EP3515597A1

EP3515597A1 - Method for the hydrogenation of organic compounds in the presence of co and a fixed catalyst bed which contains monolithic shaped catalyst body

Info

Publication number: EP3515597A1
Application number: EP17768106.1A
Authority: EP
Inventors: Rolf Pinkos; Irene DE WISPELAERE; Michael Schwarz; Michael Schreiber; Zeljko KOTANJAC; Michael Nilles
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2016-09-23
Filing date: 2017-09-14
Publication date: 2019-07-31
Also published as: WO2018054754A1; CN109789404A; JP2019532059A; US20190210010A1; KR20190052674A

Abstract

The present invention relates to a method for the hydrogenation of organic compounds in the presence of CO and a fixed catalyst bed which contains immobilized structured shaped catalyst body.

Description

A process for hydrogenating organic compounds in the presence of CO and a fixed catalyst bed containing monolithic catalyst form bodies

BACKGROUND OF THE INVENTION

The present invention relates to a process for the hydrogenation of organic compounds in the presence of CO and a fixed catalyst bed containing immobilized structured structured catalyst. STATE OF THE ART

It is basically known to carry out hydrogenation reactions in the presence of carbon monoxide (CO). On the one hand, the CO can be added to the hydrogen used for the hydrogenation and / or originate from the starting materials or their intermediates, by-products or products. If catalysts are used for hydrogenation which contain CO-sensitive active components, it is known as a countermeasure to carry out the hydrogenation at a high hydrogen pressure and / or a low catalyst load. Otherwise, the implementation may be incomplete, so that z. For example, a secondary reaction in at least one further reactor is absolutely necessary. It can also lead to the increased formation of by-products. Disadvantages associated with the use of high hydrogen pressures are the formation of methane by hydrogenation of CO and thus an increased consumption of hydrogen and increased investment costs. The US 6,262,317 (DE 196 41 707 A1) describes the hydrogenation of 1, 4-butynediol with hydrogen in the liquid continuous phase in the presence of a heterogeneous hydrogenation catalyst at temperatures of 20 to 300 ° C, a pressure of 1 to 200 bar and values of liquid-side volume-related mass transfer coefficient kl_a of 0.1 s ^_1 to 1 s ^_1 . The reaction can be carried out either in the presence of a catalyst suspended in the reaction medium or in a fixed-bed reactor operated in cocurrent in a cyclic gas mode. It is generally described that one can provide fixed bed reactors by directly coating packages, such as are commonly used in bubble columns, with catalytically active substances. Further details can not be found here. In the exemplary embodiments, suspension catalysts or reactor fillers based on Raschig rings with a diameter of 5 mm were used. For the hydrogenation in fixed bed mode, a ratio of supplied gas flow to the reactor leaving the gas stream from 0.99: 1 to 0.4: 1 is described, ie at least 60% of the gas supplied are still present at the end of the reactor. In suspension mode, good hydrogenation results are described in Example 1 at a loading of about 0.4 kg of butynediol / liter of reaction space xh. If the load is increased to about 0.7 (Example 2), then the Butandiolausbeute goes back and the proportion of undesirable by-products, such as 2-methylbutanediol, butanol and propanol increases. The problem with the hydrogenations in suspension is the handling of the suspended catalyst, which must remain in the reactor, so that a filter system for retaining the catalyst is absolutely necessary. Such filters tend to occupy with catalyst particles, so that they must either be periodically cleaned consuming, or the travel time is correspondingly short, before the passage through the filter is uneconomical. Also in Examples 5 and 6 using supported catalysts, a filter was still used to keep the particles of catalyst bed in the reactor. The load corresponded to about 0.25 kg of butynediol / liter of reaction space x h. The total amount of by-products 2-methylbutanediol, butanol and propanol is relatively high at 6%. The implementation of the process described in DE 196 41 707 A1 is technically complex for the reasons mentioned. In addition, it is necessary to provide a gaseous circulation stream in the fixed-bed mode, since at least 60% of the gas supplied to the reactor exit at the reactor end. With such a cycle gas method, however, the danger is particularly high that level up unwanted components in the gas stream; This is especially true for CO.

DE 199 629 07 A1 describes a process for the preparation of Cio-C3o-alkenes by partial hydrogenation of alkynes on fixed-bed supported catalysts, wherein CO is added to the hydrogenation gas. The hydrogenation-active metal used is exclusively palladium. As suitable starting materials, in particular dehydrolinalool, hydrodehydrolinalool, 1-ethynyl-2,6,6-trimethyl-cyclohexanol, 17-ethynylandrost-5-en-3β, 17β-diol, 3,7,1 1, 15-tetramethyl 1-hexadecano-3-ol (dehydroisophytol), 3,7,1-trimethyl-6-dodecen-1-yn-3-ol (dehydrodihydronerolidol), 4-methyl-4-hydroxy-2-decyne,

1,1-diethoxy-2-octyne and bis (tetrahydro-2-pyranyloxy) -2-butyne. EP 0 754 664 A2 describes a process for the preparation of alkenes by partial hydrogenation of alkynes on fixed-bed supported catalysts, wherein CO is added to the hydrogenation gas. In turn, only palladium is used as hydrogenation-active metal. As a suitable starting material is in addition to a large number of others also 1, 4-butynediol called. In the embodiments, however, only the selective hydrogenation of 2-dehydrolinalool to 2-linalool is described.

DE 433 32 93 A1 describes partially hydrogenating 1,4-butynediol at 60 ° C. over a structured Pd catalyst 1, 4-butynediol to 1,4-butenediol. Nothing is said about CO formation or its contents. Also, nothing about the amount of hydrogen that was used for hydrogenation, but only the pressure (15 bar). Thus, it can be assumed that the hydrogenation was not operated continuously, but educt was pumped only in trickle mode without significant hydrogen flow.

Known types of catalysts for hydrogenation reactions are precipitated, supported or Raney metal catalysts. Raney metal catalysts have found wide commercial use, especially for the hydrogenation of mono- or polyunsaturated organic compounds. Usually, Raney's

Catalysts around alloys containing at least one catalytically active metal and at least one alkali-soluble (leachable) alloy component. Typical catalytically active metals include Ni, Fe, Co, Cu, Cr, Pt, Ag, Au and Pd, and typical leachable alloy components are e.g. B. Al, Zn and Si. Such Raney metal catalysts and processes for their preparation are, for. For example, in US Pat. No. 1,628,190, US Pat. No. 1,915,473 and US Pat. No. 5,563,587. Prior to their use in heterogeneously catalyzed chemical reactions, especially in a hydrogenation reaction, Raney metal alloys generally require activation. Conventional methods for activating Raney metal catalysts include grinding the alloy into a fine powder if it is not already powdered by the prior art. For activation, the powder is subjected to treatment with an aqueous liquor, wherein the leachable metal is partially removed from the alloy and the highly active non-leachable metal remains. The powders thus activated are pyrophoric and are usually stored under water or organic solvents in order to avoid contact with oxygen and the associated deactivation of the Raney metal catalysts.

According to a known method for activating suspended Raney nickel catalysts, a nickel-aluminum alloy with 15 to 20 wt .-% strength sodium hydroxide solution is treated at temperatures of 100 ° C or higher. In US 2,948,687 it is described to prepare a Raney nickel molybdenum catalyst from a milled Ni-Mo-Al alloy having particle sizes in the range of 80 mesh (about 0.177 mm) or finer by first placing the alloy at 50 ° C with 20 wt .-% NaOH solution treated and the temperature to 100 to 1 15 ° C raises.

A significant disadvantage of powdered Raney metal catalysts is the need to separate them from the reaction medium of the catalyzed reaction by expensive sedimentation and / or filtration processes.

It is known to use Raney metal catalysts in the form of larger particles. Thus, US Pat. No. 3,448,060 describes the preparation of structured Raney metal catalysts, wherein in a first embodiment an inert carrier material is coated with an aqueous suspension of a pulverulent nickel-aluminum alloy and freshly precipitated aluminum hydroxide. The resulting structure is dried, heated and contacted with water, releasing hydrogen. Subsequently, the structure is hardened. Optionally, leaching with an alkali hydroxide solution is provided. In a second embodiment, an aqueous suspension of a powdered nickel-aluminum alloy and freshly precipitated aluminum hydroxide is subjected to shaping without the use of a carrier material. The structure thus obtained is activated analogously to the first embodiment. Other suitable for use in fixed bed catalysts Raney metal catalysts may have hollow bodies or spheres or otherwise supported. Such catalysts are z. In EP 0 842 699, EP 1 068 900, US 6,747,180,

US 2,895,819 and US 2009/0018366. US 2,950,260 describes a method for activating a catalyst of a granular nickel-aluminum alloy by treatment with an aqueous alkali solution. Typical particle sizes of this granular alloy range from 1 to 14 mesh (about 20 to 1.4 mm). It has been found that contacting a Raney metal alloy, such as a Ni-Al alloy, with an aqueous liquor results in an exothermic reaction to produce larger amounts of hydrogen. The following reaction equations are intended to illustrate, by way of example, possible reactions which take place when a Ni-Al alloy is brought into contact with an aqueous alkali metal hydroxide, such as NaOH:

2 NaOH + 2 Al + 2 H ₂ 0 - 2 NaAI0 ₂ + 3 H ₂

2 Al + 6 H ₂ O - 2 Al (OH) ₃ + 3 H ₂

2 Al (OH) ₃ - ^> Al ₂ O ₃ + 3 H ₂ O US 2,950,260 has for its object to provide an activated granular hydrogenation catalyst of a Ni-Al alloy with improved activity and lifetime available. For this purpose, the activation is carried out with a 0.5 to 5 wt .-% strength NaOH or KOH, wherein the temperature is maintained by cooling to below 35 ° C and the contact time is chosen so that not more than 1, 5 parts H2 mole per mole equivalent Leach are liberated. In contrast to a powdery, suspended catalyst, the treatment of granular Raney metal catalysts removes a significantly lower proportion of aluminum from the structure. This is in a range of only 5 to 30 wt .-%, based on the amount of aluminum originally present. Catalyst particles having a porous activated nickel surface and an unchanged metal core are obtained. A disadvantage of the catalysts thus obtained, in which only the outermost layer of the particles is catalytically active, is their sensitivity to mechanical stress or abrasion, which can lead to a rapid deactivation of the catalyst. The teaching of US Pat. No. 2,950,260 is restricted to granular shaped catalyst bodies which fundamentally differ from larger structured shaped bodies. Moreover, this document also does not teach that the catalysts may contain promoter elements in addition to nickel and aluminum. It is known to subject hydrogenation catalysts, such as Raney metal catalysts, a doping with at least one promoter element in order, for. B. to achieve an improvement in the yield, selectivity and / or activity in the hydrogenation. Thus, as a rule, products of improved quality can be obtained. Such dopants are disclosed in US 2,953,604, US 2,953,605, US 2,967,893, US Pat.

US 2,950,326, US 4,885,410 and US 4,153,578.

The use of promoter elements serves, for example, unwanted side reactions such. B. isomerization reactions to avoid. Promoter elements are also suitable to modify the activity of the hydrogenation catalyst to z. B. in the hydrogenation of starting materials with several hydrogenatable groups to achieve either a targeted partial hydrogenation of a particular group or more specific groups or a complete hydrogenation of all hydrogenatable groups. So z. For example, it is known to use a copper-modified nickel or palladium catalyst for the partial hydrogenation of 1,4-butynediol to 1,4-butenediol (see, for example, US Pat.

GB832141). In principle, the activity and / or the selectivity of a catalyst can thus be increased or decreased by doping with at least one promoter metal. Such doping should not adversely affect the other properties of the doped catalyst as far as possible. For the modification of shaped catalyst bodies by doping, the following four methods are known in principle:

The promoter elements are already present in the alloy for producing the shaped catalyst bodies (method 1),

the shaped catalyst bodies are brought into contact with a dopant during activation (method 2),

the shaped catalyst bodies are brought into contact after activation with a dopant (Method 3),

the catalyst bodies are brought into contact with a dopant in the hydrogenation feed stream during hydrogenation, or a dopant is otherwise introduced into the reactor during hydrogenation (Method 4).

