WO2009003796A1

WO2009003796A1 - Method for the synthesis of neral by the isomerization of isocitrals

Info

Publication number: WO2009003796A1
Application number: PCT/EP2008/057173
Authority: WO
Inventors: Joachim Schmidt-Leithoff; Christoph JÄKEL; Rocco Paciello; Gunnar Heydrich; Thomas Heidemann
Original assignee: Basf Se
Priority date: 2007-06-29
Filing date: 2008-06-09
Publication date: 2009-01-08

Abstract

The present invention relates to a method for the synthesis of neral and/or geranial by the isomerization of one or more isocitrals. In particular, the invention relates to a method for the synthesis of neral in pure or enriched form, starting out from a mixture of materials containing neral and geranial and one or more isocitrals.

Description

PROCESS FOR THE PREPARATION OF CITRAL (NERAL AND / OR GERANIAL) BY ISOMERIZATION OF ISOCITRALES

Description:

The present invention relates to a process for the preparation of neral and / or geranial by isomerization of one or more isocitrals. Specifically, the invention relates to a process for the production of neral in pure or enriched form of neral starting from mixtures containing neral and geranial and one or more isocitrals.

Citral (3,7-dimethyl-octa-2,6-diene-1-al) is an important aroma chemical as well as a starting or intermediate product for the production of a wide variety of active substances. It is particularly important that citral is an α, β-unsaturated aldehyde which is attractive on the one hand as a synthesis building block, but on the other hand, due to its high reactivity, also tends to have side reactions, for example isomerization. Citral can be isolated from natural sources as well as synthesized and usually accumulates in the form of mixtures of the E / Z isomers Neral and Geranial. For specific applications in the field of aroma or synthetic chemistry, it may be desirable to be able to use the two aforementioned double bond isomers in pure or enriched form.

The separation of E / Z mixtures of the citral usually leads to the formation of further double-bond isomers, which are characterized by the fact that one of the ethylenic double bonds of the citral has migrated to a different position in the molecule. These constitutional isomers, collectively referred to as isocitrals, are undesirable by-products because they reduce the yield of purified recyclables to be obtained, are difficult to separate, and are not economically desirable to recycle.

US 556,944 discloses a process for isomerizing specific structurally citral-related compounds by the action of dilute sulfuric acid to give lower boiling point and higher specific gravity isomers. In particular, the reaction of geranylic acid to isogeranilic acid and of the corresponding nitrile to isogeranylsitrile is described. In addition, the isomerization of geranides (CgHiε) is described to isogeranides.

DE 25 51 783 relates to a process for the isomerization of one of the geometric isomers of an α, ß-unsaturated aldehyde in the corresponding other geometric see isomers based on a double bond in the α, ß-position. The method is characterized in that it is heated at a temperature of 30 to 400 ⁰ C in the presence of an acid having a pKa of 1 to 7 as a catalyst. The example becomes Isomerization of the two isomers of citral into each other in the presence of organic or inorganic acidic catalysts described.

EP 0 481 798 discloses a process for the separation of citral from citral-containing mixtures having a pH of 3 to 7 by fractional distillation to obtain a substantially pure citral-containing fraction. The setting of said pH value suppresses isomerization of citral to isocitral during the distillation. Preferred embodiments relate to distillation under reduced pressure, the preferred pH range of 4 to 5 and preferred acids having a pKa of 4 to 5. The application further relates to a method for suppressing the thermally induced isomerization of citral to isocitral.

W.A.M. Wolken et al. describe in J. Agric. Food Chem. 2000, 48, 5401 - 5405 describe the cis-trans isomerization of citral in the presence of amino acids as catalysts in aqueous alkaline solutions. In this case, mixtures of the two double bond isomers are obtained from samples of geranial and neral.

JP 51133216 relates to a process for the preparation of trans-citral by isomerization of cis-citral in the presence of a cyclic tertiary amine having a pKa value of 7 to 13.

JP 51 113803 discloses a process for producing trans-citral by isomerization of cis-citral in the presence of an acid at a temperature of 0 to 75 ° C. As acids dilute hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, p-toluenesulfonic acid and periodic acid are called.

JP 51 113802 relates to a corresponding process for the preparation of cis-citral by isomerization of trans-citral in the presence of an acid at a temperature of 0 to 75 ° C.

EP 1 514 955 relates to a process for the distillative workup of the electrolysis of the electrochemical oxidation of 1, 1, 2,2-tetramethoxyethane with methanol to trimethyl orthoformate in a liquid electrolyte, wherein a Trennwandko- lonne is used with 30 to 150 theoretical plates ,

DE 103 30 934 discloses a process for the continuous isolation of citronella IaI or citronellol from a crude mixture containing at least one of these compounds by rectification. In this case, preference is given to using those starting mixtures which can be obtained by partial hydrogenation of citral or citronellal. DE 102 23974 relates to a process for the continuous isolation of two stereoisomeric isoprenoid alcohols, especially nerol and geraniol, from a crude mixture by rectification, wherein the crude mixture is introduced laterally into a feed column, at least one is provided with the feed column coupled withdrawal column and from the discharge column a first and withdrawing a second isoprenoid alcohol. In this case, the inlet and the discharge column are coupled in such a way that, at least in the region of the withdrawal of the isoprenoid alcohols, there is no cross-mixing of vapors and condensate.

DE 102 23 971 discloses a process for the continuous isolation of an α, β-unsaturated aldehyde, especially citral, from a crude mixture containing it by rectification. In this case, the crude mixture is introduced laterally into an inflow column with a reinforcing part situated above the feed point and a stripping section located below the feed point, an upper unification column with condenser at the upper end of the column and a co-ordinating column communicating with the lower end of the stripping section communicating with the upper end of the reinforcing part Provided heater at the lower end of the column and provided communicating with the upper union column and the lower union column union column. The oφ-unsaturated aldehyde is withdrawn as a side draw from the withdrawal column and withdrawn at the top of the upper union column lower boiling compounds and higher boiling compounds in the bottom of the lower union column.

In view of the cited prior art, there is still a need for processes which make it possible to obtain isocitrals which are formed by isomerization in the separation or purification of neral or geranial or mixtures thereof, in particular in the context of processes carried out on an industrial scale To make it usable.

The object has been achieved according to the invention by the provision of a process for the preparation of compounds of the formula (I)

and / or geranial of the formula (II)

by isomerization of one or more isocitrals selected from the group of isocitrals of the formulas (III), (IV) and (V)

(IN) (IV) (V)

Surprisingly, it has been found that the isocitrals of the formulas (III), (IV) and / or (V) obtained by isomerization, usually by thermal isomerization of neral or geranial or mixtures thereof, can be re-isomerized to give neral and / or geranial. The re-isomerization can in principle be carried out thermally or be carried out under acidic or basic conditions. According to the invention, preference is given to carrying out the isomerization of said isocitrals under thermal conditions and / or under basic conditions, ie. in the presence of one or more different bases, by.

