WO2004022515A1

WO2004022515A1 - Continuous method for the production of carbonyl compounds

Info

Publication number: WO2004022515A1
Application number: PCT/EP2003/008096
Authority: WO
Inventors: Werner Aquila; Walter Dobler; Gerd Kaibel; Christian Miller; Carsten Oost; Manfred Stroezel; Mathias Haake
Original assignee: Basf Aktiengesellschaft
Priority date: 2002-08-15
Filing date: 2003-07-24
Publication date: 2004-03-18
Also published as: AU2003251465A1; DE10238140A1

Abstract

The invention relates to a method for the continuous production of higher-chained carbonyl compounds by reacting lower-chained carbonyl compounds with aldehydes on basic or acidic catalysts in a rectification column.

Description

Continuous process for the production of carbonyl compounds

description

The present invention relates to a process for the continuous production of higher-chain carbonyl compounds by reacting lower-chain carbonyl compounds with aldehydes over basic or acidic catalysts in a rectification column.

The reaction of carbonyl compounds with aldehydes over acidic or basic catalysts, apart from the improvements according to the invention, is already known in its essential characteristics. For example, in Römpp Chemie Lexikon (Vol. 1., 9. extended, revised edition, Thieme Verlag 1995) the base-catalyzed addition of carbanions, which are generated from activated methylene groups, to the carbonyl group of aldehydes or Ketones are described. This type of reaction is called Aldol addition. When acids are used as catalysts, the aldol addition is generally followed by water elimination, so that in this case one speaks of an aldol condensation. According to Römpp Chemie Lexikon, the aldol addition of two different aldehydes or an aldehyde with a ketone can only be used preparatively if the aldehyde component does not have an α-hydrogen atom, so that it can only function as a carbonyl component. This type of reaction is referred to in the literature as the Claisen-Schmidt reaction. Since the aldol addition is a reversible reaction, there is a risk of cleavage back into the starting compounds. Information on the technical implementation of this reaction is not given in Römpp Chemie Lexikon.

In the Organikum (16th edition, VEB Deutscher Verlag der Wissenschaften, Berlin 1986) the reaction of aldehydes and ketones with themselves or with other aldehydes and ketones as CH-acidic compounds is defined as an aldol reaction. It should be noted that the simple aldols can only be isolated when working at a low temperature. In many cases, dehydration follows extremely easily. In addition, with ketones with two reactive centers, such as acetone or butanone, there is a risk of the formation of di-aldolization products. The general working instructions for the Aldolization is not suitable for implementation on an industrial scale.

A process for the preparation of pseudoionone by reacting citral with acetone using LiOH as a catalyst is described in US-4874900. The reaction is then carried out batchwise or continuously at temperatures from -20 to 240 ° C. The pressure is adjusted so that the reaction mixture remains in the liquid phase at the appropriate temperature. In the case of discontinuous operation, the reactants are stirred in a vessel and the catalyst is filtered off after the reaction has ended, while in the continuous mode of operation the premixed reactants are pumped through a column filled with catalyst. In both cases, the reaction mixture is neutralized with CO at the end of the reaction and the excess ketone is distilled off. In this process, with a molar ratio of acetone to citral of 20 mol / mol yields of 89.5%. Citral achieved. This low yield is unsatisfactory for an industrial process. In addition, the high excess of ketone leads to high energy and investment costs in the processing.

Patent PL147748 describes a process for the preparation of ionone by condensation of citral and acetone on basic ion exchangers at 56 ° C. Thereafter, acetone and citral are stirred discontinuously in a flask with the catalyst for 5 hours. No details are given in this patent regarding the technical implementation of the reaction. The disadvantage of this process is the very low space-time yields.

A method for the aldolization of acetone in a reaction column is described by Podrebarac, Ng and Rempel in Chemtech (May 1997, page 41). The catalyst is installed in the upper part of a distillation column, the acetone is pumped into the column at a point not mentioned and a product mixture of diacetone alcohol, mesityl oxide, acetone and water is drawn off at the bottom. Podrebarac points out that the balance of aldolization of acetone is positively influenced by reactive distillation. In the present invention, however, the formation of condensation products of the ketone is an undesirable side reaction to be avoided.

CN1109860-A describes a process for the preparation of diacetone alcohol. Here, acetone is condensed in a reactor and the reaction product is fed into a distillation column in which the acetone is distilled off overhead and in the Reactor is recycled. The reaction product is drawn off at the bottom of the column. This process is therefore a conventional combination of reaction with subsequent distillation and recycling of unreacted starting materials.