The above-mentioned method 1, in which at least one promoter element is already contained in the alloy for the preparation of the shaped catalyst body is z. B. in the already mentioned US 2,948,687 described. Thereafter, a finely ground nickel-aluminum-molybdenum alloy is used for catalyst preparation to produce a molybdenum-containing Raney nickel catalyst. The above methods 2 and 3 are z. Example in US 2010/01741 16 A1

(= US 8,889.91 1) described. Thereafter, a doped catalyst is prepared from a Ni / Al alloy which is modified during and / or after its activation with at least one promoter metal. In this case, the catalyst can optionally be subjected to a first doping before activation. The promoter element used for doping by absorption on the surface of the catalyst during and / or after activation is selected from Mg, Ca, Ba, Ti, Zr, Ce, Nb, Cr, Mo, W, Mn, Re, Fe, Co, Ir, Ni, Cu, Ag, Au, Bi, Rh and Ru. If the catalyst precursor is already subjected to doping before activation, then the promoter element is selected from Ti, Ce, V, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Pd, Pt and Bi ,

The above method 3 is also described in GB 2104794. This document relates to Raney nickel catalysts for the reduction of organic compounds, especially the reduction of carbonyl compounds and the preparation of 1,4-butanediol from 1,4-butynediol. To prepare these catalysts, a Raney nickel catalyst is subjected to a doping with a molybdenum compound, which may be solid, as a dispersion or as a solution. Other promoter elements, such as Cu, Cr, Co, W, Zr, Pt or Pd may additionally be used. In a specific embodiment, an already activated commercially available undoped Raney nickel catalyst is suspended in water together with ammonium molybdate and the suspension Pension stirred until a sufficient amount of molybdenum was added. In this document only particulate Raney nickel catalysts are used for doping, especially the use of structured shaped bodies is not described. There is also no indication as to how the catalysts in the form of a structured fixed catalyst bed can be introduced into a reactor and how the catalyst fixed bed introduced into the reactor can then be activated and doped.

The above method 4 is z. In US Pat. No. 2,967,893 or US Pat. No. 2,950,326. Thereafter, copper in the form of copper salts is added to a nickel catalyst for the hydrogenation of 1,4-butynediol in the aqueous.

According to EP 2 486 976 A1, supported activated Raney metal catalysts are subsequently doped with an aqueous metal salt solution. Specifically, as the carrier, the usual bulk materials are used, such. B. SiO 2 -coated glass body with a diameter of about 3 mm. It is not described to carry out the doping and optionally already the activation on a stationary fixed catalyst bed of structured catalyst bodies in a reactor. Thus, with the process described in this document, it is impossible to provide a fixed catalyst bed which has a gradient with respect to the concentration of the promoter elements in the direction of flow of the reaction medium of the reaction to be catalyzed.

EP 2 764 916 A1 describes a process for producing foam-form catalyst bodies which are suitable for hydrogenations, in which: a) a metal foam molding is provided which contains at least one first metal, which is selected, for example, from Ni, Fe, Co, Cu, Cr, Pt, Ag, Au and Pd, b) on the surface of the metal foam molding at least a second leachable component or an alloyable by alloy in a leachable component component applies, for example, is selected from Al, Zn and Si, and c) by alloying the metal foam molding obtained in step b)

at least forms an alloy on a part of the surface, and d) subjecting the foam-like alloy obtained in step c) to a treatment with an agent capable of leaching the leachable components of the alloy. This document teaches to use for the step d) a 1 to 10 molar, ie 4 to 40% by weight aqueous NaOH. The temperature in step d) is 20 to 98 ° C and the treatment time is 1 to 15 minutes. It is quite generally mentioned that the foam-like shaped bodies according to the invention can also be formed in situ in a chemical reactor, although any concrete details are missing. EP 2 764 916 A1 further teaches that promoter elements can be used in the preparation of foam-like shaped catalyst bodies. The doping can be carried out together with the application of the leachable component on the surface of the previously prepared metal foam molding. The doping can also take place in a separate step following the activation.

EP 2 764 916 A1 does not contain the slightest information on the dimension of the chemical reactors for the use of the foam-shaped moldings, the type, amount and dimensioning of the moldings introduced into the reactor and for introducing the moldings into the reactor. In particular, there is no indication as to how a fixed catalyst bed actually located in a chemical reactor can first be activated and then doped.

It is an object of the present invention to provide an improved process for the hydrogenation of organic compounds which overcomes as many of the aforementioned disadvantages as possible.

It has been found that unsaturated organic compounds can be hydrogenated to saturated compounds in an advantageous manner if monolithic fixed-bed catalysts are used for the hydrogenation and the CO content in the gas phase within the reactor is in a range from 0.1 to 10,000 ppm by volume, wherein the conversion is at least 90% and wherein the fixed catalyst bed contains shaped catalyst bodies having pores and / or channels and wherein at any cut in the normal plane to the flow direction through the fixed catalyst bed at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, have an area of at most 3 mm ² . SUMMARY OF THE INVENTION

The invention relates to a process for the hydrogenation of a hydrogenatable organic compound in at least one reactor containing a fixed catalyst bed containing monolithic shaped catalyst bodies or consists of monolithic shaped catalyst bodies containing at least element selected from Ni, Fe, Co, Cu, Cr , Pt, Ag, Au, Mn, Re, Ru, Rh and Ir, wherein during the hydrogenation, the CO content in the gas phase within the reactor is in a range of 0.1 to 10,000 ppm by volume, and wherein the fixed catalyst bed is shaped catalyst contains at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, at an arbitrary section in the normal plane to the flow direction through the fixed catalyst bed, an area of at most 3 mm ² . PREFERRED EMBODIMENTS OF THE INVENTION

The invention includes the following preferred embodiments:

1 . A process for the hydrogenation of a hydrogenatable organic compound in at least one reactor containing a fixed catalyst bed containing monolithic shaped catalyst bodies or consisting of monolithic shaped catalyst bodies containing at least one element selected from Ni, Fe, Co, Cu, Cr, Pt , Ag, Au, Mn, Re, Ru, Rh and Ir, wherein during the hydrogenation, the CO content in the gas phase within the reactor is in a range of 0.1 to 10,000 ppm by volume, and wherein the fixed catalyst bed contains shaped catalyst bodies, have at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, an area of at most 3 mm ² at any section in the normal plane to the flow direction through the fixed catalyst bed.

2. The method of embodiment 1, wherein the hydrogenatable organic compound is selected from compounds having at least one carbon-carbon double bond, carbon-nitrogen double bond, carbon-oxygen double bond, carbon-carbon triple bond, carbon-nitrogen triple bond or Having nitrogen-oxygen double bond.

3. The method according to any one of the preceding embodiments wherein the compound used for the hydrogenation is selected from 1, 4-butynediol, 1, 4-butenediol, 4-hydroxybutyraldehyde, hydroxypivalic, hydroxypivalaldehyde, n-butyraldehyde, iso-butyraldehyde, n-valeraldehyde, iso-valeraldehyde, 2-ethylhex-2-enal, 2-ethylhexanal, the isomeric nonanals, 1, 5,9-cyclododecatriene, benzene, furan, furfural, phthalic acid esters, acetophenone and alkyl-substituted acetophenones. Process according to one of the preceding embodiments, where the compound used for the hydrogenation is selected from 1,4-butynediol, 1,4-butenediol, n- and isobutyraldehyde, hydroxypivalaldehyde, 2-ethylhex-2-enal, the isomeric nonanals and 4-isobutylacetophenone , Method according to one of the preceding embodiments, wherein the hydrogenation is carried out continuously.

Method according to one of the preceding embodiments, wherein the reactor has an internal volume in the range of 0.1 to 100 m ³ , preferably from 0.5 to 80 m ³ .

Method according to one of the preceding embodiments, wherein the conversion in the hydrogenation at least 90 mol%, preferably at least 95 mol%, in particular at least 99 mol%, especially at least 99.5 mol%, based on the total molar amount of hydrogenatable compounds in the starting material used for the hydrogenation is.

Method according to one of the preceding embodiments, wherein during the hydrogenation, the CO content in the gas phase within the reactor in a range of 0.15 to 5000 ppm by volume, in particular in a range of 0.2 to 1000 ppm by volume.

Method according to one of the preceding embodiments, wherein the reactor in the flow direction of the reaction medium through the fixed catalyst bed has a gradient with respect to the CO concentration.

Method according to one of the preceding embodiments, wherein the CO content at the outlet of the reaction medium from the fixed catalyst bed by at least 5 mol%, preferably by at least 25 mol%, in particular by at least 75 mol% higher than the CO content at Entry of the reaction medium into the fixed catalyst bed. Method according to one of the preceding embodiments, wherein the catalyst fixed bed at any cut in the normal plane to the flow direction through the fixed catalyst bed, based on the total area of the cut, at most 5%, preferably at most 1%, in particular at most 0.1% free surface which does not Part of the catalyst bodies is.

Method according to one of the preceding embodiments, wherein the fixed catalyst bed to at least 90% length in the flow direction through the fixed catalyst bed to at least 95% of the reactor cross section, preferably at least 98% of the reactor cross section, in particular at least 99% of the reactor cross section is filled with shaped catalyst bodies.

Process according to one of the preceding embodiments, wherein the flow rate of the liquid reaction mixture through the reactor containing the fixed catalyst bed is at least 30 m / h, preferably at least 50 m / h, in particular at least 80 m / h.

Process according to one of the preceding embodiments, wherein the flow rate of the liquid reaction mixture through the reactor containing the fixed catalyst bed is at most 1000 m / h, preferably at most 500 m / h, in particular at most 400 m / h.

Method according to one of the preceding embodiments, wherein the hydrogenation reaction mixture is at least partially conducted in a liquid circulation stream.

Method according to one of the preceding embodiments, wherein the ratio of circulating stream outgoing reaction mixture to freshly supplied reactant stream in a range from 1: 1 to 1000: 1, preferably from 2: 1 to 500: 1, in particular from 5: 1 to 200 : 1, lies.

Method according to one of the preceding embodiments, wherein a discharge is taken from the reactor and subjected to a gas / liquid separation, whereby a hydrogen-containing gas phase and a product-containing liquid phase are obtained.

Method according to one of the preceding embodiments, wherein the absolute pressure in the hydrogenation in a range of 1 to 330 bar, preferably in a In the range of 5 to 100 bar, in particular in a range of 10 to 60 bar, is located.

Method according to one of the preceding embodiments, wherein the temperature in the hydrogenation in a range of 40 to 300 ° C, more preferably from 70 to 220 ° C, in particular from 80 to 200 ° C, is located. Method according to one of the preceding embodiments, wherein the fixed catalyst bed during the hydrogenation has a temperature gradient. Method according to one of the preceding embodiments, wherein the monolithic shaped catalyst bodies, based on the entire shaped body, have a maximum dimension in a direction of at least 1 cm, preferably at least 2 cm, in particular at least 5 cm. Method according to one of the preceding embodiments, wherein the monolithic shaped catalyst bodies contain at least one element selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, preferably selected from Ni, Co and Cu. Method according to one of the preceding embodiments, wherein the monolithic shaped catalyst bodies are in the form of a foam. Method according to one of the preceding embodiments, wherein the reactor used for the hydrogenation contains a fixed catalyst bed, the monolithic

Contains shaped catalyst bodies or consists of monolithic shaped catalyst bodies which contain at least one first metal which is selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, and which contain at least one second component which is selected from Al, Zn and Si, subjecting the fixed catalyst bed to activation with an aqueous base treatment.

Process according to embodiment 25, in which a fixed catalyst bed containing monolithic shaped catalyst bodies or consisting of monolithic catalyst bodies containing at least one first metal selected from Ni, Fe, Co, Cu, Cr, Pt, Ag is introduced into a reactor , and Au, and containing at least one second component selected from Al, Zn and Si, b) subjecting the fixed catalyst bed to the activation of a treatment with an aqueous base, c) optionally subjecting the activated fixed catalyst bed obtained in step b) to a treatment with a washing medium selected from water, C 1 -C 4 alkanols and mixtures thereof d) optionally contacting the fixed catalyst bed obtained after activation in step b) or after the treatment in step c) with a dopant having at least one element selected from the first

Metal and the second component of the catalyst molding used in step a) is different.

26. The method according to any one of embodiments 25 or 26, wherein to prepare the catalyst molding: a1) provides a metal foam molded body containing at least one first metal selected from Ni, Fe, Co, Cu, Cr, Pt , Ag, and Au, a2) on the surface of the metal foam molding at least a second

Component which contains an element which is selected from Al, Zn and Si, and a3) forms an alloy by alloying the metal foam molding obtained in step a2) at least on a part of the surface.

