DE10238140A1 - Continuous production of carbonyl compounds such as pseudoionone from lower carbonyl compounds involves a continuous aldolisation process in which at least one of the products is removed from the reaction mixture - Google Patents

Abstract

Carbonyl compounds are obtained from shorter-chain carbonyl compounds by a continuous aldolisation process in which at least one of the products is removed from the reaction mixture. A method for the production of carbonyl compounds of formula R1R2C(A)-CR3(B)-CO-R4 (I) by reaction of continuously-introduced carbonyl compounds of formula R1-CO-R2 (II) with continuously-introduced carbonyl compounds of formula R4-CO-R5 (III), in which the reaction is a continuous process and at least one of the products is removed from the reaction mixture. R1-R4 = H, methoxy-substituted 1-37C aliphatic hydrocarbyl, 3-12C cycloalkyl, 5-30C cycloalkylalkyl or aryl; A, B = H, hydroxyl, or hydrocarbon groups as above, or A and B may form an additional bond between the carbon atoms to which they are attached; R5 = as for R1-R4, with R4 or R5 being different from R1 or R2

Description

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

Implementation of carbonyl compounds with aldehydes on acidic or basic catalysts one of the improvements according to the invention ab, already known in its essential characteristics. So becomes Example in Römpp Chemie Lexikon (Vol. 1., 9. extended, revised edition, Thieme Verlag 1995) the base-catalyzed addition of carbanions, the generated from activated methylene groups to the carbonyl group described by aldehydes or ketones. This type of reaction is called Aldol addition called. When using acids as Catalyst closes usually refer to the aldol addition water splitting off, so that in this case one speaks of an aldol condensation. The aldol addition of two different aldehydes or one aldehyde with a ketone is according to Römpp Chemistry lexicon only preparative usable if the aldehyde component does not have a? hydrogen atom, so that it can only act as a carbonyl component. This type of reaction is referred to in the literature as the Claisen-Schmidt reaction. There the aldol addition is a reversible reaction a cleavage into the output connections. Information on the technical implementation of this Reaction are in Römpp Chemistry lexicon not made.

In the Organikum (16th edition, VEB Deutscher Verlag der Wissenschaften, Berlin 1986) is the aldol reaction Implementation of aldehydes and ketones with yourself or with others Aldehydes and ketones defined as CH-acidic compounds. It will pointed out that the simple aldols only isolate themselves leave when working at low temperature. In many make includes extremely easy dehydration. In addition, ketones with two reactive centers such as. Acetone or butanone, the risk of the formation of di-aldolization products. The general working instructions for the implementation of Aldolization is not for suitable for implementation on a technical scale.

A process for the preparation of pseudoionone by reacting citral with acetone using LiOH as a catalyst is described in US 4874900 described. 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 ₂ after 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.

In the 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 process for the aldolization of Acetone in a reaction column is from Podrebarac, Ng and Rempel in Chemtech (May 1997, page 41). The catalyst will installed in the upper part of a distillation column, the acetone pumped into the column at an undisclosed location and over the sump a product mixture of diacetone alcohol, mesityl oxide, acetone and Withdrawn water. Podrebarac points out that the balance the aldolization of acetone by reactive distillation positive being affected. However, in the present invention Formation of condensation products of the ketone an undesirable side reaction, that should be avoided.

In 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 is returned to the reactor. 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. Sci. (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 developed. It is pointed out that the equilibrium of the reaction can be influenced positively with the reactive distillation. The catalyst activity and the selectivity of the reaction are determined via the liquid distribution and the flow tion profile influenced in the column, but this is undesirable for a technical application. 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), page 323-330 are studies on mass transport at the Production of diacetone alcohol and mesityl oxide in a reaction column using catalyst pockets as column internals described. According to this, the catalyst pockets have no significant influence to the number of separators. This is for reaction columns in the Usually disadvantageous because the reaction and distillation take place simultaneously should. In Chem. Eng. Sci. (1998), 53 (19), pp. 3489-3499 Model for the mathematical description of a reaction column for production indicated by diacetone alcohol, which is based on laboratory experiments.

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

In 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. Distillation zones are located below and / or above the reaction zone. 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.