The production of diacetone alcohol or mesityl oxide in a reaction column is described in a number of references. For example, in Chem. Eng. Be. (1998), 53 (5), pages 1067-1088 documented experimental data for the preparation of diacetone alcohol from acetone in a reaction column. In addition, a mathematical model for the description of the reaction column is being developed. It is pointed out that the equilibrium of the reaction with the reactive distillation can be positively influenced. The catalyst activity and the selectivity of the reaction are influenced by the liquid distribution and the flow profile in the column, but this is undesirable for industrial use. In addition, in the present invention, the diacetone alcohol is a by-product, the formation of which should be avoided.

In Can. J. Chem. Eng. (1998), 76 (2), pages 323-330, studies on mass transport in the production of diacetone alcohol and mesityl oxide in a reaction column are described using catalyst pockets as column internals. According to this, the catalyst pockets have no significant influence on the number of separation stages. This is generally disadvantageous for reaction columns, since the reaction and distillation should take place simultaneously. In Chem. Eng. Be. (1998), 53 (19), pp. 3489-3499 a model for the mathematical description of a reaction column for the production of diacetone alcohol is given, which is based on laboratory experiments.

The production of diacetone alcohol on strongly basic ion exchangers is described in Cuihua Xuebao (1996), 17 (5), pages 466-471. According to this reference, high-frequency oscillations in the reaction column are required for satisfactory activity of the catalyst. This is unsuitable for large-scale implementation.

ZA 9805328-A describes a process for the preparation of methyl isobutyl ketone. In this process, acetone and hydrogen are metered into the column in cocurrent below the reaction zone, which consists of a bed of catalyst. The acetone reacts to the mesityl oxide by aldol condensation, which is then hydrogenated to the methyl isobutyl ketone. Below and / or above the reaction zone there are distillation zones. The reaction product is separated off in the distillation zone and drawn off at the bottom, while unreacted acetone is separated off at the top and is returned to the column as reflux. A bifunctional catalyst is installed in the reaction zone, which accelerates both the aldol condensation and the hydrogenation. Ion exchangers, zeolites or aluminum oxide with a metal of group VIII or IB, such as nickel, palladium or copper, are mentioned as examples. With this process, selectivities of 61.2% based on acetone are achieved. This selectivity is unsatisfactory for an industrial process. The patent is also limited to directing the reactants in direct current.

A process for the aldolization of aldehydes in the presence of a basic catalyst is described in JP 10053552-A. An aldehyde with at least one hydrogen atom in the α position is then metered into a reaction column with sieve trays. This process can be used, for example, to produce 2-ethylhexenal from n-butyl aldehyde. The dimerization of aldehydes is not the subject of the present invention.

DE19605078A1 describes a process for the preparation of a dimerized aldehyde in a reaction column in the presence of an aqueous solution of a basic catalyst. The process is characterized in that the feed aldehyde has one or two hydrogen atoms in the α position. The aldehyde and an aqueous solution of the basic catalyst are metered in at the same feed point into a reaction column in which the reaction takes place. The unreacted reactant is separated off at the top of the column and some of it is returned to the column. The reaction product is removed from the column on a gaseous side draw together with water. As water forms a miscibility gap with the product, a phase separation vessel is required. The aqueous basic catalyst solution and high-boiling compounds are drawn off via the bottom of the column, so that a phase separation is likewise necessary at this point. The phase separations and associated returns in this process are associated with additional investment costs. In addition, the recycling of the homogeneous catalyst is complex.

DE 3319-430-A claims the production of higher ketones by condensation of methyl ketones and unsaturated aldehydes over mixed metal catalysts in the presence of hydrogen at 100 to 280 ° C. and 10 to 60 bar in a tubular reactor. The catalysts claimed are one Combination of oxides or phosphates of rare earth metals, Mg, Al, Zn or Ti and a Group VIII metal. 5 wt.% Pr0 ₃ and 0.5 wt.% Pd on aluminum oxide are mentioned as examples.