DESCRIPTION OF THE INVENTION

hydrogenation

In the context of the invention, hydrogenation is understood in general to mean the reaction of an organic compound with H 2 addition to this compound. Preferably, functional groups are hydrogenated to the correspondingly hydrogenated groups. These include, for example, the hydrogenation of nitro groups, nitroso groups, nitrile groups or imine groups to amine groups. This includes, for example, the hydrogenation of aromatics to saturated cyclic compounds. This also includes, for example, the hydrogenation of carbon-carbon triple bonds to double bonds and / or single bonds. This includes, for example, the hydrogenation of carbon-carbon double bonds to single bonds. Also includes finally, for example, the hydrogenation of ketones, aldehydes, esters, acids or anhydrides to alcohols.

The hydrogenation of carbon-carbon triple bonds, carbon-carbon double bonds, aromatic compounds, carbonyl-containing compounds, nitriles and nitro compounds is preferred. Carbonyl-containing compounds suitable for hydrogenation are ketones, aldehydes, acids, esters and anhydrides. Particularly preferred is the hydrogenation of carbon-carbon triple bonds, carbon-carbon double bonds, nitriles, ketones and aldehydes.

The hydrogenatable organic compound is particularly preferably selected from 1,4-butynediol, 1,4-butenediol, 4-hydroxybutyraldehyde, hydroxypivalic acid, hydroxypivaldehyde, n- and isobutyraldehyde, n- and isovaleraldehyde, 2-ethylhex-2 -enal,

2-ethylhexanal, the isomeric nonanals, 1, 5,9-cyclododecatriene, benzene, furan, furatural, phthalic acid esters, acetophenone and alkyl-substituted acetophenones. Very particular preference is given to the hydrogenatable organic compound selected from 1,4-butynediol, 1,4-butenediol, n- and isobutyraldehyde, hydroxypivalaldehyde,

2-ethylhex-2-enal, the isomeric nonanals and 4-isobutylacetophenone.

The hydrogenation according to the invention leads to hydrogenated compounds which accordingly no longer contain the group to be hydrogenated. Contains a compound at least two different hydrogenatable groups, it may be desirable to hydrogenate only one of the unsaturated groups, for. For example, when a compound has an aromatic ring and additionally a keto group or an aldehyde group. This includes z. Example, the hydrogenation of 4-isobutylacetophenone to 1 - (4'-isobutylphenyl) - ethanol or the hydrogenation of a C-C-unsaturated ester to the corresponding saturated ester. In principle, at the same time or instead of a hydrogenation in the sense of the invention, an undesired hydrogenation of other hydrogenatable groups can be carried out, for. B. carbon-carbon single bonds or of

C-OH bonds to water and hydrocarbons. This includes z. For example, the hydro- genolysis of 1, 4-butanediol to propanol or butanol. These latter hydrogenations usually lead to undesirable by-products and are therefore not desirable. Preferably, the hydrogenation according to the invention in the presence of a suitably activated catalyst is characterized by a high selectivity with respect to the desired hydrogenation reactions. These include in particular the hydrogenation of 1, 4-butynediol or 1, 4-butenediol to 1, 4-butanediol. In particular, this includes the hydrogenation of n- and iso-butyraldehyde to n- and iso-butanol. This includes further in particular the hydrogenation of hydroxypivalaldehyde or hydroxypivalic acid to neopentyl glycol. In particular, this includes the hydrogenation of 2-ethylhex-2-enal to 2-ethylhexanol. In particular, this includes the hydrogenation of nonanals to nonanols. In particular, this includes the hydrogenation of 4-isobutylacetophenone to give 1- (4'-isobutylphenyl) ethanol.

The hydrogenation is preferably carried out continuously.

In the simplest case, the hydrogenation takes place in a single hydrogenation reactor. In a specific embodiment of the process according to the invention, the hydrogenation is carried out in n hydrogenation reactors connected in series (in series), n being an integer of at least 2. Suitable values for n are 2, 3, 4, 5, 6, 7, 8, 9 and 10. Preferably, n is 2 to 6 and in particular 2 or 3. In this embodiment, the hydrogenation is preferably carried out continuously.

The reactors used for the hydrogenation may have a fixed catalyst bed, which is formed from the same or different shaped catalyst bodies. The fixed catalyst bed may have one or more reaction zones. Various reaction zones may have shaped catalyst bodies of different chemical composition of the catalytically active species. Different reaction zones may also have catalyst moldings of the same chemical composition of the catalytically active species but in different concentrations. If at least 2 reactors are used for the hydrogenation, the reactors may be the same or different reactors. These can be z. B. each have the same or different mixing characteristics and / or be subdivided by internals one or more times.

Suitable pressure-resistant reactors for the hydrogenation are known to the person skilled in the art. These include the commonly used reactors for gas-liquid reactions, such as. B. tube reactors, tube bundle reactors and gas circulation reactors. A special embodiment of the tube reactors are shaft reactors.

The process according to the invention will be carried out in a fixed bed procedure. The fixed bed mode can be z. B. in sump or in trickle run.

The reactors used for the hydrogenation contain a catalyst fixed bed activated by the method according to the invention, through which the reaction medium flows. The fixed catalyst bed can consist of a single type of shaped catalyst bodies or be formed from various shaped catalyst bodies. The fixed catalyst bed may have one or more zones, wherein at least one of the zones contains a material active as a hydrogenation catalyst. Each zone can have one or more different catalytically active materials and / or one or more different inert materials. Different zones may each have the same or different compositions. It is also possible to provide a plurality of catalytically active zones, which are separated from each other, for example, by inert beds or spacers. The individual zones may also have different catalytic activity. For this purpose, various catalytically active materials can be used and / or at least one of the zones an inert material can be added. The reaction medium flowing through the fixed catalyst bed contains at least one liquid phase. The reaction medium may also contain a gaseous phase in addition. During the hydrogenation, the CO content in the gas phase within the reactor is preferably in a range from 0.1 to 10,000 ppm by volume, more preferably in a range from 0.15 to 5000 ppm by volume, in particular in a range from 0, 2 to 1000 ppm by volume. The total CO content within the reactor is composed of CO in the gas and liquid phases, which are in equilibrium with each other. Conveniently, the CO content is determined in the gas phase and the values given here refer to the gas phase.

In this case, a concentration profile over the reactor is advantageous, wherein the concentration of CO in the flow direction of the reaction medium of the hydrogenation along the reactor should increase.

It has now surprisingly been found that a particularly high selectivity is achieved in the hydrogenation, when the concentration of CO increases in the flow direction of the reaction medium of the hydrogenation and if the fixed catalyst bed contains shaped catalyst bodies having pores and / or channels and wherein at any Section in the normal plane to the flow direction through the fixed catalyst bed at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, have an area of at most 3 mm ² . The CO content at the outlet of the reaction medium from the fixed catalyst bed is preferably at least 5 mol% higher, more preferably at least 25 mol% higher, in particular at least 75 mol% higher, than the CO content at the onset of the Reaction medium in the fixed catalyst bed. To generate a CO gradient in the direction of flow of the reaction medium through the fixed catalyst bed can For example, CO at one or more locations in the fixed catalyst bed are fed.

The content of CO will be determined, for example, by gas chromatography by taking individual samples or by online measurement. Preferred is the determination by online measurement. When taking the samples before the reaction medium enters the reactor, it is advantageous to remove and relax both gas and liquid in order to ensure that a balance has formed between the gas and the liquid. The content of CO is then determined in the gas phase.

The online measurement can be done directly in the reactor, z. B. before the reaction medium enters the fixed catalyst bed and after the exit of the reaction medium from the fixed catalyst bed.

The CO content may, for. B. be adjusted by the addition of CO to the hydrogen used for the hydrogenation. Of course, CO can also be fed separately from the hydrogen in the reactor. If the hydrogenation reaction mixture is at least partly conducted in a liquid circulation stream, CO can also be fed into this circulation stream. CO can also be formed from components contained in the hydrogenation reaction mixture, e.g. B. as starting materials to be hydrogenated or as incurred in the hydrogenation intermediates or by-products. So can CO z. B. formed in the reaction mixture of the hydrogenation formic acid, formates or formaldehyde are formed by decarbonylation the. Similarly, CO can also be formed by decarbonylation of aldehydes other than formaldehyde or by dehydrogenation of primary alcohols to aldehydes and subsequent decarbonylation. These undesirable side reactions include, for. As C-C or C-X cleavages, such as the formation of propanol or butanol formation of 1, 4-butanediol. It has furthermore been found that the conversion in the hydrogenation can only be insufficient if the CO content in the gas phase within the reactor is too high, ie. H. specifically above 10,000 ppm by volume.

The conversion in the hydrogenation is preferably at least 90 mol%, particularly preferably at least 95 mol%, in particular at least 99 mol%, especially at least 99.5 mol%, based on the total molar amount of hydrogenatable compounds in the hydrogenation used starting material. The conversion refers to the amount of target compound obtained, regardless of how many molar equivalents of hydrogen have taken up the starting compound to reach the target compound. When a starting compound used in the hydrogenation contains a number of hydrogenatable groups or contains a hydrogenatable group which can take up several equivalents of hydrogen (eg an alkyne group), the desired target compound can be either the product of partial hydrogenation (eg alkyne to alkene) or full hydrogenation (e.g. Alkyne to alkane).

It is important for the success of the hydrogenation according to the invention that the hydrogenation (i.e., gas and liquid) reaction mixture flows predominantly through the structured catalyst and does not flow past it, as is the case, for example, with ordinary, packed, fixed bed catalysts.

Preferably, over 90% of the material stream (i.e., the sum of gas and liquid streams) should flow through the fixed catalyst bed, preferably over 95%, more preferably> 99%. The fixed catalyst beds used according to the invention preferably have free surface at any section in the normal plane to the flow direction (ie, horizontal) through the fixed catalyst bed, based on the total area of the section, preferably at most 5%, particularly preferably at most 1%, in particular at most 0.1% free area, which is not part of the catalyst bodies. The area of the pores and channels which open at the surface of the shaped catalyst body is not calculated to this free area. The indication of the free area refers exclusively to sections through the fixed catalyst bed in the region of the shaped catalyst body and not any internals, such as power distribution.

If the catalyst fixed beds used in accordance with the invention comprise shaped catalyst bodies which have pores and / or channels, then at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, have an area at any section in the normal plane to the flow direction through the fixed catalyst bed of at most 1 mm ² .

If the fixed catalyst beds used in accordance with the invention comprise shaped catalyst bodies which have pores and / or channels, then at least 90% of the pores and channels, particularly preferably at least 98% of the pores and channels, preferably have an arbitrary section in the normal plane to the flow direction through the catalyst bed. an area of at most 0.7 mm ² .

In the fixed catalyst beds according to the invention is preferably at least 90% length in the flow direction through the fixed catalyst bed at least 95% of Reactor cross section, particularly preferably at least 98% of the reactor cross section, in particular at least 99% of the reactor cross section filled with shaped catalyst bodies. In order for good mass transfer to take place in the structured catalysts, the rate at which the reaction mixture flows through the fixed catalyst bed should not be too low. The flow rate of the liquid reaction mixture through the reactor containing the fixed catalyst bed is preferably at least 30 m / h, preferably at least 50 m / h, in particular at least 80 m / h. The flow rate of the liquid reaction mixture through the reactor containing the fixed catalyst bed is preferably at most 1000 m / h, particularly preferably at most 500 m / h, in particular at most 400 m / h.

The flow direction of the reaction mixture is, in principle, not of critical importance, especially in the case of an upright reactor. The hydrogenation can thus be carried out in bottoms or Rieselfahrweise. The upflow mode, wherein the reaction mixture to be hydrogenated is fed to the marsh side of the fixed catalyst bed and is discharged at the top end after passing through the fixed catalyst bed, may be advantageous. This is especially true when the gas velocity should be low (eg <50 m / h). These flow rates are generally achieved by recycling a portion of the liquid stream leaving the reactor, with the recycle stream combining with the reactant stream either before the reactor or in the reactor. The educt stream can also be supplied distributed over the length and / or width of the reactor.

In a preferred embodiment, the hydrogenation reaction mixture is at least partially conducted in a liquid recycle stream.