The isocitrals to be isomerized according to the invention are usually obtained in the form of mixtures with one another and / or in the form of mixtures with geranial and / or neral and can be used in this form in the context of the process according to the invention. Typical mixtures which can be used in the process according to the invention contain, for example, usually in addition to neral and / or geranial, about 10% by weight to about 100% by weight, preferably about 15 to about 80% by weight and particularly preferably about 20 to about 70 wt .-%, preferably up to about 60 wt .-% of said isocitrals (based on the sum of the isocitrals and based on the mixture to be used).

By means of the isomerization according to the invention, neral and / or geranial normally accumulate in the form of mixtures thereof, the mixtures obtained according to the invention being distinguished by a lower content of isocitrals of the formulas (III), (IV) and / or (V) than the respective starting material mixtures used or accordingly by a higher content of neral and / or geranial than the mixtures used, provided that they contain neral and / or geranial. Accordingly, net, the inventive method a way to produce Neral, or of mixtures containing Neral and Geranial in enriched form.

The isomerization according to the invention can be thermally induced or preferably carried out under basic conditions. The thermal isomerization can be carried out, for example, such that the isocitrals mentioned in pure form or in the form of the mixtures described above to temperatures in the range of 50 to 300 ⁰ C, preferably in the range of 80 to 250 ⁰ C, particularly preferably in the range of 1 10 to 210 ⁰ C over a period of usually about 1 minute to about 10 hours, preferably about 10 minutes to about 8 hours, more preferably about 30 minutes to about 4 hours, preferably under a protective gas atmosphere heated.

The isomerization according to the invention can also be carried out under acidic or preferably under basic conditions, i. in the presence of basic reagents or preferably catalysts. The stated basic reagents or catalysts may be organic or inorganic compounds and be used in homogeneous or heterogeneous form. The reagents or catalysts which can be used according to the invention can be Bronsted bases and / or Lewis bases, preferably Bronsted bases or inorganic Lewis bases. The term basic reagents or catalysts are preferably those bases which have a pKa of from 25 to 40, preferably from 28 to 38 or their conjugated acids have a pKa of from 3 to 13, preferably from 5 to 10, wherein the term pKa value is defined as described in MB Smith, J.March, March's Advanced Organic Chemistry, 5th ed., 2001, John Wiley & Sons, Inc., New York (p. 327 et seq.). The isomerization according to the invention is preferably carried out in the presence of a basic catalyst.

Preferred basic catalysts according to the invention are primary and secondary amines, for example aniline, ring-substituted and / or N-substituted anilines, octylamine, dibutylamine, dicyclohexylamine, diisopropylamine, piperidine and the like more or tertiary amines such as, for example, tridodecylamine, collidine, lutidine, N- Methylpiperidine and the like more. Within the scope of a particularly preferred embodiment, the process according to the invention is carried out in the presence of a tertiary amine as the basic catalyst.

Further basic catalysts which can advantageously be used in the manner according to the invention are basic ion exchange resins which contain ammonium groups or amine groups, preferably tertiary amine groups. Suitable basic ion exchange resins are examples of a wide variety of different suitable ion exchangers: Amberlite® IRA 67, Amberlite® IRA-96, Amberlyst® A21, Amberlyst® A23, Amberlyst® A24, Dowex® 66, Dowex® Monoshere® 77, Dowex® Marathon® WBA, Dowex® M-43, having tertiary amine groups, and Ambersep® 900, Amberlyst® A26, Amberlyst® A27, Amberlite® 900, Amberlite® 904, Amberlite® 400, Amberlite® 401, Amberlite® 410. Dowex® 22, Dowex® 1, Dowex® Marathon® A, which have quaternary ammonium groups.

Further basic catalysts which can advantageously be used in the manner according to the invention are inorganic basic catalysts, preferably inorganic basic fixed-bed catalysts. Examples of suitable catalysts of this type are: Catalysts containing Al 2 O 3 or O 2 O or ZrO 2 or MgAbO ₄ (in various modifications) and metal oxides of the first or second main group of the Periodic Table of the Elements and catalysts containing Al 2 O 3 or TiO 2 or ZrO 2 and metal oxides from the Group of lanthanides and further optionally contain metal oxides of the first or second main group of the Periodic Table of the Elements. In a preferred embodiment of the process according to the invention, use is made of an alkaline earth-doped and / or rare earth oxide-doped aluminum oxide, titanium dioxide or zirconium oxide as the inorganic basic catalyst.

The amount of basic reagents or catalysts to be used according to the invention is not critical and can be varied over a wide range. The chosen catalyst or catalysts are usually employed in an amount of from 0.01 to 20% by weight, preferably from 0.1 to 15% by weight and more preferably in an amount of from 0.5 to 10% by weight. %, based on the amount of educt used.

The isomerization under basic conditions can be carried out, for example, by preference for the stated isocitrals in the pure form or in the form of the mixtures described above (in the presence of the selected basic reagents or catalysts) at temperatures in the range from 20 to 200 ^° C. in the range of 50 to 150 ⁰ C, more preferably in the range 80 to 130 ⁰ C over a period of usually about 1 minute to about 10 hours, preferably about 10 minutes to about 8 hours, more preferably about 30 minutes to about 4 hours preferably under a protective gas atmosphere, heated.

The inventive thermally induced or under basic conditions to be carried out isomerization can be carried out in all suitable for such reactions reactors such as stirred reactors (individually or cascade of several stirred reactors) or tubular reactors. If the isomerization is carried out under basic conditions, especially in the presence of homogeneous basic reagents or catalysts, separation of the catalyst or reagent used advantageously takes place after isomerization, for example by extractive work-up or by filtration or distillation according to processes known per se to those skilled in the art. In a preferred embodiment, the present invention relates to a process for the preparation of neral of the formula (I) in pure or enriched form starting from mixtures containing neral and geranial of the formula (II) and one or more isocitrals selected from the group of isocitrals of the formulas (III), (IV) and (V)

comprising the steps

a) distillative separation of the mixture containing neral, geranial and isocitral into one or more fractions of pure or enriched neral and one or more fractions containing isocitrals of the formulas (III), (IV) and / or (V) , which is greater than that of the mixture used (I-socitral fractions), and optionally other fractions; b) separating one or more isocitral fractions and one or more fractions of pure or enriched neral; c) isomerization of the isocitrals of the formulas (III), (IV) and / or (V) to geranial and / oreral contained in the isocitral fractions to obtain a mixture containing geranial and / or neral and d) recycling of the step c ) obtained substance mixture in step a).

The process according to the invention is preferably carried out continuously.

