WO2007009904A1

WO2007009904A1 - Catalyst with bimodal distribution of the particles of the catalytically active material, method for the production thereof and for the regeneration thereof and the use of the catalyst

Info

Publication number: WO2007009904A1
Application number: PCT/EP2006/064073
Authority: WO
Inventors: Stefan Kotrel; Peter Lechtken; Gerd Rohrbacher
Original assignee: Basf Aktiengesellschaft
Priority date: 2005-07-18
Filing date: 2006-07-11
Publication date: 2007-01-25
Also published as: DE102005034004A1; EP1907120A1; CN101282786A

Abstract

The present invention relates to a catalyst, containing a carrier and a catalytically active material. The particles of the catalytically active material are distributed bimodally according to size. The fraction of larger particles of the catalytically active material and the fraction of smaller particles of the catalytically active material are evenly mixed in the catalytically active layer of the catalyst. The catalytically active materials amounts to 50 wt. % or less relative to the catalyst. The invention also relates to a method for producing or for regenerating a catalyst such as that claimed. In a first step of the method, a catalytically active material located on a carrier is coagulated. In a further step, an additional catalytically active material is applied to the carrier. The invention also relates to the use of the catalytically active material for the dehydrogenation of five or six-membered carbon-containing molecular rings to produce aromatic compounds.

Description

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.

description

The subject of the present invention is a catalyst containing a carrier and a catalytically active material. The particles of the catalytically active material are bimodal size distributed. 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.

The invention further relates to a process for the preparation or regeneration of a catalyst according to the invention. A catalytically active material located on a support is coagulated in a first step. In a further step, a further catalytically active material is applied to the carrier.

The invention further relates to the use of the catalytically active material for the dehydrogenation of five- or six-membered carbon-containing molecule rings to aromatic compounds.

Catalysts with a bimodal size distribution of the catalytically active material are known, for example Sayari et al. (Journal of Electron Spectroscopy and Related Phenomena, 58 (4) (1992) 285 to 298). Sayari et al. but suggest that a bimodal size distribution with a fraction of the smaller particles of the catalytically active material, which is homogeneously distributed over the carrier, and a fraction of the larger particles of the catalytically active material, which are arranged only on the outer surface of the carrier material 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 the catalytically active Material. The outside on the nanotubes arranged palladium particles have a diameter of 20 to 28 nm. On the other hand, the smaller palladium particles arranged on the inside of the nanotube have a mean diameter of approximately 2.6 nm. Thus, there is no uniform distribution of the bimodal distributed palladium particles on the support. Tsang et al. The good catalytic activity is attributed to the smaller palladium particles located on the inside of the nanotube. 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 sweep ratio for optimum catalytic activity. Instead, a monomodal size distribution of the metal-coated catalytically active material is recommended.

It is also known that a deactivated catalyst can be regenerated. It is generally endeavored to prevent coagulation of the catalytically active material, for example by a glow of the carrier, since the coagulated particles of the catalytically active material in principle show a poorer catalytic activity.

It was an object of the present invention to provide a catalyst having a long service life, a high catalytic activity and a high desired selectivity. The support of the catalyst should continue to have a 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 material should be possible.

This object is achieved according to the invention by providing the catalyst described at the outset and a process for the preparation or regeneration of the catalyst according to the invention.

The catalytically active material may be a substance of Groups 7 to 11 of the Periodic Table. The periodic table according to IUPAC applies at the time of February 4, 2005. This means in particular the elements Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au. In a particularly preferred embodiment, the catalytically active material is palladium. The catalytically active material can be applied to the support in all forms. The application is possible in metallic or in elementary form, for 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 bound 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 can be applied to the support, for example by the method described in DE 19 533 665.

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 from 5% by weight to 20% by weight, preferably from 10% by weight to 15% by weight, particularly preferably from 11% by weight to 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, based on the carrier.

The impregnation can also be carried out with other Pd salts or complexes known to the person 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 present in the active form on the carrier. This active form depends on the particular catalytically active material.

The catalytically active material is generally active in the reduced form. The catalytically active material must therefore be reduced in the case of covalently or electrostatically bonded forms of the catalytically active material, as a rule.