The ratio of reaction mixture conducted in the circulation stream to freshly fed educt stream is preferably in a range from 1: 1 to 1000: 1, preferably from 2: 1 to 500: 1, in particular from 5: 1 to 200: 1.

A discharge is preferably taken from the reactor and subjected to a gas / liquid separation, a hydrogen-containing gas phase and a product-containing liquid phase being obtained. For gas / liquid separation, it is possible to use the customary devices known to the person skilled in the art, such as the customary separation containers (separators). The temperature in the gas / liquid separation is preferably equal to or lower than the temperature in the reactor. The pressure in the gas / liquid separation is preferably equal to or less than that Pressure in the reactor. The gas / liquid separation preferably takes place essentially at the same pressure as in the reactor. This is particularly the case when the liquid phase and optionally the gas phase are conducted in a circulation stream. The pressure difference between the reactor and gas / liquid separation is preferably at most 10 bar, in particular at most 5 bar. It is also possible to design the gas / liquid separation in two stages. The absolute pressure in the second gas / liquid separation is then preferably in a range of 0.1 to 2 bar.

The product-containing liquid phase obtained in the gas / liquid separation is generally at least partially discharged. From this discharge, the product of the hydrogenation can be isolated, if appropriate after a further work-up. In a preferred embodiment, the product-containing liquid phase is at least partially recycled as a liquid circulation stream in the hydrogenation. The hydrogen-containing gas phase obtained in the phase separation can be at least partially discharged as exhaust gas. Furthermore, the hydrogen-containing gas phase obtained in the phase separation can be at least partially attributed to the hydrogenation. The amount of hydrogen discharged via the gas phase is preferably 0 to 500 mol% of the amount of hydrogen which is consumed in molar amounts of hydrogen in the hydrogenation. For example, with a consumption of one mole of hydrogen, 5 moles of hydrogen can be discharged as exhaust gas. Particularly preferably, the amount of hydrogen discharged via the gas phase is at most 100 mol%, in particular at most 50 mol%, of the amount of hydrogen which is consumed by molar amount of hydrogen in the hydrogenation. By means of this discharge stream can control the CO content in the gas phase in the reactor. In a specific embodiment, the hydrogen-containing gas phase obtained in the phase separation is not recycled. However, if it should be desired, this is preferably up to 1000% of the amount based on the amount of gas required chemically for the reaction, more preferably up to 200%.

The gas loading, expressed by the gas empty tube velocity at the reactor outlet, is generally at most 200 m / h, preferably at most 100 m / h, particularly preferably at most 70 m / h, in particular at most 50 m / h. The gas loading consists essentially of hydrogen, preferably at least 60% by volume. The gas velocity at the reactor inlet is extremely variable, since hydrogen can also be added to intermediate feeds. If all the hydrogen is added at the reactor inlet, the gas velocity is generally higher than at the reactor outlet. The absolute pressure in the hydrogenation is preferably in a range from 1 to 330 bar, particularly preferably in a range from 5 to 100 bar, in particular in a range from 10 to 60 bar. The temperature in the hydrogenation is preferably in a range of 40 to 300 ° C, particularly preferably from 70 to 220 ° C, in particular from 80 to 200 ° C.

In a specific embodiment, the fixed catalyst bed has a temperature gradient during the hydrogenation. Preferably, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed is maintained at a maximum of 50 K. Preferably, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed is maintained in a range of 0.5 to 40K, preferably in a range of 1 to 30K.

catalyst

In the context of the invention, a fixed catalyst bed is understood to mean a device installed in a reactor which is stationary (immobilized) during the hydrogenation and which comprises one or preferably several shaped catalyst bodies. The introduction of the fixed catalyst bed in the reactor is carried out by fixed incorporation of the shaped catalyst body. The resulting fixed catalyst bed has a plurality of channels through which the reaction mixture of the hydrogenation reaction flows.

To produce a suitable fixed catalyst bed, the monolithic shaped catalyst bodies can be installed side by side and / or one above the other in the interior of the reactor. Processes for incorporation of catalyst form bodies are known in principle to the person skilled in the art. Thus, for example, one or more layers of a foam-like catalyst can be introduced into the reactor. Monoliths, each consisting of a ceramic block, can be stacked next to and above each other in the interior of the reactor. It is essential to the invention that the reaction mixture of the hydrogenation reaction flows exclusively or essentially through the shaped catalyst bodies and not past them. In order to ensure a bypass-free flow as possible, the monolithic shaped catalyst bodies can be sealed against each other and / or to the inner wall of the reactor by means of suitable devices. These include z. As sealing rings, sealing mats, etc., which consist of an inert material under the treatment and reaction conditions. The shaped catalyst bodies are preferably incorporated into the reactor in one or more essentially horizontal layers with channels, which make it possible to flow through the catalyst bed in the flow direction of the aqueous base used for activation and of the reaction mixture of the catalyzed reaction. The installation preferably takes place in such a way that the fixed catalyst bed fills the reactor cross-section as completely as possible. If desired, the fixed catalyst bed can also contain other internals, such as power distributors, devices for feeding gaseous or liquid reactants, measuring elements, in particular for a temperature measurement, or inert packings.

For the hydrogenation by the process according to the invention are in principle pressure-resistant reactors, as they are usually used for exothermic, heterogeneous reactions with the introduction of a gaseous and a liquid starting material. These include the commonly used reactors for gas-liquid reactions, such as. B. tube reactors, tube bundle reactors and gas circulation reactors. A special embodiment of the tube reactors are shaft reactors. Such reactors are known in principle to the person skilled in the art. In particular, a cylindrical reactor with a vertical longitudinal axis is used, which has at the bottom or top of the reactor one or more inlet devices for feeding in a starting material mixture containing at least one gaseous and at least one liquid component. Partial streams of the gaseous and / or the liquid educt may, if desired, additionally be fed to the reactor via at least one further feed device. The hydrogenation reaction mixture is generally present in the reactor in the form of a two-phase mixture having a liquid and a gaseous phase. It is also possible that in addition to the gas phase two liquid phases are present, for. B. if more components are present in the hydrogenation.

The processes according to the invention are particularly suitable for hydrogenations which are to be carried out on an industrial scale. The reactor then preferably has an internal volume in the range from 0.1 to 100 m ³ , preferably from 0.5 to 80 m ³ . The term internal volume refers to the volume including the fixed catalyst beds present in the reactor and optionally further existing internals. Of course, the technical advantages associated with the process according to the invention also already appear on reactors with a smaller internal volume.

In the process according to the invention "monolithic" shaped catalyst bodies are used. Monolithic shaped bodies in the sense of the invention are structured shaped bodies which are suitable for the production of immobilized, structured fixed catalyst beds are. In contrast to particulate catalysts, it is possible to produce fixed monolithic beds from monolithic shaped bodies which are substantially coherent and seamless. This corresponds to the definition of monolithic in the sense of "consisting of one piece". The monolithic catalyst moldings according to the invention are distinguished, in contrast to catalyst beds, for example from B. from pellets, often by a higher ratio of axial flow (longitudinal flow) over radial flow (cross-flow) from. Monolithic shaped catalyst bodies accordingly have channels in the flow direction of the reaction medium of the hydrogenation reaction. Particulate catalysts usually have the catalytically active sites on an external surface. Catalyst fixed beds of monolithic moldings have a plurality of channels, wherein the catalytically active sites are arranged on the surface of the channel walls. The reaction mixture of the hydrogenation reaction can flow through these channels in the flow direction through the reactor. Thus, a much stronger contacting of the reaction mixture with the catalytically active sites usually takes place than with catalyst beds of particulate moldings.

The monolithic shaped bodies used in accordance with the invention are not shaped bodies of single catalyst bodies having a greatest length extension in any direction of less than 1 cm. Such non-monolithic moldings lead to fixed catalyst beds in the form of conventional catalyst beds. The monolithic shaped catalyst bodies used in accordance with the invention have a regular planar or spatial structure and thus differ from carriers in particle form, which are used as loose debris. The monolithic catalyst form body used according to the invention have, based on the entire molded body, a smallest dimension in a direction of preferably at least 1 cm, more preferably at least 2 cm, in particular at least 5 cm. The maximum value for the largest dimension in one direction is in principle not critical and usually results from the production process of the moldings. So z. B. moldings in the form of foams be plate-like structures having a thickness in the range of millimeters to centimeters, a width in the range of a few centimeters to several hundred centimeters and a length (as the largest dimension in one direction) of up to several meters can.

In contrast to bulk solids, the monolithic shaped catalyst bodies used according to the invention can preferably be connected in a form-fitting manner to form larger units or consist of units which are larger than bulk materials. The monolithic shaped catalyst bodies used according to the invention generally also differ from particulate catalysts or their supports in that they are present in substantially fewer parts. Thus, according to the invention, a fixed catalyst bed can be used in the form of a single shaped body. In general, however, several moldings are used to prepare a fixed catalyst bed. The monolithic shaped catalyst bodies used according to the invention generally have extensive three-dimensional structures. The shaped catalyst bodies used according to the invention are generally permeated by continuous channels. The continuous channels can have any desired geometry, for example they can be present in a honeycomb structure. Suitable shaped catalyst bodies can also be produced by deforming flat carrier structures, for example by rolling up or buckling the two-dimensional structures into three-dimensional structures. Starting from flat substrates, the outer shape of the molded bodies can be easily adapted to given reactor geometries.

The monolithic shaped catalyst bodies used according to the invention are distinguished by the fact that they can be used to produce fixed catalyst beds in which a controlled flow through the fixed catalyst bed is possible. A movement of the catalyst bodies under the conditions of the catalyzed reaction, for. B. a juxtaposition of the shaped catalyst body is avoided. Due to the ordered structure of the shaped catalyst bodies and the resulting fixed catalyst bed, improved possibilities for fluidically optimum operation of the fixed catalyst bed result.

The monolithic shaped catalyst bodies used in the process according to the invention are preferably in the form of a foam, mesh, woven fabric, knitted fabric, knitted fabric or monoliths different therefrom. The term monolithic catalyst in the context of the invention also includes catalyst structures known as "honeycomb catalysts".

In a specific embodiment, the shaped catalyst bodies are in the form of a foam. The shaped catalyst bodies may have any suitable outer shapes, for example cubic, cuboid, cylindrical, etc. Suitable fabrics may be produced with different weaves, such as smooth fabrics, body fabrics, woven fabrics, five-shaft atlas fabrics or other special weave fabrics. Also suitable are wire mesh made of weavable metal wires, such as iron, spring steel, brass, phosphor bronze, pure nickel, monel, aluminum, silver, nickel silver (copper-nickel-zinc alloy), nickel, chrome nickel, chrome steel, non-corrosive, acid-resistant and highly heat-resistant chrome-nickel steels as well as titanium. The same applies to knitted and knitted fabrics. Also, woven, knitted or knitted fabrics of inorganic materials such as AI2O3 and / or S1O2 may be used. Also suitable are woven, knitted or knitted fabrics made of synthetic materials, such as polyamides, polyesters, polyolefins (such as polyethylene, polypropylene), polytetrafluoroethylene, etc. The abovementioned fabrics, knitted or knitted fabrics, but also other flat structured catalyst supports can lead to larger spatial Structures, so-called monoliths are deformed. It is also possible not to build monoliths from laminar supports, but to produce them directly without intermediate stages, for example the ceramic monoliths with flow channels known to those skilled in the art.

Suitable catalyst bodies are those which are described, for example, in EP-A 0 068 862, EP-A-0 198 435, EP-A 201 614, EP-A 448 884, EP 0 754 664 A2, DE 433 32 93, EP 2 764 916 A1 and US 2008/0171218 A1 are described.

Thus, EP 0 068 862 describes a monolithic molded body comprising alternating layers of smooth and corrugated sheets in the form of a roll having channels and wherein the smooth sheets contain woven, knitted or knitted textile materials and the corrugated sheets contain a mesh material.

EP-A-0 198 435 describes a process for the preparation of catalysts in which the active components and the promoters are applied to support materials by vapor deposition in an ultra-high vacuum. The carrier materials used are reticulated or web-like carrier materials. The vapor-deposited catalyst webs are assembled into "catalyst packages" for incorporation into the reactor, and the shape of the catalyst packages is adapted to the flow conditions in the reactor. Suitable methods for vapor deposition and sputtering of metals in vacuum are known.