Suitable starting materials for carrying out the process according to the invention in the context of this preferred embodiment are mixtures of substances which contain neral and geranial, preferably those which consist predominantly of the double bond isomers Neral and Geranial. Preference is given to those compositions which consist of at least 90 wt .-% to 100 wt .-%, particularly preferably at least 95 to 98 wt .-% of geranial and neral and in addition to a small extent, i. to a proportion of up to 10% by weight, preferably up to 5% by weight, of further components, for example the isocitrals of the formulas (III) to (V) mentioned above,

May contain by-products or impurities. A preferred feedstock is synthetically produced citral, in particular such that by thermal cleavage of 3-methyl-2-butene-1-al-diprenylacetal with elimination of prenol to cis / trans-prenyl- (3-methyl-butadienyl) ether, Claisen rearrangement thereof to 2,4,4-trimethyl-3-formyl-1,5-hexadiene and subsequent Cope rearrangement thereof, as described, for example, in EP 0 992 477. When using mixtures of substances which, in addition to geranial and neral, have none of the isocitrals mentioned, they are known to be formed by thermal stress in the course of the distillative separation according to step a) of the process preferred according to the invention and are accordingly to be regarded as usable mixtures within the scope of this embodiment. In another preferred embodiment of the process according to the invention, use is made of a substance mixture comprising from 30 to 70% by weight, preferably from 40 to 60% by weight, of neral, from 70 to 30% by weight, preferably from 60 to 40% by weight of geranial and 0 to 5% by weight, preferably 1 to 5% by weight, of further components, preferably from the isocitrals of the formulas (III), (IV) and / or (V ), the percentages adding up to 100% by weight.

The distillative separation according to the invention in step a) of the process according to the invention is advantageously carried out by separating the used mixture containing neral and geranial into one or more low-boiling, medium-high and high-boiling fractions or fractions, and pure or enriched neral Form as medium boiler fraction at the side take-off point of the invention preferably used dividing wall column or the interconnection of two distillation columns in the form of a thermal coupling in liquid or gaseous form takes.

Accordingly, the process according to the invention is also a process for the isolation of neral, preferably a continuous process for the isolation of neral in pure or enriched form by distillative separation of neral from mixtures containing neral and geranial.

The distillative separation to be carried out in the context of the preferred embodiment of the process according to the invention in step a) is particularly preferably carried out in a dividing wall column or in an interconnection of two distillation columns in the form of a thermal coupling with 80 to 200 theoretical plates and one or more side draw-off points absolute operating pressure of 5 to 200 mbar, preferably 5 to 100 mbar before.

The dividing wall column preferably used according to the invention in this embodiment or the interconnection of two distillation columns in the form of a thermal coupling has or have 80 to 200, preferably 100 to 180 theoretical plates and one or more, preferably 1 to 3, particularly preferably 1 or 2 Side trigger points on. According to the invention, preference is given to using a dividing wall column as described above.

The inventive distillative separation according to step a) is preferably at an absolute operating pressure in the dividing wall column or in the interconnection of two distillation columns in the form of a thermal coupling of 5 to 200 mbar, preferably from 5 to 70 mbar and more preferably from 10 to 40 mbar performs. It is preferred to operate the dividing wall column or the interconnection of two distillation columns in the form of a thermal coupling so that the absolute top pressure is 10 to 50 mbar, preferably 10 to 40 mbar. Also It is preferred to operate the dividing wall column or the interconnection of two distillation columns in the form of a thermal coupling so that the absolute bottom pressure is 5 to 200 mbar, preferably 20 to 50 mbar.

The reflux ratio can be varied within wide limits when carrying out step a) of the preferred embodiment of the process according to the invention and is usually from about 5 to 1 to about 2000 to 1, preferably about 20 to 1 to 1000 to 1. A dephlegmator is also advantageous -Fahrweise, ie it is condensed in the top condenser of the column only the return and fed back to the column. In such an energetically favorable case of the partial condensation, the top product to be discharged falls exclusively in the aftercooler, which can be operated at a lower temperature.

The term Neral in an enriched form is to be understood as meaning neral-containing mixtures which have a higher content of neral than the mixture of substances containing neral and geranic acid used in accordance with the invention. Preferably, the term Neral in enriched form means such Neral that a purity, i. a Neral content of 80 to 95 wt .-%, preferably from 85 to 95 wt .-% and particularly preferably from 90 to 95 wt .-%. The process according to the invention also makes it possible to prepare neral (cis-citral) in pure form. The term neral in pure form is understood to mean neral with a content of greater than or equal to 95, 96 or 97% by weight, preferably greater than or equal to 98% by weight and particularly preferably 98 to 99.5% by weight. Particularly preferably, the term Neral in pure form is to be understood as meaning such a mineral that a geranial content of up to 1% by weight, preferably from 0.05 to 0.5% by weight and particularly preferably from 0.1 to 0 , 3 wt .-%. Also preferably, according to the invention accessible Neral in pure form has a content of isocitrals of the formulas (III), (IV) and (V) of up to 2 wt .-%, preferably from 0.1 to 1 wt .-%, wherein All information in the context of the present invention refers to the respective mixtures.

The feed, i. the mixture of substances to be used in step a) within the scope of the preferred embodiment can be passed into the dividing wall column or the interconnection of two distillation columns in the form of a thermal coupling, preferably into the dividing wall column, where they are in a head and sump fraction and one or more several side courses are separated. In a side run, the desired product Neral is obtained in the desired purity. In a particular embodiment, the head condenser of the column is followed by a post-condenser which is cooled with cooling liquid (for example brine) and in which a low-sulfur low-boiling fraction is obtained.

For the distillative decomposition of multicomponent mixtures, different process variants are customary in the prior art. In the simplest case, the supply is running mixture in two fractions, a low-boiling overhead fraction and a high-boiling bottom fraction, decomposed. In the separation of feed mixtures into more than two fractions, a plurality of distillation columns must be used according to this process variant. In order to limit the expenditure on equipment, it is possible in the separation of multi-component mixtures, if possible, columns with liquid or vapor side draws. However, the possibility of using distillation columns with side draws is severely limited by the fact that the products removed at the side draw-off points are never completely clean. With side withdrawals in the reinforcing part, which usually take place in liquid form, the side product still contains portions of low-boiling components which are to be separated off via the top. The same applies to side withdrawals in the stripping section, which usually take place in vapor form, in which the side product still has high boilers. The use of conventional side draw columns is therefore limited to cases where contaminated side products are allowed.

One remedy is provided by dividing wall columns. This column type is described, for example, in US 2,471,134; US 4,230,533; EP 0 122 367; EP 0 126 288; EP 0 133 510; Chem. Eng. Technol. 10 (1987) 92-98; Chem-Ing.-Tech. 61 (1989) No.1, 16-25; Gas Separation and Purification 4 (1990) 109-14; Process Engineering 2 (1993) 33-34; Trans IChemE 72 (1994) Part A 639-644 and Chemical Engineering 7 (1997) 72-76.

With this design, it is possible to remove side products also in pure form. In the central area above and below the feed point and the Seitenent- would take a partition wall is attached, which seals the inlet part relative to the removal part and prevents cross-mixing of liquid and vapor streams in this column part. This reduces the number of total distillation columns required in the separation of multicomponent mixtures. Since this column type represents a simplified apparatus for thermally coupled distillation columns, it also has a particularly low energy consumption. A description of thermally coupled distillation columns, which may be embodied in various apparatus design, can also be found in the abovementioned points in the specialist literature. Dividing wall columns and thermally coupled columns offer advantages over the arrangement of conventional distillation columns both in terms of energy requirements and investment costs and are therefore increasingly used industrially.