As an example, ion exchangers, Zeolites or alumina with a Group VIII or IB metal such as nickel, palladium or copper. With this Processes become selectivities achieved by 61.2% based on acetone. This selectivity is for a technical Procedure unsatisfactory. The patent is also limited to the management of the DC reactants.

A process for the aldolization of aldehydes in the presence of a basic catalyst is described in JP 10053552-A described. 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.

In 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.

In DE 3319-430-A the production of higher ketones is claimed 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 claimed catalysts are a combination of oxides or phosphates of rare earth metals, Mg, Al, Zn or Ti and a metal from Group VIII. 5% by weight of Pr ₂ O ₃ and 0.5% by weight are used as examples .-% called Pd on alumina.

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 La ₂ O ₃ and ZrO 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 La ₂ O ₃ , Nd ₂ O ₃ , and Sm ₂ O _{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 CeO 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 (OH) ₂ , La (OH) ₃ , ZrO ₂ and CeO _{2 were} investigated for the condensation of acetone in the gas phase. In US5254743-A 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 area of at least 150 m ² / g patented. In JP-162329 La ₂ O ₃ , Nd ₂ O ₃ or Pr ₂ O ₃ on β-alumina is used as a catalyst for "various" chemical reactions Nannt.

The state of the art set out above makes it clear that hitherto a continuous process for aldolization of two different carbonyl compounds at the same time Separation of at least one of the reaction products does not exist. In addition, all known methods for dimerizing carbonyl compounds significant disadvantages.

The discontinuous process for aldolization of different carbonyl compounds Disadvantage of high dwell times and therefore low space-time yields, high investment costs and low yields. With the continuous Process for aldolization of different carbonyl compounds become the reactants first mixed, over a catalyst bed headed and the excess ketone only separated after the reaction. On the one hand, this leads to increased investment costs and a strong thermal load on the products with a reduced yield is connected. On the other hand, to achieve sufficient selectivity a reactant in high excess from above 20 mol / mol can be used.

In the continuous process for aldolization of acetone as well as for the condensation of n-Butyraldehyde only requires one reactant to enter a reaction column is dosed. The reaction is therefore trivial. In addition, it is described in the literature that the Self-aldolization of ketones or aldehydes in a reaction column is highly preferred, because the reaction balance is positively influenced. consequently self-condensation must be used when reacting carbonyl compounds with acetone of acetone as the preferred side reaction. With aldolization of different carbonyl compounds are due to the state technology through self-condensation always low selectivities with respect to at least one of the reactants expected. It is also in the literature strong influence on the selectivities described by the liquid distribution and the use of separator internals without the number of isolators only at simple reaction systems tolerable.

For those described in the literature Process for the preparation of methyl isobutyl ketone is analogous to Aldolization of acetone requires only a liquid reactant. Nevertheless the selectivities are extremely unsatisfactory. In terms of the problems in the implementation of different carbonyl compounds the aspects described above apply. The reactants are always led in cocurrent through the column.

Those described in the literature Process for aldolization of different carbonyl compounds point as explained above significant disadvantages. The invention was therefore based on the object new process for the continuous aldolization of different Carbonyl compounds with beneficial properties are available too provide, which no longer has the disadvantages of the prior art and the corresponding products in high selectivities as well delivers high space-time yields.

The implementation should be continuous feasible in a single reactor be, with high product selectivities regarding both carbonyl compounds if possible short response times can be achieved. In particular, should be avoided be that a reactant in large excess to achieve high selectivities used and must be separated after the reaction.

in der R1 bis R4 für Wasserstoff oder für einen gesättigten oder ungesättigten, verzweigten oder unverzweigten, gegebenenfalls durch eine oder mehrere Methoxygruppen substituierten aliphatischen Kohlenwasserstoffrest mit 1 bis 37 C-Atomen, eine Cycloalkylgruppe mit 4 bis 12 C-Atomen, eine Cycloalkylalkylgruppe mit 5 bis 30 C-Atomen oder einen Aromaten mit 6 bis 18 C-Atomen steht, und in der A und B beide Wasserstoff bedeuten, oder A oder B unabhängig voneinander eine Hydroxygruppe bedeuten oder dieselbe Bedeutung wie R1 bis R4 haben können, oder A und B zusammen eine zusätzliche Bindung zwischen den A und B tragenden C-Atomen bedeutet,
indem man kontinuierlich zugeführte Carbonylverbindungen der allgemeinen Formel (II) oder kontinuierlich zugeführte Gemische von Carbonylverbindungen der allgemeinen Formel (II)