Preferably, the shaped catalyst bodies contain at least one element selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, Au and Pd. In a specific embodiment, the shaped catalyst bodies contain Ni. In a specific embodiment, the shaped catalyst bodies contain no palladium. This is understood to mean that no palladium is actively added to produce the shaped catalyst bodies, neither as a catalytically active metal nor as a promoter element, nor to provide the shaped bodies which serve as a carrier material. The catalyst form bodies are preferably a Raney metal catalyst. The reactor used for the hydrogenation preferably contains a fixed catalyst bed containing monolithic shaped catalyst bodies or consisting of monolithic shaped catalyst bodies which contain at least one first metal selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, and contain at least one second component which is selected from Al, Zn and Si, wherein subjecting the fixed catalyst bed for activating a treatment with an aqueous base.

A preferred embodiment is a process comprising a) introducing into a reactor a fixed bed of catalyst containing monolithic shaped catalyst bodies or consisting of monolithic catalyst bodies containing at least one first metal selected from Ni, Fe, Co, Cu , Cr, Pt, Ag, and Au, and containing at least one second component which is selected from Al, Zn and Si, b) subjecting the fixed catalyst bed for activation of an aqueous base, c) optionally, in step b) subjecting the activated fixed catalyst bed to a treatment with a washing medium selected from water, C 1 -C 4 -alkanols and mixtures thereof; d) optionally the fixed catalyst bed obtained after activation in step b) or after the treatment in step c) with a dopant in Contact having at least one element of the first metal and the second component in step a) used catalyst molding is different.

The monolithic shaped catalyst bodies are particularly preferably in the form of a foam. In principle, metal foams with different morphological properties with regard to pore size and shape, layer thickness, areal density, geometric surface, porosity, etc. are suitable. The preparation can be carried out in a manner known per se. For example, a foam of an organic polymer may be coated with at least a first metal and then the polymer removed, e.g. Example by pyrolysis or dissolution in a suitable solvent, wherein a metal foam is obtained. For coating with at least one first metal or a precursor thereof, the organic polymer foam may be contacted with a solution or suspension containing the first metal. This can be z. B. done by spraying or dipping. Also possible is a deposition by means of chemical vapor deposition (CVD). So z. B. a polyurethane foam coated with the first metal and then the polyurethane foam are pyrolyzed. A suitable for the production of catalyst form in the form of a foam polymer foam preferably has a pore size in the range of 100 to 5000 μηη, more preferably from 450 to 4000 μηη and in particular from 450 to 3000 μηη. A suitable polymer foam preferably has a layer thickness of 5 to 60 mm, particularly preferably 10 to 30 mm. A suitable polymer foam preferably has a density of from 300 to 1200 kg / m ³ . The specific surface area is preferably in a range of 100 to 20000 m ² / m ³ , particularly preferably 1000 to 6000 m ² / m ³ . The porosity is preferably in a range of 0.50 to 0.95. The order of the second component can be done in many ways, for. Example by bringing the molded article obtained from the first component with the second component by rolling or dipping in contact or applying the second component by spraying, sprinkling or pouring. For this purpose, the second material may be liquid or preferably in the form of a powder. Also possible is the application of salts of the second component and subsequent reduction. It is also possible to apply the second component in combination with an organic binder. The production of an alloy on the surface of the molding is carried out by heating to the alloying temperature. The alloying conditions make it possible, as stated above, to control the leaching properties of the alloy. When Al is used as a second component, the alloying temperature is preferably in a range of 650 to 1000 ° C, more preferably 660 to 950 ° C. When a NiAl powder is used as the second component, the alloying temperature is preferably in a range of 850 to 900 ° C, more preferably 880 to 900 ° C. It may be advantageous to continuously raise the temperature during the alloy and then keep it at the maximum for a time. Subsequently, the foam-shaped coated and heated shaped catalyst body is allowed to cool.

In a preferred embodiment, to provide the shaped catalyst bodies: a1) a metal foam molding is provided which contains at least one first metal selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, a2) applied to the surface of the metal foam molding at least a second component containing an element which is selected from Al, Zn and Si, and a3) by alloying the metal foam molding obtained in step a2) at least on a part of the surface an alloy formed.

Such shaped catalyst bodies and processes for their preparation are described in EP 2 764 916 A1, to which reference is made in its entirety.

Suitable alloying conditions result from the phase diagram of the metals involved, z. B. the phase diagram of Ni and Al. So z. B. the proportion of AI-rich and leachable components, such as NiA and N12AI3, are controlled. The shaped catalyst bodies may contain dopants in addition to the first and second components. These include z. Mn, V, Ta, Ti, W, Mo, Re, Ge, Sn, Sb or Bi.

Preference is given to shaped catalyst bodies in which the first metal contains Ni or consists of Ni. Preference is furthermore given to shaped catalyst bodies in which the second component contains Al or consists of Al. A particular embodiment is catalyst form bodies containing nickel and aluminum.

For the production of a monolithic shaped catalyst body in the form of a foam, preference is given to using an aluminum powder having a particle size of at least 5 μm. The aluminum powder preferably has a particle size of at most 75 μm.

For the production of a monolithic shaped catalyst body in the form of a foam a1), it is preferred to provide a metal foam body containing Ni, a2) applying to the surface of the metal foam body an aluminum-containing suspension in a solvent, a3) by alloying in step a2) obtained metal foam molding formed at least on a part of the surface of an alloy.

Particularly preferably, the aluminum-containing suspension additionally contains polyvinylpyrrolidone. The amount of polyvinylpyrrolidone is preferably 0.1 to 5% by weight. %, particularly preferably 0.5 to 3 wt .-%, based on the total weight of the aluminum-containing suspension. The molecular weight of the polyvinylpyrrolidone is preferably in a range of 10,000 to 1,300,000 g / mol. Particularly preferably, the aluminum-containing suspension contains a solvent which is selected from water, ethylene glycol and mixtures thereof.

The alloying is preferably carried out by stepwise heating in the presence of a gas mixture which contains hydrogen and at least one gas which is inert under the reaction conditions. Nitrogen is preferably used as the inert gas. Suitable is z. Example, a gas mixture containing 50 vol .-% N2 and 50 vol .-% H2. The alloy formation can z. B. done in a rotary kiln. Suitable heating rates are in a range of 1 to 10 K / min, preferably 3 to 6 K / min. It may be advantageous to maintain the temperature substantially constant (isothermal) once or several times during the high heating for a certain time. So z. B. during heating, the temperature at about 300 ° C, about 600 ° C and / or about 700 ° C are kept constant. The time during which the temperature is kept constant is preferably about 1 to 120 minutes, more preferably 5 to 60 minutes. Preferably, the temperature is kept constant in a range of 650 to 920 ° C during the heating. When the temperature is kept constant several times, the last stage is preferably in a range of 650 to 920 ° C. The alloy formation is furthermore preferably carried out with gradual cooling. Cooling is preferably carried out to a temperature in the range from 150 to 250 ° C. in the presence of a gas mixture which contains hydrogen and at least one gas which is inert under the reaction conditions. Nitrogen is preferably used as the inert gas. Suitable is z. Example, a gas mixture containing 50 vol .-% N2 and 50 vol .-% H2. Preferably, the further cooling takes place in the presence of at least one inert gas, preferably in the presence of nitrogen. Preferably, the weight of the monolithic shaped catalyst body in the form of a foam is 35 to 60%, particularly preferably 40 to 50% higher than the weight of the metal foam molding used for its production.

Preferably, the intermetallic phases thus obtained on the support metal skeleton consist mainly of N12Al3 and NlAl3. Activation (step b))

Preferably, the shaped catalyst bodies used for activation have, based on the total weight, 60 to 95% by weight, particularly preferably 70 to 80% by weight, of a first metal which is selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, Au, Mn, Re, Ru, Rh and Ir.

With particular preference the catalyst moldings used for activation, based on the total weight, have 60 to 95% by weight, in particular 70 to 80% by weight, of a first metal which is selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au.

Preferably, the shaped catalyst bodies used for activation, based on the total weight of 5 to 40 wt .-%, particularly preferably 20 to 30 wt .-%, of a second component which is selected from Al, Zn and Si.

Preferably, the shaped catalyst bodies used for activation based on the total weight of 60 to 95 wt .-%, particularly preferably 70 to 80 wt .-%, Ni.

Preferably, the shaped catalyst bodies used for activation based on the total weight of 5 to 40 wt .-%, particularly preferably 20 to 30 wt .-%, AI.

During the activation, the fixed catalyst bed is subjected to a treatment with an aqueous base as the treatment medium, wherein the second (leachable) component of the catalyst bodies is at least partially dissolved and removed from the catalyst bodies. In this case, the treatment with the aqueous base is exothermic, so that the fixed catalyst bed is heated as a result of the activation. The heating of the fixed catalyst bed is dependent on the concentration of the aqueous base used. If no heat is removed from the reactor by active cooling, but instead is transferred to the treatment medium, so that an adiabatic mode of operation is achieved to some extent, a temperature gradient is formed in the fixed catalyst bed during activation, the temperature in the current direction of the aqueous base increases. However, even if heat is removed from the reactor by active cooling, a temperature gradient is formed in the fixed catalyst bed during activation.

Preferably 30 to 70 wt .-%, particularly preferably 40 to 60 wt .-%, of the second component, based on the original weight of the second component removed from the shaped catalyst bodies by the activation. Preferably, the catalyst moldings used for activation contain Ni and Al and, by activation, becomes 30 to 70% by weight, particularly preferably 40 to

60 wt .-%, of AI, based on the original weight removed. The determination of the dissolved out of the catalyst moldings amount of the second component, for. As aluminum, for example, can be done by elemental analysis by determining the content of the second component in the total amount of discharged laden aqueous base and the washing medium. Alternatively, the determination of the amount dissolved out of the shaped catalyst bodies on the second component can be determined by the amount of hydrogen formed during the course of the activation. In the case in which aluminum is used, in each case 3 mol of hydrogen are produced by dissolving 2 mol of aluminum. The activation of the fixed catalyst bed can be carried out in a sump or trickle mode. Preference is given to the upflow method, wherein the fresh aqueous base is fed to the marsh side of the fixed catalyst bed and is discharged at the top end after passing through the fixed catalyst bed. After passing through the fixed catalyst bed, a loaded aqueous base is obtained. The loaded aqueous base has a lower base concentration than the aqueous base before passing through the fixed catalyst bed and is enriched in the reaction products formed during activation and at least partially soluble in the base. These reaction products include, for. Example, when using aluminum as the second (leachable) component alkali aluminates, aluminum hydroxide hydrates, hydrogen, etc. (see, for example, US 2,950,260).

The statement that the fixed catalyst bed has a temperature gradient during the activation is understood in the context of the invention as meaning that over a longer period of the total activation the fixed catalyst bed has this temperature gradient. The fixed catalyst bed preferably has a temperature gradient until at least 50% by weight, preferably at least 70% by weight, in particular at least 90% by weight, of the amount of aluminum to be removed has been removed from the shaped catalyst bodies. Unless during the activation the strength of the aqueous base used is increased and / or the temperature of the fixed catalyst bed is increased by less cooling than at the beginning of activation or external heating, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed in the course the activation become increasingly smaller and can then take on the value of zero towards the end of the activation.

Preferably, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed is kept at a maximum of 50 K. To determine the temperature difference in the course of the fixed catalyst bed, this can be provided with conventional measuring devices for temperature measurement. For determining the temperature difference between the warmest point of the fixed catalyst bed and the coldest point of the fixed catalyst bed, it is generally sufficient for a non-actively cooled reactor to determine the temperature difference between the most upstream location of the fixed catalyst bed and the most downstream location of the fixed catalyst bed , In an actively cooled reactor, it may be useful to provide at least one additional temperature sensor in the flow direction between the most upstream location of the fixed catalyst bed and the most downstream location of the fixed catalyst bed (eg, 1, 2, or 3 more temperature sensors).

Particularly preferably, the temperature difference between the coldest point of the catalyst fixed bed and the warmest point of the fixed catalyst bed is maintained at a maximum of 40 K, in particular at a maximum of 25 K.

Preferably, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed at the beginning of activation in a range of 0.1 to 50 K, preferably in a range of 0.5 to 40 K, in particular in a range of 1 to 25 K, held. It is possible initially to initially introduce an aqueous medium without base and then to add fresh base until the desired concentration has been reached. In this case, the temperature difference between the coldest point of the fixed catalyst bed and the warmest point of the fixed catalyst bed at the beginning of activation means the time at which the desired base concentration at the reactor inlet is reached for the first time.

