the support and then drying or drying and calcining. In addition to or instead of a ruthenium compound, suitable catalysts may also contain compounds of other metals, for example gold, palladium, platinum, osmium, iridium, silver, copper, chromium, uranium or rhenium. Suitable catalysts may further contain chromium (III) oxide.

The catalytic hydrogen chloride oxidation may be adiabatic or preferably isothermal or approximately isothermal, batchwise, but preferably continuously or as a fixed bed process, preferably as a fixed bed process, more preferably in tube bundle reactors to heterogeneous catalysts at a reactor temperature of 180 to 450 ° C, preferably 200 to 400 ° C, more preferably 220 to 350 ° 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 multiple 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 be done by different impregnation of the catalyst support with active material or by different dilution of the catalyst with an inert material. As an inert material, for example, rings, cylinders or balls of titanium dioxide, zirconium dioxide or mixtures thereof, alumina, steatite, ceramic, glass, graphite or stainless steel can be used. In the preferred use of shaped catalyst bodies, the inert material should preferably have similar external dimensions.

Suitable shaped catalyst bodies starting from uranium oxide are shaped bodies of any desired shape, preference being given to tablets, rings, cylinders, stars, carriage wheels or spheres, particular preference being given to spheres, rings, cylinders or star strands as molds.

The shaping of the catalyst can take place after or preferably before the impregnation of the support material.

The conversion of hydrogen chloride in a single pass may preferably be limited to 15 to 90%, preferably 40 to 85%, particularly preferably 50 to 70%. After conversion, unreacted hydrogen chloride can be partly or completely recycled to the catalytic hydrogen chloride oxidation. The volume ratio of hydrogen chloride to oxygen at the reactor inlet is preferably 1: 1 and 20: 1, preferably 2: 1 and 8: 1, more preferably 2: 1 and 5: 1.

The heat of reaction of the catalytic hydrogen chloride oxidation can be used advantageously for the production of high-pressure steam. This can be used to operate a phosgenation reactor and / or distillation columns, in particular of isocyanate distillation columns.

The hydrogen chloride oxidation catalyst of the present invention is characterized by high activity at a low temperature. Without wishing to be bound by theory, it is believed that the uranium oxide can positively contribute to the catalytic cycle via the ability to provide lattice oxygen. Examples

Example 1: Uranium (VI) oxide support with Ru

In a beaker, 1 g of a uranium (VI) oxide (from Strem Chemicals) precalcined at 500 ° C. for 4 hours was suspended in 2.8 ml of water in a solution of 0.053 g of Ru (III) chloride hydrate and the mixture was stirred for 60 minutes Room temperature stirred. Subsequently, the water was separated in an air stream at 60 ° C / 4 h. The calcining was carried out at 250 ° C for 16 h in the air stream, whereby a ruthenium catalyst with theoretically calculated (2 wt .-%) Ru supported on uranium (VI) oxide was obtained.

Example 2: Uranium (IV) oxide support with Ru

A 2 wt .-% Ru catalyst on uranium (FV) -Oxid carrier was prepared analogously to Example 1, with the only difference that at 500 ° C for 4 h precalcined U (IV) oxide (Strem Chemicals) was used.

Example 3: U ₃ O _{8 support} with Ru

A 2 wt .-% Ru catalyst on uranium (V / VI) -Oxid carrier was prepared analogously to Example 1, with the only difference that at 500 ⁰ C for 4 h precalcined U (V / VI) oxide (Strem Chemicals) was used.

Example 4 U-oxide support with Ru

1 g of uranyl acetate dihydrate (from Fluka) were calcined for 2 hours at 300 ° C. and for 4 hours at 800 ° C. RuCl ₃ hydrate was applied to 0.3 g of the oxidic U-support analogously to Example 1, so that the Ru content was 2% by weight.

Example 5: Pure Uranium (IV) Oxide Carrier

2 g of powdered uranium (IV) oxide (Strem Chemicals) were dried overnight at 150 ° C in a drying oven at ambient pressure and then calcined for 2 h under air at 500 ⁰ C.

Example 6: Pure Uranium (VI) Oxide Carrier 2 g of powdered uranium (VI) oxide (Strem Chemicals) were dried overnight at 150 ° C in a drying oven at ambient pressure and then calcined for 2 h under air at 500 ° C.

Example 7: Mixed uranium (V / VI) oxide carrier

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

Example 8: Mixed uranium (V / VI) oxide carrier with pretreatment

The catalyst obtained from Example 7 was subjected to pretreatment for 100 hours at 540 ° C under 80 ml / min HCl and 80 ml / min O ₂ . The result is a pretreated catalyst according to Example 8.

Example 9: Preparation of a uranium and alumina carrier

In a beaker, 2 g of gamma-Al ₂ O ₃ shaped bodies (diameter about 1.5 mm, Fa. Saint Gobain, BET of 260 m ² / g) with a 10 wt% aqueous solution of uranyl acetate dihydrate (Fa Riedel de Haen) by spraying. After a contact time of 1 h, the water was separated in an air stream at 80 ⁰ C for 2 h. The process was repeated until a proportion of calculated 12 wt .-% uranium results on the moldings.

