DE102005034004A1 - Catalyst with bimodal distribution of the particles of the catalytically active material, process for its preparation and for its regeneration and use of the catalyst - Google Patents

Abstract

The subject of the present invention is a catalyst which contains a support and a catalytically active material. The particles of the catalytically active material are bimodally distributed in size. The fraction of the larger particles of the catalytically active material and the fraction of the smaller particles of the catalytically active material are uniformly mixed in the catalytically active layer of the catalyst. The catalytically active material is 50% by weight or less, based on the catalyst. DOLLAR A The invention also relates to a method for producing or regenerating a catalyst according to the invention. A catalytically active material located on a carrier is coagulated in a first step. In a further step, a further catalytically active material is applied to the carrier. DOLLAR A The invention further relates to the use of the catalytically active material for the dehydrogenation of five- or six-membered carbon-containing molecular rings to give aromatic compounds.

Description

Of the The present invention is a catalyst comprising a carrier and a catalytically active material. The particles of the catalytic active material are distributed bimodal size. The fraction of larger particles of the catalytically active material and the fraction of the smaller ones Particles of the catalytically active material are uniformly mixed in the catalytically active layer of the catalyst. The catalytic active material is 50% by weight or less based on the catalyst.

The Invention further relates to a process for the preparation or for the regeneration of a catalyst according to the invention. One on one carrier befindliches catalytically active material is doing in a first Step coagulates. In a further step, another catalytically active material applied to the carrier.

The The invention further relates to the use of the catalytically active Material for the dehydration of five or six-membered carbon-containing molecular rings to aromatic compounds.

catalysts with a bimodal size distribution the catalytically active material are known, such as Sayari at al. (Journal of Electron Spectroscopy and Related Phenomena, 58 (4) (1992) 285 to 298). Sayari et al. but point out that a bimodal size distribution with a fraction of the smaller particles of the catalytically active Materials that are homogeneous over the carrier is distributed, and a fraction of the larger particles of the catalytic active material, the only on the outer surface of the support material are arranged systematically occurs in the catalysts.

Tsang et al. (Fullerenes and Fullerene Nanostructure, Proceedings of the International Winter School on Electronic Properties of Novel Materials, 10th, Kirchberg, Austria, March 2 to 9 1996, page 250 to 254, Editor: Kuzmany, H.) shows a carbon nanotube catalyst with palladium as catalytically active material. The outside arranged on the nanotubes Palladium particles have a diameter of 20 to 28 nm. The smaller palladium particles arranged on the inside of the nanotube on the other hand have a mean diameter of about 2.6 nm on. So there is no even distribution the bimodal distributed palladium particles on the support. Tsang et al. to lead the good catalytic activity just on the smaller palladium particles on the inside the nanotubes are arranged back.

DE 19 900 176 describes a catalyst with a bimodal size distribution of the catalytically active material. The catalytically active material is nickel. Zirconium is used as a carrier. The nickel content of the catalyst is 60% or more.

EP 1 205 240 discloses palladium as a catalytically active material and γ-alumina as a carrier. A coagulated metal phase coats the particles of the catalytically active material. A bimodal size distribution of the particles of the catalytically active material is considered to be negative, since it can not achieve the desired coating ratio for optimal catalytic activity. Instead, a monomodal size distribution of the metal-coated catalytically active material is recommended.

It It is also known that regenerates a deactivated catalyst can be. It is generally endeavored to coagulate the catalytic active material, for example, by annealing the carrier to prevent, as the coagulated particles of the catalytically active material in principle a worse show catalytic activity.

It It was an object of the present invention to provide a catalyst with a long service life, with a high catalytic activity and with a high desired Selectivity. The carrier of the catalyst should continue to have low abrasion.

It was a further object of the present invention to provide a process for the regeneration of a catalyst. In particular, consuming carrier to be produced should be regenerated again. The process should be as cost-effective as possible by a few process steps and the dispensability of chemical substances such as solvents. Furthermore, a repeated regeneration of the carrier be possible.

These Problem was solved by the invention Provision of the catalyst described above and a Process for the preparation or the regeneration of the catalyst according to the invention.

The catalytically active material can be a substance of groups 7 to 11 of the periodic table. The periodic table according to IUPAC applies at the time of 4 February 2005. In particular, the Elements Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au meant meant. In a particularly preferred embodiment is the catalytically active material palladium.

The catalytically active material can be applied to the support in all forms. The application is possible in metallic or elemental form in example by vapor deposition. The catalytically active material can also be applied in a covalently bonded form. It is also possible to apply in an electrostatically bonded form. An example is the application in the form of a salt or in the form of a complex of the catalytically active material. The further catalytically active material may, for example, with the in DE 19 533 665 described method can be applied to the carrier.

An oxide support is preferably impregnated with an aqueous nitric acid Pd (NO ₃ ) ₂ solution. The Pd content of a Pd (NO ₃ ) ₂ solution is generally 5% by weight to 20% by weight, preferably 10% by weight to 15% by weight, particularly preferably 11% by weight 13 wt .-% based on the solution.

In a further embodiment, each impregnation step with a Pd (NO ₃ ) ₂ solution increases the Pd content of the support by 1% by weight or less, preferably from 0.1% by weight to 0.5% by weight on the carrier.

The impregnation can also be used with other Pd salts or complexes known to those skilled in the art such as nitrosyl nitrates, halides, carbonates, carboxylates, Acetylacetonates, chloro complexes, nitrite complexes or amine complexes.

The Catalytically active material is generally in the active form on the carrier in front. This active form is dependent from the one chosen catalytically active material.

The Catalytically active material is generally in the reduced state Form active. The catalytically active material must therefore in the case of covalently or electrostatically bonded forms of the catalytic active material is usually reduced.

This reduction can be carried out for example by heat treatment under pure Hz, for example in Pd (NO ₃ ) ₂ at 230 ° C to 300 ° C, preferably at 240 ° C to 260 ° C for 2 to 3 h, preferably for 1 h to 3 h , The reduction is also possible by CO, hydrazine and all other reduction methods known in the art.

