JPWO2020099461A5 - - Google Patents

Description

The present invention relates to an apparatus for producing pseudoionones and hydroxypseudoionones. Furthermore, the present invention relates to a method for producing pseudoionones and hydroxypseudoionones, comprising the steps of (i) preparing a first aqueous mixture comprising a first concentration of acetone, citral and hydroxide, (ii) producing a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time, and (iii) producing a third aqueous mixture by adding a second amount of hydroxide to the second aqueous mixture such that an additional amount of pseudoionone is formed in the third aqueous mixture. Still further, the present invention relates to the use of the aforementioned apparatus in the production of pseudoionones and hydroxypseudoionones.

Pseudoionones are key intermediates in the industrial synthesis of vitamins A and E, and carotenoids, for example natural and natural equivalent products, e.g., flavors, flavorings, nutritional foods or dietary supplements.

The document Dutch Patent No. 6704541 describes a method for preparing liquid, soluble condensation products by reacting a ketone with an aldehyde in the presence of an alkaline condensing agent.

The document EP 0062291 A1 discloses an improved method for producing polyunsaturated ketones.

The document WO 2004/041764 A1 describes a continuous process for producing pseudoionones and ionones.

The document WO 2005/056508 A1 relates to a method for the preparation of tetrahydrogeranyl acetone.

In light of the existing prior art, there is still a need for improvements in producing pseudoionones and hydroxypseudoionones, particularly pseudoionones, more efficiently, and particularly in higher yields, when compared to known apparatus and methods.

In view of this, it was an object of the present invention to provide an apparatus for producing pseudoionone and hydroxypseudoionone, particularly in a continuous operation, which has a higher efficiency and, in particular, a higher yield of pseudoionone.

It is therefore a further object of the present invention to provide a method for producing pseudoionones and hydroxypseudoionones, in particular pseudoionone, which can be carried out as an industrial process, in particular as a continuous process, with higher efficiency, in particular with a higher yield of pseudoionone.

In a first aspect, the present invention achieves the object by proposing an apparatus according to claim 1. The present invention in particular relates to an apparatus for producing pseudoionones and hydroxypseudoionones, comprising a substantially vertically oriented first reactor arranged for the flow of components through the first reactor in a first flow direction, and a substantially vertically oriented second reactor in fluid communication with the first reactor, the second reactor being oriented for the flow of components through the second reactor in a second flow direction different from the first flow direction, the first reactor receiving a first component feed through an inlet, the first component feed comprising a first aqueous mixture, the first component feed being arranged for the flow of components through the first reactor in a second flow direction different from the first flow direction, the first reactor receiving a first component feed through an inlet ... the second reaction vessel is configured to receive the first and second component feeds combined in the mixing device from the first reaction vessel and to produce a third aqueous mixture from the first and second aqueous mixtures, the apparatus comprising a mixing device located downstream of a first component feed inlet of the first reaction vessel and configured to add a second component feed to the first component feed when the second aqueous mixture is formed, the second reaction vessel being configured to receive the first and second component feeds combined in the mixing device from the first reaction vessel and to produce a third aqueous mixture from the first and second aqueous mixtures.

Preferably, the mixing device is located inside the first reaction vessel, or inside the second reaction vessel, or between the first and second reaction vessels.

Vertical orientation is understood to include each reactor vessel(s) being oriented within +/- 15° of perpendicular to the ground on which the apparatus is located.

Aqueous solutions are understood to include mixtures that contain water.

The present invention is based on the recognition that an improvement in yield can be achieved by further adding a second component feed to the first component feed after a certain reaction time has elapsed in the first reactor. This is achieved in particular by integrating a mixing device into the first reactor towards its downstream end. If the first reactor is an upflow reactor, the mixing device is preferably attached to the ceiling end of the first reactor. If the first reactor is a downflow reactor, the mixing device is preferably attached to the bottom end of the first reactor.

The first component feed preferably contains acetone, citral and hydroxide at a first concentration. Particularly preferably, a first amount of water, acetone, citral and hydroxide are combined in the first component feed . More preferably, the reaction of the components of the first component feed in the first reaction vessel produces pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one, and acetone, citral and hydroxide are consumed. The second aqueous mixture preferably contains 4-hydroxy-4-methylpentan-2-one at a concentration higher than its concentration in the first aqueous mixture, acetone, citral and hydroxide, and pseudoionone and hydroxypseudoionone at a second concentration lower than the first concentration. More preferably, the second component feed contains a second amount of hydroxide so that an additional amount of pseudoionone is formed in the third aqueous mixture.