A large number of other catalysts are described in the literature for aldol condensation. For example, in Appl. Catal. 1988, 36 (1-2), pages 189-97 mentioned the alkaline earth metal oxides MgO, CaO, SrO and BaO as well as La0 ₃ and Zr0 ₂ as a catalyst for the aldol condensation of acetone. In Izv. Akad. Nauk. SSSR, Ser. Khim. (1978), (12), page 2731-7, rare earth metal oxides such as La0 ₃ , Nd0, and Sm0 _{3 are} investigated for the condensation of butyraldehyde. The use of ZnO with oxides of Ti, Ce, Mg or Be as a catalyst for the aldolization of acetone is described in GB-11881 416-R. In J. Catal. (1995), 155 (2), pages 219-37 describes Ce0 ₂ with Pd or Co as a catalyst for the aldol condensations. In addition, J. Mol. Catal. (1991), 69 (2), page 199-214 basic catalysts such as Ca (0H) ₂ , La (OH) ₃ , Zr0 and Ce0 for the condensation of acetone in the gas phase. US5254743-A describes the use of Mg, Ca, Ba, Ni, Co, Fe, Cu or Zn oxides on oxides of the elements Al, Ga, Cr, Co, Fe or La with a surface patented of at least 150 m ² / g. JP-162329 mentions La0 ₃ , Nd0 ₃ or Pr ₂ 0 ₃ on β-aluminum oxide as a catalyst for "various" chemical reactions.

The prior art set out above makes it clear that a continuous process for the aldolization of two different carbonyl compounds with simultaneous removal of at least one of the reaction products has hitherto not existed. In addition, all known processes for the dimerization of carbonyl compounds have considerable disadvantages.

The discontinuous processes for the aldolization of different carbonyl compounds have the disadvantage of high residence times and therefore low space-time yields, high investment costs and low yields. In the continuous process for the aldolization of different carbonyl compounds, the reactants are first mixed, passed over a bed of catalyst and the excess ketone is only separated off after the reaction. On the one hand, this leads to increased investment costs and a high thermal load on the products, which is associated with a reduced yield. On the other hand, a reactant in a large excess of over 20 mol / mol must be used to achieve sufficient selectivity. In the continuous processes for the aldolization of acetone, just as in the condensation of n-butyraldehyde, only one reactant is required, which is metered into a reaction column. The reaction procedure is therefore trivial. In addition, the literature describes that the self-aldolization of ketones or aldehydes in a reaction column is highly preferred because the reaction equilibrium is influenced positively. Consequently, when carbonyl compounds are reacted with acetone, the self-condensation of acetone must take place as a preferred side reaction. In the aldolization of different carbonyl compounds, low selectivities with respect to at least one of the reactants can always be expected due to the prior art through self-condensation. In addition, the strong influence on the selectivities described in the literature through the liquid distribution and the use of separating internals without a number of separating stages can only be tolerated in simple reaction systems.

In the processes for the production of methyl isobutyl ketone described in the literature, analogously to the aldolization of acetone, only a liquid reactant is required. Nevertheless, the selectivities are extremely unsatisfactory. With regard to the problems in the implementation of different carbonyl compounds, the aspects described above apply. The reactants are always passed through the column in cocurrent.

The processes described in the literature for the aldolization of different carbonyl compounds have considerable disadvantages, as explained above. The object of the invention was therefore to provide a new process for the continuous aldolization of different carbonyl compounds with advantageous properties, which no longer has the disadvantages of the prior art and which provides the corresponding products in high selectivities and high space-time yields.

The reaction should be able to be carried out continuously in a single reactor, with high product selectivities for both carbonyl compounds being achieved with the shortest possible reaction times. In particular, it should be avoided that a large excess of a reactant is used to achieve high selectivities and that it has to be separated off again after the reaction. Accordingly, a process for the continuous production of carbonyl compounds of the general formula (I) has been found

in the Rl to R4 for hydrogen or for a saturated or unsaturated, branched or unbranched, optionally substituted by one or more methoxy groups aliphatic hydrocarbon radical having 1 to 37 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkylalkyl group 4 to 30 carbon atoms or an aromatic having 6 to 18 carbon atoms, and in which A and B both represent hydrogen, or A or B independently of one another represent a hydroxyl group or can have the same meaning as R 1 to R 4, or A and B together means an additional bond between the C and A atoms,

by continuously feeding carbonyl compounds of the general formula (II) or continuously feeding mixtures of carbonyl compounds of the general formula (II)

in which R1 and R2 have the meaning given above, with continuously added carbonyl compounds of the general formula (III) or continuously added mixtures of carbonyl compounds of the general formula (III)

O

R4 — C — R5 (III) -

in which R4 has the meaning given above and R5 can have the same meaning as Rl to R4, and either R4 or R5 is different from Rl or R2,

continuously implemented and at least one of the reaction products separated from the reaction mixture during the reaction. The carbonyl compound of the general formula (II) used in the process according to the invention is particularly preferably one in which R 2 is hydrogen and R 1 is a group of the general formula (IV)

stands in which n stands for an integer from 1 to 6 and X and Y either both stand for H, or X and Y together means an additional bond between the X and Y-bearing carbon atoms.