The control of the size of the temperature gradient in the fixed catalyst bed can be carried out in a non-actively cooled reactor by selecting the amount and concentration of the supplied aqueous base according to the heat capacity of the medium used for activation. In order to control the size of the temperature gradient in the fixed catalyst bed in an actively cooled reactor, heat is also removed from the medium used for activation by heat exchange. Such heat extraction can be achieved by cooling the medium used for activation take place in the reactor used and / or, if present, the liquid circulation stream.

The monolithic shaped catalyst bodies are preferably subjected to the activation of a treatment with a maximum of 3.5% by weight aqueous base. Particularly preferred is the use of a maximum of 3.0 wt .-% aqueous base. The shaped catalyst bodies are preferably subjected to the activation of a treatment with a 0.1 to 3.5% by weight aqueous base, particularly preferably a 0.5 to 3.5% strength by weight aqueous base. The concentration specification refers to the aqueous base prior to its contact with the shaped catalyst bodies. If, for activation, the aqueous base is brought into contact with the catalyst former only once, then the concentration is based on the fresh aqueous base. If, for activation, the aqueous base is passed at least partly in a liquid circulation stream, then the charged base obtained after the activation can be added with fresh base before it is used again to activate the shaped catalyst bodies. The previously indicated concentration values apply analogously.

By maintaining the above-mentioned concentrations for the aqueous base catalyst shaped bodies of Raney metal catalysts are obtained with high activity and very good stability. This is especially true for the activation of fixed catalyst beds for hydrogenation reactions on an industrial scale. Surprisingly, an excessively high temperature increase and the uncontrolled formation of hydrogen in the activation of the catalysts are effectively avoided with the given concentration ranges of the base. This advantage has a special effect on reactors on an industrial scale.

In a preferred embodiment, the aqueous base used for activation is at least partially conducted in a liquid circulation stream. In a first embodiment, the reactor with the catalyst to be activated is operated in a swamp mode. Then, in a vertically oriented reactor, the aqueous base is fed to the sump side of the reactor, passed from bottom to top through the fixed catalyst bed, taken above the fixed catalyst bed a discharge and returned to the sump side in the reactor. The discharged stream is preferably a workup, z. B. by separation of hydrogen and / or the out-Schleusung a part of the loaded aqueous base to be subjected. In a second embodiment, the reactor is operated in trickle mode with the catalyst to be activated. Then, in a vertically oriented reactor, the aqueous base is fed into the top of the reactor, passed from top to bottom through the fixed catalyst bed, and a discharge is taken below the fixed catalyst bed and returned to the top of the reactor. In this case, the discharged current is preferably in turn a workup, z. B. by separation of hydrogen and / or the discharge of a portion of the loaded aqueous base. Preferably, the activation takes place in a vertical reactor in the upflow mode (ie with an upward flow through the fixed catalyst bed). Such

Driving is advantageous if the formation of hydrogen during activation also produces a low gas load, as this can be more easily dissipated overhead. In a preferred embodiment, fresh aqueous base is added to the fixed catalyst bed in addition to the base carried in the liquid recycle stream. The supply of fresh base can be done in the liquid recycle stream or separately in the reactor. In this case, the fresh aqueous base may also be concentrated higher than 3.5 wt .-%, provided that after mixing with the recycled aqueous base, the base concentration is not higher than 3.5 wt .-%.

The ratio of aqueous base passed in the circulation stream to freshly supplied aqueous base is preferably in a range from 1: 1 to 1000: 1, more preferably from 2: 1 to 500: 1, in particular from 5: 1 to 200: 1.

Preferably, the feed rate of the aqueous base (when the aqueous base used for activation is not conducted in a liquid recycle stream) is at most 5 L / min per liter fixed catalyst bed, preferably at most 1.5 L / min per liter fixed catalyst bed, more preferably at most 1 L / min per liter of fixed catalyst bed, based on the total volume of the fixed catalyst bed.

Preferably, the aqueous base used for activation is at least partially conducted in a liquid circulation stream and the feed rate of the freshly supplied aqueous base is at most 5 L / min per liter of fixed catalyst bed, preferably at most 1, 5 L / min per liter of fixed catalyst bed, more preferably at most 1 L / min per liter of fixed catalyst bed, based on the total volume of the fixed catalyst bed.

Preferably, the feed rate of the aqueous base (when the aqueous base used for activation is not carried in a liquid recycle stream) is in the range of 0.05 to 5 L / min per liter of fixed catalyst bed, more preferably in the range of 0.1 to 1, 5 L / min per liter of fixed catalyst bed, in particular in a range of 0.1 to 1 L / min per liter of fixed catalyst bed, based on the total volume of Kata lysatorf estbetts. Preferably, the aqueous base used for the activation is at least partially conducted in a liquid circulation stream and the feed rate of the freshly supplied aqueous base is in a range of 0.05 to 5 L / min per liter of fixed catalyst bed, more preferably in a range of 0.1 to 1.5 L / min per liter of fixed catalyst bed, in particular in a range of 0.1 to 1 L / min per liter of fixed catalyst bed, based on the total volume of the fixed catalyst bed.

This control of the feed rate of the fresh aqueous base is an effective way of keeping the temperature gradient resulting in the fixed catalyst bed in the desired value range.

The flow rate of the aqueous base through the reactor containing the fixed catalyst bed is preferably at least 0.5 m / h, more preferably at least 3 m / h, especially at least 5 m / h, especially at least 10 m / h.

In order to avoid mechanical stress and abrasion of the newly formed porous catalyst metal, it may be useful not to choose the flow rate too high. The flow rate of the aqueous base through the reactor containing the catalyst fixed bed is preferably at most 100 m / h, particularly preferably at most 50 m / h, in particular at most 40 m / h.

The above-mentioned flow rates can be achieved particularly well if at least some of the aqueous base is conducted in a liquid circulation stream.

The base used to activate the fixed catalyst bed is selected from alkali metal hydroxides, alkaline earth metal hydroxides and mixtures thereof. Preferably, the base is selected from NaOH, KOH, and mixtures thereof. Specifically, NaOH is used as the base. The base is used for activation in the form of an aqueous solution.

The procedure described above makes it possible to effectively minimize a detachment of the catalytically active metal, such as nickel, during the activation. A suitable measure of the effectiveness of the activation and the stability of the obtained Raney metal catalyst is the metal content in the loaded aqueous base. When using a liquid recycle stream, the metal content in the recycle stream is a convenient measure of the effectiveness of the activation and the stability of the resulting Raney metal catalyst. Preferably, the content of nickel during activation in the laden aqueous base or, if the used for activating a liquid circulation stream, in the circulation stream at most 0.1 wt .-%, more preferably at most 100 ppm by weight, in particular at most 10 ppm by weight. The determination of the nickel content can be done by elemental analysis. The same advantageous values are generally also achieved in the following process steps, such as treatment of the activated catalyst fixed bed with a washing medium, treatment of the fixed catalyst bed with a dopant and use in a hydrogenation reaction. The inventive method allows a homogeneous distribution of the catalytically active Raney metal on the moldings used and a total of the resulting activated fixed catalyst bed. No or only a slight gradient with respect to the distribution of the catalytically active Raney metal in the direction of flow of the activation medium through the fixed catalyst bed is formed. In other words, the concentration of catalytically active sites upstream of the fixed catalyst bed is substantially equal to the concentration of catalytically active sites downstream of the fixed catalyst bed. This advantageous effect is achieved in particular if the aqueous base used for activation is at least partially guided in a liquid circulation stream. The inventive method also allow a homogeneous distribution of the leached second component, z. As the aluminum, on the moldings used and a total of the resulting activated fixed catalyst bed. There is no or only a slight gradient with respect to the distribution of the leached second component in the flow direction of the activation medium through the fixed catalyst bed.

Another advantage, if the aqueous base used for activation is at least partially conducted in a liquid circulation stream, is that the required amount of aqueous base can be significantly reduced. For example, a straight pass of the aqueous base (without recycling) and the subsequent removal of the laden base result in a high requirement for fresh base. By supplying suitable amounts of fresh base in the recycle stream, it is ensured that there is always sufficient base for the activation reaction. All in all, significantly lower quantities are required for this. After passing through the fixed catalyst bed, a laden aqueous base is obtained which has a lower base concentration than the aqueous base before passing through the fixed catalyst bed and which is enriched in the reaction products formed and at least partially soluble in the base. Preferably, at least a portion of the loaded aqueous base is excluded. discharged. Thus, even if a portion of the aqueous base is passed in a recycle stream, excessive dilution and accumulation of undesirable impurities in the aqueous base used for activation can be avoided. The amount of aqueous base freshly supplied per unit time preferably corresponds to the amount of laden aqueous base removed.

A discharge of laden aqueous base is preferably taken from the activation and subjected to a gas / liquid separation, a hydrogen-containing gas phase and a liquid phase being obtained. For gas / liquid separation, it is possible to use the customary devices known to the person skilled in the art, such as the customary separation containers. The hydrogen-containing gas phase obtained in the phase separation can be discharged from the process and z. B. a thermal utilization can be supplied. The liquid phase obtained in the phase separation, which contains the discharged laden aqueous base, is preferably at least partially recycled as a liquid circulation stream into the activation. Preferably, part of the liquid phase obtained in the phase separation, which contains the discharged laden aqueous base, is discharged. Thus, as previously described, excessive dilution and accumulation of undesirable impurities in the aqueous base used for activation can be avoided.

To control the progress of the activation and to determine the amount of the second component dissolved out of the shaped catalyst bodies, e.g. As aluminum, the amount of hydrogen formed during the activation can be determined. In the case in which aluminum is used, in each case 3 mol of hydrogen are produced by the dissolution of 2 mol of aluminum.

The activation according to the invention preferably takes place at a temperature of at most 50 ° C., preferably at a temperature of at most 40 ° C. The activation according to the invention preferably takes place at a pressure in the range from 0.1 to 10 bar, more preferably from 0.5 to 5 bar, especially at ambient pressure.

Treatment with a Wash Medium (step c)) In optional step c) of the process according to the invention, the activated catalyst fixed bed obtained in step b) is subjected to a treatment with a washing medium which is selected from water, C 1 -C 4 alkanols and mixtures thereof. Suitable C 1 -C 4 -alkanols are methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

Preferably, the washing medium used in step c) contains water or consists of water.

The treatment with the washing medium is preferably carried out in step c) until the effluent washing medium has a conductivity at 20 ° C. of at most 200 mS / cm, particularly preferably at most 100 mS / cm, in particular at most

10 mS / cm.

In step c), water is preferably used as the washing medium and the treatment with the washing medium is carried out until the effluent washing medium has a pH at 20 ° C. of not more than 9, particularly preferably not more than 8, in particular not more than 7.

The treatment with the washing medium is preferably carried out in step c) until the effluent washing medium has an aluminum content of at most 5% by weight, more preferably of at most 5000 ppm by weight, in particular of at most 500 ppm by weight.

In step c), the treatment with the washing medium is preferably carried out at a temperature in the range from 20 to 100.degree. C., particularly preferably from 20 to 80.degree. C., in particular from 25 to 70.degree.

Doping (step d))

A doping refers to the introduction of foreign atoms in a layer or in the base material of a catalyst. The amount introduced in this process is generally small compared to the rest of the catalyst material. The doping specifically changes the properties of the starting material.

In a specific embodiment, the fixed catalyst bed is brought into contact with a dopant after activation (ie following step b)) and optionally after treatment with a wash medium (ie also following step c), if it is carried out). which has at least one element which is different from the first metal and the second component of the shaped catalyst bodies used in step a). Such elements are referred to hereinafter as "promoter elements". Preferably, this is done in contact with the animal agent during and / or after the treatment of the activated fixed catalyst bed with a washing medium (ie during and / or after step c)).

The dopant preferably contains at least one promoter element selected from Ti, Ta, Zr, V, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pt, Cu, Ag , Au, Ce and Bi.