This reduction can, for example, by heat treatment under pure H ₂ , for example at Pd (NO ₃ ) 2 at 230 ⁰ C to 300 ⁰ C, preferably at 240 ⁰ C to 260 ⁰ C for 2 to 3 h, preferably for 1 h to 3 h respectively. The reduction is also possible by CO, hydrazine and all other reduction methods known in the art.

Only a catalytically active material, for example Pd, can be applied to the carrier. However, it is also possible for a plurality of catalytically active elements, for example two, three or four different elements, to be applied in covalent or in electrostatically bound or in elemental form to the support.

The catalytically active material is generally present in such amounts as to ensure catalytic activity. This depends on the respective catalytic active material for example in Pd usually at a content of the catalytically active material of 0.1 wt .-% or more preferably at 0.3 wt .-% and particularly preferably at 0.5 wt .-% or more based on the Catalyst the case.

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

As carriers, in principle all substances which are inert with respect to the reaction to be catalyzed are possible. A carrier according to the invention is generally a solid that is heat stable up to the sintering temperature of the catalytically active material.

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 just 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 0C-Al 2 O 3 or ZrO 2.

An α-AbCv support according to the invention is preferably prepared according to DE 19 533 665. 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 of the invention, the catalyst is formed as a shell catalyst. In the context of the present invention, shell-type catalyst is to be understood as meaning a catalyst in which the catalytically active material occurs only in the outer layer. This outer layer is understood to mean the outer 600 μm or less, preferably the outer 400 μm or less and in particular the outer 200 μm of the carrier.

A bimodal size distribution of the particles of the catalytically active material is present when the mean diameters of the particles of the catalytically active material are distributed such that they form two maximas.

The measurement of this Maximas takes place in the case of noble metals of group 10 as a catalytically active material, such as Pd, preferably by a CO Chemisorption according to DIN 66136-3. A spectrum obtained by CO chemisorption leads to dispersity according to JR Anderson (Structure of Metallic Catalysts, London, 1975, pp. 358-364). The average diameters of the particles of the catalytically active material can also be calculated from the dispersity according to JR Anderson. The dispersity describes the percentage of the atoms that are located on the surface of the particles of the catalytically active material, based on the total number of atoms of the catalytically active material, which are on the support of a catalyst according to the invention.

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 advisable to reduce the catalyst before the CO chemisorption at 200 ⁰ C for 30 min under hfe. 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 fraction of the smaller particles of the catalytically active material of a catalyst according to the invention can be determined, for example, in particular in the case of Pd as the catalytically active material, as follows. The catalytically active material is first applied to the support, for example in the manner described in Comparative Example 1. This is followed by a CO chemisorption measurement. This CO chemisorption measurement gives the mean diameter and dispersity of the particles of the fraction of the smaller particles of the catalytically active material. Such a value can be seen, for example, in Table 2 for Inventive Example 1 on the catalysis analyzers α2 to αδ. The proportion of the impregnated catalytically active material which falls on the particles of the fraction of the larger particles of the catalytically active material in the application of a further catalytically active material was neglected in the calculation of the average diameter and the dispersion, since this area in the As a rule, only 10% of the area of the particles makes up the fraction of the smaller particles of the catalytically active material. This can be seen in Table 2, column Dispersity, sub-column Pd metal surface.

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 example given in Example 1 The method of calcination leads to 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 two maximas determined by the CO chemisorption described above can be confirmed, for example, by a transmission electron micrograph. In general, a TEM bright field image is made in review. As a measuring device for a TEM with field emission source, for example, a FEI-Tecnai F20 of the manufacturer FEI, Holland is suitable.

The fixation of the catalyst can take place by embedding in synthetic resin. The ultrathin sections (floated on water) can be made with a Microtom Leica Ultracut from the manufacturer Leica.

The verification of the catalytically active material can be carried out by an EDXS (Energy Dispersive X-Ray Spectroscopy). The EDXS is particularly suitable for a core charge of greater than 7. HAADF STEM images (High Angle Annular Dark Field Scanning TEM) can be made complementary to the TEM images for better localization of the particles of the catalytically active material.

