DE10226120A1 - Supported catalyst, for an aldol condensation column, has one or more metal oxides as active components to give an increased catalyst activity - Google Patents

Abstract

The supported catalyst has one or more metal oxides as active components on a carrier for aldol condensation. The catalyst carrier is gamma -aluminum oxide. The active components include one or more oxides of rare earth metals. The concentration of the active components is 5-12 wt.% of the catalyst carrier weight. The active component is preferably yttrium oxide or praseodymium oxide. The condensation column packing (1) is composed of packing sheets (2) with straight kinks (5) forming angled kink surfaces (6). Catalyst particles (4) fill the space (3) between neighboring sheets.

Description

The invention relates to a supported catalyst containing one or more Metal oxides as an active component for carrying out an aldol condensation, a column for Carrying out an aldol condensation by reactive distillation using a supported catalyst and a process.

Aldol condensation is known in a known manner as a rule basic catalyzed reaction of a carbonyl component with a methylene component. in this connection the same compound can act as a carbonyl and methylene component at the same time. Are each different compounds as carbonyl or methylene component it is often advantageous to use one of the components in excess, especially in up to a hundredfold excess over the other component.

In addition to homogeneous catalysis in the presence of aqueous alkali or Alkaline earth metal hydroxides are heterogeneous catalysis, for example by metal oxides of lanthanum or the lanthanides.

US 3,578,702 describes the use of oxides of the metals with the Atomic numbers 57 to 71 as an active component on a carrier made of an inert material, for example aluminum oxide, diatomaceous earth or preferably silica gel, the Concentration of the active component in the range of 0.5 to 10 wt .-%, based on the Total weight of the supported catalyst.

In contrast, it was an object of the invention to carry supported catalysts to provide an aldol condensation that are known to supported catalysts through increased catalyst activity or an improved space Mark time yield.

The task is carried out by a supported catalyst containing one or more Metal oxides dissolved as an active component for performing an aldol condensation, wherein the catalyst support is γ-aluminum oxide, the active component is one or more oxides of elements with atomic numbers 39 or 57 to 71 and the concentration of Active component, based on the total weight of the supported catalyst, in Range is 5 to 12 wt .-%.

As a result of extensive screening studies, it was surprisingly found that a significant improvement in catalyst activity while adhering to the above defined conditions is reached.

The supported catalysts according to the invention are preferred for carrying out the Aldol condensation of citral and acetone to pseudo-ionone suitable. Pseudojonon is a important intermediate for vitamin and fragrance production. Will be beneficial Citral to acetone used in a molar ratio of 1 to 2 to 50. Are particularly advantageous Reaction temperatures between 30 and 100 ° C and pressures between 1 and 10 bar absolutely.

It has been found that the appropriate choice of catalyst support is the most Catalyst activity significantly influenced. With γ-alumina as the catalyst support it became clear get improved space-time yields.

In a preferred embodiment, the geometry of the catalyst carrier is determined in such a way that the ratio of the outer surface to the volume is in the range from 0.5 to 10 mm ^-1 , preferably in the range from 1 to 5 mm ^-1 , in particular that the catalyst carrier is in shape of solid or hollow cylinders, balls, honeycomb bodies, trilobes or gears.

Another condition that is decisive for the activity of the invention supported catalysts is compliance with the concentration of the active component that according to the invention, based on the total weight of the supported catalyst in the range must be from 5 to 12% by weight. It was found that if the Concentration in the above range good space-time yields can be obtained, and that Concentrations outside the specified limits for the decrease in space-time yield to lead.

Concentrations of the active component, based on the Total weight of the supported catalyst, in the range of 7.5 to 10% by weight.

The supported catalysts according to the invention can in principle be used in any of heterogeneously catalyzed reactions suitable reactor can be used. Without restriction the general population may be mentioned as examples: suspension reactor, stirred tank, Stirred tank cascade, tubular reactor, tray reactor, tube bundle reactor, fixed bed reactor, fluidized bed reactor, Reactive distillation column. The reaction can take place at different temperatures and Pressures are driven, the optimum being determined by the starting materials used becomes. As a rule, the reaction temperatures are between 20 and 200 ° C and Pressures between 0.1 and 100 bar absolute.