It can only a catalytically active material, such as Pd on the carrier be applied. It can but also several catalytically active elements, for example two, three or four different elements in covalent or in electrostatic bonded or in elemental form are applied to the carrier.

The Catalytically active material is generally present in such amounts that a catalytic activity is ensured. This depends on respective catalytically active material, for example in Pd in usually at a content of the catalytically active material of 0.1 wt% or more preferably at 0.3 wt%, and more preferably at 0.5 wt .-% or more based on the catalyst of the case.

The catalytically active material is 50% by weight or less, preferably 10% by weight or less, and especially preferably 5% by weight or less, and more preferably 1% by weight or less based on the catalyst.

When carrier are basically all concerning the inert gas to be catalyzed reaction possible. An inventive carrier is generally a solid which is up to the sintering temperature of the catalytically active Material is heat stable.

A support according to the invention may be selected from the group metal oxides, nitrites, carbides, silicates, aluminosilicates, spinels or carbons. However, a carrier according to the invention can also consist of more than one material. The metal oxides are preferably used as a carrier according to the invention. The preferred carriers in the context of the present invention are α-Al ₂ O ₃ or ZrO ₂ .

An inventive α-Al ₂ O _{3 support} is preferably according to DE 19 533 665 produced. The support generally has a BET specific surface area of from 1 m ² / g to 10 m ² / g, preferably from 4 m ² / g to 8 m ² / g, a pore diameter of 5 nm to 300 μm, preferably 20 nm to 50 microns and especially from 20 nm to 10 microns and a pore volume of 0.1 cm ³ / g to 0.5 cm ³ / g, preferably from 0.2 cm ³ / g to 0.3 cm ³ / g.

In a particularly preferred embodiment According to the invention, the catalyst is shaped as a shell catalyst. Under coated catalyst is in connection with the present Invention to understand a catalyst in which the catalytic active material only in the outer layer occurs. Under this outer Layer is the outer one 600 μm or less, preferably the outer ones 400 μmm or less and in particular the outer 200 μm of the carrier.

A bimodal size distribution the particle of the catalytically active material is present when the average diameter of the particles of the catalytically active material are distributed so that they form two Maximas.

The Measurement of this maximas occurs in the case of precious metals of the group 10 is preferred as the catalytically active material, such as Pd by CO chemisorption according to DIN 66136-3. A spectrum obtained by CO chemisorption leads to J.R. Anderson (Structure of Metallic Catalysts, London 1975, p. 358-364) for dispersity. The middle one Diameter of the particles of the catalytically active material can be out the dispersity also according to J.R. Anderson be calculated.

The dispersity describes the percentage of atoms that attach to the surface of the Particles of the catalytically active material are based on the total number of atoms of the catalytically active material, who are on the carrier a catalyst according to the invention are located.

The standard DIN 66136-3 is applicable for chemisorption with regard to the metals platinum and copper. DIN 66136-3 is applied to Pd in the context of the present invention. The chemisorption is preferably carried out with a single Anaylsegas. This analysis gas is preferably CO. This is the so-called CO chemisorption. Helium can be used preferably as a carrier gas for the CO. A comparison of the thermal conductivity detector signal of an injection (loop) with the signal of a manually performed injection serves as a calibration (gas syringe). The gravimetric control can be done by filling the loop with water. This is described in point 3.4.1 of DIN 66136-3. It is recommended to reduce the catalyst before CO chemisorption measurement at 200 ° C for 30 min below Hz. The ramp is preferably 5 ° C / min. The H ₂ can then preferably be washed away with helium. The evaluation of the measurement results of the Anderson CO chemisorption described above is based on the assumption that the particles of the catalytically active material are spherical particles. Spherical means spherical.

The dispersity and the mean diameter of the particles of the smaller fraction Particles of the catalytically active material of a catalyst according to the invention can be, for example, especially in the case of Pd as catalytic determine active material as follows. The catalytically active material is the first time on the carrier for example, in the manner described in Comparative Example 1 and manner applied. This is followed by a CO chemisorption measurement. This CO chemisorption measurement gives the mean diameter and the dispersity the particle of the fraction of the smaller particles of the catalytic active material. Such a value is for example in table 2 for the inventive example 1 to the catalysis analyzers α2 to α8 too see. The proportion of the imbibed catalytically active material on the particles of the fraction the larger particles of the catalytically active material in the application of another catalytically active material falls, was used in the calculation of the mean diameter and the dispersion vernachlässtigt, there this area usually only 10% of the area the particle of the fraction of the smaller particles of the catalytic active material. This is at Table 2, column Dispersity, subcolumns Pd metal surface to see.

The dispersity and the mean diameter of the particles of the fraction of the larger particles of the catalytically active material can be determined, for example, in particular in the case of Pd as the catalytically active material as follows. The method of calcination described in Example 1 results in the coagulation of the particles of the catalytically active material. A subsequent CO chemisorption measurement according to the method described above then gives the dispersity and the average diameter of the particles of the fraction of the larger particles of the catalytically active material. Such a value can be seen, for example, in the first row of Table 2, for example, 1 in the catalyst V5.

These both determined by the CO chemisorption described above Maximas can for example, by a transmission electron micrograph approved become. It is generally a TEM bright field image made in review. As measuring device for a TEM with field emission source For example, a FEI-Tecnai F20 from the manufacturer FEI is suitable, Holland.

The Fixation of the catalyst can be achieved by embedding in synthetic resin respectively. The ultrathin cuts (floated on water) with a Microtom Leica Ultracut made by the manufacturer Leica.

The Verification of the catalytically active material can by a EDXS (Energy Dispersive X-Ray Spectroscopy). The EDXS is especially suitable for an atomic number greater than 7. HAADF-STEM photographs (High Angle Annular Dark Field Scanning TEM) can be complementary to the TEM recordings for better localization of the particles of the catalytically active Materials are made.