According to the invention, the transmission electron micrographs show two different fractions of the particles of the catalytically active material.

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

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

In a particular embodiment, the dispersity of the particles of the smaller fraction of the catalytically active material is 10% or more, preferably 15% or more and particularly preferably 20% or more and in particular 25% or more. The dispersity of the particles of 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. In the context of the present invention, this is also applied correspondingly to Pd. 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 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 ⁰ C for 30 min under hfe. 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:

Dpd = 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 is determined by the CO absorption amount per g of catalyst measured in CO chemisorption.

The calculation of the mean diameter of the particles of the catalytically active material was carried out according to Anderson with the following formula:

dpd = 6 * (vpd / a _Pd ) * (1 / Dpd)

Vpd effective volume of a Pd atom in a Pd particle apd effective area of a Pd atom located on the surface of a Pd particle Dpd dispersity with respect to the last impregnation with Pd, see Table 2 for example

1. dpd diameter

According to Anderson p. 296, apd was assumed to be 1.27 * 10 ¹⁹ atoms per m ² . vpd calculates according to the formula:

vpd = molecular weight of Pd / (density of Pd * Avogadro constant)

In a particular embodiment, the average diameter of the fraction of the larger particles of the catalytically active material is ten times or more of the mean diameter of the fraction of the smaller particles of the catalytically active material. The measurement of this diameter of the fraction of the smaller particles of the catalytically active material takes place after the same CO chemisorption and after the same evaluation, after which the measurement of the Maximas took place.

In a further embodiment, the fraction of the larger particles and the fraction of the smaller particles of the catalytically active material are monodisperse. In the context of the present invention, monodisperse means a small deviation from the mean value of the diameters within a fraction of the particles of the catalytically active material. A low deviation is generally present when the average diameter of the particles of the catalytically active material measured by CO chemisorption is 20% or less, preferably 15% or less, and more preferably 10% or less and in particular 5% or less exceeded or by 20% or less, preferably by 15% or less and more preferably by 10% or less and in particular by 5% or less.

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 can be seen, for example, in Example 1, FIG.

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

A uniform mixing of the fractions of the smaller particles and the larger particles of the catalytically active material is understood in the context of the present invention that the particles have no size-dependent preferred arrangement. The particle size of the catalytically active material thus generally does not determine the arrangement on the carrier. In general, therefore, no surfaces can be observed on the surface of the support on which only particles of the fraction of the larger particles of the catalytically active material occur. In general, no surfaces can be observed on the surface of the carrier on which only particles of the fraction of the smaller particles of the catalytically active material occur. Of course, a natural limit is the surface structure of the catalyst. The distribution is therefore generally uniform considering the physical limits imposed by the surface structure of the carrier. In a preferred embodiment, the physical structure of the carrier allows a uniform distribution of the particles 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. This may not be the case for zeolites or nanotubes, for example.

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, when using the transmission electron microscopy described above to obtain a distribution of the particles of the catalytically active material as in FIG. For example, Figure 2 shows that the particles of 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 material or only the larger particles of the catalytically active material occur.

Another object of the present invention is a process for the preparation of a catalyst according to the invention. In this case, a catalytically active material located on a carrier is coagulated on the carrier in a first step. In a second step, a catalytically active material is applied to this carrier with the coagulated catalytically active material.

In a particularly preferred embodiment of the present invention, coagulation takes place by sintering the catalytically active material supported on a support. By sintering is meant 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 also be carried out at elevated temperatures.

A coagulation of the particles of the catalytically active material by sintering of the catalytically active material is generally carried out until the particles of the catalytically active material are coagulated. The duration of sintering is generally dependent on the type of catalytically active material. For example, in the case of palladium as a catalytically active material, the particles can also be coagulated by calcining, for example for 2 hours, at temperatures of 900 ^° C. or more on a support. However, it can also be sintered shorter or longer depending on the catalytically active material.

The carrier used is preferably an α-AbOs carrier prepared according to DE 19 533 665, 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 preparation teach either DE 19 533 468 or DE 19 533 665. The removal of the polymeric binder can be carried out either by calcination or by debindering with other oxidants such as nitric acid.