In a preferred embodiment, the first flow direction is oriented upward and the second flow direction is oriented downward, or vice versa.

In a further preferred embodiment, the mixing device is located at the outlet end of the first reaction vessel. The mixing device preferably has an inlet and an outlet, the outlet being positioned such that the third aqueous mixture flows into the second reaction vessel.

In a further preferred embodiment, the inlet of the first reactor for receiving the first component feed is a first inlet, and the first reactor further comprises a second inlet for receiving the second component feed located upstream from the mixing device. Preferably, the second inlet is located at the side of the first reactor and is configured to introduce the second component feed into the first component feed at a portion of the first reactor, where by reaching the respective point, the second aqueous mixture has already been formed due to its residence time in the reactor. Preferably, the second inlet comprises several outlet orifices oriented towards the mixing device. In general, the term "several" is understood to mean one element or a plurality of elements. For example, several outlet orifices may be one or more outlet orifices, for example 1 to 50 outlet orifices.

More preferably, the second inlet is located immediately upstream of the mixing device or at a distance upstream of the mixing device. This is understood to mean that the second inlet is located such that its outlet (or at least one of its outlets, if there are several) is attached upstream of the mixing device. The distance is preferably selected so that the entire second component feed is drawn into the mixing device without preceding backflow inside the first reaction vessel. For practical purposes, it has been found that a distance of not more than 50 cm, particularly preferably not more than 25 cm, from the inlet of the mixing device in the flow direction of the first component feed ensures that the entire second component feed is drawn directly into the first component feed and withdrawn into the mixing device without preceding undesirable backflow.

In general, when using the terms upstream and downstream in relation to the present invention, upstream is understood to mean opposite the direction of flow, i.e., toward the source of the flow, while downstream is understood to mean in the direction of flow, i.e., toward the destination of the flow.

In a further preferred embodiment, the first reaction vessel is provided with a tapered section upstream of the inlet of the mixing device, preferably immediately upstream of the second inlet, in order to accelerate the flow rate of the second aqueous mixture. Since the tapered section is mounted upstream of the inlet of the mixing device and tapers towards it, this has the advantageous effect of accelerating the flow rate inside the reaction vessel, in particular in the mixing device. The increased flow rate improves the mixing result of the mixing device and contributes to obtaining a homogenous mixture of acetone and hydroxide, thereby avoiding undesired segregation of the hydroxide from the mixture.

The first reactor preferentially comprises some further mixing elements - i.e. one or more - or some packings upstream of the mixing device, configured to match the residence time of the first component feed between the inlet to the first reactor and the mixing device. Under matching, it should be understood that almost all parts, preferably all parts, of the first component feed have a uniform residence time inside the first reactor. The mixing elements preferably comprise so-called x-type mixing elements, which are provided in sections that are mounted one after the other, respectively, in the flow direction of the first component feed . Adjacent mixing elements are preferably installed at an offset angle, preferably in the range of 60° to 120°, more preferably 90°. The mixing elements upstream of the mixing device contribute to provide a uniform fluid distribution and a uniform component distribution in the first component feed and also help to minimize undesirable free convection and backmixing, thereby matching a plug flow behavior that at least approximates the residence time spent by the first component feed in the first reactor. Although plug flow is generally understood to mean that media moves through a conduit at a constant velocity across the entire cross section of the conduit, the present invention applies the term more broadly. In the context of the present invention, plug flow behavior need not be achieved in precise terms. Instead, as pointed out throughout this document, it is considered sufficient if the residence times of all media passing through the reactor are substantially consistent, and small local variations in flow rate over portions of the reactor diameter may be ignored.

According to another embodiment, the inlet for the first component feed is in fluid communication with a feed line configured to produce the first component feed from a plurality of starting materials. Preferably, the feed line comprises a first mixer configured to combine the first and second starting material feeds , and a second mixer downstream of the first mixer configured to combine the combined first and second starting feeds from the first mixer with a third starting material feed into the first component feed .

One of the starting material feeds , e.g., the first starting material feed, preferably comprises citral, a further one of the starting material feeds , e.g., the second starting material feed , preferably comprises acetone, and another one of the starting material feeds , e.g., the third starting material feed , preferably comprises hydroxide.

The feed lines are further preferably equipped with at least one heating device, preferably at least one heat exchanger, configured to heat the first and second starting material feeds to a predetermined temperature higher than the temperature of the third starting material feed .