The Transmission electron micrographs according to the invention show two different Fractions of the particles of the catalytically active material.

The Maximum of the fraction of larger particles and their dispersity are clearly from the maximum of the fraction of smaller particles the catalytically active material and their dispersibility distinguishable.

In a preferred embodiment is the maximum of the particles of the smaller fraction of the catalytic active material from 1 nm to 10 nm, more preferably from 3 nm to 7 nm. In a further embodiment of the invention, the maximum is the larger fraction the particle of the catalytically active material from 50 nm to 100 nm, preferably from 60 nm to 80 nm.

The dispersity the particle of the smaller fraction of the catalytically active material is in a particular embodiment 10% or more, preferably 15% or more, and more preferably 20% or more and especially 25% or more. The dispersity of the particles the larger fraction of the catalytically active material is generally 10% or less, preferably 5% or less, and more preferably 2% Or less.

The measurement of this Maximas takes place by CO chemisorption according to DIN 66136-3. This is also applied to Pd in the context of the present invention. The CO chemisorption is carried out with a single analysis gas, the CO. This is the so-called CO chemisorption. Helium is used as a carrier gas for the CO. A comparison of the thermal conductivity detector signal of an injection (loop) with the signal of a manually performed injection serves as a calibration (gas syringe). The gravimetric control is done by filling the loop with water. This is described in point 3.4.1 of DIN 66136-3. The catalyst is reduced before the CO Chemisorptionsmessung at 200 ° C for 30 min under H ₂ . The ramp is 5 ° C / min.

The calculation of the dispersity from the chemisorption spectrum was carried out according to Anderson with the following parameters:
D _Pd = N / total number of Pd atoms in the Pd particles

N is the number of Pd atoms on the surface of a Pd particle. N becomes determined by the CO absorption amount measured in CO chemisorption per g of catalyst.

V_Pd

effektives Volumen eines Pd-Atoms in einem Pd-Partikel

a_Pd

effektive Fläche eines Pd-Atoms, welches sich an der Oberfläche eines Pd-Partikels befindet

D_Pd

Dispersität bezogen auf die letzte Tränkung mit Pd, siehe Tabelle 2 zum Beispiel 1.

d_Pd

Durchmesser

The calculation of the mean diameter of the particles of the catalytically active material was carried out according to Anderson with the following formula: d Pd = 6 · (V Pd / a Pd ) · (1 / D Pd )

V _Pd

effective volume of a Pd atom in a Pd particle

a _pd

effective area of a Pd atom located on the surface of a Pd particle

D _Pd

Dispersity based on the last impregnation with Pd, see Table 2 for example 1.

d _Pd

diameter

a _Pd was assumed to be 1.27 · 10 ¹⁹ atoms per m ² according to Anderson p. 296. v _{Pd is} calculated according to the formula: v Pd = Molar mass of Pd / (density of Pd · Avogadro constant)

In a particular embodiment is the mean diameter of the fraction of the larger particles of the catalytic active material ten times or more of the mean diameter the fraction of the smaller particles of the catalytically active material.

The Measurement of this diameter of the fraction of the smaller particles the catalytically active material is carried out after the same CO chemisorption and according to the same evaluation, according to the measurement of Maximas took place.

In a further embodiment are the fraction of larger particles and the fraction of the smaller particles of the catalytically active Materials monodisperse in front. Monodisperse is understood in context with the present invention a low deviation from the mean the diameter within a fraction of the particles of the catalytic active material. A low deviation is generally when the measured by CO Chemisorption mean diameter of Particles of the catalytically active material by 20% or less, preferably by 15% or less, and more preferably by 10% or less and in particular by 5% or less, or by 20% or less, preferably 15% or less, and more preferably by 10% or less and in particular by 5% or less becomes.

This undershoot or overshoot can also be detected, for example, by the transmission electron microscopy described above. A monodisperse distribution according to the invention of the diameter of the particles of the fraction of the larger particles of the catalytically active material and the fraction of the smaller particles of the catalytically active material is, for example, in Example 1, 2 to see.

In a further embodiment the particles of the catalytically active material are spheroidal a relationship from the smallest to the largest diameter a particle of 0.5 to 1, preferably 0.7 to 1 and especially preferably from 0.9 to 1 before.

Under a uniform mixing the fractions of the smaller particles and the larger particles of the catalytic active material is understood in the context of the present Invention that the particles no size-dependent preferred arrangement exhibit. The particle size of the catalytic active material therefore usually does not determine the arrangement on the carrier. So there are generally no surfaces on the surface of the carrier to observe, on which only particles of the fraction of the larger particles of the catalytically active material occur. They are in general also no surfaces on the surface of the carrier to observe, on which only particles of the fraction of the smaller ones Particles of the catalytically active material occur. A natural border forms of course the surface structure of the catalyst. The distribution is therefore generally uniformly below Attention to the physical limits created by the surface structure of the carrier are predetermined.

In a preferred embodiment lets the physical structure of the carrier a uniform distribution the particle of the fraction of the larger particles and the fraction of the smaller particles of the catalytically active Material in the catalytically active layer of the catalyst too. This can be for example Zeolites or for Nanotubes under circumstances not be given.

A uniform mixing of the fraction of the smaller particles and the fraction of the larger particles of the catalytically active material is given, for example, if, with the transmission electron microscopy described above, a distribution of the particles of the catalytically active material as in 2 for example 1 receives. The 2 For example, Figure 1 shows that the particles of the catalytically active material are evenly distributed on the surface of the carrier. There are no surfaces of the catalyst to see on which preferably only the particles of the fraction of the smaller particles of the catalytically active Ma terials or only the larger particles of the catalytically active material occur.

One Another object of the present invention is a method for the preparation of a catalyst according to the invention. It will in a first step, a supported on a carrier catalytically active Material on the support coagulated. In a second step, a catalytically active Material on this carrier applied with the coagulated catalytically active material.