The method according to the invention can in principle be applied to all aldolization reactions. However, the process is of particular importance for the aldolization of citral with acetone for the production of pseudoionon and for the production of methylpseudoionon, dirnethylpseudoionon and ethylpseudoionon, since these compounds are important intermediates for the production of vitamin A and fragrances.

As C ₁ -C ₃ aliphatic carbon radical for R 1 to R 4 and A and B straight-chain or branched saturated or one or more unsaturated radicals with 1 to 37, preferably with 1 to 20 C atoms, particularly preferably with 1 to 15 C atoms Consider.

Examples include methyl, ethyl, propyl, isopropyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, heptenyl, octyl, nonyl, oxyl, 1 Propenyl, 2-propenyl, 2-methyl-2-propenyl, 1-pentyl, l-methyl-2-pentenyl, isopropenyl, 1-butenyl, hexenyl, heptenyl, octenyl, Nonenyl or the decenyl radical.

The preferred cycloalkyl radicals for R 1 to R 4 and A and B are C ₃ -C ₁ -cycloalkyl radicals such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl or cyclodecenyl, which may be one or more C 1 -C ₄ - Alkyl, halogen (fluorine, chlorine, bromine, iodine), nitro, cyano, amino, C 1 -C ₄ -alkylamino, C 1 -C ₄ -dialkylamino, hydroxyl or other atoms or optionally 1 to 3 heteroatoms such as sulfur, nitrogen or oxygen in the ring contain. Cycloalkylalkyl radicals contain a cycloalkyl radical linked to a C ₁ -C ₂ aliphatic hydrocarbon radical.

Examples of aryl radicals are, for example, benzyl, aryl, naphthyl or biphenyl.

With the process according to the invention, selectivities of over 97% based on the carbonyl compound of the general formula (II) and at the same time over 84% based on the carbonyl compound of the general formula (III) are achieved. The space-time yield is a factor of 3 greater than in the previously known methods. In addition, the heat of reaction released during the reaction can be used for distillation and thus energy costs can be saved.

Another advantage of the process according to the invention is that the carbonyl compounds of the formulas (II) and (III) can be used in a molar ratio of less than 20 and nevertheless high selectivities with regard to both reactants are achieved. A molar ratio between 5 and 15 is preferably set, the chemically more stable component of the two carbonyl compounds generally forming the excess component. In particular in the case of chemical reactive carbonyl compounds with double bonds which tend to oligomerize, much higher molar ratios have hitherto been required to achieve satisfactory selectivities. An example of this is the conversion of citral with acetone to pseudoionone.

In addition, in the process according to the invention, the reaction product is immediately removed from the reaction mixture, so that subsequent reactions are avoided and the yield is thereby increased. In addition, the water which may be formed during the reaction can be separated off via the top of the column. This has a positive influence on the equilibrium setting and considerably simplifies the working up of the reaction product by distillation.

If the process is designed as a reactive distillation, the concentration profile in the column is preferably adjusted by energy input and reflux ratio so that a belly of the more stable carbonyl compound forms, into which the chemically unstable reactant is metered. As a rule, the two reactants are conducted in countercurrent for this purpose.

In contrast to the previously known methods, the method according to the invention makes it possible to isolate the products of the aldol addition. As products of Aldol addition denotes compounds of the formula (I) in which A denotes a hydroxyl group and B can have the same meaning as R1 to R4. Subsequent separation of the addition product from the reaction zone can avoid subsequent aldol condensation or cleavage of the product.

With the method according to the invention it is also possible to shift the equilibrium to the side of the product of the aldol condensation with elimination of water by appropriate concentration control. The products of the aldol condensation are compounds of the formula (I) in which A and B mean an additional bond. In order to implement this application, the water formed must be removed continuously from the reaction zone, so that the balance is shifted to the product side.

Furthermore, it is possible with the process according to the invention to produce the hydrogenated products of the aldol condensation. The products of the aldol condensation are compounds of the formula (I) in which A and B are hydrogen. For this purpose, a bifunctional catalyst is used in the reaction zone of the reactor, which catalyzes both the aldolization and the hydrogenation, and the reaction is carried out in the presence of hydrogen.

The amounts used in the process according to the invention are selected so that a molar ratio of carbonyl compound (II) to carbonyl compound (III) is between 1 and 50, preferably between 5.0 and 15.

Pressure and temperature are set so that high reaction rates result with a sufficiently high selectivity. When using a reaction column, the pressure at the top of the column is preferably set so that the temperature in the bottom is between 50 and 300 ° C., preferably between 80 and 180 ° C. In the hydrogenating aldolization, the hydrogen partial pressure is set between 1 and 100 bar, preferably between 1 and 20 bar. The residence time in the reactor system should be between 10 minutes and 10 hours, preferably between 0.5 and 3 hours.