FIG. 1 shows schematically a preferred embodiment of the preferred separation according to the invention of the material mixture containing neral and geraniums into a low-pitch head fraction (j), a rich-rich side fraction (f) and a low-sulfur bottom fraction (g). The neral and geranial-containing feed to the dividing wall column can be liquid (b) gaseous (c), or gaseous and liquid. Figure 2 shows schematically a particularly preferred embodiment of the present invention preferred method for producing Neral in pure or enriched form, in addition to the features mentioned in Figure 1 including borrowing the side draw (f) the Seitenabzugsstellen (n) and (o) provided are.

The process according to the invention is carried out continuously. Consequently, the mixtures of substances containing neral and geranio to be used as starting material are fed continuously to the dividing wall column or the interconnection of two distillation columns in the form of a thermal coupling and the products (fractions) or by-products obtained according to the invention are discharged continuously.

The column is usually followed by another capacitor whose working temperature is 10 to 40 K, preferably 20 to 30 K below the working temperature of the top condenser of the dividing wall column. With its help, a large part of the low boilers still contained in the overhead stream (k) can be precipitated.

Dividing wall columns can also be replaced by two thermally coupled columns. This is especially beneficial if the columns are already present or the columns are to be operated at different pressures. In the case of thermally coupled columns, it may be advantageous to partially or completely vaporize the bottom stream of the first column in an additional evaporator and then to feed it to the second column. This pre-evaporation is particularly suitable when the bottom stream of the first column contains relatively large amounts of middle sieve. In this case, the pre-evaporation can be done at a lower temperature level and the evaporator of the second column are relieved. Furthermore, can be substantially relieved by this measure, the output part of the second column. The pre-evaporated stream can be fed to the second column in two phases or in the form of two separate streams.

In addition, it may be advantageous both in dividing wall columns and in thermally coupled columns to subject the feed stream to a pre-evaporation and then to feed it to the column in two-phase or in the form of two streams. This pre-evaporation is particularly useful when the feed stream contains larger amounts of low boilers. By pre-evaporation of the stripping section of the column can be significantly relieved.

Dividing wall columns and thermally coupled columns can be carried out both as packed columns with random packings or ordered packings or as tray columns. In the process according to the invention for the production of neral in pure or enriched form, it is recommended to use packed columns. In this case, ordered sheet metal or fabric packings with a specific surface from about 100 to 750 m ² / m ³ , preferably about 350 to 500 m ² / m ³ particularly suitable.

If, as in the case of the present invention, particularly high demands are placed on the purities of the products, it is advantageous to provide the partition with thermal insulation. A description of the various possibilities of thermal insulation of the partition can be found in EP-A 0 640 367. A double-walled design with an intermediate narrow gas space is particularly favorable.

Various control strategies have been described for the control of dividing wall columns and thermally coupled column. Descriptions can be found in US 4,230,533; DE 35 22 234; EP 0 780 147; Process Engineering 2 (1993) 33-34 and Ind. Eng. Chem. Res. 34 (1995), 2094-2103.

When separating multicomponent mixtures into a low-boiling, medium-high and high-boiling fractions, there are usually specifications for the maximum permissible fraction of low-boiling and high-boiling fractions in the medium boiler fraction. Here, either individual components critical for the separation problem, so-called key components, or the sum of several key components are specified. In the context of the present invention, these key components are geranial as high-boiling secondary component and isocitral or a mixture of isomeric isocitrals as low-boiling secondary component.

The compliance with the specification for the high boilers in the medium boiler fraction can be regulated, for example, by means of the distribution ratio of the liquid at the upper end of the dividing wall. In this case, the distribution ratio of the liquid at the upper end of the partition wall is preferably adjusted so that the concentration of the key components for the high boiler fraction in the liquid at the top of the partition is 10 to 80%, preferably 30 to 50%, of the value obtained in the side draw product is to be set, and the liquid distribution is preferably set to the effect that at higher levels of key components of the high boiler fraction more and at lower levels of key components of the high boiler fraction less liquid is directed to the inlet part.

Accordingly, the specification for the low boilers in the medium boiler fraction can be regulated by the heating power. Here, for example, the heating power in the evaporator is adjusted so that the concentration of key components of the low boiler fraction in the liquid at the bottom of the partition 10 to 80%, preferably 30 to 50% of the value to be achieved in the Seitenabzugsprodukt, and the heating power is Preferably set to the effect that at higher content of key components of the low boiler fraction, the heating power increases and at lower content of key components of the low boiler fraction, the heating power is reduced.

To compensate for disturbances in the feed quantity or the feed concentration, it was also found to be advantageous to ensure, by means of a corresponding regulating mechanism (control instructions in the process control system), that the flow rates of the liquids flowing onto the column parts (2), i. the reinforcement part of the inlet part, and (5), i. The output part of the sampling part, can not fall below 30% of its normal value.

For collecting and dividing the liquids at the upper end of the dividing wall and at the side extraction point, internally disposed as well as outside of the column collecting spaces for the liquid, which take over the function of a pump reservoir or provide a sufficiently high static fluid level, are suitable Actuators, such as valves, allow regulated fluid transfer. When using packed columns, the liquid is first collected in collectors and from there into an internal or external collecting space.

Instead of a dividing wall column - which is to be preferred in a new building in terms of investment costs - it is also possible to connect two distillation columns in the manner of a thermal coupling so that they correspond to the energy requirements of a dividing wall column. They can be a useful alternative to dividing wall columns if existing columns are available. Depending on the number of separation stages of the existing columns, the most suitable forms of interconnection can be selected.

If in the context of this embodiment of the process according to the invention two distillation columns are used in an interconnection in the form of a thermal coupling, it has proved to be advantageous to equip both distillation columns thermally coupled in this way each with its own evaporator and condenser. In addition, the two thermally coupled columns can be operated at different pressures and only liquids are conveyed in the connecting streams between the two columns. In a preferred embodiment, the bottom stream of the first column is partially or completely evaporated in an additional evaporator and then fed to the second column in two phases or in the form of a gaseous and a liquid stream.

Within the scope of a particularly preferred embodiment, the process according to the invention is carried out in a plant, as shown schematically in FIG. The preferred embodiment is characterized in that one uses a dividing wall column (TK), a partition wall (T) in the column longitudinal direction Forming an upper common column area (1), a lower common column area (6), an inlet part (2, 4) with reinforcement part (2) and output part (4) and a removal part (3, 5) with output part (3) and reinforcement part (3). 5).

According to the invention, the substance mixture (a) containing feedstock and geranic acid is preferably fed into the middle region of the feed part (2, 4), the pure in enriched or enriched form being extracted as side draw from the middle region of the removal part (3, 5) and one or more low boiler fractions from the upper common column region (1) and one or more

High boiler fractions removed from the lower common column area (6).