In a particularly preferred embodiment In the present invention coagulation is by sintering on a support located catalytically active material. Under sintering understands a thermal treatment at 50% or more, preferably at 60% or more based on the absolute melting temperature.

The Coagulation of the particles of the catalytically active material can but also at higher Temperatures occur.

One Coagulating the particles of the catalytically active material Sintering of the catalytically active material usually takes place in this way long until the particles of the catalytically active material coagulate are. The duration of sintering is generally dependent on the nature of the catalytically active material. For example, the Particles in palladium as catalytically active material also at Temperatures of 900 ° C or more on a carrier for example Be coagulated by calcining for 2 hours. It can also be dependent on catalytically active material are also sintered for shorter or longer.

As a carrier is preferably after DE 19 533 665 prepared α-Al ₂ O ₃ carrier, which was preferably impregnated with palladium salt solution. It is preferably a CIM carrier.

In the context of the present invention, CIM carrier is to be understood as meaning oxidic carrier which is produced by sintering an oxide powder with the aid of a polymer former. Details of the manufacture either teaches DE 19 533 468 or DE 19 533 665 , Removal of the polymeric binder can be accomplished either by calcining or debinding with other oxidants such as nitric acid.

For the preparation of such an α-Al ₂ O ₃ -CIM carrier, for example, α-Al ₂ O ₃ powder having a particle size of 0.2 .mu.m to 4 .mu.m, preferably from 0.5 .mu.m to 1.0 .mu.m with a Polymer former kneaded, melted and processed via a Schwerwalzene extruder to a granulate with the size of 1 mm to 10 mm, preferably from 3 mm to 6 mm. In a further production step, the green compact is preferably freed from the polymeric binder by pyrolysis and then calcined. A resulting CIM carrier is characterized by a particularly narrow pore radius distribution.

The finished carrier can then be impregnated in particular with a palladium salt solution, particularly preferably with Pd (NO ₃ ) ₂ . The Pd content of Pd (NO ₃ ) ₂ can vary within wide limits. In a preferred embodiment, the palladium content of the palladium nitrate solution is 0.05% by weight to 2% by weight, more preferably 0.12% by weight to 0.14% by weight, based on the catalyst according to the invention.

Of the Soaked Catalyst can subsequently be dried. Drying can be done with a variety of suitable Drying done. The drying is preferably carried out gentle on the carrier. This is, for example, during drying with slight heating in a weak stream of air with constant turning the case. The Residual moisture of the carrier is generally 1% by weight or less based on the carrier α.

One Sintering of the catalytically active material on the support can to tensions and cracks in the carrier to lead. These tensions and cracks can eliminated, for example, by annealing following drying become. Annealing may also be the decomposition of nitrates to the serve corresponding oxides. Annealing means heating the Catalyst over a longer one Period. The temperature profile during annealing is preferred dependent on from the material of the carrier and the catalytically active material of a catalyst according to the invention to determine.

One after DE 19 533 665 produced α-Al ₂ O ₃ -CIM carrier, which was preferably impregnated with palladium salt solution, can be heated for example in 2 h at 350 ° C and annealed for a further 4 h at this temperature.

One more catalytically active material can basically be any be catalytically active material. They are preferably the ones above listed used catalytically active materials. A particularly preferred catalytically active material is Pd.

One Another catalytically active material is in a preferred embodiment the chemically identical catalytically active material as the coagulated catalytically active material. In a preferred embodiment Pd is coagulated and Pd as another catalytically active material applied.

A Coagulation of the catalytically active material and the subsequent application a catalytically active material can take place once. The coagulation and the subsequent one Applying the catalytically active material can also be two, three, four five-, six, seven, eight, nine or ten times or more than ten times respectively. It increases the content of the catalytically active material of the carrier. The coagulation and applying a further catalytically active material are generally so often possible until the catalytically active material in economically unprofitable Quantities in the catalyst is present.

The inventive method can be done with a fresh catalyst. Under a fresh catalyst is in the context of the present invention in particular, to understand a catalyst that is not yet catalysis was used. It is generally one newly prepared catalyst without significant impurities by by-products of the reaction to be catalyzed, and in particular without organic deposits.

However, the process of the invention can also be used for the regeneration of a deactivated catalyst. A deactivated catalyst is understood as meaning a catalyst which, for example, can be prepared according to the method described in DE 19 533 665 was industrially impregnated with palladium and, for example, more than 50 days in a large-scale plant at a feed load of 0.12 kg of 2,3,6-trimethylphenol per liter of catalyst per hour was in use. Deactivation means, in particular, that the catalytic activity of a catalyst has fallen below an economically viable level, so that the catalyst would have to be replaced in large-scale operation. This is generally the case for a selectivity to the desired reaction product of 80% or less.

One Such deactivated catalyst is inventively by a coagulation of the on-carrier catalytically active material and in a further step an application of another catalytically active material the carrier regenerated.

The Coagulation takes place, for example, by means of a heat treatment the sintering temperature of the catalytically active material of a catalyst according to the invention. Sintering usually takes place over such a period, coagulating the particles of the catalytically active material allows.

A deactivated α-Al ₂ O ₃ carrier after DE 19 533 665 can be regenerated by the annealing at an unusually high temperature of 900 ° C over a period of 2 h. Another catalytically active material is applied in a further step on the carrier thus regenerated.

there is a regeneration according to the invention possible. It can but also several regenerations take place. A disabled one Catalyst can be regenerated by the process according to the invention and subsequently are used during operation until a further deactivation is made becomes. Thereupon, the second time deactivated catalyst according to the inventive method be regenerated so that it will be used a second time can. There are two, three, four, five, six, seven, eight, nine, but also ten or more regeneration steps possible.