In principle, all aldolization catalysts mentioned in the literature, such as, for example, alkali metal oxides, alkaline earth metal oxides, alkali metal hydroxides, alkaline earth metal hydroxides or rare earth metal oxides in pure form, as an aqueous solution or can be used on a carrier. Sodium hydroxide solution and potassium hydroxide solution are preferably used as homogeneous catalysts, since these can be pumped liquid into the fractionation column. It is particularly preferred to use heterogeneous catalysts which can be accommodated in a targeted manner in the reaction zone of the column and thus do not lead to contamination of the product or necessitate neutralization of the reaction product. Preferred catalysts are catalysts containing elements of the lanthanide series, preferably La, Ce and / or Pr, in a concentration of 0.1 to 20% by weight, preferably 1 to 10% by weight, on aluminum oxide, preferably on γ-alumina. The catalyst is used in a concentration of 1 to 99% by volume, based on the empty volume of the reactor, preferably between 10 and 30% by volume.

The catalyst is installed on the internals or as internals of a fractionation column or in a residence time container connected in parallel with the column.

An advantageous implementation of the method according to the invention is described below with reference to FIG. 1.

The process according to the invention is advantageously carried out in such a way that the carbonyl compound of the general formula (II), the carbonyl compound of the general formula (III) and, if appropriate, the catalyst via the feeds (3), (2) and (1) to the internals as Reaction column acting fractionation column (4) metered. It is advantageous, but not mandatory, if the higher-boiling reactants are fed separately or continuously together with the catalyst above the lower-boiling reactant into the fractionation column (4), thus forcing a countercurrent of the reactants. It may be advantageous to meter the lower-boiling reactants into the column (4) in gaseous or superheated form, since then a split in the bottom (19) of the column at high temperatures and the formation of by-products are avoided. The pressure at the top of the column (23) is adjusted so that the temperature in the bottom (19) is between 100 and 300 ° C, preferably between 130 and 180 ° C. Depending on the material system, this can be done with a vacuum pump (10) and / or a pressure control device (11).

The reaction of the carbonyl compound of the formula (II) with the carbonyl compound of the formula (III) takes place on the internals (21) of the fractionation column (4). The superimposed distillation continuously removes the carbonyl compound of the formula (I) from the reaction equilibrium and the reaction zone and reaches the bottom (19) of the Fractionation column and is withdrawn via stream (14). When an aldol condensation is carried out, the water formed by the reaction is also continuously removed from the reaction zone. The superimposed distillation thus, on the one hand, has a positive influence on the reaction equilibrium and, on the other hand, prevents subsequent reactions and thus high selectivities.

The reaction product collects in the bottom (19) of the column (4) and is drawn off via the bottom stream (14) by means of a pump (16) together with any unreacted reactants and high-boiling by-products. A part of the bottom stream (14) is evaporated with an evaporator (18) and fed into the column via the vapor line (15). This creates the vapor required for the distillation. The raw product is made over the

Product line (17) fed to the downstream workup. This workup can consist, for example, of a downstream evaporator, with which the crude product is freed from low boilers, in particular from unreacted reactants. It is possible to remove low-boiling

Components additionally feed an inert gas (30) into the bottom of the column. However, the workup can also be carried out directly in subsequent columns, preferably in dividing wall columns. The unreacted reactants are preferably returned to the column.

At the top (23) of the column (4), the lower-boiling reactant, if appropriate together with low-boiling by-products, accumulates in the case of aldol additions. This is fed via line (7) into the condenser (8), condensed out and fed back into the column via line (12), optionally after a partial flow has been discharged via line (13). In this way, the internal reflux in the column can be used to set a high concentration of the low-boiling reactant, if required, without setting a high molar ratio of the reactants to be fed in.

If an aldol condensation is carried out, the water of reaction formed leaves the column together with any unreacted reactants and / or low boilers formed as a by-product during the reaction via the top stream (7) and reaches the condenser (8) in which the condensable constituents of this vapor stream be condensed out. Part of the condensate is returned to the column as reflux (12) and the other part (13) is drawn off. A reflux ratio between 1 and 20, preferably between 2 and 4 should be set. However, it is also possible to completely to be withdrawn continuously (reflux ratio = 0) if the higher boiling reactant is added at the top of the column. When carrying out aldol condensations, the distillate (13) generally consists of water and low boilers or of an azeotrope of water and one of the reactants, which is passed on for further processing. When pseudoionone is produced from citral and acetone, for example, the azeotrope acetone / water is obtained at the top of the column and is separated in a subsequent column. If a heteroazeotrope occurs at the top of the column, the water of reaction can be discharged in a targeted manner using a phase separation vessel. It is also possible to discharge the water over the column sump and to drive the column as with the Aldol addition.