Particularly preferred, the at least one heating device is configured to heat the first and second starting materials such that the first component feed reaches a predetermined set point temperature prior to entering the first reaction vessel as a function of the first, second and third starting material feed rates and the temperature of the third starting material feed.

At least one heating device is preferentially located between the first and second mixers.

According to a further preferred embodiment, the second reaction vessel is configured to be reversibly opened and closed by means of a corresponding cover and is provided with an opening dimensioned for introducing a packing material, preferably comprising or consisting of a loose packing material, into the second reaction vessel. The loose packing material has the advantage that it is easier to install compared to a structured packing material and with no or little sacrifice in overall performance. The packing material inside the second reaction vessel contributes to preventing undesired laminar flows or undesired free convection across the second reaction vessel (which may be caused by density fluctuations, especially at low flow rates) and contributes to a uniform distribution of the material inside the second reaction vessel throughout.

In a particularly preferred embodiment, at least one of the first and second reaction vessels is a reaction tube. Preferably, both reaction vessels are reaction tubes.

The second reaction chamber is preferably at least partially formed as a ring chamber.

The two previous embodiments can be advantageously combined, the first and second reactors being part of one common reactor having an inner and outer tube, where the first reactor is bounded by the volume of the inner tube and the second reactor is bounded by the volume of the outer tube minus the volume of the inner tube. The first reactor, preferably as the inner tube of the double-tube reactor, has a smaller overall cross-section than the second reactor. This again contributes to an increase in the flow rate of the first and second component feeds in the first reactor, leading to better mixing and reduced segregation of hydroxides from the reaction mixture.

A further advantage of the above-described configuration of the annular vessel around the first reactor is that the portion of the first reactor that is surrounded by the annular vessel is automatically insulated to at least some degree from environmental influences, e.g., ambient temperature. Also, the design of the inventive apparatus is very space-saving compared to more conventional assemblies having two reactors arranged side-by-side in series with each other, e.g., in an industrial manufacturing environment.

In a further preferred embodiment, at least one of the reactors, and preferably both reactors, is formed from a number of tubular sections mounted in series with one another. This provides a particularly advantageous modular design for maintenance and removal purposes.

The second reaction vessel comprises at least one outlet for withdrawing the third aqueous mixture from the apparatus. Preferably, the second reaction vessel comprises a plurality of these outlets, more preferably 2, 3, 4, 5, 6, 7, 8 or more of these outlets. In preferred embodiments with a plurality of outlets, at least some, preferably all, of the outlets are distributed along the circumference of the reaction vessel. Particularly preferably, the outlets are uniformly distributed along the circumference of the reaction vessel. More preferably, the outlets are mounted at the same position of the reaction vessel with respect to the flow path of the third aqueous mixture - for example, the length or height depending on the orientation of the reaction vessel.

In a further preferred embodiment of the device, the outlets are in fluid communication with a downstream manifold configured to combine each partial feed flowing through the outlets into one common outlet feed. The manifold preferably includes at least one of a collecting tube, a collecting ring, one or more Y-pieces, or a combination of some or all of the foregoing.

In a further alternative embodiment, the second reactor comprises at least one, preferably a plurality of flow guiding baffles. The at least one flow guiding baffle is preferably oriented parallel to the longitudinal axis, i.e. the flow axis, of the second reactor. More preferably, the at least one flow guiding baffle extends along at least a portion of the longitudinal extension (i.e. in the direction of the longitudinal axis) of the second reactor. In a preferred variant, the second reactor comprises 2, 3, 4, 5, 6, 7, 8 or more baffles.

The present invention is described above in relation to an apparatus in a first aspect. In a second aspect, the present invention also relates to a method for producing pseudoionones, preferably in an apparatus as described above, comprising:
- feeding a first component feed to a first reaction vessel, the first component feed preferably comprising a first aqueous mixture including a first concentration of acetone, citral and hydroxide by combining a first amount of water, acetone, citral and hydroxide;
- producing a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time such that pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one are preferably formed and acetone, citral and hydroxide are consumed, the second aqueous mixture preferably comprising 4-hydroxy-4-methylpentan-2-one in a concentration higher than its concentration in the first aqueous mixture, acetone, citral and hydroxide, and pseudoionone and hydroxypseudoionone in a second concentration lower than the first concentration;
- adding a second component feed containing a second amount of hydroxide preferably within the first reaction vessel to the first component feed , particularly when a second aqueous mixture is formed;
- producing a third aqueous mixture by supplying the first and second component feeds to a second reaction vessel and reacting the second aqueous mixture and the second component feeds in the second reaction vessel for a reaction time such that an additional amount of pseudoionone is formed in the third aqueous mixture in the second reaction vessel.