A particular advantage of the supported catalysts according to the invention is that a simple regeneration by calcination or by washing with alkaline Solutions is possible. It was found that with a decrease in catalyst activity, the is noticeable in a reduction in the space-time yield, it is possible that Regenerate catalyst and restore the original activity. The Regeneration can be achieved by treatment with aqueous alkaline solutions, in particular Alkali, alkaline earth or ammonium hydroxide solutions or by calcinations in The presence of oxygen can be carried out at temperatures between 150 and 700 ° C. In addition, it is also possible to control the activity of the fresh catalyst by a Increase base treatment before use in aldol condensation. Regeneration as well Pretreatment points to a base-catalyzed mechanism of aldol condensation out.

The invention also relates to a column for carrying out a Aldol condensation by reactive distillation in the presence of a heterogeneous particulate Catalyst with a packing or packing, the spaces in the interior of the column train, the quotient of hydraulic diameter for the gas flow through the Pack or the packing and the equivalent diameter of the catalyst particle is in the range from 2 to 20, preferably in the range from 5 to 10, such that the Catalyst particles loose under the influence of gravity in the spaces introduced, distributed and discharged, and being supported as catalyst particles Catalysts are used as described above.

The hydraulic diameter is defined in a known manner as the ratio between four times the area flowed through and the circumference thereof. The concrete calculation of the same for a pack with rectilinear kinks is explained in the description of the figures in connection with FIG. 2.

The hydraulic diameter of packing is determined via the porosity of the bed ψ, ie empty volume of the bed / total volume and the equivalent diameter of the packing,


where d _hydraulic = hydraulic diameter, d _p = diameter of the packing and ψ = porosity. The equivalent diameter of the packing is defined by the ratio between six times the volume and the surface of the packing (see VDI Wärmeatlas, 5th edition, 1988, Lk 1).

The equivalent diameter of particles, in the present case catalyst particles, is determined by the Ratio defined between six times the volume and the surface of the particle (see also VDI Wärmeatlas, 5th edition, 1988, Lk 1.

By quoting the hydraulic diameter for the gas flow through the Pack or the packing and the equivalent diameter of the catalyst particles in the The range defined above is met, the invention ensures that the Catalyst particles loose under the influence of gravity in the spaces between Pack or the packing can be introduced, distributed and discharged.

In principle, there are no packs or fillers that can be used Restrictions: Column internals that are used regularly in the Distillation technology can be used to determine the phase interface between the Countercurrent through the column moving phases, the gaseous and the liquid Phase, enlarge. The packs or packing form in the interior of the column Spaces that must be connected to each other in order to create the for the distillative separation effect required opposite flow of gaseous and liquid phase.

The inventors have thus recognized that it is possible, in principle, to interact with each other connected spaces between the packing or the packing in the interior of the column train, loose catalyst particles under the influence of gravity in the Gap spaces, distribute and the used catalyst particles again unsubscribe.

It should be noted that there is enough free space for the distillation emerging gas flow are present, so that it does not lead to a build-up of the im Countercurrent to the gas flow flowing liquid stream comes. this will This ensures according to the invention that the quotient of the hydraulic diameter for the Gas flow through the packing or through the packing and the equivalent diameter the catalyst particles are very small, i.e. with values in the ranges defined above, is chosen.

The invention is not restricted with regard to the shape and size of the usable catalyst; However, to improve the space-time yield are high specific ones Surfaces and thus small catalyst particles preferred. In bulk from It is known that catalyst particles increase the pressure drop with increasingly smaller ones Catalyst particles and limits the liquid and in the case of reactive distillation Steam throughputs to uneconomically small values. Because of the generally strong pronounced creek formation of the liquid in catalyst beds can be for large Column diameters, which are required for production-scale systems, are only small achieve distillative separation performance. These disadvantages have prevented the per se desirable use of catalyst beds as separating internals in Reactive distillations. In contrast, according to the invention, small catalyst particles are just that too preferred in terms of catalytic activity, particularly suitable for Combined use with a pack or with packing, because it is all the easier bring and, the smaller their dimensions compared to the dimensions of the There are spaces between the pack or the packing.

Suitable dimensions of the catalyst particles are, for example fully cylindrical catalyst particles about 1 × 4 mm to about 4 × 40 mm.

Structured packings are preferably used as column internals, that is to say in regular geometry systematically structured packs with defined Passage areas for the counterflow phases. Packs are usually made up essentially Metal sheets, expanded metal or wire mesh layers arranged parallel to each other built up. Compared to other column internals, they are characterized by higher resilience, a better separation effect and a lower specific pressure loss. Packs are usually made of kinks that are arranged essentially parallel to one another Metal sheets, expanded metal or fabric layers built up, mostly with straight bends, that subdivide the packing sheet, the expanded metal or fabric layer into kinked surfaces, and wherein the angle of inclination of the kink surface to the vertical is usually 30 to 45 ° amounts. For the present invention, packs with an inclination angle of Kink surface to the vertical in the range of 10 to 45 °, preferably 30 °, used become. By arranging successive packing sheets in the same The well-known angles arise in relation to the vertical, but with the opposite sign Cross-channel structures, such as, for example, the packs of the types Mellapak, CY or BX from Sulzer AG, CH-8404 Winterthur or types A3, BSH, B1 or M from Fa. Montz GmbH, D-40723 Hilden.