It is possible that the dopant contains at least one promoter element which simultaneously fulfills the definition of a first metal in the sense of the invention. Such promoter elements are selected from Ni, Fe, Co, Cu, Cr, Mn, Re, Ru, Rh, Ir, Pt, Ag and Au. In this case, the monolithic molded article contains, based on the reduced metallic form, a major amount (ie, more than 50% by weight) of the first metal and a minor amount (ie, less than 50% by weight) of a different metal as a dopant , When specifying the total amount of the first metal that contains the monolithic shaped catalyst body, however, all metals which fulfill the definition of a first metal in the meaning of the invention are expected to have their full weight fraction (irrespective of whether they function as a hydrogenation-active component or as a promoter). , In a specific embodiment, the dopant does not contain a promoter element which fulfills the definition of a first metal in the sense of the invention. The dopant then preferably contains exclusively one promoter element or more than one promoter element which is selected from Ti, Ta, Zr, Ce, V, Mo, W and Bi. The dopant preferably contains Mo as promoter element. In a specific embodiment, the dopant contains Mo as the sole promoter element.

The promoter elements are particularly preferably used for doping in the form of their salts. Suitable salts are, for example, the nitrates, sulfates, acetates, formates, fluorides, chlorides, bromides, iodides, oxides or carbonates. The promoter elements either separate by themselves in their metallic form due to their nobler character compared to Ni or can be brought into contact with a reducing agent such as e.g. As hydrogen, hydrazine, hydroxylamine, etc., are reduced in their metallic form. If the promoter elements are added during the activation process, then they can also be in their metallic form. In this case, it may be useful for the formation of metal-metal compounds to subject the fixed catalyst bed after the storage of the promoter metals first an oxidative treatment and then a reducing treatment. In a specific embodiment, the fixed catalyst bed is contacted during and / or after treatment with a wash medium in step c) with a dopant containing Mo as a promoter element. More specifically, the dopant contains Mo as the sole promoter element. Suitable molybdenum compounds are selected from molybdenum trioxide, the nitrates, sulfates, carbonates, chlorides, iodides and bromides of molybdenum and the molybdates. Preference is given to the use of ammonium molybdate. In a preferred embodiment, a molybdenum compound is used which has good water solubility. Good solubility in water is understood to mean a solubility of at least 20 g / l at 20 ° C. When using molybdenum compounds, which have a lower water solubility, it may be useful before they are used as a dopant to filter the solution. Suitable solvents for doping are water, polar solvents which are different from water and inert solvents under the doping conditions with respect to the catalyst, and mixtures thereof. Preferably, the solvent used for doping is selected from water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and mixtures thereof.

The temperature during the doping is preferably in a range from 10 to 100 ° C., more preferably from 20 to 60 ° C., in particular from 20 to 40 ° C.

The concentration of the promoter element in the dopant is preferably in a range of about 20 g / L to the maximum soluble amount of the dopant under the doping conditions. As a rule, one will assume a maximum of one solution saturated at ambient temperature.

The duration of the doping is preferably 0.5 to 24 hours.

It may be advantageous for the doping to take place in the presence of an inert gas. Suitable inert gases are for. As nitrogen or argon.

In a specific embodiment for doping foam-shaped shaped catalyst bodies, a molybdenum source is dissolved in water and this solution is passed through the previously activated foam. When using hydrates of ammonium molybdate, such as. B. (ΝΗ4) 6Μθ7θ24 x 4 H2O, this is dissolved in water and this solution is used. The usable amount depends strongly on the solubility of the ammonium molybdate and is in principle not critical. Conveniently, less than 430 grams of ammonium molybdate are dissolved per liter of water at room temperature (20 ° C). If the doping is carried out at a higher temperature than room temperature, then larger amounts can be used. The ammonium molybdate solution is closing at a temperature of 20 to 100 ° C, preferably at a temperature of 20 to 40 ° C, passed over the activated and washed foam. The treatment time is preferably 0.5 to 24 hours, more preferably 1 to 5 hours. In a specific embodiment, the contacting takes place in the presence of an inert gas, such as nitrogen. The pressure is preferably in a range of 1 to 50 bar, especially at about 1 bar absolute. Thereafter, the doped Raney nickel foam can be used either without further workup or after repeated washing for the hydrogenation. The doped catalyst bodies preferably contain 0.01 to 10 wt .-%, particularly preferably 0.1 to 5 wt .-%, promoter elements based on the reduced metallic form of the promoter elements and the total weight of the shaped catalyst bodies. The fixed catalyst bed may contain the promoter elements substantially homogeneously or heterogeneously distributed in their concentration. In a specific embodiment, the fixed catalyst bed has a gradient in the flow direction with respect to the concentration of the promoter elements. In particular, the fixed catalyst bed contains or consists of Ni / Al catalyst moldings which are activated by the process according to the invention and / or which are doped with Mo and has a gradient with respect to the Mo concentration in the flow direction.

It is possible to obtain a fixed bed catalyst which is fixedly installed in a reactor and which contains at least one promoter element which substantially homogeneously distributes its concentration, ie does not exist in the form of a gradient. To provide such a fixed bed catalyst, it is possible not to dope the catalyst in built-in form in the fixed bed reactor itself, possibly with circulation, whereby a concentration gradient can arise. Preferably, the doping is then carried out in an external container without circulation, which is infinitely back-mixed, such. B. a batch reactor without continuous feed and drain. After doping and, if appropriate, washing, such catalysts can be incorporated in a fixed bed reactor with or without a circulation and are therefore without gradients. To provide a fixed catalyst bed having a gradient in the flow direction with respect to the concentration of promoter elements, one can proceed by passing a liquid stream of the dopant through the fixed catalyst bed. If the reactor has a circulation stream, it is alternatively or additionally possible to feed the dopant in liquid form into the circulation stream. At a Such a procedure forms over the entire length of the fixed catalyst bed in the flow direction, a concentration gradient of the promoter elements. If it is desired that the concentration of the promoter element in the flow direction of the reaction medium of the reaction to be catalyzed decreases, the liquid flow of the dopant is conducted in the same direction as the reaction medium of the reaction to be catalyzed by the fixed catalyst bed. If it is desired that the concentration of the promoter element increases in the direction of flow of the reaction medium of the reaction to be catalyzed, the liquid flow of the dopant is directed in the opposite direction as the reaction medium of the reaction to be catalyzed by the fixed catalyst bed.

In a first preferred embodiment, the catalyst fixed bed obtained by the process of the invention or a reactor containing such a fixed catalyst bed is used for the hydrogenation of 1,4-butynediol to give 1,4-butanediol. It has now surprisingly been found that a particularly high selectivity is achieved in the hydrogenation, if one uses a fixed catalyst bed of Ni / Al catalyst moldings which are activated by the novel process and / or which are doped with Mo and wherein the concentration of the molybdenum in the flow direction of the reaction medium of the hydrogenation reaction increases. Preferably, the molybdenum content of the shaped catalyst bodies at the entry of the reaction medium in the fixed catalyst bed 0 to 3 wt .-%, particularly preferably 0.05 to 2.5 wt .-%, in particular 0.1 to 2 wt .-%, based on metallic molybdenum and the total weight of the shaped catalyst bodies. The molybdenum content of the shaped catalyst bodies at the outlet of the reaction medium from the fixed catalyst bed is preferably from 0.1 to 10% by weight, more preferably from 0.1 to 7% by weight, in particular from 0.2 to 6% by weight, based on metallic molybdenum and the total weight of the shaped catalyst bodies.

In a second preferred embodiment, the catalyst fixed bed obtained by the process according to the invention or a reactor containing such a fixed catalyst bed is used for the hydrogenation of butyraldehyde to give n-butanol. It has now surprisingly been found that a particularly high selectivity is achieved in the hydrogenation, if one uses a fixed catalyst bed of Ni / Al catalyst moldings which are activated by the novel process and / or which are doped with Mo and wherein the concentration of the molybdenum in the flow direction of the reaction medium of the hydrogenation reaction decreases. Preferably, the molybdenum content of the catalyst molding is at the entry of the reaction medium in the fixed catalyst bed 0.5 to 10 wt .-%, particularly preferably 1 to 9 wt .-%, in particular 1 to 7 wt .-%, based on metallic molybdenum and the total weight the shaped catalyst body. Preferably, the molybdenum content of the shaped catalyst bodies at the outlet of the reaction medium from the fixed catalyst bed 0 to 7 wt .-%, particularly preferably 0.05 to 5 wt .-%, in particular 0.1 to 4.5 wt .-%, based on metallic molybdenum and the total weight of the shaped catalyst bodies.

It has been found that it is advantageous for the efficiency of the doping of Raney metal catalysts and especially Raney nickel catalysts with a promoter element, especially Mo, if after activation and before doping the activated fixed catalyst bed of a treatment is subjected to a washing medium. This is especially true when foam-like Raney nickel catalysts are used for the doping. It has been found, in particular, that the adsorption of molybdenum on the shaped catalyst bodies is incomplete if, after activation, the content of washable aluminum is still too high. Preference is therefore given to the treatment with a washing medium in step c) is carried out prior to doping in step d) until the effluent washing medium at a temperature of 20 ° C has a conductivity of at most 200 mS / cm. The treatment with the washing medium is preferably carried out in step c) until the effluent washing medium has an aluminum content of at most 500 ppm by weight. The activated catalyst fixed beds obtained by the process according to the invention, which optionally contain doped shaped catalyst bodies, are generally distinguished by high mechanical stability and long service life. Nevertheless, the fixed bed catalyst is mechanically stressed when it is flowed through in the liquid phase with the components to be hydrogenated. In the long term, wear or removal of the outer layers of the active catalyst species may occur. If the Raney nickel foam catalyst was prepared by leaching and doping, then the subsequently doped metal element is preferably on the outer active catalyst layers, which can also be removed by mechanical liquid or gas loading. If the promoter element is removed, this can result in a reduced activity and selectivity of the catalyst. Surprisingly, it has now been found that the original activity can be restored by the doping process is carried out again. Alternatively, the dopant can also be added to the hydrogenation, which is then post-doped in situ (Method 4).

The following examples serve to illustrate the invention without limiting it in any way. Unless otherwise stated, the reactors were operated in the upflow mode. EXAMPLES

Example 1: Hydrogenation of 4-isobutylacetophenone to 1 - (4 ^{'-lsobutylphenyl)} ethanol A wire cloth in plain weave of an alloyed with yttrium and hafnium aluminum miniumhaltigen ferritic chromium steel with the material number 1.4767 with a mesh size of 0.18 mm and. a wire diameter of 0.1 12 mm was annealed for 5 h at 1000 ° C in air. Subsequently, the thus pretreated carrier fabric was coated in an electron beam evaporation plant with 1 10 mg copper / m ² (based on the tissue surface). The coated fabric was heated in a muffle for 0.5 hour in the air at 400 ° C to form the catalyst. From the catalyst fabric thus prepared, a monolithic body was molded. For this purpose, a part of the tissue was corrugated by means of a gear wheel. This corrugated tissue was folded with a smooth fabric strip and wound up. This gave a monolithic shaped body which was fixed by spot welding. The diameter of the winding was 2.5 cm, the length 20 cm. In the apparatus described below also used for the hydrogenations, this catalyst was reduced at 180 ° C at ambient pressure for one hour with hydrogen. The hydrogenation apparatus consisted of a storage vessel, a feed pump, a

Compressed gas supply, a double-jacket tubular reactor, which was heated in the outer jacket with oil, a gas-liquid separator and a circulation pump. In the separator, the reactor discharge into reactor exhaust gas and liquid discharge was separated, the gas via a pressure-holding valve and the liquid discharged in a controlled manner (that is, depending on the liquid level in the separator). The gas and Eduktzulaufstelle was between circulation pump and reactor inlet.

The plant was filled after activation of the catalyst with ethanol and pumped a circulating flow of 46 liters / h through the reactor. Subsequently, hydrogen was supplied by means of gas supply with a CO content of 2 ppm by volume and the

Reactor brought to 50 bar pressure and heated to 120 ° C. After reaching this temperature, a feed of 4-isobutylacetophenone of 31 g / h was set and fed about 4.7 standard liters of gas / h. The amount of exhaust gas was about 0.6 standard liters / h with a CO content of about 10 ppm by volume. After an operating time of 48 hours, an analysis of the yield showed a conversion of 4-isobutylacetophenone of 99.7% with a selectivity of

> 99.5%. As a minor component, 4-isobutylethylbenzene was obtained. The hydrogenation was run for 10 days without any adverse effect on catalyst activity and selectivity. Comparative Example 1

The procedure was analogous to Example 1, with the difference that the CO content was less than 0.1 ppm by volume at the reactor inlet and at the reactor outlet. The conversion of 4-isobutylacetophenone was 99.9% with a selectivity of approx.