One after DE 19 533 665 produced and regenerated or treated according to the inventive catalyst surprisingly shows in a further embodiment, no losses in the catalytic performance. The catalytic performance in this context mainly describes the catalytic performance via a stress test, as described in Example 4 of the invention. In a preferred embodiment, a catalyst regenerated by the process according to the invention even has a better catalytic performance than a fresh catalyst.

By good catalytic performance is generally meant a selectivity to the desired product of 90% or greater, more preferably 94% or greater, most preferably 98% or greater. One after DE 19 533 665 prepared and regenerated or prepared by the process according to the invention catalyst, for example, in the dehydrogenation of 2,3,6-trimethyl-2-cyclohe xen-1-one has a selectivity of 2,3,6-trimethylphenol of 98% or more.

This surprising good catalytic performance of a regenerated according to the invention Catalyst is in a further embodiment also after a Loading of the catalyst still available. The catalytic performance is generally not significantly worse by a burden as with a fresh catalyst. The inventively regenerated carrier So, in general, does not show any significant aging phenomena or even a better aging behavior than a fresh catalyst.

This good catalytic performance of the catalyst regenerated according to the invention is particularly surprising, because according to the classic Regeneriermethode with a removal of the carbonaceous deposits by O ₂ -containing regenerating gases at 400 ° C to 500 ° C only a worse catalytic performance is achieved than with a fresh catalyst (Applied Heterogeneous Catalysis, Le Page JF, CL, 1987 Editions Technip, Paris; page 69).

The inventive method for regeneration of a deactivated catalyst is generally cost-effective, because only a few process steps are used. Furthermore are usually additional chemical substances, such as solvents, dispensable.

In a further embodiment, a catalyst produced by the process according to the invention has an improved service life in industrial operation. An improved service life generally means a service life of 30 days or more, in particular of 40 days or more, more preferably of 50 days or more, and in particular of 50 days to 60 days in the feed amount described above. An inventively regenerated or after DE 19 533 665 For example, prepared catalyst may have a 2,3,6-trimethylphenol selectivity in the 2,3,6-trimethyl-2-cyclohexene-1-one hydrogenation of 95% or more with a life of 50 days.

These long service life of a catalyst regenerated according to the invention is in a further embodiment without a significant drop in catalytic performance achieve.

In a further embodiment of the present invention especially in the form of coagulation the particle of the catalytically active material by annealing or Sintering shows the catalyst of the invention a reduced abrasion. Under a reduced abrasion understands the dust produced by a mechanical movement. The tendency to abrasion of a catalyst is generally in a rotary drum test measured according to ASTM 4058.

The inventive method allows in a further embodiment a cost-effective production a catalyst according to the invention. The same carrier can be used several times. There are, for example, one, two three four five, six, seven, eight, nine, but also ten or more regeneration cycles possible.

The process of the invention for producing or regenerating a catalyst according to the present invention may allow reuse of a catalyst of a desired quality. The method according to the invention thus in a further embodiment, for example, detects the quality fluctuations of a catalyst preparation DE 19 533 665 independently.

The inventive method allows continue a cost-effective Recovery of the catalytically active material. A multiple Inventive regeneration a catalyst leads to an enrichment of the catalytically active material on the Carrier. Such enriched catalytically active material can then be recovered inexpensively become.

It is still the subject of the present invention, a catalyst to provide that available is or regenerable by a in a first step on a carrier catalytically active material coagulated on the carrier and another catalytically active material in a further step on this carrier is applied.

One Another object of the present invention relates to the use a catalyst according to the invention. A catalyst according to the invention or one according to the method of the invention produced or regenerated catalyst is in general dependent on of the catalytically active material and carrier for a variety of reaction types used.

It For example, hydrogenations or dehydrations are possible. Further possible Catalysing reaction types include oxidation reactions Pd-Pt catalysts, reductive amination of carbonyl groups, isomerization reactions including skeletal rearrangement and double bond isomerizations, water gas shift reactions, metathesis on rhenium catalysts or steam reforming of hydrocarbons (also autothermic).

Thus, a catalyst according to the invention or a catalyst prepared or regenerated by the process according to the invention can be used for the dehydrogenation of 5- or 6-membered carbon-containing molecular rings to give aromatic compounds. In particular, for the embodiment of an after DE 19 533 655 prepared catalyst can be used.

In a particular embodiment, a particular after DE 19 533 665 prepared and regenerated by the novel process or regenerated catalyst for the preparation of substituted aromatics and heteroaromatics by the catalytic dehydrogenation of non-aromatic, six-membered rings used.

A particular after DE 19 533 665 prepared and prepared by the process according to the invention or regenerated catalyst can be used for the dehydrogenation of 2,3,6-trimethyl-2-cyclohexen-1-one to 2,3,6-trimethylphenol.

A particular after DE 19 533 665 produced and produced by the novel process or regenerated catalyst can be used in a further preferred embodiment for the dehydrogenation of 3-methylpiperidine to 3-picoline.

It become the following abbreviations used:

TMP 2,3,6-trimethyl TMCH 2,3,6-trimethyl-2-cyclohexen-1-one 3-MPIP 3-methylpiperidine 3-PIC 3-picoline TEM transmission electron microscope

• – Träger α-Al₂O₃-Träger hergestellt gemäß DE 19 533 665 mit einer spezifischen Oberfläche nach BET von ca. 7 m²/g, einem Porendurchmesser von 100 nm und einem Porenvolumen von 0,23 cm³/g
• – Träger β: handelsüblicher ZrO₂-Träger mit einer spezifischen Oberfläche nach BET von 70 m²/g, einem Porendurchmesser von 20 nm und einem Porenvolumen von 0,27 cm³/g
• – Katalytisch aktives Material: Pd diente bei allen Versuchen als katalytisch aktives Material
• – Vergleichskatalysatoren V1 bis V4: ein Träger α mit Pd, wobei das Pd erstmals nach dem Verfahren in Vergleichsbeispiel 1 auf den Träger α aufgebracht wurde.
• – Erfindungsgemäße Katalysatoren α1 bis α8: ein Träger α mit Pd, wobei das Pd erstmals nach dem Verfahren in Vergleichsbeispiel 1 aufgebracht wurde. Dieser Träger wurde zusätzlich nach dem erfindungsgemäßen Beispiel 1 behandelt.
• – Erfindungsgemäßer Katalysator β: ein Träger β mit Pd, wobei das Pd erstmals nach dem Verfahren in Vergleichsbeispiel 1 aufgebracht wurde. Dieser Träger wurde zusätzlich nach dem erfindungsgemäßen Beispiel 1 behandelt.