Special ones are preferred for use in reactive distillation Embodiments of structured packings are used, which allow an increased gas flow.

A particularly preferred embodiment is characterized in that a or several packing sheets with a high specific surface area with one or more Packing sheets with a low specific surface can be arranged alternately. This creates gaps with different hydraulic diameters educated. The specific surfaces of the packing sheets are particularly preferred chosen such that on the one hand spaces are formed for the Quotient of the hydraulic diameter and the equivalent diameter of the Catalyst particles is less than 1 and on the other hand spaces for which the quotient is made the hydraulic diameter and the equivalent diameter of the Catalyst particles is greater than 2, in particular in the range between 2 and 20 defined above, in particular between 5 and 10. In the first gaps, with a Ratio of hydraulic diameter and equivalent diameter of the Catalyst particles smaller than 1, no catalyst particles are filled, they will be According to the invention, only filled in the spaces in which the quotient mentioned is greater than 2. This particular embodiment results in an increased gas flow guaranteed with low pressure drops.

The starting material for packs according to the invention is usually preferred in addition provided with openings, for example with circular holes with about 4 to 6 mm Diameter to raise the flood limit of the pack and a higher one To allow column loading. Under the flood limit of a pack, the gas or Liquid volume per time and cross-sectional area understood at which the trickle liquid in and pent up above the pack until completely flooded or from the gas flow gets carried away. Exceeding this load has a rapid decrease in the Separation effect and a steep increase in pressure loss result.

Instead of packings, fillers can be used equally, whereby it there are basically no restrictions on the shape of the same. So can for example all forms of packing known in distillation technology, such as Raschig rings, Pal rings or saddles can be used.

Packs or fillers which have horizontal areas are advantageous. The horizontal surface areas absorb part of the weight of the catalyst particles and lead him to the column wall. This will reduce the mechanical stress on the Reduced catalyst.

Packings are preferred which consist of packing sheets for vertical installation in the Column are formed with straight folds that fold the packing sheet into folds subdivide, the angle of inclination of the articulated surfaces to the horizontal in the range of 90 to 45 °, preferably 60 °.

The specific surface area of packages for distillation is approximately 250 to 750 m ² / m ³ . Packings with lower specific surface areas in the range from about 50 to 250 m ² / m ^{3 are} preferably used for columns for carrying out heterogeneously catalyzed reactive distillation.

Typically, wall thicknesses of the metal sheets are sufficient for distillation packs 0.07 to 0.1 mm. In the case of heterogeneously catalyzed Reactive distillation depending on the catalyst weight and mechanical stability of the catalyst grains Wall thicknesses of the metal sheets in the range from 01 to 5 mm, preferably from 0.15 to 0.3 mm used.

Packs or fillers are preferably used which have a surface have reduced flow resistance, this reduced Flow resistance in particular through perforations and / or roughening of the material of the pack or the packing or by forming the packing as expanded metal. The perforations are preferred in terms of their number and dimensions dimensioned such that at least a share of 20%, preferably a share of 40 to 80% of the liquid reaction mixture passes through these perforations and onto the ones below lying catalyst particles flows.

In a preferred embodiment, the packing material consists of expanded metal, wherein the packaging material is designed such that the film on the packaging material draining liquid as completely as possible through the packing material downwards can run off, the dripping is supported by drain edges.

The perforations in the vicinity of the lower crease edges are preferred in the vertical direction Column arranged packing plates are provided, as described in DE-A 100 31 119. As a result, the fluid is preferably directed onto the top of the inclined kink surfaces and reduces the liquid load on the critical bottom. To do this Packings of packing sheets used for vertical installation in the column, with rectilinear creases that subdivide the packing sheets into creases and one of Bend edge to bend edge have width a to be measured as well as perforations and where a proportion X of at least 60% of the perforations a distance b of at most 0.4a to the lower crease edge of each crease surface. The proportion of 5 to 40%, in particular 10, of the area of the perforations up to 20% of this kink area.