in der R1 und R2 die oben genannte Bedeutung haben, mit kontinuierlich zugeführten Carbonylverbindungen der allgemeinen Formel (III) oder kontinuierlich zugeführten Gemischen von Carbonylverbindungen der allgemeinen Formel (III)

in der R4 die oben genannte Bedeutung hat und R5 die selbe Bedeutung wie R1 bis R4 haben kann, und entweder R4 oder R5 verschieden von R1 oder R2 ist,
kontinuierlich umsetzt und bei der Umsetzung mindestens eines der Reaktionsprodukte aus dem Reaktionsgemisch abtrennt.Accordingly, a process for the continuous production of carbonyl compounds of the general formula (I) has been found

in the R1 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 4 to 12 carbon atoms, a cycloalkylalkyl group having 5 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 R1 to R4, or A and B together means an additional bond between the A and B bearing C 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 fed carbonyl compounds of the general formula (III) or continuously fed mixtures of carbonyl compounds of the general my formula (III)

in which R4 has the meaning given above and R5 can have the same meaning as R1 to R4, and either R4 or R5 is different from R1 or R2,
continuously implemented and at least one of the reaction products separated from the reaction mixture during the reaction.

steht, in der n für eine ganze Zahl von 1 bis 6 steht und X und Y entweder beide für H stehen, oder aber X und Y zusammen eine zusätzliche Bindung zwischen den X und Y tragenden C-Atomen bedeutet.The carbonyl compound of the general formula (II) used in the process according to the invention is particularly preferably one in which R2 is hydrogen and R1 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 be apply in principle to all aldolization reactions. Special However, the process is important for the aldolization of citral with acetone for the production of pseudoionon and for the production of methylpseudoionon, Dimethylpseudoionon and ethylpseudoionon as these compounds important intermediates for the production of vitamin A and fragrances.

As a C ₇ -C ₃₇ aliphatic carbon radical for R1 to R4 and A and B there are straight-chain or branched saturated or mono- or polyunsaturated radicals with 1 to 37, preferably with 1 to 20 C atoms, particularly preferably with 1 to 15 C atoms into consideration.

For example, the 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, 1-methyl-2-pentenyl, isopropenyl, 1-butenyl, hexenyl, heptenyl, Octenyl, nonenyl or the decenyl group.

The preferred cycloalkyl radicals for R1 to R4 and A and 8 are C ₃ -C ₁₂ cycloalkyl radicals such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl or cyclodecenyl, which are optionally substituted one or more times by C ₁ -C ₄ -Alkyl, halogen (fluorine, chlorine, bromine, iodine), nitro, cyano, amino, C ₁ -C ₄ -alkylamino, C ₁ -C ₄ -dialkylamino, hydroxy or other atoms may be substituted or optionally 1 to 3 heteroatoms such as Contain sulfur, nitrogen or oxygen in the ring. Cycloalkylalkyl radicals contain a cycloalkyl radical linked to a C ₅ -C ₃₀ aliphatic hydrocarbon radical.

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

With the method according to the invention become selectivities from above 97% based on the carbonyl compound of the general formula (II) and at the same time about 84% based on the carbonyl compound of the general formula (III) reached. The space-time yield is greater by a factor of 3 than in the previously known methods. In addition, the reaction released heat of reaction be used for distillation and thus save energy costs become.

Another advantage of the method according to the invention is that the carbonyl compounds of formulas (II) and (III) in a molar ratio less than 20 can be used and still high selectivities in both Reactants can be achieved. A molar ratio between is preferred 5 and 15 set, the chemically more stable component of two carbonyl compounds usually forms the excess component. Especially with chemical reactive carbonyl compounds with double bonds, which tend to oligomerize have so far been much higher molar ratios required to achieve satisfactory selectivities. As an an example therefor the conversion of citral with acetone to pseudoionone is mentioned.

In addition, the inventive method the reaction product is immediately removed from the reaction mixture, so that subsequent reactions are avoided and thereby the yield is increased. moreover the water that may be formed during the reaction can be added to the Column head are separated. This will set the balance positively influenced and the distillative processing of the reaction discharge much simplified.