When carrying out hydrogenating aldolizations, a corresponding catalyst, preferably a Pd / Pr / AlO ₃ catalyst, is installed in the reaction zone (4) and hydrogen is fed into the column via the stream (29). A hydrogen partial pressure of 1 to 50 bar, preferably 1 to 20 bar, is set. The hydrogen is separated off via the top (23) of the column and returned to the column using a compressor (10).

The reaction column (4) generally consists of several zones with different functions. In the column internals of the reaction zone (21) between the feed points (2) and (3) of the column (4), the reactants are essentially reacted with simultaneous removal of the resulting products by distillation. Separation zones (20, 22) which are provided with distillative separation elements are generally located above and / or below the segment (21). In the lower separation zone (20), the reaction product is largely separated from the water which may be formed and from the low-boiling components, in particular from the low-boiling reactant added at point (3). The upper separation zone (22) ensures that the reactant added at the upper feed point (2) does not get into the distillate. The separation zones (20) and (22) are generally advantageous, but not absolutely necessary.

In the reaction zone (21), trays with a long residence time of the liquid, such as valve trays, preferably bubble trays or related types such as tunnel trays or Thormann trays, are advantageously installed. However, it is also possible to use metal mesh packs or sheet metal packs with an ordered structure or packed beds as column internals. If heterogeneous catalysts are used, this can be accommodated on the trays or as a catalyst bed be installed in the reaction zone (21). However, it is also possible to use catalyst-containing packings, such as Montz MULTIPAK or Sulzer KATAPAK, or to introduce the catalyst into the column in the form of packing. It is also possible to use catalytically active distillation packs or fabric bags filled with catalyst (so-called Bales or Texas tea bags). The catalyst is used in a concentration of 1 to 50% by volume, based on the empty volume of the column, preferably between 10 and 30% by volume.

To increase the residence time in the reaction zone, it is possible to pass a partial stream through one or more side draws (23) from the fractionation column (4) through the container or containers (26) and with the help of a pump (27) each leaving these containers Partial streams (25) are returned to the column (4). The containers can be filled with heterogeneous catalyst. Additional catalyst and / or reactants can optionally be metered into the containers (26) with the aid of a feed line (24). The heating of the container (26) makes sense.

In the separation zones (20, 22), column internals with a large number of separation stages, such as metal mesh packs or sheet metal packs with an ordered structure, such as Sulzer Melapak, Sulzer BX, Montz Bl types or Montz A3 types, are preferably used.

It has proven to be advantageous if the heat supply into the reaction system consisting of the column bottom (19) and fractionation column (4) and optionally container (26) does not only take place via the evaporator (18), but also via external heat exchangers (28) or via heat exchangers located directly on the column internals (21).

To carry out the reaction, fractionation columns are advantageously used which have internals 10 to 100 of the trays described in more detail above, preferably between 10 and 40 trays. It is advantageous to work in such a way that the higher-boiling reactants are introduced into the upper part of the column and the lower-boiling reactants into the lower part of the column. It has proven to be particularly advantageous if 0 to 50 trays, preferably 5 to 20 trays, in the separation zone (22) above the feed stream (2) for the higher-boiling reactants, 0 to 100 trays, preferably 5 to 30 trays, in the reaction zone and 0 to 50, preferably 5 to 20 trays, in the lower part of the column (20) below the feed stream (3), be provided. The same applies to the so-called theoretical plates in other column internals.

The following examples are intended to explain the invention in more detail, but without restricting it thereto.

Example 1: Production of pseudo ionone by aldolization of acetone and citral

A. Description of the equipment

The experimental apparatus consisted of a heatable 2 liter stainless steel reaction flask equipped with a stirrer, on which a distillation column (length: 1.2 m, diameter: 50 mm) was placed. The column was in the lower area

(Separation zone (20)) with 6 segments of a structured tissue pack of type A3-750 (total height: 30 cm) and in the upper area (separation zone (22)) with 5 segments of a structured tissue pack of type A3-750 (total height: 25 cm) filled. The reaction zone (21) in the middle of the column was filled with a bed of 1100 g (approx. 1650 ml) of the catalyst. Strands of 5% Pr on γ-Al0 were used as the catalyst, which were prepared by impregnating γ-Al0 ₃ with an aqueous solution of Pr nitrate and subsequent calcination. The column was equipped with thermocouples at regular intervals, so that the temperature could be measured at every 3rd to 4th theoretical stage, except in the bottom and at the top of the column. In addition to the temperature profile, the concentration profile in the column could be determined with the help of appropriate sampling points.