Another preferred embodiment is characterized in that the pack is formed from corrugated or kinked layers, and that between two corrugated or kinked layers, a flat intermediate layer is arranged, the Do not extend flat intermediate layers to the edge of the pack or in the edge zone the pack has an increased gas permeability, in particular holes, according to DE-A 196 01 558.

It is also possible to use less corrugated or instead of flat intermediate layers to provide kinked layers.

A concentric volume element is referred to as the edge zone of the pack, which is between an outer cylindrical surface and an inner cylindrical surface (the packings typically have cylindrical shape), with the outer cylindrical surface extending through the outer ends of the corrugated or kinked layers are defined and the inner Cylinder surface is defined by the outer ends of the flat layers. It cuts that oriented parallel to the packing layers and running through the column axis horizontal connecting line of the inner with the outer cylinder surface one to twenty, preferably three to ten, each formed by layers arranged side by side Channels. In the case of flat layers which do not reach the edge zone, up to twenty are thus obtained Channels in the edge zone released side by side. Second reaching into the peripheral zone Layers are preferably 20 to 90%, particularly preferably 40 to 60%, of them Surface, gas-permeable, for example provided with holes.

At the points where the channels formed by the sheets meet the column wall touch, the rising gas flow is blocked because the channels from the Column wall to be completed. That leads to a much worse one Separation performance of the pack. By opening the packing channels in the wall zone, this can Eliminates the cause of reduced separation performance in a simple and effective manner become. In this case, the gas can flow in from the channels ending on the column wall change other channels that continue in the opposite direction.

The invention also relates to a method for producing pseudojons by Aldolization of citral and acetone by reactive distillation in one, as in the present case described column. The column is preferred with regard to its gas and Liquid load operated such that a maximum of 50 to 95%, preferably 70 to 80% of the Flood exposure is reached.

The invention is described below with reference to a drawing and exemplary embodiments explained in more detail.

It show in detail

Fig. 1 is a schematic representation of an embodiment of a package according to the invention,

Fig. 2 is a schematic representation of a packing sheet with straight bends and

Fig. 3 is a schematic representation of a packing sheet with perforations and

Fig. 4 is a schematic representation of an embodiment of a column according to the invention.

The schematic representation in FIG. 1 shows a pack 1 with packing sheets 2 , which have rectilinear kinks 5 with the formation of kink surfaces 6 , an intermediate space 3 being formed between two successive packing sheets 2 . According to the invention, catalyst particles 4 are filled into the same.

Fig. 2 shows schematically a packing sheet 2 having linear corrugations 5, and kink surfaces 6. a represents the width of a kink surface 6 , measured from kink edge 5 to kink edge 5 , c the distance between two adjacent kink edges 5 and h the height of a kink.

Fig. 3 shows a particular embodiment schematically shows a packing sheet 2 with bent edges 5, corrugated surfaces 6 and a width a of the corrugated surfaces 6 with perforations which b has a distance to the lower corrugated edge 5 each corrugated surface 6 may have.

The reactive distillation column 7 shown schematically in FIG. 4 has two pure separation zones 8 , each in the upper and lower region of the reactive distillation column 7 , which are equipped with structured fabric packs. A reaction zone 9 is arranged in the central column area and has a lower area 9 a with a packing without introduced catalyst particles and an upper area 9 b with a packing according to the invention with introduced catalyst particles. The reactive distillation column 7 is equipped with a bottom evaporator 10 and a condenser 11 at the top of the column. The starting materials are introduced as streams I or II in the upper region of the column, the reaction mixture is taken off as bottom stream III and a top stream IV is taken off at the top of the column. A pressure regulator PC is arranged on the column head.