The process is designed as a reactive distillation off, so the concentration profile in the column by energy input and reflux ratio preferred adjusted so that there is 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.

With the method according to the invention in contrast to the previously known methods, it is possible Aldol addition products isolate. As products of the aldol addition, compounds of Denoted formula (I) in which A represents a hydroxy group and B can have the same meaning as R1 to R4. Because of the reaction Removal of the addition product from the reaction zone can subsequent Aldol condensation or cleavage of the product can be avoided.

With the method according to the invention it is also possible balance by appropriate concentration management the side of the product of aldol condensation with elimination of water to postpone. As products of the aldol condensation Designates compounds of formula (I) in which A and B an additional Bond mean. To implement this use case, the water formed is continuously removed from the reaction zone so that the balance is shifted to the product side becomes.

Furthermore, it is with the method according to the invention possible, to produce the hydrogenated products of the aldol condensation.

As products of aldol condensation compounds of the formula (I) in which A and B is hydrogen. This is done in the reaction zone of the reactor a bifunctional catalyst is used, which both aldolization as well as catalyzing the hydrogenation, and the reaction in the presence of Performed hydrogen.

The quantities used in the method according to the invention so choose that is a molar ratio Carbonyl compound (II) to carbonyl compound (III) between 1 and 50, preferably between 5.0 and 15.

Pressure and temperature are set so that high reaction rates at. sufficiently high selectivity result. When using a reaction column, the pressure on Column head is preferably set so that the temperature in the swamp between 50 and 300 ° C, preferably between 80 and 180 ° C lies. In the hydrogenating aldolization, the hydrogen partial pressure is 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.

As a catalyst for the process according to the invention 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 on a carrier be used. Sodium hydroxide solution is preferred as homogeneous catalyst and potassium hydroxide solution used, as this is liquid in the fractionation column can be pumped. Particularly preferred is the use of heterogeneous catalysts that are targeted can be accommodated in the reaction zone of the column and not to contaminate the product or require a neutralization of the reaction discharge. preferred Catalysts are catalysts containing elements of the lanthanoid series, preferably La, Ce and / or Pr, in a concentration of 0.1 to 20% by weight, preferably from 1 to 10% by weight, on aluminum oxide, preferred on? -alumina. The catalyst is in a concentration from 1 to 100% by volume, based on the empty volume of the reactor, is preferred between 10 and 30 vol .-%, used.

The catalyst is on the internals or as internals of a fractionation column or in one of the columns dwell tank connected in parallel installed.

An advantageous implementation of the method according to the invention is described below using the 1 described.

The process according to the invention is expediently carried out in such a way that the carbonyl compound of the general formula (II), the carbonyl compound of the general formula (III) and optionally the catalyst are fed in via the feeds ( 3 ), (2) and (1) on the internals of a fractionation column functioning as a reaction column ( 4 ) dosed. It is advantageous, but not essential, if the higher-boiling reactant is separated or continuously together with the catalyst above the lower-boiling reactant in the fractionation column ( 4 ) feeds and in this way forces a countercurrent of the reactants. It may be advantageous to feed the lower-boiling reactants in gaseous or superheated form into the column ( 4 ) to be dosed, because then a split in the swamp ( 19 ) the column at high temperatures and the formation of by-products is avoided. The pressure at the top of the column ( 9 ) is set so that the temperature in the sump ( 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 ) happen.

On the internals ( 21 ) of the fractionation column ( 4 ) the reaction of the carbonyl compound of formula (II) with the carbonyl compound of formula (III) takes place. The superimposed distillation continuously removes the carbonyl compound of the formula (2) from the reaction equilibrium and the reaction zone, enters the bottom ( 19 ) of the fractionation column and is over the stream ( 14 ) deducted. When an aldol condensation is carried out, the water formed by the reaction is also continuously removed from the reaction zone. The superimposed distillation therefore has a positive influence on the reaction equilibrium on the one hand and on the other hand prevents subsequent reactions and thus high selectivities.