The feed stream (a) can be introduced via a preheater (VH) as a liquid (b), gaseous (c) or partially liquid and gaseous stream in the column (TK). The top stream of the column is completely or partially condensed in the condenser (K). In a partial condensation (dephlegmator operation), the exhaust gas flow (k) of the top condenser (K) usually still significant amounts of condensable low boilers, which can then be deposited in a low-temperature operated after-condenser.

In the context of the process according to the invention, the top product precipitated in the condenser (K) has a higher content of isocitrals than the mixtures of substances used and can be separated off in step b) of the process preferred according to the invention. This, referred to in the context of the present invention as the Isocitral fraction mixture usually contains 30 wt .-% or more, preferably 30 to 50 wt .-% isocitrals of the formulas (III), (IV) and / or (V) and is fed according to step c) of the present invention preferred method of isomerization as described above. The isocitrals of the formulas (III), (IV) and / or (V) are completely or partially isomerized to geranial and / or neral. This gives a geranial and / or neral-containing mixture having a lower content of isocitrals than the separated according to step b) isocitral fraction or the separated isocitral fractions and, accordingly, a higher content of geranial and / or Neral.

The mixture of substances thus obtained according to step c) and enriched in the mineral and / or geranial content geranial and / or neral is recycled according to step d) of the preferred embodiment of the inventive method in the distillative separation of the neral, geranial and isocitral-containing material according to Step a) of the present invention.

The isomerization according to step c) may, as described above, be thermal and / or acidic or basic, preferably thermal or basic. conditions. Preferably, according to step c), a base-catalyzed isomerization, particularly preferably in the presence of tertiary amines, is carried out.

The bottom stream obtained using the separation process shown can advantageously be supplied via the circulation pump (UP) to the bottom evaporator (V), which is preferably designed as a falling-film evaporator. This recycle stream can also be withdrawn from the bottom product (g) of the column (TK).

The desired product, i. the Neral in pure or enriched form, is usually withdrawn as a liquid side draw, stream (f) from the withdrawal section of the dividing wall column (TK). It is also possible, if necessary, the value product stream (f) as gaseous

To take deduction, but then usually another capacitor is needed.

The upper common portion (1) of the column usually has 5 to 50%, the rectifying section (2) of the inlet section of the column 5 to 50%, the stripping section (4) of the inlet section of the column 2 to 50%, the output part (2) of Entnahmeteils the column 5 to 50%, the reinforcing part (5) of the sampling 2 to 50%, and the common lower part (6) of the column from 5 to 50% of the total number of theoretical plates of the column, wherein the selected percentages to 100 Add%.

Preferably, the upper common portion (1) of the column 10 to 25%, the rectifying section (2) of the inlet section of the column 15 to 30%, the stripping section (4) of the inlet section of the column 5 to 20%, the output part (2) of Entnahmeteils the column 15 to 30%, the reinforcing part (5) of the sampling 5 to 20%, and the common lower part (6) of the column 10 to 25% of the total number of theoretical plates of the column, wherein the selected percentages add up to 100%.

The sum of the number of theoretical plates of subregions (2) and (4) in the feed section is preferably 80 to 110%, particularly preferably 95 to 105% of the total number of plates of subregions (3) and (5) in the taking part.

Advantageously, the feed point and the side take-off point are arranged at different heights in the column with respect to the position of the theoretical plates by arranging the feed point by 1 to 50, preferably by 30 to 45 theoretical separation stages higher or lower than the Seitenabzugsstelle.

It has also proven to be advantageous if the divided by the partition portion of the column consisting of the sub-areas (2), (3), (4) and (5) or parts thereof with ordered packings or packing (for example, tissue packs such Montz A3-500, Sulzer BX or CY). Furthermore, it has proven to be advantageous if the partition wall is designed heat-insulating in these sub-areas. The vapor stream at the lower end of the dividing wall can be adjusted by the choice and / or dimensioning of the separating internals and / or the installation pressure loss generating devices, such as orifices, that the ratio of the vapor stream in the inlet part to that of the sampling part 0.8 to 1, 2, preferably 0.9 to 1, 1.

The liquid flowing out of the upper common part (1) of the column is advantageously collected in a collecting space arranged in the column or outside the column and deliberately divided by a fixed setting or regulation at the upper end of the dividing wall such that the ratio of the liquid flow to the Inlet part to the extraction part for 0.1 to 2.0 at largely liquid feed and 1, 0 to 2 at gaseous feed. In this case, the liquid feed is preferred according to the invention.

The liquid draining from the upper common sub-area (1) onto the inlet part can be conveyed via a pump or quantity-controlled via a static inlet height of at least 1 m, preferably via a cascade control in conjunction with the liquid level control of the collecting space. The control is preferably set so that the amount of liquid applied to the inlet part can not fall below 30% of the desired normal value. In addition, the division of the effluent from the portion (3) in the withdrawal section of the column liquid on the side draw and on the sub-area (5) in the withdrawal section of the column is advantageously adjusted by a control so that the on the portion (5) discontinued amount of liquid not below a level of 30% of the desired normal value. The normal value are advantageously two to four times the amount, based on the feed amount of geranial / Neral mixture to assume.

The dividing wall column preferably has sampling possibilities at the upper and lower end of the dividing wall, from which samples can be taken from the column continuously or at intervals in liquid or gaseous form and analyzed with regard to their composition, preferably by gas chromatography.

The distribution ratio of the liquid at the upper end of the partition wall is preferably adjusted so that the concentration of those components of the high boiler fraction for which a certain limit value for the concentration is to be achieved in the side draw (especially geranial) in the liquid at the upper end of the Partition is 10 to 80% of the value to be achieved in the Seitenabzugsprodukt. The liquid partition should preferably be adjusted so that at higher contents of components of the high boiler fraction more and at lower levels of components of the high boiler fraction less liquid is passed to the inlet part. The heating power in the evaporator (SV) is preferably adjusted so that the concentration of those components of the low boiler fraction for which a certain limit value for the concentration is to be achieved in the side draw (especially isocitrals), at the lower end of the partition so that the Concentration of components of the low boiler fraction in the liquid at the lower end of the partition is 10 to 80% of the value to be achieved in the Seitenabzugsprodukt. The heating power is advantageously set to the effect that, with a higher content of components of the low boiler fraction, the heating power is increased and with a lower content of components of the low boiler fraction, the heating power is reduced.

The distillate removal, i. the removal of the low-boiling by-products is preferably carried out with temperature control. As a control temperature is advantageously used a measuring point in the sub-region (1) of the column, which is arranged to 3 to 8, preferably 4 to 6 theoretical see separation stages below the upper end of the column.

The removal of the bottom product is preferably carried out in a quantity-controlled manner, preferably as a function of the feed quantity.

The removal of the product obtained as a side product Neral in pure or enriched form is preferably carried out in a level-controlled manner as the controlled variable preferably the liquid level is used in the bottom of the column.