For the production of such an α-AbOs CIM carrier, for example, OC-Al2O3 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 kneaded with a polymer former, melted and over a Schwerwalzene extruder to a granulate having the size of 1 mm to 10 mm, preferably processed 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 support is characterized by a particularly narrow pore radius distribution.

The finished carrier can then in particular be impregnated with a palladium salt solution, particularly preferably with Pd (NO 3) 2. The Pd content of the Pd (NC "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, particularly preferably 0.12% by weight. -% to 0.14 wt .-% based on the catalyst of the invention.

The soaked catalyst can then be dried. The drying can be carried out with a variety of suitable drying methods. The drying is preferably carried out gently for the carrier. This is the case, for example, during drying with gentle heating in a weak stream of air with constant rotation. The residual moisture of the carrier is generally 1% by weight or less based on the carrier α.

Sintering of the catalytically active material on the carrier can lead to stresses and cracks in the carrier. These stresses and cracks can be removed, for example, by annealing following drying. Annealing may also serve to decompose the nitrates to the corresponding oxides. Annealing means heating the catalyst for an extended period of time. The temperature profile during annealing is preferably determined as a function of the material of the carrier and of the catalytically active material of a catalyst according to the invention.

A produced according to DE 19533665 α subscriptions CIM support which has been preferably impregnated with palladium salt solution, for example, heated in 2 hours to 350 ⁰ C and are annealed for a further 4 h at this temperature. In principle, another catalytically active material can be any catalytically active material. The catalytically active materials listed above are preferably used. A particularly preferred catalytically active material is Pd.

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

Coagulation of the catalytically active material and the subsequent application of a catalytically active material can take place once. However, the coagulation and the subsequent application of the catalytically active material can also take place two, three, four, five, six, seven, eight, nine, or ten times or more than ten times. In this case, the content of the catalytically active material of the carrier increases. Coagulation and application of another catalytically active material is generally possible until the catalytically active material is present in economically unviable amounts in the catalyst.

The process according to the invention can be carried out with a fresh catalyst. In the context of the present invention, a fresh catalyst is to be understood as meaning, in particular, a catalyst which has not yet been used for catalysis. It is generally a 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 has been prepared, for example, by the process described in DE 19 533 665, has been impregnated with palladium on an industrial scale and, for example, for more than 50 days in a large-scale plant at a feed load of 0.12 kg 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 for the desired reaction product of 80% or less.

According to the invention, such a deactivated catalyst is regenerated by coagulating the catalytically active material present on the carrier and, in a further step, by applying a further catalytically active material to the carrier. The coagulation is carried out, for example, by a heat treatment at the sintering temperature of the catalytically active material of a catalyst according to the invention. The sintering is usually carried out over such a period of time, which allows coagulation of the particles of the catalytically active material.

A deactivated α-AbCvTräger, which was prepared according to DE 19 533 665, can be regenerated by the annealing at an unusually high temperature of 900 ⁰ C over a period of 2 h. Another catalytically active material is applied in a further step on the carrier thus regenerated.

In this case, regeneration is possible according to the invention. But it can also take several regenerations. A deactivated catalyst can be regenerated by the process according to the invention and then used during operation until a further deactivation is carried out. Then, the catalyst deactivated for the second time can be regenerated by the method according to the invention, so that it can be used a second time. There are two, three, four, five, six, seven, eight, nine, but also ten or more regeneration steps possible.

A catalyst prepared according to DE 19 533 665 and regenerated or treated by the process according to the invention surprisingly shows no further losses in the catalytic performance in a further embodiment. The catalytic performance in this context primarily describes the catalytic performance via a stress test, as described in Example 4 according to 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. A catalyst prepared according to the process of the invention and prepared according to the process of the invention can, for example, in the dehydrogenation of 2,3,6-trimethyl-2-cyclohexene-1-one, have a selectivity to 2,3,6-trimethylphenol of 98%. or more.

This surprisingly good catalytic performance of an inventively regenerated catalyst is still present in a further embodiment, even after a load on the catalyst. The catalytic performance is generally not significantly degraded by a load compared to a fresh catalyst. The carrier regenerated according to the invention thus generally shows no significant lent other aging phenomena or even a better aging behavior than a fresh catalyst.