The reactants were metered into the column from feed containers standing on scales with a mass flow-controlled pump. The evaporator (18), 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 (17) was level-controlled from the evaporator with a pump conveyed into a container standing on a scale. The top stream (7) of the column was condensed out in a condenser (8) which was operated with a cryostat. Part (13) of the condensate ran through a return divider into a feed tank standing on a balance, while the other part (12) was fed as return to the column. The apparatus was equipped with a pressure regulator (11) and designed for a system pressure of 20 bar. All incoming and outgoing material flows were continuously monitored with a PLS nuously recorded and registered. The apparatus was operated in 24-hour operation (stationarity).

B. Experimental Procedure

55.0 g / h (0.35 mol / h) of citral (97%) were continuously added to the top stage of the column. About 20 cm below the reaction zone, 210.0 g / h (3.58 mol / h) acetone (99% pure) preheated to 80 ° C. were pumped continuously. Strands of 5% Pr on γ-Al0 _{3 were} used as catalyst in the reaction zone (21). A system pressure of 3 bar and a reflux ratio of 3 kg / kg were set. The bottom temperature was 92.5 ° C. and the residence time in the reactor system was about 1.2 hours, which was composed of 0.6 hours in the reaction part (21) of the column and 0.6 hours in the bottom (19). The bottom stream of the column was 183.9 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 pseudoionone and 2.18% by weight of high boilers. At the top of the column, 80.8 g / h of distillate consisting of 95.8% by weight of acetone and 4.2% by weight of water were drawn off. Pseudoionone with a selectivity of 97.3% based on citral and 84.4% based on acetone was obtained. The yield was 66.7% based on citral. The space-time yield was about 330 g / (l * h).

Example 2: Production of pseudo ionone with separation of the water overhead

In the apparatus described in Example 1, 55.0 g / h (0.35 mol / h) of citral (97% strength) were continuously added to the top stage of the column. About 10 cm below the reaction zone, 210.0 g / h (3.58 mol / h) acetone (99% pure) preheated to 80 ° C. were pumped continuously. Strands of 5% Pr on γ-Al0 _{3 were} used as catalyst in the reaction zone (21). A system pressure of 3 bar and a reflux ratio of 3 kg / kg were set. The bottom temperature was 92.5 ° C. and the residence time in the reactor system was about 1.3 hours, which consisted of 0.7 hours in the reaction part (21) of the column and 0.6 hours in the bottom (19). 185.0 g / h of crude product with 61.11% by weight of acetone, 0.08% by weight of water, 1.02% by weight of mesityl oxide, 1.52% by weight of diacetone alcohol, 4 , 34% by weight of citral, 30.08% by weight of pseudo-ionone and 1.85% by weight of high boilers. 78.0 g / h of distillate consisting of 95.7% by weight of acetone and 4.3% by weight of water were taken off at the top of the column. It was pseudoionone with a selectivity of 97.2% related to Citral and 83.8% obtained acetone. The yield was 82.6% based on citral. The space-time yield was about 409 g / (l * h).

Example 3: Preparation of pseudoionone by aldolization of acetone and citral

A Description of the equipment

The experimental apparatus consisted of a distillation column (length: 1.8 m, diameter: 50 mm) with a thin-film evaporator. The column was in the lower area (separation zone (20)) with segments of a structured tissue pack of the type Sulzer DX (total height: 125 cm) and in the upper area (separation zone (22)) with 3 segments of a structured tissue pack of the type Sulzer EX (total height: 15 cm) filled. The reaction zone (21) in the middle area of the column was filled with a bed of 600 g of the catalyst. Strands of 1% Pr on γ-Al ₂ 0 _{3 were} used as the catalyst, which were prepared by impregnating γ-Al0 with an aqueous solution of Pr nitrate and then calcining. The

The column was equipped with thermocouples at regular intervals so that the temperature could be measured at every 3rd to 4th theoretical stage, except in the bottom and at the top of the column. In addition to the temperature profile, the concentration profile in the column could be determined with the help of appropriate sampling points.