The feed stream is preferably partially or completely pre-evaporated and fed to the column in two-phase or in the form of a gaseous and a liquid stream.

Within the scope of a preferred embodiment, a dividing wall column is used whose dividing wall is not welded into the column but is designed in the form of loosely inserted and adequately sealed subsegments.

The liquid distribution in the individual subregions of the column can preferably be set unevenly in a targeted manner, the liquid in particular in the subregions (2) and (5) being more intensively applied in the wall region and the liquid being reduced in the subregions (3) and (4) abandoned in the wall area.

The distribution ratio of the returning liquid between the take-off and feed side of the partition wall is preferably about 1 to 1 to about 3 to 1, preferably about 1 to 1 to about 1.5: 1. The position of the partition wall in the individual subregions of the column can be advantageously adapted so that the cross sections of the inlet and outlet part have different surfaces.

A preferred embodiment of the process according to the invention is characterized in that at least one low boiler fraction is obtained as liquid side draw (s) in the upper section (1) of the column, preferably 4 to 10 theoretical steps below the top of the column. In this case, it is expedient to divide the upper column section (1) into two sections ((1 a) and (1 b)). Between these sections, the liquid draining from the section (1a) is collected by a suitable collector and redistributed to the section (1b) below (see FIG. 2). From the collector a low-boiling and low-Neral-poor fraction can be deducted, which contains mainly isomeric citrals.

A further preferred embodiment of the process according to the invention is characterized in that at least one high boiler fraction is obtained as gaseous side draw (o) in the lower part of the column, preferably 1 to 5 theoretical steps above the column bottom (see FIG. 2). As a result, a particularly high-low-boiling geranial-rich product can be obtained. In this case, it may be appropriate to divide the lower column section (6) into two sections (6a and 6b). Between these sections, the liquid draining from the section (6a) is collected by a suitable collector and redistributed to the section (6b) below (see FIG. 2) and the gas stream for the side take-off is removed.

As a bottom evaporator for the dividing wall column may advantageously be a thin-film apparatus, such as a falling film evaporator, are used.

The top condenser (K) can be designed, for example, as a plate apparatus and integrated into the column jacket.

If an upper side draw (s) as described above provided, there may be obtained a by-product mixture, which usually has a Neral content of less than 80 wt .-%, a Geranial content of less than 0.1 wt .-% and a Content of other isomers, in particular of the citral isomers of the formulas (III), (IV) and (V) of more than 30 wt .-% (isocitral fraction). In addition, in a lower side draw, if desired, as well as in the bottom fraction (g), a product mixture having a neral content of less than 20% by weight and a geranial content of more than 70% by weight. The top fraction (j) usually has a Neral content of less than 30% by weight. The low boiler fraction (k or I) separated therefrom usually has a Neral content of less than 5% by weight in addition to isocitrals as main components. The isocitral-rich fractions (isocitral fractions) thus obtainable can be recycled further in the manner according to the invention by subjecting them to the above-described isomerization according to the invention and subsequently recirculating them to the distillation.

The following examples are illustrative of the invention without in any way limiting it:

In the following examples, the compound of formula (I) is cis-citral, the compound of formula (II) is trans-citral, the compound of formula (III) iso-citral (methylene), the compound of formula (IV ) as iso-citral (ice) and the compound of formula (V) as iso-citral (trans).

Example 1: Obtaining the isocitral-rich cis-citral stream:

The dividing wall column used for the following examples was constructed from five 1, 2 m long glass shots with 64 mm inner diameter. In the three middle shots a partition of sheet metal was inserted. Below and above the dividing wall area, laboratory packings (Sulzer CY) and in the dividing wall area, metal stainless steel rings of 5 mm diameter were installed. In separation performance measurements, which were carried out with the xylene isomer mixtures at a top pressure of 60 mbar, a total separation efficiency of 100 th. Soils over the entire column and about 55 th. Floors in the partition wall area are measured. Thus, the total number of theoretical plates present was about 155. The column was equipped with an oil-heated thin-film evaporator (0.1 m ² ) and a cooled with cooling water condenser.

Temperatures at various heights in the column as well as the head pressure and the pressure drop across the column were measured by means of a data acquisition system. The column had flow measurements in the inlets and outlets as well as a flow rate measurement, which served as a control variable for the flow temperature of the oil thermostat. This regulation ensured a constant return flow, which also resulted in a constant differential pressure. The distribution of the amount of liquid above the dividing wall on inlet and outlet part of the partition was realized via a timed clocking swivel funnel.

The column was at a height of 136 cm to the inlet part of the partition 461 g / h of a pre-heated to 110 ⁰ C liquid mixture of 48.7 GC area% Neral, 47.8 GC Area% Geranial and 1.4 GC area% fed to other citral isomers. The column was operated at 10 mbar head pressure and a reflux of 2.5 kg / h. This resulted in a pressure drop of about 34 mbar (± 1 mbar). At the top of the column, a temperature of 82.3 ° C and in the sump, a temperature of 128.4 ⁰ C (± 0.5 K) was measured. The bottom draw was fixed by means of a balance control to 240 g / h and the distillate decrease to 20 g / h (± 1 g / h). The reflux ratio was thus about 125: 1. The liquid was divided above the dividing wall in a ratio of 1: 1, 1 (inlet: withdrawal part). At a height of 490 cm in the removal part of the partition, a gaseous side draw (f) was removed and condensed in a glass cooler, from which about 200 g / h of pure product was withdrawn via a pump depending on the sump level.

The recovered fractions were analyzed by gas chromatography using a standard GC. Gas chromatographic analyzes were carried out by the following methods:

25 m OV-1, ID .: 0.32 mm, FD .: 0.31 μm; 50 ⁰ C / 2 min - 10 ° C / min to 150 ⁰ C, 5 min - 20 ° C / min to 280 ⁰ C / 15 min; t _R (citral isomer III): 10.4 min; t _R (citral isomer IV): 10.7 min; t _R (citral isomer V): 11, 0 min; t _R (Neral I): 12.3 min; t _R (Geranial II): 12.6 min

The pure product recovered on the side draw contained, in addition to 98.5 GC area% neral, also 0.3 GC area% geranial and 0.65 GC area% other citral isomers. In the bottom draw, GC analysis revealed 92.5 GC area% Geranial and 6.8 GC area% Neral, the distillate contained 32.1 GC area% Neral and 39.6 GC area% other citral isomers.

Examples 2 to 6: isomerizations with homogeneous catalysts

For each of the experiments described below, a mixed mixture was used which consisted of 95.6 GC% by mass of isomeric citrals and 1.1% GC% of citral dimers.