This good catalytic performance of the inventively regenerated catalyst is particularly surprising because after the classic Regeneriermethode with a removal of the carbonaceous deposits by 02-containing regeneration gases at 400 ⁰ C to 500 ⁰ 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 regenerating a deactivated catalyst is generally inexpensive, since only a few process steps are used. Furthermore, additional chemical substances, such as solvents, are usually 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 case of the feed quantity described above. A catalyst regenerated according to the invention or prepared according to DE 19 533 665 can, for example, have a 2,3,6-trimethylphenol selectivity in the 2,3,6-trimethyl-2-cyclohexene-1-one hydrogenation of 95% or more in a Have a service life of 50 days.

This long service life of a catalyst regenerated according to the invention can be achieved in another embodiment without a significant drop in the catalytic performance.

In a further embodiment of the present invention, in particular in the form of coagulation of the particles of the catalytically active material by annealing or sintering, the catalyst according to the invention exhibits reduced abrasion. A reduced abrasion is understood to mean the dust produced by a mechanical movement. Abrasion tendency of a catalyst is generally measured in a rotary drum test according to ASTM 4058.

The inventive method allows in a further embodiment, a cost-effective production of a catalyst according to the invention. The same carrier can be used several times. For example, one, two, three, four, five, six, seven, eight, nine, but also ten or more regeneration cycles are possible. The process according to the invention of preparing or regenerating a catalyst according to the invention can enable a reuse of a catalyst of a desired quality. The method according to the invention thus makes, in a further embodiment, independent of the variations in quality of a catalyst preparation, for example according to DE 19 533 665.

The process according to the invention furthermore makes possible a cost-effective recovery of the catalytically active material. A repeated regeneration of a catalyst according to the invention leads to an enrichment of the catalytically active material on the support. Such enriched catalytically active material can then be recovered inexpensively.

It is a further object of the present invention to provide a catalyst which is available or can be regenerated by coagulation in a first step, a catalytically active material on a carrier on the carrier and another catalytically active material in a further step on this carrier is applied.

Another object of the present invention relates to the use of a catalyst according to the invention. A catalyst according to the invention or a catalyst prepared or regenerated by the process according to the invention can generally be used as a function of the catalytically active material and of the carrier for a large number of reaction types.

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

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

In a particular embodiment, a catalyst prepared in particular according to DE 19 533 665 and prepared or regenerated by the process according to the invention is used for the preparation of substituted aromatics and heteroaromatics by the catalytic dehydrogenation of non-aromatic, six-membered rings. A catalyst prepared in particular according to DE 19 533 665 and prepared or regenerated by the process according to the invention can be used for the dehydrogenation of 2,3,6-trimethyl-2-cyclohexene-1-one to 2,3,6-trimethylphenol.

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

Examples

The following abbreviations are used:

TMP 2,3,6-trimethylphenol TMCH 2,3,6-trimethyl-2-cyclohexene-1-one

3-MPIP 3-methylpiperidine

3-PIC 3-picoline

TEM transmission electron microscope

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-AbCvTräger 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 a catalytically active material in all experiments

Comparative Catalysts V1 to V4: a carrier α with Pd, wherein the Pd was first applied to the support α by the method in Comparative Example 1.

Catalysts according to the invention α1 to α8: a carrier α with Pd, wherein 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 of the catalysts according to the invention in contrast to the comparative catalysts are shown in overview in Table 1.

Table 1: Overview of the comparative catalysts and the catalysts of the invention

Description First application Subsequent coagulation of the Pd of the support from Pd to and re-application of Pd:

Catalyst Comparative Number of cycles

For comparison

Comp. 1 V1 α 1 -

Comp. 2 V2 α 1 -

Comp. 3 V3 ß 3 -

Comp. 4 V4 α 4 -

According to the invention

Ex. 1 α1 α 1 1

Ex. 2 o2 α 1 1

Ex. 2 α3 α 1 2

Ex. 2 oc4 α 1 3

Ex. 2 α5 α 1 4

Ex. 2 α6 α 1 5

Ex. 2 α7 α 1 6

Ex. 2 α8 α 1 7

Ex. 3 ß ß 1 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 ⁰ 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 ⁰ C to a residual moisture content of 0.2 wt .-% based on the catalyst. Figure 1 shows a TEM brightfield image 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 sections (floated on water) were made with a microtome Leica Ultracut manufacturer Leica.