The following substances and the following processes were used for the following comparative examples and for the following examples according to the invention:

• Carrier α-Al ₂ O ₃ supports prepared according to DE 19 533 665 with a BET specific surface area of about 7 m ² / g, a pore diameter of 100 nm and a pore volume of 0.23 cm ³ / g
• Carrier β: commercially available ZrO _{2 support} with a BET specific surface area of 70 m ² / g, a pore diameter of 20 nm and a pore volume of 0.27 cm ³ / g
• - Catalytically active material: Pd served as catalytically active material in all experiments
• Comparative Catalysts V1 to V4: a carrier α with Pd, the Pd being first applied to carrier α by the method in Comparative Example 1.
• - Catalysts according to the invention α1 to α8: a support α with Pd, the Pd was first applied by the method in Comparative Example 1. This support was additionally treated according to Example 1 of the invention.
• Inventive catalyst β: a carrier β with Pd, the Pd being first applied by the method in Comparative Example 1. This support was additionally treated according to Example 1 of the invention.

The individual embodiments the catalysts of the invention in contrast to the comparative catalysts are in overview shown in Table 1.

Comparative Example 1 Preparation of a Comparative Catalyst V1

The starting material was a support α, to which no catalytically active material had yet been applied. This carrier α was first annealed at 950 ° C in air. The support α was then impregnated with a Pd (NO ₃ ) ₂ solution having a Pd content of 0.13% by weight, based on the support α. The impregnation volume corresponded to 95 based on the water absorption of the carrier α. The moist catalyst was then dried at 120 ° C to a residual moisture content of 0.2 wt .-% based on the catalyst. 1 shows a TEM bright field recording in review of such a catalyst. A FEI-Tecnai F20 from the manufacturer FEI, Holland was used as the measuring device for such a field emission source TEM.

The Fixation of the catalyst was carried out by embedding in synthetic resin. The ultrathin cuts (floated on water) with a microtome Leica Ultracut made by the manufacturer Leica.

The Verification of the catalytically active material was carried out by EDXS (Energy Dispersive X-Ray Spectroscopy). An EDXS is particular suitable for an atomic number greater than 7.

Pd particles with a diameter of 1 nm to 3 nm were observed. Pd particles with a diameter of up to 8 nm were observed very sporadically. The 1 thus shows a monomodal distribution of the particles of the catalytically active material.

Comparative Example 2: selectivity of the comparative catalyst V2 after a load

Of the Comparative Catalyst V2 was prepared according to Comparative Example 1. The comparative catalyst V2 was more than 50 days in a large scale Plant for the dehydration of TCMH to TMP at a feed of 0.12 kg TMCH per liter of catalyst per hour in use. This comparative catalyst V2 became 450 ° C in 2 h heated and for 5 h at 450 ° C annealed. It became an activity test according to the example of the invention 4 performed. The TMP selectivity was 89.8%.

Comparative Example 3 Preparation of a Comparative Catalyst V3

A support β was impregnated with a Pd (NO ₃ ) ₂ solution having a Pd content of 0.13% by weight based on the support β. The comparative catalyst V3 was heated to 120 ° C (2.3 ° C / min). This temperature was held for 6 h. The comparative catalyst V3 was then heated to 450 ° C (2.6 ° C / min) and calcined for 135 min at this temperature.

Comparative Example 4 Producing a higher loaded comparative catalyst V4

A carrier α was heated in 2 h in air at 900 ° C and calcined at 900 ° C for a further 2 h. This support α was impregnated after cooling with a Pd (NO ₃ ) ₂ solution having a Pd content of 0.26 wt .-% (V4.1). Another support α was also soaked after cooling with a Pd (NO ₃ ) ₂ solution having a Pd content of 0.52 wt% (V 4.2). The wt .-% information refers to the carrier α. The impregnation volume corresponded to 95% based on the water absorption of the carrier α. The wet comparative catalysts V4 were then dried with slight warming in a small stream of air and thereby constantly rotated. The comparative catalysts V4 were then dried for 2 h at 120 ° C, heated to 350 ° C in 2 h and annealed for a further 4 h at this temperature.

Inventive example 1: Inventive catalyst α1

A comparative catalyst 1 was heated in 2 h in air at 900 ° C and calcined at 900 ° C for a further 2 h. After cooling, the catalyst thus obtained was impregnated with a Pd (NO ₃ ) ₂ solution having a Pd content of 0.13% by weight, based on the carrier α. The impregnation volume corresponded to 95% based on the water absorption of the carrier α. The catalyst so impregnated was then dried with gentle heating (at 40 to 50 ° C for 10 min) in a gentle stream of air and thereby rotated constantly. Thereafter, the catalyst was dried for 2 h at 120 ° C, heated to 350 ° C in 2 h and annealed for a further 4 h at this temperature.

2 shows the TEM image of a catalyst according to the invention α1. The TEM image was prepared as described in Example 1.

It were homogeneously distributed, crystalline Pd particles with a diameter from about 1 nm to 5 nm and Pd particles with a diameter of 40 nm to 80 nm can be seen. It is a fraction of the larger particles of the catalytically active material. Furthermore, a faction to see the smaller particle of the catalytically active material. The catalyst of the invention α1 thus shows a bimodal distribution of the particles of the catalytically active material.

Example 2: Pd content, Pd surface and size distribution regenerated by the invention Catalysts α2 to α8.