The mixture used had the composition given in Table 1 with respect to the monomeric ingredients:

Table 1 :

Experimental procedure for the following experiments

An inert gas-purged glass apparatus was filled with iso-citral-containing cis-citral, catalyst and decane (for quantitative GC analysis) and heated to the particular temperature indicated. Samples were taken at fixed intervals and analyzed by gas chromatography as described below.

a) high boiler determination:

GC: FID (Chi) 10 mx 0.32 mm OV-1 FD = 0.5 microns 50 °, 2 min, 207min, 300 ⁰ C Probenkomentar: 20 ⁰ C; 2 minutes; 20 ° C / min; 300 ⁰ C

Retention times: Citral Sum: RT 5 - 8 min; Dimers: RT 9 - 14.5 min; Trimers: RT 9 - 14.5 min; High boilers: not chromatographable (from difference to 100% determined)

b) Determination of the distribution of citral species: GC: 25m ^* 0.25mm Optima 1 FD = 0.5μm Sample Momentar: 120 ° C; 5 minutes; 5 ° C / min; 145 ° C

Example 2: Isomerization with dibutylamine (1 mol%) as base at 120 ^° C.

Iso-citral (109 g, 713 mmol), dibutylamine (1.1 g, 8.1 mmol, 1 mol%) and decane (12.3 g) were reacted as described above at a reaction temperature of 120 ° C. A mixture was obtained with the composition shown in Table 2 (all data in GC area%). Table 3 shows the amount of by-products formed in the reaction.

Table 2:

Table 3:

EXAMPLE 3 Isomerization with tridodecylamine (1 mol%) as a base at 120 ⁰ C:

Iso-citral (71, 2 g, 468 mmol), tridodecylamine (2.7 g, 5.2 mmol, 1 mol%) and decane (12.8 g) were obtained as described above at a reaction temperature of 120 ⁰ C reacted , A mixture with the composition shown in Table 4 was obtained (all data in GC area%). Table 5 shows the amount of by-products formed in the reaction.

Table 4:

Table 5:

EXAMPLE 4 Isomerization with tridodecylamine (10 mol%) as a base at 120 ⁰ C:

Iso-citral (73.2 g, 481 mmol), tridodecylamine (26.7 g, 51, 1 mmol, 10 mol%) and decane (17.8 g) were at a reaction temperature of 120 ⁰ as described above C implemented. A mixture was obtained with the composition shown in Table 6 (all data in GC area%). Table 7 shows the amount of by-products formed in the reaction. Table 6:

Table 7:

Example 5 Isomerization with Lutidine as Base at 120 ^° C.

Iso-citral (90.5 g, 595 mmol), lutidine (0.74 g, 6.9 mmol, 1, 2 mol%) and decane (19.0 g) were obtained as described above at a reaction temperature of 120 ⁰ C implemented. A mixture was obtained with the composition shown in Table 8 (all data in GC area%). Table 9 shows the amount of by-products formed in the reaction.

Table 8:

Table 9:

Example 6: Isomerization in the presence of an acid

Iso-citral (110.2 g, 724 mmol), citronellic acid (1, 12 g, 6.6 mmol, 0.9 mol%) and decane (20.6 g) were as described above at a reaction temperature of 120 ^0th C implemented. A mixture with the composition shown in Table 10 was obtained (all data in GC area%). Table 1 shows the amounts of by-products formed in the reaction.

Table 10:

Table 11:

Example 7 Isomerization with a Lewis Base

Iso-citral (95.2 g, 625 mmol), triphenylphosphine (16.0 g, 61.0 mmol, 9.75 mol%) and decane (8.95 g) were as described above at a reaction temperature of 120 ^0th C implemented. A mixture with the composition shown in Table 12 was obtained. composition (all data in GC area%). Table 13 shows the amounts of by-products formed in the reaction.

Table 12:

Table 13:

Example 8: Thermal isomerization at 160 ^° C.

Iso-citral (150 ml) was reacted without further additions as described above at a reaction temperature of 160 ^° C. It became a mixture with that in table

14 composition shown (all data in GC area%). table

Figure 15 shows the amounts of by-products formed in the reaction.

Table 14:

Table 15:

Example 9: Thermal Isomerization at 120 ^° C.

Iso-citral (150 ml) was reacted without further additions as described above at a reaction temperature of 120 ^° C. It became a mixture with that in table

16 composition shown (all data in GC area%). table

17 indicates the amounts of by-produced reaction products.

Table 16:

Table 17:

Examples 10-13: Isomerization with Heterogeneous Catalysts

For the experiments described below, a mixture of substances (referred to as "iso-citral") was used which consisted of 95.6% by mass of isomeric citrals and 1.1% by mass of citral dimers.

The same batch of iso-citral-containing cis-citral was used in each case for the experiments described below.

The mixture used had the composition given in Table 18 with respect to the monomeric ingredients:

Table 18:

Example 10: Isomerization with Amberlite® IRA 67:

Iso-citral (49.7 g, 322 mmol), Amberlite IRA-67 (13.0 g, 0.26 mass equiv.) And decane (12.69 g) were prepared as described above at a reaction temperature of 100 ⁰ C implemented. A mixture was obtained with the composition shown in Table 19 (all data in GC area%). Table 20 shows the amounts of by-products formed in the reaction.

Table 19:

Table 20:

^* The error of this measurement was +/- 5%.

If the reaction was carried out at 60 ^° C. or 80 ^° C., the results shown in Tables 21 (indicated in GC area%) and 22 were obtained after a reaction time of 4 h.

Table 21:

Temp. Iso-citral iso-citral iso-citral cis-citral trans- Other [° C] (methylene) (ice) (trans) Citral

80 0.64 18.1 17.29 30.59 30.08 3.3

60 0.96 30,61 23,14 27,86 16,22 1, 21

Table 22:

Time Citral Sum Dimers Trimers HS [h] [mass%] ^* [mass%] ^* [mass%] ^* [mass%]

80 100.52 4.45 0.50 -

60 108.03 2.46 0.56 -

^* The error of this measurement was +/- 5%.

For the experiments described below, in each case a mixture of substances was used which comprises 98.93 GC% by mass of isomeric citrals and 1.45 GC% by mass of dimers of the citral and 0.95% by mass GC% of trimers of the citral.

The mixture used had the composition given in Table 23 with respect to the monomeric ingredients:

Table 23:

Example 1 1: Isomerization with QBT-145 (γ-Al ₂ O ₃ / La / Ca) as catalyst

Preparation of the catalyst QBT-145:

64.76 g of La (NO ₃ ) ₃ -6H ₂ O and 34.44 g of Ca (NO ₃ MH ₂ O) were dissolved in 140 g of distilled water in a beaker, which solution became 250 g of Y-Al ₂ at RT O ₃ -., where extrudates (1, 5 mm extrudates, D10-10), and all mixed well Then, the extrudates were dried on a rotary evaporator for 20 min at 80 ⁰ C (25 U / min, 10 mbar) and then at 500 ⁰ C in air for 10 h calcined (temperature program: heating to 120 ⁰ C, hold for 4 hours, further to 500 ⁰ C, 10 h hold, cooling) There were 291, 7 g extrudates with a Ca content of 2.0%. and a La content of 7.1%.

Iso-citral (25.0 g, 164 mmol), QBT-145 (3.5 g, 0.14 mass equiv.) And decane (12.69 g) were prepared as described above at a reaction temperature of 100 ⁰ C reacted , A mixture was obtained with the composition shown in Table 24 (all data in GC area%). Table 25 shows the amounts of by-products formed in the reaction.