The method according to the invention under its second aspect envisages the same benefits and advantages as the device under its first aspect. Preferred embodiments of the device discussed above are therefore preferred embodiments of the method discussed hereinafter and vice versa.

Preferably, the method comprises:
- the second amount of hydroxide added to the second aqueous mixture is in the range of 5% to 50% by weight, preferably in the range of 10% to 40% by weight, of the first amount of hydroxide in the first aqueous mixture;
and/or
- controlling a feed rate of the second component feed material relative to the feed rate of the first component feed material such that a concentration of dissolved hydroxide is present in the third aqueous mixture is greater than in the second aqueous mixture.

More preferably, the method includes the step of accelerating the flow rate of the second aqueous mixture prior to adding the second component feed .

In a further preferred embodiment, the method comprises the steps of:
- combining a first starting material feed, preferably comprising citral, and a second starting material feed , preferably comprising acetone, and subsequently combining the combined first and second starting materials with a third starting material feed , preferably comprising hydroxide, to produce a first component feed .

The method preferably further comprises the step of heating the first and second feedstocks to a predetermined temperature, higher than the temperature of the third feedstock, prior to entering the first reactor, preferably by heating the first and second feedstocks as a function of the first, second and third feedstock feed rates and the temperature of the third feedstock, such that the first component feed reaches a predetermined setpoint temperature. Control to the predetermined setpoint temperature contributes to improved reactor performance.

In a further preferred embodiment, the method comprises controlling the feed rate of the first component feed such that the first component feed in the first reactor has a predetermined residence time, preferably in the range of 3 minutes or more, more preferably 5 minutes or more, before reaching the second reactor and/or before the addition of the second component feed . This time interval provides an advantageous compromise between a desired short residence time on one side and a good conversion rate of the first component feed on the other side.

Still further, the method includes the step of matching the residence time of the first component feed in the first reactor, preferentially by providing several - i.e., one or more - mixing elements.

To enable an optimized yield for the input resources, the method contemplates process monitoring and control, preferably comprising the following steps:
b1) The following:
- the amount of hydroxide that accumulates unnecessarily inside the first reaction vessel;
- the amount of citral entering the first reaction vessel;
- the amount of citral at the outlet or downstream of the first reactor;
- the amount of citral at the outlet or downstream of the second reactor;
- the amount of water at the outlet or downstream of the second reactor;
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the first reactor;
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the second reactor;
- a reactor feed temperature of at least one of the first or second component feeds ;
- the reactor residence time of at least one of the first or second component feeds ; or
- determining at least one of a feed rate of a first component feed ;
b2) If the amount calculated in b1) falls outside the respective specified threshold ranges,
- the feed rate of the second component feed relative to the first component feed , or
- increasing or decreasing at least one of the feed rates of said starting material feed comprising hydroxide, preferably the third starting material feed , relative to the first component feed so that the amount determined in b1) is brought back inside the threshold range.

The aforementioned amounts are preferably obtained by measuring their absolute amounts in the sample volume, or by measuring their concentrations in each feed and calculating their amounts according to the flow rates of each feed.

The method preferably further comprises the step of providing a packing material in the second reaction vessel. The packing material may be a structured packing material, but in a particularly preferred variant consists of or at least comprises a loose packing material. The latter facilitates installation and in this context achieves the desired function of packing, the minimization of streaking or undesired laminar flow, in other words free convection, and an overall improved distribution of the content of the third aqueous mixture throughout the second reaction vessel.

The method preferably further comprises the step of determining the pressure difference between the first and second reactors, preferably at respective locations upstream and downstream of the mixing device. By determining the pressure difference between the first and second reactors, in particular between the inlet and outlet sides of the mixing device located at the outlet of the first reactor, an operator can monitor whether the mixing device is functioning or malfunctioning, e.g. due to clogging. Monitoring the pressure difference can be performed with minimal device cost, allowing for rapid decision making and replacement or repair.