embodiments example 1 bulk tests

• 1. Schüttversuche mit γ-Al₂O₃-Vollzylindern, Durchmesser 1,5 mm. Es wurden Packungen des Typs B1 der Firma Montz mit jeweils unterschiedlichen spezifischen Oberflächen und unterschiedlichen Neigungswinkeln der Knickflächen zur Horizontalen eingesetzt.
• 2. 1A₁) Es wurde eine Blechpackung des Typs B1-125.80 mit einer spezifischen Oberfläche von 125 m²/m³ und einem Winkel von 80° gegen die Horizontale eingesetzt. Dabei konnte 90% des Leerrohrvolumens mit den oben genannten Katalysatorteilchen gefüllt werden. Die Packung hatte einen hydraulischen Durchmesser von 19 mm. Der Katalysator ließ sich sehr gut einbringen und rieselte im trockenen Zustand auch vollständig wieder heraus. Das Verhältnis des äquivalenten Durchmessers der Katalysatorteilchen zum hydraulischen Durchmesser der Packung betrug 9.
• 3. 1A₂) Es wurde eine Packung des Typs B1-250.80 mit einer spezifischen Oberfläche von 250 m²/m³ und einem Winkel von 80° gegen die Horizontale mit den oben genannten Katalysatorteilchen befüllt. Hierbei konnten 80% des Leerrohrvolumens mit Katalysatorteilchen gefüllt werden. Die Packung hat einen hydraulischen Durchmesser von 9,4 mm. Der Katalysator ließ sich sehr gut einbringen und rieselte im trockenen Zustand auch vollständig wieder heraus. Das Verhältnis des äquivalenten Durchmessers der Katalysatorteilchen zum hydraulischen Durchmesser der Packung betrug 4,7.
• 4. 1A₃) Eingesetzt wurde eine Packung des Typs B1-250.60, das heißt mit einer spezifischen Oberfläche von 250 m²/m³ und einem Winkel von 60° gegen die Horizontale. 80% des Leerrohrvolumens derselben konnten mit den oben genannten Katalysatorteilchen gefüllt werden. Die Packung hat einen hydraulischen Durchmesser von 9,4 mm. Der Katalysator ließ sich sehr gut einbringen und rieselte im trockenen Zustand auch vollständig wieder heraus. Das Verhältnis des äquivalenten Durchmesser der Katalysatorteilchen zum hydraulischen Durchmesser der Packung betrug 4,7.

A column section with a diameter of 0.3 m was equipped with two distillation packs of type B1 from the Montz company, offset by 90 °, the height of each pack being 23 cm. Catalyst particles were poured into the distillation packs. The filling volume and the manageability of the introduction and removal of the catalyst particles were determined. Γ-Al ₂ O ₃ full cylinders coated with 5% praseodymium oxide were used as catalyst particles. The γ-Al ₂ O ₃ full cylinders with a diameter of 1.5 mm and a height of 1 to 4 mm have an equivalent particle diameter of 2 mm.

• 1. Bulk tests with γ-Al ₂ O ₃ full cylinders, diameter 1.5 mm. Packs of type B1 from Montz were used, each with different specific surfaces and different angles of inclination of the buckling surfaces to the horizontal.
• 2. 1A ₁ ) A sheet metal packing of the type B1-125.80 with a specific surface area of 125 m ² / m ³ and an angle of 80 ° to the horizontal was used. 90% of the empty tube volume could be filled with the catalyst particles mentioned above. The pack had a hydraulic diameter of 19 mm. The catalyst could be introduced very well and, in the dry state, also trickled out completely. The ratio of the equivalent diameter of the catalyst particles to the hydraulic diameter of the packing was 9.
• 3. 1A ₂ ) A package of the type B1-250.80 with a specific surface area of 250 m ² / m ³ and an angle of 80 ° to the horizontal was filled with the above-mentioned catalyst particles. Here, 80% of the empty tube volume could be filled with catalyst particles. The pack has a hydraulic diameter of 9.4 mm. The catalyst could be introduced very well and, in the dry state, also trickled out completely. The ratio of the equivalent diameter of the catalyst particles to the hydraulic diameter of the packing was 4.7.
• 4. 1A ₃ ) A package of the type B1-250.60 was used, ie with a specific surface area of 250 m ² / m ³ and an angle of 60 ° to the horizontal. 80% of the empty tube volume of the same could be filled with the catalyst particles mentioned above. The pack has a hydraulic diameter of 9.4 mm. The catalyst could be introduced very well and, in the dry state, also trickled out completely. The ratio of the equivalent diameter of the catalyst particles to the hydraulic diameter of the packing was 4.7.

In contrast, in the case of commercially available catalyst packs in which the Catalyst is placed in pockets, for example of the Katapack type from Sulzer or Multipack from Montz only 20 to 30% in exceptional cases a maximum of 50% of the Empty pipe volume to be filled with catalyst.

Example 2 Pressure loss measurements

In a column section with a diameter of 0.1 m, pressure loss measurements were made with the test mixture nitrogen / isopropanol. For this purpose, the catalyst bed was introduced into the column section and sprinkled with a defined amount of isopropanol (one drip point). In counterflow, a defined amount of nitrogen was passed through the packing / bed from bottom to top. In the tests, the specific pressure loss per packing or bed height was measured and the flood point was determined. Γ-Al ₂ O ₃ full cylinders coated with 5% praseodymium oxide were used as catalyst particles. The solid cylinders (d = 1.5 mm, h = 1-4 mm) had an equivalent particle diameter of 2 mm. The specific pressure drop and the flood point were then determined from a bed placed in a structured packing.