97%. Secondary component was with a selectivity of about 2.5% 4-isobutylethylbenzene and about 0.4% 1 - (4'-isobutylcyclohexyl) ethanol.

Example 2: Hydrogenation of 1,4-butynediol

The nickel-aluminum catalyst moldings used in the application examples were prepared as follows, following the examples in EP 2 764 916 A1 for the preparation of foam-form catalysts: Variant a):

0.5 g of polyvinylpyrrolidone (molecular weight: 40,000 g / mol) were dissolved in 29.5 g of demineralized water and 20 g of aluminum powder (particle size 75 μηη) was added. The resulting mixture was then shaken so that a homogeneous suspension was formed. Thereafter, a nickel foam having an average pore size of 580 μηη, a thickness of 1, 9 mm and a weight per unit area of 1000 g / m ^{2 was added} to the suspension and again shaken vigorously. The thus coated foam was placed on a paper towel and the excess suspension carefully blotted. In a rotary kiln, the thus coated foam was heated at a heating rate of 5 ° C / min to 300 ° C, then kept isothermally at 300 ° C for 30 min, further heated at 5 ° C / min to 600 ° C, for 30 min kept isothermal and further heated at 5 ° C / min to 700 ° C and kept isothermic for 30 min. The heating was carried out in a gas stream consisting of 20 NL / h nitrogen and 20 NL / h hydrogen. The cooling phase up to a temperature of 200 ° C was also carried out in a gas stream of 20 NL / h N2 and 20 NL / h H2. Thereafter, nitrogen was further cooled to room temperature in a stream of 100 NL / h. The foam produced in this way had a weight increase of 42% compared to the originally used nickel foam. Variant b):

A nickel foam with an average pore size of 580 μm, a thickness of 1.9 mm and a weight per unit area of 1000 g / m ² was poured into a 1% strength by weight polyvinylpyrrolidone solution (molecular weight: 40 000 g / mol). dipped. After dipping The foam was squeezed out on a flow cloth to remove the binder from the voids of the pores. The foam laden with the binder was then clamped in a shaker and coated with aluminum powder (particle size <75 μηη). By shaking, a uniform distribution of the powder was obtained on the surface of the open-pore foam structure and then removed excess aluminum powder. In a rotary kiln, the thus coated foam was heated at a heating rate of 5 ° C / min to 300 ° C, then kept isothermally at 300 ° C for 30 min, further heated at 5 ° C / min to 600 ° C, for 30 min kept isothermal and further heated at 5 ° C / min to 700 ° C and kept isothermic for 30 min. The heating was carried out in a gas stream consisting of 20 NL / h nitrogen and 20 NL / h hydrogen. The cooling phase up to a temperature of 200 ° C was also carried out in a gas stream of 20 NL / h N2 and 20 NL / h H2. Thereafter, nitrogen was further cooled to room temperature in a stream of 100 NL / h. The foam produced in this way had a weight increase of 36% compared to the originally used nickel foam.

About 30 ml (about 57 ml) of the rectangular shaped bodies obtained according to variant a) were installed in a rectangular reactor (interior dimensions 1 cm × 2 cm × 40 cm), so that in each case 5 cuboids lay flat on top of each other and 8 of these layers stacked on top of each other in the reactor. To make sure that the stacks had no space in front of the reactor wall, the space was filled with PTFE tape (thickness = 0.5 cm) and sealed. Thus, at least 95% of the reactor cross-section through the fixed catalyst bed was filled with the catalyst moldings and 98% of the pores and channels had an area of at most 0.7 mm ² . The reactor used furthermore had an outer jacket which could be heated with oil. In addition, the experimental apparatus included a stand-controlled gas-liquid separator, a circulation pump, a feed pump for aqueous 1, 4-butynediol, a hydrogen supply, pressure holdings in the exhaust gas and liquid discharge, and devices for temperature measurement and sampling points.

The reactor and the circulation stream were filled with demineralized water and a circulation stream of about 20 L / h at atmospheric pressure and 25 ° C was set. Then about 650 mL / h of a 0.5 wt .-% sodium hydroxide solution were supplied. Liberated hydrogen and excess liquid were discharged from the separator and the remaining liquid returned to the reactor. The content of nickel in the liquid discharge stream was below the detection limit of 1 ppm. After about 6 hours, the evolution of hydrogen dropped significantly and the supply of sodium hydroxide solution was stopped and then rinsed with 5 L / h of demineralized water until the pH in the discharge to 7 and the conductivity had fallen to 254 με / ηηη. Subsequently, 0.6 g (ΝΗ4) of 6Μθ7θ24 x 4 H2O in 60 ml of water via the feed pump again at 25 ° C in trickle mode supplied. The solution was pumped for 3 h at 20 kg / h until the Mo was taken up by the catalyst.

For the hydrogenation, a 1, 4-butynediol feed was used, which was prepared according to Example 1 of EP 2121549 A1. The feed had a pH of 7.5 and in addition to 1, 4-butynediol and water still contained about 1 wt .-% propynol, 1, 2 wt .-% formaldehyde and a number of other by-products with proportions of clearly lent under 1% by weight. The hydrogenation was carried out at 45 bar pressure and a temperature of 155 to 160 ° C and a circulating current of 13 to 20 kg / h. The molar ratio of hydrogen to 1,4-butynediol was 2.5 to 1. In Table 1, the results (each after 48 h run time with appropriate experimental parameter setting) are shown, with the GC% data in area% (ie no water was taken into account). The CO concentration is given in ppm by volume at the beginning and at the end of the reactor.

The CO concentration is given in ppm by volume at the beginning and at the end of the reactor.

Comparative Example 2:

Cube-shaped shaped catalyst bodies according to variant a) were prepared as described in Example 2. 30 cuboids were cut into approximately 2 x 2 x 1, 9 mm pieces and introduced as a bed (about 70 ml) in the reactor also described in Example 2 and activated analogously to Example 2 and doped with Mo. The reactor cross section was filled to about 80% with shaped catalyst bodies and about 10% of the channels had at least an area of 0.7 mm ² . The hydrogenation of 1, 4-butynediol was carried out under a load of 0.5 kg of 1, 4-butynediol / L xh and a Kreisström of 20 kg / h analogously to Example 2. The hydrogenation was significantly poorer in terms of selectivity or conversion than in Inventive Example 2 (see Table 2). Table 1 (according to the invention)

BDO = 1, 4-butanediol

BuOH = n-butanol

MeOH = methanol

PrOH = n-propanol

MBDO = 2-methylbutane-1, 4-diol

BID = 2-butyne-1,4-diol

BED = 2-butene-1, 4-diol

Example 3: Hydrogenation of n-butyraldehyde

Analogously to Example 2, n-butyraldehyde, which still contained about 1500 ppm of isobutyraldehyde, was hydrogenated on nickel-aluminum cuboids (prepared according to variant b)), after activation the doping with Mo in the reverse flow direction through the Reactor as in Example 2 was carried out. Thereafter, the reaction system was drained and the water was replaced by n-butanol. The hydrogenation was carried out at 40 bar, the temperature was maintained between 135 and 140 ° C. The molar ratio of hydrogen to butyraldehyde was 1, 1 to 1. At a loading of 1, 5 kg butyraldehyde / liter of catalyst x h and 23 kg / h liquid circulation was found according to GC analysis (area%) in the discharge 99.6% n-butanol. In addition, the main secondary components were still 0.05% butyl acetate, 0.01% dibutyl ether, 0.15% isobutanol and 0.07% ethylhexanediol. The CO content upstream of the reactor was 0.2 vol. Ppm, after the reactor vol. 15 ppm.

Claims

claims

1 . A process for the hydrogenation of a hydrogenatable organic compound in at least one reactor containing a fixed catalyst bed containing monolithic catalyst shaped bodies or consisting of monolithic shaped catalyst bodies containing at least one element selected from Ni, Fe, Co, Cu, Cr, Pt , Ag, Au, Mn, Re, Ru, Rh and Ir, wherein during the hydrogenation, the CO content in the gas phase within the reactor is in a range of 0.1 to 10,000 ppm by volume, and wherein the fixed catalyst bed is shaped catalyst contains, which have pores and / or channels and wherein at any

Section in the normal plane to the flow direction through the fixed catalyst bed at least 90% of the pores and channels, more preferably at least 98% of the pores and channels, an area of at most 3 mm ² ..

Process according to claim 1, wherein the compound used for the hydrogenation is selected from 1,4-butynediol, 1,4-butenediol, 4-hydroxybutyraldehyde, hydroxypivalic acid, hydroxypivalaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isobutyl Valeraldehyde, 2-ethylhex-2-enal, 2-ethylhexanal, the isomeric nonanals, 1, 5,9-cyclododecatriene, benzene, furan, furfural, phthalic esters, acetophenone and alkyl substituted acetophenones.

Method according to one of the preceding claims, wherein the conversion in the hydrogenation at least 90 mol%, preferably at least 95 mol%, in particular at least 99 mol%, especially at least 99.5 mol%, based on the total molar amount of hydrogenatable compounds in the starting material used for the hydrogenation is.

Method according to one of the preceding claims, wherein during the hydrogenation, the CO content in the gas phase within the reactor in a range of 0.15 to 5000 ppm by volume, in particular in a range of 0.2 to 1000 ppm by volume.

Method according to one of the preceding claims, wherein the reactor in the flow direction of the reaction medium through the fixed catalyst bed has a gradient with respect to the CO concentration.

6. The method according to any one of the preceding claims, wherein the CO content at the outlet of the reaction medium from the fixed catalyst bed by at least 5 mol%, preferably by at least 25 mol%, in particular by at least Is 75 mol% higher than the CO content when the reaction medium enters the fixed catalyst bed.

7. The method according to any one of the preceding claims, wherein the fixed catalyst bed at any section in the normal plane to the flow direction through the fixed catalyst bed, based on the total area of the section, at most 5%, preferably at most 1%, in particular at most 0.1% free area, which is not part of the catalyst form body.

8. The method according to any one of the preceding claims, wherein the flow rate of the liquid reaction mixture through the fixed catalyst bed reactor containing at least 30 m / h, preferably at least 50 m / h, in particular at least 80 m / h.

9. The method according to any one of the preceding claims, wherein the reaction mixture of the hydrogenation is at least partially conducted in a liquid circulation stream, wherein the ratio of recycled in the circulation reaction mixture to freshly supplied educt stream in a range of 1: 1 to 1000: 1, preferably from 2: 1 to 500: 1, especially from 5: 1 to 200: 1.

10. The method according to any one of the preceding claims, wherein the fixed catalyst bed during the hydrogenation has a temperature gradient. 1 1. Method according to one of the preceding claims, wherein the monolithic shaped catalyst bodies, based on the entire shaped body, have a maximum dimension in a direction of at least 1 cm, preferably at least 2 cm, in particular at least 5 cm.

A method according to any one of the preceding claims, wherein the monolithic shaped catalyst bodies contain at least one element selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, preferably selected from Ni, Co and Cu. 13. The method according to any one of the preceding claims, wherein the monolithic shaped catalyst bodies are in the form of a foam.

14. The method according to any one of the preceding claims, wherein the reactor used for the hydrogenation contains a fixed catalyst bed, the monolithic catalyst contains torform body or consists of monolithic catalyst form bodies containing at least one first metal selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, and containing at least one second component, which is selected from Al, Zn and Si, wherein subjecting the fixed catalyst bed for activating a treatment with an aqueous base, which is introduced into a reactor, a fixed catalyst bed containing monolithic shaped catalyst body or consists of monolithic shaped catalyst bodies containing at least a first metal, the is selected from Ni, Fe, Co, Cu, Cr, Pt, Ag, and Au, and containing at least one second component selected from Al, Zn, and Si, which subjects catalyst fixed bed to activation with an aqueous base, optionally subjecting the activated fixed catalyst bed obtained in step b) to a treatment with a washing medium which is selected t under water, C 1 -C 4 alkanols and mixtures thereof, optionally the catalyst fixed bed obtained after activation in step b) or after the treatment in step c), is contacted with a dopant having at least one element selected from the first metal and the second component of the catalyst molding used in step a) is different.