The verification of the catalytically active material was carried out by EDXS (Energy Dispersive X-Ray Spectroscopy). An EDXS is particularly 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. Figure 1 thus shows a monomodal distribution of the particles of the catalytically active material.

Comparative Example 2: Selectivity of Comparative Catalyst V 2 After Loading Comparative Catalyst C 2 was prepared according to Comparative Example 1. Comparative catalyst V2 was used for more than 50 days in a large-scale plant for the dehydrogenation of TCMH to TMP at a feed of 0.12 kg TMCH per liter of catalyst per hour. This comparative catalyst V2 was heated in 2 hours to 450 ⁰ C and annealed for 5 hours at 450 ⁰ C. An activity test according to Inventive Example 4 was carried out. The TMP selectivity was 89.8%.

Comparative Example 3 Preparation of a Comparative Catalyst V3

A support was covered with a ß Pd (NC "3) 2 solution having a Pd content of 0.13 wt .-% to the carrier impregnated ß The comparative catalyst was V3. Doing to 120 ⁰ C (2.3 ° C / heated min). this temperature was maintained for 6 h. The comparative catalyst V3 was then heated to 450 ⁰ C (2.6 ° C / min) and calcined for 135 min at this temperature. Comparative Example 4: Preparation of a Comparative Catalyst V4 Which Has a Larger Loading

A support α was heated in 2 h in air at 900 ⁰ C and calcined at 900 ⁰ C for a further 2 h. This support α was impregnated after cooling with a Pd (NO3) 2 solution having a Pd content of 0.26 wt .-% (V4.1). Another carrier α was also soaked after cooling with a Pd (NO3) 2 solution having a Pd content of 0.52 wt% (V4.2). 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 ⁰ C, heated in 2 h at 350 ⁰ C 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 ⁰ C and calcined at 900 ⁰ 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 thus impregnated was then dried with slight warming (at 40 to 50 ⁰ C for 10 min) in a weak stream of air and thereby constantly rotated. Thereafter, the catalyst was dried for 2 h at 120 ⁰ C, heated in 2 h at 350 ⁰ C and annealed for a further 4 h at this temperature.

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

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

Example 2: Pd content, Pd surface area and size distribution of the catalysts α2 to α8 regenerated according to the invention.

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 by the method of Example 1 according to the invention and impregnated with Pd (NC "3) 2 solution The annealing and subsequent soaking were repeated a total of 7 times on the same catalyst A sample for measurement was taken after each annealing and after every other potions retained (inventively regenerated catalysts α2 to αδ). The measurement results after each annealing and after each subsequent impregnation are shown in Table 2.

Table 2: Pd content, catalytic performance, Pd surface area and average measured by CO chemisorption

Dispersity calculated size of the Pd particles with error estimation of the inventive catalysts α2 to α8 and the comparative catalysts V5, V4,1 and V4,2.

TMP *** - selectivity Pd-

Coagulation + feeds Pd * - dispersity

KataMetal size Pd- Application of content [%] lysaPd solution Before after top- Post- article Catalytic support α H ₂ O Weight total gate 11, 05% Load Impact surface Impregnation [nm] Active material [g] [g] [%] ^** [%]

[g] g ng [m ² / g] [%]