Example 2 comparison

At a dumping height of 45 cm, an F factor of 0.038 Pa ^{∧ 0.5} (corresponding to a gas flow of 1000 l / h) and a sprinkling density of 0.178 m ³ / m ² h (corresponding to a liquid flow of 1.4 l / h h) a specific pressure drop of 3.33 mbar / m was measured. The pack began to flood at a constant liquid load of 0.178 m ³ / m ² h from an F factor of 0.0575 Pa ^{∧ 0.5} (corresponding to a gas flow of 1500 l / h).

Example 2 According to the invention

Poured into two layers of a structured packing of the Type BS-250.60 from Montz.

At a dumping height of 46 cm, an F factor of 0.038 Pa ^{∧ 0.5} (corresponding to a gas flow of 1000 l / h) and a sprinkling density of 0.178 m ³ / m ² h (corresponding to a liquid flow of 1.4 l / h h) a specific pressure drop of 1.09 mbar / m was measured. The pack began to flood at a constant liquid load of 0.178 m ³ / m ² h from an F factor of 0.114 Pa ^{∧ 0.5} (corresponding to a gas flow of 3000 l / h). The maximum gas load could thus be increased by a factor of 2 compared to the bed, which was not placed in a pack.

The calculation of the hydraulic diameter for a pack with straight-line kinks is illustrated below with reference to FIG. 2:

The packing sheet 2 illustrated as an example in Fig. 2 has parallel to each other arranged, rectilinear bends 5, which divide the packing sheet 2 in articulated surfaces 6. The width of a buckling surface 6 , measured from buckling edge 5 to buckling edge 5 , is denoted by a, the distance between two successive buckling edges 5 by c and the height of the buckling by h. The hydraulic diameter of the gas flow for a packing constructed from such packing sheets is then calculated using the formula

Example 3 catalyst screening 3.1 Catalyst preparation

The supported catalysts to be tested were tested as standard Pore volume impregnation made. For this purpose, the carrier with the active component was in shape impregnated with a metal salt solution, dried in a drying cabinet at 120 ° C. and then calcined in air. Unless otherwise stated, the calcination is carried out for 2 hours 450 ° C, with a heating rate of 3.5 ° C / min.

For the production of catalysts with praseodymium oxide as an active component a praseodymium nitrate stock solution of 1170 g praseodymium oxide, 2276 g 65% Nitric acid and 1557 g of water used. This solution contained 18.1% by weight of praseodymium oxide and then became full depending on the fluid intake of the carrier deionized water.

3.2 Catalyst screening

The aim of the catalyst screening was to use catalysts with a high space-time yield and thus finding high catalyst activity.

The catalyst screening was carried out in an apparatus consisting of a reservoir, a pump and a tempered metal tube reactor. A mixture of 79% by weight of acetone and 21% by weight of citral, with a mass flow of 200 g / h, was passed from the storage container from the bottom upwards by means of a pump through the tube reactor filled with 50 g of catalyst and heated by accompanying heating. The reaction was carried out at 90 ° C. and 2.5 bar _abs . The samples were taken after 2, 4 and 6 h, the values obtained were averaged.

3.3 Evaluation

The samples were analyzed by gas chromatography (GC). The concentrations of the individual components were determined using an internal standard (N-methyl-pyrrolidone, NMP). The data of the analysis method can be found in the following table:

3.4 Variation of the catalyst carrier composition

All tested support materials for the catalyst support were each coated with 5% praseodymium oxide as an active component. The results listed in the table below were achieved by varying the catalyst support composition:
The abbreviation BET in the table header describes the catalyst surface in a known manner according to the method of determination by Stephen Brunauer, Paul Emmett and Edward Teller, according to DIN 66131. RZA denotes the space-time yield in gPSJ / gKat / h, ie in grams of pseudo-ionone per gram of catalyst and hour. Table 1

The results in the table show that among the tested carrier materials, γ-alumina has by far the best space-time yield.

3.5 Variation of the catalyst carrier geometry

The abbreviations in the table header have the same meaning as listed in section 3.4 above. The determination of the space-time yields was also carried out under the same conditions as in 3.4, that is, when the catalyst supports were coated with 5% praseodymium oxide. The test results are summarized in the table below: Table 2

The results in the table show that the use of catalyst supports with large ratio of outer surface to volume to catalysts with good Space-time exploitation leads. The catalyst supports marked as comparison show in the Geometry of 4 mm and 3 mm strands, space-time yields <0.5 g pseudojonon / g Catalyst / h (comparative tests in the first two rows of the table).