The moldings were then calcined for four hours at 800 ° C in an air stream.

Example 10: Preparation and Analysis of a Uranium and Alumina Support

Analogously to Example 9, 40 g of gamma-Al ₂ O ₃ shaped bodies (Saint Gobain, BET of 200 m ² / g) were impregnated with uranium and calcined.

Examination by XRD (theta / theta reflection diffractometer SIEMENS D 5000) showed the presence of gamma-Al ₂ O ₃ , as well as U ₃ Og.

Example 11-14: Using the catalysts of Examples 1-4 in the HCl oxidation at 300 ⁰ C 0.2 g of the catalysts obtained according to Example 1-4 were ground and introduced as a mixture with 1 g of silica sand (100-200 microns) in a quartz reaction tube (diameter ~ 10 mm).

The quartz reaction tube was heated to 300 ⁰ C and operated in the following at this temperature.

A gas mixture of 80 ml / min HCl and 80 ml / min oxygen was passed through the quartz reaction tube. After 30 minutes, the product gas stream was passed into a 16% by weight potassium iodide solution for 10 minutes, and the resulting iodine was back titrated with a 0.1 N thiosulfate solution to determine the amount of chlorine introduced.

The productivities of the catalysts shown in Table 1 were found to be 300 ^° C.

Table 1: Productivities of the catalysts according to Examples 1-4 according to Examples 11-14

Examples 15-19: Use of the catalysts of Examples 5-9 in the HCl oxidation at 540 ⁰ C

Were carried out analogous to those of Examples 1 1-14 for the catalysts of Examples 5-9 experiments in which now heats the quartz reaction tube to 540 ⁰ C and was operated in the following at this temperature.

The productivities of the catalysts shown in Table 2 were found to be 540 ^° C. Examples 20-24: Use of the catalysts of Examples 5-9 in the HCl oxidation at 600 ⁰ C

Experiments were carried out analogously to those of Examples 11-14 for the catalysts according to Examples 5-9, wherein now the quartz reaction tube was heated to 600 ° C and subsequently operated at this temperature.

The productivities of the catalysts shown in Table 2 were found to be 600 ^° C.

Table 2: Productivities of the catalysts according to Examples 5-9 of Examples 15-24

Claims

claims

A catalyst for hydrogen chloride oxidation which comprises at least one active ingredient in the catalysis of oxidation reactions and a carrier therefor, characterized in that the carrier is based on a uranium-containing compound, in particular uranium oxide.

2. Catalyst according to claim 1, wherein the support UO ₃ , UO ₂ , UO or the mixtures of these species resulting nichtstöchimoetrischen phases such as U ₃ O ₅ , U ₂ O ₅ , U ₃ O ₇ , U ₃ O ₈ , U ₄ O. ₉ U ₁₃ O ₃₄ contains.

3. A catalyst according to claim 1 or 2, characterized in that the carrier uranium oxides or mixtures thereof with a stoichiometric composition of U0 _2i i to UO _{2; 9} contains.

4. Catalyst according to claim 1, 2 or 3, wherein the carrier additionally contains silica, titania with rutile or anatase structure, zirconium dioxide, alumina or mixtures thereof.

5. Catalyst according to one of claims 1 to 4, wherein this comprises as further catalytically active ingredient at least one element which is selected from the group consisting of: ruthenium, osmium, rhodium, iridium, palladium, platinum, copper, silver, Gold, rhenium, bismuth, cobalt, vanadium, chromium, manganese, nickel, tungsten and iron.

The catalyst of claim 5, wherein the further catalytically active ingredient comprises ruthenium.

7. A catalyst according to any one of claims 1 to 6, characterized in that the further catalytically active ingredient is applied in the form of an aqueous solution or suspension to the carrier and the solvent is removed.

8. Catalyst according to one of claims 1 to 7, characterized in that the further catalytically active ingredient is applied as an aqueous solution or suspension of ruthenium halides, oxides, hydroxides or oxyhalides each alone or in any mixture on the carrier and the solvent is removed.

9. Catalyst according to one of claims 1 to 4, characterized in that the active ingredient is identical to at least one component of the carrier and a uranium oxide or a mixture of uranium oxides.

10. A catalyst according to claim 8, characterized in that it is pretreated with a stoichiometric mixture of oxygen and HCl at temperatures of at least 400 ° C for at least 10 h.

11. Use of a catalyst according to any one of claims 1 to 10 in the catalytic gas phase oxidation of hydrogen chloride with oxygen.

12. A process for the preparation of chlorine comprising the catalytic gas phase oxidation of hydrogen chloride with oxygen, characterized in that a catalyst according to any one of claims 1 to 10 is used.