The reaction product collects in the swamp ( 19 ) the column ( 4 ) and is pumped ( 16 ) together with possibly unreacted reactants and high-boiling by-products via the bottom stream ( 14 ) deducted. Part of the bottom stream ( 14 ) with an evaporator ( 18 ) evaporated and via the vapor line ( 15 ) led into the column. This creates the vapor required for the distillation. The raw product is fed through the product line ( 17 ) the downstream processing. 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 also possible to use an inert gas ( 30 ) feed 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.

On the head ( 23 ) the column ( 4 ) accumulates the lower-boiling reactant with aldol additions, possibly together with low-boiling by-products. This is via the line ( 7 ) in the capacitor ( 8th ) led, condensed and over the line ( 12 ), if necessary after a partial flow has been discharged via the line ( 13 ), returned to the column. 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 overhead stream ( 7 ) and gets into the condenser ( 8th ), in which the condensable components of this vapor stream are condensed out. Part of the condensate is used as return ( 12 ) added to the column and the other part ( 13 ) deducted. A reflux ratio between 1 and 20, preferably between 2 and 4 should be set. However, it is also possible to remove the condensate completely continuously (reflux ratio = 0) if the higher boiling reactant is introduced at the top of the column. The distillate ( 13 ) usually 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, the reaction zone ( 4 ) an appropriate catalyst, preferably a Pd / Pr / Al ₂ O ₃ catalyst, is installed and over the stream ( 29 ) Hydrogen fed into the column. A hydrogen partial pressure of 1 to 50 bar, preferably 1 to 20 bar, is set. The hydrogen is over the head ( 23 ) separated from the column and with a compressor ( 10 ) returned to the column.

The reaction column ( 4 ) usually consists of several zones with different functions. On the column internals of the reaction zone ( 21 ) between the inlet points ( 2 ) and (3) the column ( 4 ) essentially the reaction of the reactants takes place with simultaneous distillative removal of the resulting products. Above and / or below the segment ( 21 ) there are usually separation zones ( 20 . 22 ), which are provided with separating elements. In the lower separation zone ( 20 ) the reaction product is largely from the water that may be formed and from the low-boiling components, in particular from that at the point ( 3 ) added low-boiling reactants, separated. The upper separation zone ( 22 ) ensures that the at the upper inlet point ( 2 ) added reactant does not get into the distillate. The separation zones ( 20 ) and (22) are usually advantageous, but not essential.

In the reaction zone ( 21 ) Soils with a long dwell time of the liquid, such as valve bottoms, preferably bell bottoms or related types such as tunnel bottoms or Thormann bottoms, 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 in the reaction zone ( 21 ) can be installed. However, it is also possible to use catalyst-containing packings, such as Montz MULTI-PAK 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 separate 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 ) the partial flows leaving these containers ( 25 ) back into the column ( 4 ) attributed. The containers can be filled with heterogeneous catalyst. In the container ( 26 ) can with the help a supply line ( 24 ) optionally additional catalyst and / or reactants are metered. Heating the tanks ( 26 ) makes sense.

In the separation zones ( 20 . 22 ) Column internals with a high number of plates, such as metal mesh packings or sheet metal packings with an ordered structure, such as Sulzer Melapak, Sulzer BX, Montz B1 types or Montz A3 types, are preferably used.

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

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 inlet flow ( 2 ) for the higher boiling reactant, 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 flow ( 3 ) can be provided. The same applies to the so-called theoretical plates in other column internals.

The following examples are intended the invention closer explain, but without restricting it to that.

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 )) filled with 5 segments of a structured tissue pack of type A3-750 (total height: 25 cm). 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-A1 ₂ O _{3 were} used as the catalyst, which were prepared by impregnating γ-Al ₂ O 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 help of a thermostat, had a hold-up between 50 and 150 ml during operation, depending on the dwell time. 17 ) was conveyed from the evaporator with a pump to a container on a scale. The head stream ( 7 ) the column was placed in a condenser ( 8th ), which was operated with a cryostat, condensed out. A part ( 13 ) of the condensate ran via a return divider into a storage container standing on a balance, while the other part ( 12 ) was added to the column as reflux. 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. Execution of the experiment

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. As a catalyst in the reaction zone ( 21 ) strands of 5% Pr on γ-Al ₂ O _{3 were} used. 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 approximately 1.2 hours, which resulted from 0.6 hours in the reaction part ( 21 ) of the column and 0.6 hours in the swamp ( 19 ) composed. 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 % Water withdrawn. 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 / (1 * h).