Table 24:

Table 25:

^* The error of this measurement was +/- 5%.

When the amount of catalyst used was reduced to 0.02 and 0.06 mass equivalents, respectively, the results summarized in Tables 26 and 27 were obtained. A mixture was obtained having the composition shown in Table 26 (all data in GC area%). Table 27 shows the amounts of by-products formed in the reaction. Table 26:

Table 27:

The error of this measurement was +/- 5%.

Example 12: Isomerization with a MgAbCu catalyst with a slight Mg excess

Preparation of the MgAbCu catalyst with a slight Mg excess:

10 L of water were heated to 80 ⁰ C. Under pH control, a solution of 139.7 L of 20% strength Na 2 CO 3 solution was used at pH 5.5 in parallel over a period of 6 h. and 134.5 L of a solution of 46.1 kg MgNO ₃ solution. (9.1% with respect to MgO) and 129.6 kg of Al (NO ₃ ) S sol. (7.6% with respect to Al 2 O 3) added. The precipitation suspension was adjusted to a stand-still of 20 l, the supernatant liquor being continuously pumped off over a period of 6 h into a separate vessel. After the addition was at 8O ⁰ C, the precipitation suspension by adding a further 56.5 L 20% Na2CO3 solution. adjusted to pH 7.8 within 1 h. After half an hour of stirring, the suspension was cooled to room temperature and filtered. The filter cake was washed by adding water Na- or NÜ3-free (in each case <0.1% with respect to annealed filter cake). The filter cake was dried in a drying oven at 100 ⁰ C overnight. 27.8 kg of the dry mass obtained in this way (loss on ignition 46.5%) were made into a kneader with 9.4 L of H 2 O (kneading time 1.5 h) and shaped via an extruder at 80 bar molding pressure into 1.5 mm extrudates. The strands obtained were first dried overnight at 120 ⁰ C and finally calcined at 600 ⁰ C under air for 1 h in a rotary kiln. There were obtained 13.5 kg Stränglinge with a MgO: Al2θ3 ratio of 1:05.

Iso-Citral (24.8 g, 163 mmol), Catalyst 90021 (3.5 g, 0.14 mass equiv.) And decane (12.69 g) were prepared as described above at a reaction temperature of 100 ° C implemented. A mixture was obtained with the composition shown in Table 28 (all data in GC area%). Table 29 shows the amounts of by-products formed in the reaction. Table 28:

* The error of this measurement was +/- 5%.

Example 13: Continuous isomerization with Amberlite® IRA-67 as a heterogeneous catalyst

For the experiments described below, in each case a mixture of substances was used which comprises 98.93 GC% by mass of isomeric citrals, 1.45 GC% by mass of dimers of the citral, 0.95% by mass GC% of trimers of the citral and to 1.33 GC% by mass of other high boilers.

The mixture used had the composition given in Table 30 with respect to the monomeric ingredients.

Table 30:

A glass column fitted with a frit and IRA-67 with Amberlite (10 ml) was charged, dipped in a heating bath (100 ⁰ C). From below, the iso-citral feed was pumped through the column by a HPLC pump at a constant rate (12 ml / hr). An overflow at the upper end of the column caused the isomerized citral mixed into a sample container from which the samples were taken for analysis. A mixture was obtained with the composition shown in Table 31 (all data in GC area%). Table 32 shows the amounts of by-products formed in the reaction.

Table 31:

^* The error of this measurement is + 1-5%.

Example 14: Continuous thermal isomerization

The composition of the iso-citral-containing cis-citral used results from the blank samples of the respective experiment.

The following experiments were carried out in the tubular reactor with empty tube residence times of 0.5 h and 1 h. For this purpose, a jacketed tube of 1.3 m in length and 4 mm in inside diameter made of V4A (1.4571) was used, which was filled with 1 mm glass beads to reduce backmixing. The empty tube volume was 14.5 ml, the free volume 5.4 ml. With the aid of an HPLC pump iso-citral-rich isomer mixture was pumped through the reactor. The effluent stream was cooled to room temperature in a tube cooler and sampled.

The thermal isomerization in the tubular reactor was investigated at 180 ^° C. and 200 ^° C. At 200 ⁰ C, moreover, the residence time of the isomer mixture in the reactor (0.5 h and 1 h) was varied. Mixtures with the compositions shown in Table 33 were obtained (all data in GC area%). Table 34 shows the amounts of by-products formed in the respective reactions.

The error of this measurement is +/- 5%.

Claims

claims:

1. Process for the preparation of neral of the formula (I)

and / or geranial of the formula (II)

(III) (IV) (V)

2. The method of claim 1 for the preparation of Neral of the formula (I) in pure or enriched form starting from mixtures containing Neral and

Geranial of the formula (II) and one or more isocitrals selected from the group of isocitrals of the formulas (III), (IV) and (V)

comprising the steps

a) containing distillative separation of the neral, geranial and isocitral

Mixture of substances in one or more fractions of pure or enriched neral and one or more fractions containing isocitrals of formulas (III), (IV) and / or (V) greater than that of the mixture of substances used (Isocitral Fractions), and optionally other fractions; b) separating one or more isocitral fractions and one or more fractions of pure or enriched neral; c) isomerization of the isocitrals of the formulas (III), (IV) and / or (V) to geranial and / oreral contained in the isocitral fractions to obtain a mixture containing geranial and / or neral and d) recycling of the step c ) obtained substance mixture in step a).

3. The method according to claim 1 or 2, characterized in that it is carried out continuously.

4. The method according to claim 2 or 3, characterized in that the distillative separation according to step a) in a dividing wall column or in an interconnection of two distillation columns in the form of a thermal coupling with 80 to 200 theoretical plates and one or more Seitenabzugsstellen at an absolute operating pressure of 5 to 200 mbar.

5. The method according to any one of claims 2 to 4, characterized in that separated according to step b) as a top product of the distillative separation according to step a) recovered Isocitral fraction.

6. The method according to any one of claims 1 to 5, characterized in that one carries out the isomerization in the form of a thermal isomerization.

7. The method according to any one of claims 1 to 6, characterized in that one carries out the isomerization in the form of a basic isomerization.

8. The method according to claim 7, characterized in that one carries out the isomerization in the presence of a basic organic or inorganic catalyst sector.

9. The method according to claim 7 or 8, characterized in that one uses as a basic catalyst, a tertiary amine.

10. The method according to claim 7 or 8, characterized in that one uses as a basic catalyst, a basic organic ion exchanger.

1 1. A method according to claim 8, characterized in that one uses a basic inorganic catalyst.

12. The method according to claim 11, characterized in that one uses an alkaline earth-doped and / or rare earth oxide-doped alumina, titania or zirconia as inorganic basic catalyst.

13. The method according to any one of claims 1 to 12, characterized in that one carries out the isomerization at a temperature of 50 to 300 ⁰ C.