A comparative catalyst V1 was used for longer than 50 days in a large-scale plant for the dehydrogenation of TMCH to TMP in use 0.12 kg TMCH per liter of catalyst per hour. This catalyst was then annealed according to the inventive method of Example 1 and impregnated with Pd (NO ₃ ) ₂ solution. The annealing and subsequent soaking was repeated a total of 7 times on the same catalyst. A sample for measurement was retained after each annealing and after each further impregnation (regenerated catalysts α2 to α8 according to the invention). The measurement results after each annealing and after each subsequent impregnation are shown in Table 2.

The metal surfaces of the catalysts according to the invention and of the comparative experiment were determined by CO chemisorption according to DIN 66136-3. The DIN 66136-3 is intended for Chemi sorption with respect to the metals platinum and copper applicable. DIN 66136-3 is applied to Pd in the context of the present invention. The chemisorption is carried out with a single Anaylsegas. This analysis gas was CO. It was the so-called CO chemisorption. Helium was used as carrier gas for the CO. A comparison of the thermal conductivity detector signal of an injection (loop) with the signal of a manually performed injection served as a calibration (gas syringe). The gravimetric control was done by filling the loop with water. This is described in point 3.4.1 of DIN 66136-3. The samples were reduced before measurement at 200 ° C for 30 minutes under H ₂ . The temperature lamp was 5 ° C / min. He was then rinsed with He for 30 min and then measured under He at 35 ° C. The only annealed (and not soaked) material had only a very small surface and thus a low dispersity. In the context of the present invention, dispersity is to be understood as meaning the percentage of those Pd atoms of a catalyst according to the invention which are located on the surface of the Pd particles, based on the total Pd amount of a catalyst according to the invention.

The diameter of the individual Pd particles was calculated from the dispersity according to Anderson (Anderson, JR, Structure of Metallic Catalysts, Academic Press, London 1975, p. It was assumed that the Pd particles are purely spherical particles.
D _Pd = N / total number of Pd atoms in the Pd particles

N is the number of Pd atoms on the surface of a Pd particle. N becomes determined by the CO absorption amount measured in CO chemisorption per g of catalyst.

V_Pd

effektives Volumen eines Pd-Atoms in einem Pd-Partikel

a_Pd

effektive Fläche eines Pd-Atoms, welches sich an der Oberfläche eines Pd-Partikels befindet

D_Pd

Dispersität bezogen auf die letzte Tränkung mit Pd, siehe Tabelle 2 zum Beispiel 1.

d_Pd

Durchmesser

The calculation of the mean diameter of the particles of the catalytically active material was carried out according to Anderson with the following formula: d Pd = 6 · (V Pd / a Pd ) · (1 / D Pd )

V _Pd

effective volume of a Pd atom in a Pd particle

a _pd

effective area of a Pd atom located on the surface of a Pd particle

D _Pd

Dispersity based on the last impregnation with Pd, see Table 2 for example 1.

d _Pd

diameter

a _Pd was assumed to be 1.27 · 10 ¹⁹ atoms per m ² according to Anderson p. 296. V _{Pd is} calculated according to the formula: V Pd = Molar mass of Pd / (density of Pd · Avogadro constant)

The calculated value of 62 nm was determined by the TEM image in 2 confirmed large Pd particles with a diameter of 40 nm to 80 nm.

The subsequent application of the catalytically active material by the post-soak increased the measured metal surface by an order of magnitude. This increase in metal surface was due to the post-soaking Pd. Table 1 shows the "total" dispersity, which relates to the total Pd amount of a catalyst according to the invention: Table 1 also shows the "post-saturation" dispersity, which relates only to the impregnated amount of Pd of a catalyst according to the invention. In each case, 0.13% by weight of Pd, based on the catalyst material, was impregnated. The measured metal surface of the Pd remains approximately the same for the subsequent impregnation and annealing steps. The calculated from the dispersity "Nachtränkung" diameter of the Pd particles of a catalyst according to the invention confirmed in 2 found smaller Pd particles with a diameter of about 1 nm to 5 nm.

Example 3: Production a catalyst according to the invention β with a Carrier β

A comparative catalyst V3 with a Pd content of 1 wt .-% based on the support β was heated in 2 h in air at 900 ° C and calcined at 900 ° C for a further 2 h. The catalyst thus obtained, after cooling, was impregnated with a Pd (NO ₃ ) ₂ solution having a Pd content of 1% by weight, based on the support β. The impregnation volume corresponded to 95% of the water absorption of the carrier β. The moist catalyst β was then dried with gentle heating in a gentle stream of air. This catalyst was then dried for 2 h at 120 ° C, heated to 450 ° C in 127 min and annealed for a further 135 min at this temperature.

Example 4: TMP selectivity of a Inventive catalyst α1 and a Comparative catalyst V1 after a load

A comparative catalyst V1 and a catalyst according to the invention α1 were tested in a tubular reactor with an inner diameter of 21 mm on the respective activity with respect to the TMCH dehydrogenation. 35 ml of the catalyst was placed in a tube reactor and activated for 2 h at 250 ° C under pure H ₂ . The TMCH dosage was then switched on at normal pressure and 300 ° C and set to 30 ml / h. The receiver flask for the product collection was changed after a break-in period of 1 h and the formed reaction product, TMP, collected for one hour, then weighed and analyzed for the TMCH, anone and TMP content (sample "before loading"). The amount of feed was then increased to twice the value for one load run after one hour each time and the original piston for the product collection was changed, and after two times the load was increased, the initial load was continued for another hour ("after load" sample). Product quality before and after this load was compared. The inventive catalyst α1 showed a TMCH selectivity of 97.2% before loading and 96.2% after loading. Comparative catalyst V1 achieved only TMP selectivity of 93.9% before load and 91.9% after load under the same experimental conditions. TMP selectivity was measured by a Hewlett-Packard HP 5890 Siries 2 gas chromatograph flow injection method.