Example 2: Production of Pseudoionon (PJ) 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. As a catalyst in the reaction zone ( 21 ) strands of 5% Pr on γ-Al ₂ O _{3 were} used. 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 was 0.7 hours in the reaction part ( 21 ) of the column and 0.6 hours in the swamp ( 19 ) composed. 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. Pseudoionone with a selectivity of 97.2% based on citral and 83.8% based on acetone was obtained. The yield was 82.6% based on citral. The space-time yield was about 409 g / (l * h).

Example 3: Production of pseudo ionone by aldolization of acetone and citral

A description the apparatus

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 )) filled with 3 segments of a structured tissue pack of the type Sulzer EX (total height: 15 cm). The reaction zone ( 21 ) in the middle of the column was filled with a bed of 600 g of the catalyst. Strands of 1% Pr on γ-Al ₂ O _{3 were} used as the catalyst, which were prepared by impregnating γ-Al ₂ O 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 113 ° C with the help of an electric heater, had a hold-up between 50 and 150 ml during operation, depending on the dwell time. 17 ) was conveyed from the evaporator with a pump to a container on a scale. The head stream ( 7 ) the column was placed in a condenser ( 8th ), which was operated with a cryostat, condensed out. A part ( 13 ) of the condensate ran via a return divider into a storage container standing on a balance, while the other part ( 12 ) was added to the column as reflux. 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. Execution of the experiment

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. As a catalyst in the reaction zone ( 21 ) strands of 1% Pr on γ-Al ₂ O _{3 were} used. 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 approximately 1.9 hours, which resulted from 0.8 hours in the reaction part ( 21 ) of the column and 1.1 hours in the swamp ( 19 ) composed. 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 pseudoionone 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 (11)

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

where R1, R2, R3, R4 can each independently be the same or different and hydrogen, an aliphatic hydrocarbon radical with 1 to 37 C atoms substituted by one or more methoxy groups, a C ₃ -C ₁₂ cycloalkyl group, a C ₅ -C ₃₀ Are a cycloalkylalkyl group or an aryl radical and A and B are each independently or simultaneously hydrogen, a hydroxyl group or an aliphatic hydrocarbon radical having 1 to 37 C atoms, substituted by one or more methoxy groups, a C ₃ -C ₁₂ cycloalkyl group, a C ₅ - C ₃₀ -cycloalkylalkyl group or an aryl radical, or A and B together mean an additional bond between the A and B-bearing carbon atoms, by reaction of continuously supplied carbonyl compounds of the general formula (II) or mixtures thereof

wherein R1 and R2 have the meaning given above with continuously fed carbonyl compounds of the general formula (III) or mixtures thereof

in which R4 has the meaning given above and R5 has the same meaning as R1 to R4 and R4 or R5 is different from R1 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. Process according to Claim 1, characterized in that the carbonyl compound of the general formula (II) used is one in which R2 is hydrogen and R1 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. Process according to claim 1, characterized in that the carbonyl compounds of the general formula I selected are from the group pseudoions, methylpseudoions, dimethylpseudoions or ethyl pseudoions. Method according to claim 1 or 2, characterized in that the molar ratio of carbonyl compound (II) to the carbonyl compound (III) is between 1 and 50. Procedure according to a of claims 1 to 4, characterized in that the reactor is a reaction column used. Process according to one of claims 1 to 5, characterized in that the reactants are adjusted so that A is 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) is carried out 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. Procedure according to a of claims 1 to 6, characterized in that the reaction in the presence a homogeneous catalyst is carried out. Procedure according to a of claims 1 to 7, characterized in that the reaction in the presence a heterogeneous catalyst is carried out. Method according to claim 8, characterized in that the heterogeneous catalyst is an element of Contains lanthanoid series. Procedure according to a of claims 1 to 9, characterized in that the supply of heat into the reactor system not from the column bottom, fractionation column and, if applicable, container only over the evaporator, but also via external heat exchangers or about heat exchangers located directly on the column internals. Procedure according to a of claims 1 to 10, characterized in that the reaction in the presence of hydrogen and / or a hydrogenating aldolization catalyst carried out becomes.