V * 5 Coagulation only 800 - - 0,13 0,01 2 ± 0,035 2 ± 0,04 62 ± 1, 21 o2 1 x 700 8,3 168 0,26 98,2 96,9 0,08 8 ± 0,156 16 ± 0.31 7 ± 0.14 α3 2 x 609 7.2 140 0.39 98.3 96.9 0.11 7 ± 0.136 21 ± 0.41 5 ± 0.10 α4 3 x 508 6.0 112 0.52 98.2 95.7 0.11 5 ± 0.106 22 ± 0.42 5 ± 0.10 α5 4 x 410 4.8 85 0.65 98.2 95.7 0.12 5 ± 0.088 23 ± 0.44 5 ± 0.10 NJ α6 5 x 311 3.7 62 0.78 98.0 96.6 0.12 4 ± 0.076 23 ± 0.45 5 ± 0.09 α7 6 x 212 2.5 42 0.91 98.0 96.0 0.11 3 ± 0.058 21 ± 0.41 5 ± 0.11 α8 7 x 111 1, 3 22 1, 04 98.0 97.0 0.11 3 ± 0.052 21 ± 0.42 5 ± 0.10

V4.1 - 0.26 87.5 96.0

V4.2 - 0.52 96.4 93.7

_* V means comparative experiment. _** The Pd content wt .-% information refers to the carrier α.

TMP means 2, 3, 6-trimethylphenol. The TMP selectivity was measured before a load drive according to Example 4 and after a

Load travel measured according to Example 4 of the invention.

The "total" dispersity describes the percentage of Pd atoms present on the surface of the Pd metal particles, based on the total number of Pd atoms present on the support Proportion of Pd atoms located on the surface of the Pd metal particles, based on the number of Pd atoms that were re-applied to the support by post-soaking.

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 standard DIN 66136-3 is applicable for chemisorption with regard to the metals platinum and copper. DIN 66136-3 is correspondingly applied to Pd in the context of the present invention. The chemisorption is carried out with a single Anayl- segas. 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 ⁰ C for 30 min under hfe. 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.

Dpd = 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 is determined by the CO absorption amount measured in CO chemisorption per g of catalyst.

dpd = 6 * (vpd / a _Pd ) * (1 / Dpd)

Vpd effective volume of a Pd atom in a Pd particle apd effective area of a Pd atom located on the surface of a Pd particle

Dpd dispersity based on the last impregnation with Pd, see Table 2 for example 1. dpd diameter According to Anderson p. 296, apd was assumed to be 1.27 * 10 ¹⁹ atoms per m ² . vpd is calculated according to the formula:

vpd = molecular weight of Pd / (density of Pd * Avogadro constant)

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

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 amount of Pd 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 the found in Figure 2 smaller Pd particles with a diameter of about 1 nm to 5 nm.

Example 3: Preparation of a catalyst β according to the invention with a carrier β

A comparative catalyst V3 with a Pd content of 1 wt .-% based on the support ß was heated in 2 h in air at 900 ⁰ C and calcined at 900 ⁰ 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 1% by weight, based on the support β. The impregnation volume corresponded to 95% of the water absorption of the carrier ß. 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 ⁰ C, heated in 127 min at 450 ⁰ C and annealed for a further 135 min at this temperature.

Example 4: TMP selectivity of a catalyst according to the invention α1 and of a comparative catalyst V1 after a load

A comparative catalyst V1 and a catalyst α1 according to the invention were investigated in a tubular reactor with an inner diameter of 21 mm for the respective activity with respect to the TMCH dehydrogenation. 35 ml of the catalyst was placed in a tubular reactor and activated for 2 h at 250 ⁰ C under pure hfe. The TMCH dosage was then switched on at normal pressure and 300 ⁰ C and on 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 the load and 96.2% after the load. Comparative catalyst V1 achieved only TMP selectivity of 93.9% before loading and 91.9% after loading 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.

TMP selectivity [%] catalyst

Before loading After loading

Comparison V1 93,9 91, 9

According to the invention α1 97.2 96.2

Example 5 TMP Selectivity of the Inventive Catalysts α2 to α8 The catalysts α2 to α8 regenerated according to the invention were subjected to the test described in Example 4. Table 2 shows the results obtained.

The TMP selectivity decreased in all inventively regenerated catalysts by 1 to 2% after the load drive. Re-coagulation of the Pd and further application of the Pd restored the original catalytic activity of a catalyst of the present invention. The repeated coagulation and the repeated further application of the catalytically active material led to a successive increase in the Pd concentration. The catalytic performance, however, surprisingly remained essentially unimpaired. Comparative catalysts V4,1 and V4,2 were not tempered. The comparative catalysts V4.1 and V4.2 showed significantly greater TMP selectivity dips in comparison to the catalysts regenerated according to the invention with the same Pd content (catalysts α2 and α4 according to the invention).