The reactants were metered into the column from feed containers standing on scales with a mass flow-controlled pump. The evaporator (18), which was heated to 113 ° C. with the aid of an electrical heater, had a hold-up between 50 and 150 ml during operation, depending on the dwell time. The bottom stream (17) was level-regulated from the evaporator with a pump conveyed a container standing on a scale. The top stream (7) of the column was condensed out in a condenser (8) which was operated with a cryostat. Part (13) of the condensate ran through a return divider into a feed tank standing on a balance, while the other part (12) was fed as return to the column. The apparatus was equipped with a pressure regulator (11) and designed for a system pressure of 20 bar. All incoming and outgoing material flows were continuously recorded and registered with a PLS throughout the test. The apparatus was operated in 24-hour operation (stationarity). B. Experimental Procedure

27.5 g / h (0.18 mol / h) of citral (97% im) were continuously added to the top stage of the column. About 20 cm below the reaction zone, 105.0 g / h (1.79 mol / h) acetone (99% im) preheated to 80 ° C. were pumped continuously. Strands of 1% Pr on γ-Al 0 _{3 were} used as catalyst in the reaction zone (21). A system pressure of 3 bar and a reflux ratio of 3 kg / kg were set. The bottom temperature was 101 ° C. and the residence time in the reactor system was about 1.9 hours, which consisted of 0.8 hours in the reaction part (21) of the column and 1.1 hours in the bottom (19). The bottom stream of the column was 90.8 g / h of crude product with 61.33% by weight of acetone, 0.10% by weight of water, 0.55% by weight of mesityl oxide, 2.31% by weight of diaketone alcohol,

15.08% by weight of citral, 17.98% by weight of pseudo-ionone and 2.65% by weight of high boilers. 40.0 g / h of distillate consisting of 96.6% by weight of acetone and 3.4% by weight of water were taken off at the top of the column. Pseudoionone with a selectivity of 99.5% based on citral and 51.2% based on acetone was obtained.

Claims

claims

1. Process for the preparation of carbonyl compounds of the general formula (I)

in which

Rl, R2, R3, R4 can each independently be the same or different and are hydrogen, an aliphatic hydrocarbon radical having 1 to 37 C atoms and substituted by one or more methoxy groups, a C ₃ -Cχ cycloalkyl group, a C ₄ -Co-cycloalkylalkyl group or mean an aryl radical and

A and B are each independently or simultaneously hydrogen, a hydroxy group, or an aliphatic hydrocarbon radical having 1 to 37 carbon atoms substituted by one or more methoxy groups, a C 1 -C ₄ cycloalkyl group, a C ₄ -C ₃ o-cycloalkylalkyl group or one Aryl radical, or A and B together mean an additional bond between the A and B bearing carbon atoms, by reaction of continuously fed carbonyl compounds of the general formula (II) or mixtures thereof

O R1-C-R2 (»).

in which

Rl and R2 have the meaning given above

FIG. with continuously fed carbonyl compounds of the general formula (III) or mixtures thereof

0

R4-C-R5 (HI),

in which R4 has the meaning given above and R5 has the same meaning as Rl to R4 and R4 or R5 is different from Rl or R2, characterized in that the reaction is a continuous process and at least one of the reaction products is separated from the reaction mixture.

2. The method according to claim 1, characterized in that the carbonyl compound of the general formula (II) used is one in which R 2 is hydrogen and R 1 is a group of the general formula (IV)

3. The method according to claim 1 and 2, characterized in that the carbonyl compounds of the general formula I are selected from the group pseudoionone, methylpseudoionone, dimethylpseudoionone or ethylpseudoionone.

4. The method according to claim 1 to 3, characterized in that the molar ratio of carbonyl compound (II) to carbonyl compound (III) is between 1 and 50.

5. The method according to any one of claims 1 to 4, characterized in that a reaction column is used as the reactor.

6. The method according to any one of claims 1 to 5, characterized in that the reactants are adjusted so that

a) the reaction of at least one of the cabonyl compound of the formula (II) with at least one of the carbonyl compound of the formula (III) takes place on the internals and, if appropriate, in the bottom of the reaction column and

b) the carbonyl compound of the formula (I) formed during the reaction is continuously separated off with the bottom stream of the column.

7. The method according to any one of claims 1 to 6, characterized in that the reaction in the presence of a homogeneous

15 catalyst is carried out.

8. The method according to any one of claims 1 to 7, characterized in that the reaction is carried out in the presence of a heterogeneous catalyst.

20

9. The method according to claim 8, characterized in that the heterogeneous catalyst contains an element of the lanthanoid series.

25 10. The method according to any one of claims 1 to 9, characterized in that the heat supply into the reactor system from the column bottom, fractionation column and optionally container not only takes place via the evaporator, but also via external heat exchangers or directly

30 heat exchangers located in the column internals.

11. The method according to any one of claims 1 to 10, characterized in that the reaction is carried out in the presence of hydrogen and / or a hydrogenating aldolization catalyst.

40

45