Table 3: TMP selectivity of a comparative catalyst V1 and a catalyst according to the invention α1 before and after the loading described in Example 4.

Example 5: TMP selectivity of the catalysts according to the invention α2 to α8

The regenerated according to the invention Catalysts α2 were up to α8 subjected to the test described in Example 4. Table 2 shows the results obtained.

The TMP selectivity took in all inventively regenerated Catalysts by 1 to 2% after the load driving off. Another one Coagulating the Pd and another application of the Pd posed the original catalytic activity a catalyst according to the invention come back. The repeated coagulation and the repeated further Application of the catalytically active material led to a successive increase the Pd concentration. The catalytic performance, however, surprisingly remained essentially undisturbed. Comparative catalysts V4,1 and V4,2 were not tempered. Comparative catalysts V4.1 and V4.2 showed significantly greater TMP selectivity drops in comparison regenerated according to the invention Catalysts with the same Pd content (inventive catalysts α2 and α4).

Example 6: cyclohexanone dehydrogenation activity of a catalyst according to the invention and a comparative catalyst

One Comparative catalyst V1 and a catalyst according to the invention were α1 in the apparatus of Example 4 according to the invention in terms of their activity dehydrogenation of cyclohexanone to phenol. All parameters (Pressure, temperature, H2-current, reduction) except the set feed loads were identical to the conditions in the example of the invention 4. In contrast to Example 4 of the invention was in this Example: the feed load is halved in 2 steps. Subsequently was the attempt with the original one Burden completed. Each load was held for 1 hour. table Figure 4 shows the phenol and cyclohexanone concentrations of the dehydrogenation product as a function of catalyst loading.

Table 4: Results of cyclohexanone dehydrogenation experiments for a comparative catalyst V1 and for a catalyst according to the invention α1

Example 7: Catalytic Performance of a catalyst according to the invention β and a Comparative catalyst V3 for the dehydrogenation of 3-MPIP to 3-PIC.

The comparative catalyst V3 and the catalyst of the invention β were investigated for the dehydrogenation of 3-MPIP to 3-PIC. For this purpose, 100 ml of the respective catalyst was charged to a reactor. This was followed by activation for 4 h at 100 ° C. in a 20% by volume H ₂ (in N ₂ ) atmosphere and then at 200 ° C. under pure H ₂ for 3 h. Subsequently, at normal pressure and 265 ° C, the 3-MPIP dosage was turned on and set to 30 ml / h. An additional 4 l / h of H ₂ and 16 l / h of N _{2 were passed} over the catalyst bed.

To a break-in of 1 h, the original flask was changed and the reaction product formed, 3-PIC, collected for one hour, then weighed and on the 3 MPIP and 3-PIC content analyzed. For a load ride was in the further course after one hour, the 3-MPIP feed amount increased to twice the value and the template changed. After increasing the load twice, the initial Burden for drove another hour ("after Load ") and the product quality with the first sample ("vor Load "). The catalyst β of the invention gave a 3-PIC yield of 99.3% before loading and 99.2% after the burden. Comparative catalyst V3 reached the same Experimental conditions a 3-PIC yield of 99.5% before loading. The 3-PIC yield dropped to 98.5% after loading.

TABLE 5 3-PIC selectivity of a comparative catalyst V3 and of a catalyst according to the invention before and after the loading described in Example 7.

Example 8: Residual selectivity of a Inventive catalyst α1 and a Comparative catalyst V1 after loading

Of the Inventive catalyst α1 and the Comparative catalyst V1 were successively in a production plant used in two production campaigns. The reactor temperature was constant at 306 ± 2 ° C The feed with TMCH was 700 to 800 kg / h. After 50 days the following results were obtained. The comparative catalyst V1 led at a production rate of 720 t to a residual selectivity of 87.4 %. The catalyst according to the invention α1 introduced a production rate of 754 t at a residual selectivity of 96.6 %.

Claims (12)

A catalyst comprising a support and a catalytically active material, wherein a) the particles of the catalytically active material are bimodal size-distributed and b) the fraction of the larger particles of the catalytically active material and the fraction of the smaller particles of the catalytically active material are uniformly mixed in the catalytically active layer of the catalyst and c) the catalytically active material is 50 wt .-% or less based on the catalyst. Catalyst according to claim 1, wherein the fraction the larger particles of the catalytically active material has a mean diameter in Height of Ten times or more of the mean diameter of the fraction of having smaller particles of the catalytically active material. Catalyst according to claims 1 and 2, wherein the particles of the catalytically active material is spheroidal with a ratio of smallest to largest diameter of a particle of 0.5 to 1. Catalyst according to claims 1 to 3, wherein the catalytic active material is Pd. Catalyst according to claims 1 to 4, wherein the carrier is α-Al ₂ O ₃ or ZrO ₂ . Catalyst according to claims 1 to 5, wherein the catalyst is a shell catalyst. Process for the preparation of a catalyst according to claims 1 to 6, comprising a) a first step, one on one carrier catalytically active material coagulated on the carrier will and b) a further step in which another catalytically active material on the carrier is applied. Process for the regeneration of a deactivated catalyst according to claims 1 to 6, comprising a) a first step, one on one carrier is coagulated catalytically active material and b) another step, in which another catalytically active Material on the carrier is applied. Method according to claims 7 and 8, wherein the steps a) and b) take place several times. Catalyst according to claims 1 to 6, characterized in that it produces or regenerates is obtained by a method comprising a) a first step, one on a carrier catalytically active material coagulated on the carrier will and b) a further step in which another catalytically active material on the carrier is applied. Use of a catalyst according to claims 1 to 6 or 10 for the dehydrogenation of 2,3,6-trimethyl-2-cyclohexene-1-one to 2,3,6-trimethylphenol. Use of a catalyst gem. to claims 1 to 6 or 10 for the dehydrogenation of 3-methylpiperidine to 3-picoline.