The method discussed above under the second aspect focuses more on the engineering aspects of the invention. In a further aspect, the present invention also proposes a method that focuses primarily on the chemical aspects of the invention, namely a method for producing pseudoionones and hydroxypseudoionones, preferably pseudoionones, comprising the following steps:
(P1) preparing a first aqueous mixture (i.e., a mixture including water) containing a first concentration of acetone, citral, and hydroxide by combining a first amount of water, acetone, citral, and hydroxide;
(P2) The components of the first aqueous mixture are
generating a second aqueous mixture (i.e., a mixture including water) by reacting for a reaction time such that pseudoionone, hydroxypseudoionone, and 4-hydroxy-4-methylpentan-2-one are formed and acetone, citral, and hydroxide are consumed, the second aqueous mixture being:
- 4-hydroxy-4-methylpentan-2-one in a concentration higher than its concentration in the first aqueous mixture;
- acetone, citral and hydroxide in a second concentration less than the first concentration; and
- comprising pseudoionone and hydroxypseudoionone;
(P3) Producing a third aqueous mixture (i.e., a mixture including water) by adding a second amount of hydroxide to the second aqueous mixture, such that an additional amount of pseudoionone is formed in the third aqueous mixture.

The present invention and preferred variations and combinations of its parameters, properties and elements are defined in the appended claims. Preferred aspects, details, modifications and advantages of the present invention are also defined and explained in the following description and in the examples set out below.

The preferred embodiments of the device according to the first aspect and the method according to the second aspect described above are simultaneously preferred embodiments of the third aspect. Similarly, the preferred embodiments of the method according to the third aspect described below are simultaneously preferred embodiments of the device according to the first aspect and the method according to the second aspect.

According to the invention, the apparatus is configured and comprises means for carrying out the method of the second and/or third aspect. Similarly, according to the invention, the method according to the second and third aspect is carried out in a preferred embodiment by using the apparatus according to the first aspect or its preferred embodiment described above.

It has now been found that the process for producing pseudoionones and hydroxypseudoionones according to the present invention is highly efficient and highly suitable for batch, semi-batch and especially continuous performance. Surprisingly, it has been found that the process of the present invention results in a higher yield of pseudoionones when compared to similar processes known in the art. It has also been found that the process of the present invention exhibits a higher selectivity towards hydroxypseudoionone in the production or production of pseudoionones. Said higher selectivity is desirable since pseudoionones are a much more versatile intermediate product for industrial synthesis than hydroxypseudoionones.

In the context of the present invention, "pseudoionone" according to the usual meaning in the art means a mixture of the four isomers (3Z,5Z)-6,10-dimethyl-3,5,9-undecatrien-2-one, (3E,5Z)-6,10-dimethyl-3,5,9-undecatrien-2-one, (3Z,5E)-6,10-dimethyl-3,5,9-undecatrien-2-one and (3E,5E)-6,10-dimethyl-3,5,9-undecatrien-2-one. Said mixture of isomers is often also referred to as 6,10-dimethyl-3,5,9-undecatrien-2-one having the CAS® RN 141-10-6 (in this text). One of the pseudoionone isomers (i.e. (3E,5E)-6,10-dimethyl-3,5,9-undecatrien-2-one) is shown as an example in formula I below:

In the context of the present invention, "hydroxypseudoionone" refers to the compounds 4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one and 4-hydroxy-6,10-dimethyl-undeca-6,9-dien-2-one, including their isomers. In the process according to the invention, a mixture of four compounds is usually formed, namely the two isomers (5E)-4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one and (5Z)-4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one, and the two isomers (6E)-4-hydroxy-6,10-dimethyl-undeca-6,9-dien-2-one and (6Z)-4-hydroxy-6,10-dimethyl-undeca-6,9-dien-2-one. At least a portion of the four compounds (presumably (5E)-4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one and/or (5Z)-4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one) can then be at least partially decomposed again under the conditions of the method according to the invention. One of the four compounds (i.e. (5E)-4-hydroxy-6,10-dimethyl-undeca-5,9-dien-2-one) is shown by way of example in formula II below:

In the context of the present invention, "citral" according to the usual meaning in the art means a mixture of the cis-trans isomers, geranial, also known as 3,7-dimethylocta-2,6-dienal (CAS® RN 5392-40-5), (E)-3,7-dimethylocta-2,6-dienal (CAS® RN 141-27-5), and neral, also known as (Z)-3,7-dimethylocta-2,6-dienal (CAS® RN 106-26-3). The two separate isomers, geranial and neral, can also be used as starting compounds in the first aqueous mixture, like citral, but their use is not preferred for commercial reasons. Furthermore, in independent experiments, it was found that the reaction of the separate isomers neral or geranial, respectively, to pseudoionone (or pseudoionone isomer) proceeds faster than the isomerization of the separate isomers to citral. Thus, by using the separate isomers (i.e., neral or geranial) in the method of the present invention, it is possible to produce pseudoionones enriched in one isomer, however, it is not possible to produce a single isomer of pseudoionone with this variant.