In contrast, the examples according to the invention show in rows 3 to 9 of the table, that thinner strands smaller balls and special geometries (trilobes, gears and Honeycomb body), that is, catalyst carrier geometries with a larger outer surface in Ratio to volume, improved space-time yields in the range of 0.5 to 0.6 g Pseudojonon / g catalyst / h.

3.6 Variation in praseodymium oxide content

γ-aluminum oxide strands with a diameter of 1.5 mm were coated with different levels of praseodymium oxide in the manner described under 3.1 above. The test results are summarized in Table 3 below. Table 3

The results of the table show that a maximum of the space-time yields at one Praseodymium oxide occupancy between 7.5 and 10 wt .-% is exceeded. higher Allocations lead to a decrease in the space-time yield. This decline in Activity with higher occupancies was also evident optically: the originally weak greenish color of the supported catalyst changed to brownish. Therefor agglomeration of the praseodymium oxide particles could be responsible.

3.7 Varying the composition of the active component

Γ-alumina strands with a diameter of 1.5 mm were used as supports used and occupied with active components in the manner described above under 3.1. In this case, the nitrate solution of the corresponding metals was used in all cases with the exception of zinc, which was used as the zinc acetate solution. In all In some cases, 5% of the active component was assigned.

The abbreviation LnO-Mix means a commercially available rare earth mixture from Rhone-Poulenc with the composition: 13.87% CeO ₂ / 7.69% La ₂ O ₃ / 1.65% PrO _x / 5.69% Nd ₂ O _3rd

The results are shown in Table 4 below. Table 4

Example 4 Production of pseudojonon by aldolization of citral and acetone

The experimental arrangement corresponded to the schematic representation in FIG. 4. The reactive distillation column 7 was in the separation zones 8 each filled with a segment of a structured tissue pack of the A3-500 type from the Montz company, each with a total height of 23 cm. The reaction zone 9 was equipped in the lower region thereof with a layer of Montz-Pak type B1-1000 with a special element height of 30 mm. This layer served as a catalyst barrier so that the catalyst particles could not trickle into the lower separation zone. Three layers of Montz-Pak type B1-250.60 with an element height of 212 mm were installed in this layer, into which the catalyst was introduced by pouring. 3121 g of catalyst with a bulk density of 700 kg / m ^{3 were} poured in. As a catalyst were solid cylinders of 5% praseodymium on γ-Al ₂ O ₃ having a particle diameter of 1.5 mm and a height of 1 to 4 mm is used, the by impregnating γ-Al ₂ O ₃ with an aqueous solution of praseodymium Nitrate and subsequent calcination were produced. The column was equipped with thermocouples and sampling points in regular sections, so that the temperature profile and the concentration profile in the column could be determined.

The reactants citral and acetone (streams I and II in FIG. 4) were metered into the reactive distillation column with mass flow control from supply containers standing on scales.

The bottom evaporator 10 , which was heated to 124 ° C. with the aid of a thermostat, had a hold-up between 50 and 150 ml during operation, depending on the dwell time. The bottom stream III was level-controlled from the bottom evaporator 10 with a pump into a scale conveyed standing container.

The top stream of the reactive distillation column was condensed out in a condenser 11 which was operated with a cryostat. Part of the condensate was fed via a reflux divider as stream IV into a feed tank standing on a balance, while the other part was fed as reflux to the column. The apparatus was equipped with a pressure control PC and designed for a system pressure of 20 bar. All incoming and outgoing material flows were continuously recorded and registered with a process control system PLS during the entire test. The apparatus was operated continuously, 24 hours a day.

A stream 1 of 220.0 g / h, corresponding to 1.4 mol / h citral with a purity of 97%, and a stream II of 840.0 g / h corresponding to 14.32 mol / were continuously introduced into the reactive distillation column 7 described above. h acetone preheated to 80 ° C with a purity of 99%.

Experimental Procedure

Solid cylinders (d = 1.5 mm, h = 1-4 mm) made of 5% Pr on γ-Al ₂ O _{3 were} used as the catalyst in reaction zone 9 . A system pressure of 3 bar and a reflux ratio of 3 kg / kg were set. The bottom temperature was 92.5 °. The bottom stream III of the column was 735.6 g / h of crude product with 62.14% by weight of acetone, 0.71% by weight of water, 0.45% by weight of mesityl oxide, 0.95% by weight of diacetone alcohol, 9.14% by weight of citral, 24.43% by weight of pseudo-ionone and 2.18% by weight of high boilers. At the top of the column, 323.2 g / h of distillate (stream IV) consisting of 95.8% by weight of acetone and 4.2% by weight of water were drawn off.