Example 6: Cyclohexanone dehydrogenation activity of a catalyst according to the invention and of a comparative catalyst A comparative catalyst V1 and a catalyst α1 according to the invention were investigated in the apparatus of Inventive Example 4 for their activity with respect to the dehydrogenation of cyclohexanone to the phenol. All parameters (pressure, temperature, H2 flow, reduction) apart from the set feed loads were identical to the conditions in Example 4 according to the invention. In contrast to Example 4 according to the invention, in this example the feed load was halved in two steps. Subsequently, the experiment was completed with the original load. Each load was held for 1 hour. Table 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

Inventive catalysis.

Load, _Λ Comparative catalyst V1 sator αi

Cyclohexanone [kg] / kata-cyclohexanone phenol cyclohexanone phenol lysatorrj] * [h] [%] [%] [%] [%]

1, 12, 15.6, 83.5, 15.6, 83.5

0.56 14.2 84.5 14.7 84.2

0.27 15.2 83.2 16.3 82.3

1, 12 18.8 80.4 20.5 79.1

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 β of the invention 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.

After a run-in period of 1 h, the receiver flask was changed and the formed reaction product, 3-PIC, collected for one hour, then weighed and analyzed for 3-MPIP and 3-PIC content. For a load ride, the 3-MPIP feed quantity was increased to twice the value after one hour and the template changed. After increasing the load twice, the initial load was then run for an additional hour ("after loading") and the product quality compared with the first sample ("before loading"). Of the Inventive catalyst β gave a 3-PIC yield of 99.3% before loading and 99.2% after loading. Comparative catalyst V3 achieved a 3-PIC yield of 99.5% before loading under the same experimental conditions. The 3-PIC yield dropped to 98.5% after loading.

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

3-PIC selectivity [%] catalyst -

Before loading After loading

Comparison V3 99.5 98.5

According to the invention β 99.3 99.2

Example 8: Residual selectivity of a catalyst according to the invention α1 and a comparative catalyst V1 after loading

The inventive catalyst α1 and the comparative catalyst V1 were used in a production plant successively in two production campaigns. The reactor temperature was kept 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 to a residual selectivity of 87.4% at a production rate of 720 l. The catalyst α1 according to the invention led to a residual selectivity of 96.6% at a production rate of 754 l.

Claims

claims

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 uniformly mixed in the catalytically active layer of the catalyst are present and

c) the catalytically active material is 50 wt .-% or less based on the catalyst.

2. A catalyst according to claim 1, wherein the fraction of the larger particles of the catalytically active material has an average diameter equal to ten times or more of the mean diameter of the fraction of the smaller particles of the catalytically active material.

Catalyst according to claims 1 and 2, wherein the particles of the catalytically active material are spheroidal with a ratio of the smallest to the largest diameter of a particle of 0.5 to 1.

4. Catalyst according to claims 1 to 3, wherein the catalytically active material is Pd.

5. Catalyst according to claims 1 to 4, wherein the carrier is Oc-Al ₂ O ₃ or ZrO ₂ .

6. Catalyst according to claims 1 to 5, wherein the catalyst is a shell catalyst.

7. A process for the preparation of a catalyst according to claims 1 to 6, comprising

a) a first step, in which a supported catalytically active material is coagulated on the carrier, and

b) a further step, wherein a further catalytically active material is applied to the carrier.

2 Fig.

8. A process for the regeneration of a deactivated catalyst according to claims 1 to 6, comprising

a) a first step in which a supported catalytically active material is coagulated and

9. The 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 is prepared or regenerated by a process comprising

11. Use of a catalyst according to claims 1 to 6 or 10 for the dehydrogenation of 2,3,6-trimethyl-2-cyclohexen-1-one to 2,3,6-trimethylphenol.

12. Use of a catalyst gem. Claims 1 to 6 or 10 for the dehydrogenation of 3-methylpiperidine to 3-picoline.