Pseudojonon with a selectivity of 97.3% based on citral and 84.4% obtained based on acetone. The yield was 66.7% based on citral.

With F factors of 0.12 Pa ^{∧ 0.5} and sprinkling densities of 0.3 m ³ / m ² h, a differential pressure of about 1 mbar was measured across the column.

When using a random catalyst bed without packing in contrast, the double pressure loss measured.

The differential pressure is a measure of the loading (gas and liquid) of the column. ever the differential pressure increases depending on the material properties and the type of internals used with increasing load until it floods. In the state of flooding the Catalyst whirled up and strong catalyst abrasion can occur. This Condition should therefore be avoided.

When using a pack according to the invention, a higher throughput can therefore be achieved same column diameter can be achieved.

Claims (14)

1. Supported catalyst containing one or more metal oxides as active components on a catalyst support for carrying out a heterogeneously catalyzed aldol condensation, characterized in that the catalyst support is γ-aluminum oxide, that the active component is one or more oxides of the elements with atomic numbers 39 or 57 to 71 and that the concentration of the active component, based on the weight of the catalyst support, is in the range from 5 to 12% by weight. 2. Supported catalyst according to claim 1, characterized in that the Concentration of the active component, based on the weight of the catalyst support, is in the range from 7.5 to 10% by weight. 3. Supported catalyst according to claim 1 or 2, characterized in that the geometry of the catalyst carrier is determined such that the ratio of the outer surface to the volume in the range from 0.5 to 10 mm ^-1 , preferably from 1 to 5 mm ^-1 lies, preferably that the catalyst carrier is in the form of solid or hollow cylinders, balls and honeycomb bodies, trilobes or gears. 4. Supported catalyst according to one of claims 1 to 3, characterized in that the active component is yttrium oxide. 5. Supported catalyst according to one of claims 1 to 3, characterized in that the active component is praseodymium oxide. 6. Column to carry out an aldol condensation by reactive distillation in Presence of a heterogeneous particulate catalyst with a packing or Packings that form gaps in the interior of the column characterized that the quotient of the hydraulic diameter for the gas flow by the packing or the packing and the equivalent diameter of the Catalyst particles are in the range from 2 to 20, preferably in the range from 5 to 10, so that the catalyst particles loose under the influence of gravity Spaces are introduced, distributed and carried out, and that the Catalyst particles from a supported catalyst according to one of claims 1 to 5 are formed. 7. Column according to claim 6, characterized in that the packing of a structured packing, preferably a cross-channel packing. 8. Column according to one of claims 6 or 7, characterized in that the Pack or the packing have horizontal areas. 9. Column according to claim 8, wherein the packing of packing sheets for vertical Installation in the column is formed, with straight lines kinking the packing plate divide into buckling areas, characterized in that the angle of inclination of the Kink surfaces to the horizontal in the range of 90 to 45 °, preferably at 60 °. 10. Column according to one of claims 6 to 9, characterized in that the Pack or the packing on their surface a reduced Have flow resistance, preferably through perforations and / or roughening of the material the pack or the packing or by forming the pack as Expanded metal. 11. Column according to one of claims 7 to 10, characterized in that the Pack is formed from corrugated or kinked layers, and that between two corrugated or kinked layers each have a flat intermediate layer, the flat intermediate layers do not extend to the edge of the pack or an increased gas permeability in the edge zone of the pack, in particular Holes. 12. Column according to one of claims 7 to 11, wherein the packing Packing plates for vertical installation in the column is formed, with straight bends, that divide the packing sheets into folded areas and one from the folded edge As a result, the crease edge has a width a to be measured and perforations characterized in that a proportion X of at least 60% of the perforations is a distance b of at most 0.4a to the lower crease edge of each crease surface. 13. Process for the production of pseudojonon by aldolization of citral and Acetone by reactive distillation in a column according to one of claims 6 to 12, characterized in that the column with regard to its gas and Liquid load is operated so that a maximum of 50 to 95%, preferably 70 to 80% the flood load is reached. 14. Process for carrying out a heterogeneously catalyzed aldol condensation Reactive distillation in a column according to one of claims 6 to 12, characterized characterized in that the supported catalyst when the original Catalyst activity by treatment with an aqueous alkaline solution, in particular with an alkali, alkaline earth or ammonium hydroxide solution, is regenerated.