In the context of the present invention, the term "hydroxide" has its ordinary meaning in the art and refers to the hydroxide anion "HO ^- ". When the text refers to the single term "hydroxide", this means the hydroxide anion independent of any source providing said hydroxide anion, for example a metal hydroxide such as NaOH, or the exact identity of such a metal hydroxide.

In the context of the present invention, the term "concentration" (in particular the concentration of the components acetone, citral, hydroxide and/or 4-hydroxy-4-methylpentan-2-one) used in the definition of the first, second and/or third aqueous mixture, unless otherwise expressly stated in this text, preferably refers to the total mass of a component (in particular the molar mass of the components acetone, citral, hydroxide and/or 4-hydroxy-4-methylpentan-2-one) relative to the total mass of water and acetone present in the considered aqueous mixture.

In step (P1) of the method of the invention defined above, the preparation of the first aqueous mixture defined above corresponds to the starting conditions of the method according to the invention (i.e. the conditions at time "t=0").

The citral used for the preparation of the first aqueous mixture in step (P1) defined above may be pure citral (e.g. having a purity of ≧97%) or it may be recycled citral from other processes or from the process of the present invention. In independent experiments, it has been found that citral can be used in step (P1) with a purity of ≧92% by weight, preferably ≧95% by weight, based on the total weight of citral and organic impurities accompanying citral - without significant adverse effects on the process performance. Organic impurities accompanying citral are organic compounds other than citral that can only be separated from citral by additional purification steps. However, such additional purification steps are not preferred, as they usually also lead to the loss of citral.

In step (P1) of the process of the invention as defined above, 4-hydroxy-4-methylpentan-2-one may be present in the first aqueous mixture, for example in cases where a reaction mixture from another process or the process of the invention is used to prepare the first aqueous mixture, or 4-hydroxy-4-methylpentan-2-one may not be present in the first aqueous mixture.

In step (P2) of the process of the invention defined above, acetone, citral and hydroxide are reacted such that pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one are formed and acetone, citral and hydroxide are consumed. The reaction occurring in step (P2) is of the aldol condensation type known in the art. 4-hydroxy-4-methylpentan-2-one (also known as diacetone alcohol, CAS® RN 123-42-2) is formed in step (P2) as the reaction product of a competing reaction with the self-condensation of acetone. As another side reaction, mesityl oxide (also known as methylpent-3-en-2-one, CAS® RN 141-79-7) can be formed in step (P2) by elimination of water from 4-hydroxy-4-methylpentan-2-one. Further by-products can be formed as a result, as known in the art.

Due to the formation of 4-hydroxy-4-methylpentan-2-one in step (P2), its concentration is in any case higher in the second aqueous mixture (step (P2)) than is (or was) present in the first aqueous mixture (step (P1)), regardless of the concentration of 4-hydroxy-4-methylpentan-2-one previously present in the first aqueous mixture (and if 4-hydroxy-4-methylpentan-2-one is or was not present in the first aqueous mixture, see above).

In step (P2) of the process of the invention defined above, acetone and citral are mainly consumed by their reaction to form the reaction products pseudoionone and hydroxypseudoionone. The hydroxide in the process according to the invention generally functions as a catalyst, but in practice it can also be observed that it is consumed during step (P2) by participation in side reactions or competing reactions, such as the Cannizzaro reaction for example. To compensate for the hydroxide consumed in step (P2) and preferably even to increase the concentration of hydroxide, preferably the concentration of dissolved hydroxide, in the third aqueous mixture (when compared to the concentration of hydroxide or dissolved hydroxide in the first aqueous mixture), a second amount of hydroxide is added to the second aqueous mixture according to the process of the invention.

Therefore, in step (P3),
- the second amount of hydroxide added to the second aqueous mixture is in the range of 5% to 50% by weight, preferably in the range of 10% to 40% by weight, of the first amount of hydroxide in the first aqueous mixture;
and/or
- the concentration of dissolved hydroxide present in the third aqueous mixture is higher than in the second aqueous mixture;
A method according to the invention as defined herein (or a method according to the invention described as preferred above or below) is preferred.

For example, if the first amount of hydroxide in the first aqueous mixture is 0.1 g, the second amount of hydroxide added to the second aqueous mixture is preferably in the range of 0.005 g to 0.05 g, more preferably in the range of 0.01 g to 0.04 g.

From independent experiments, it appears that the second amount of hydroxide added to the above-specified amount of the second aqueous mixture under the conditions of the process according to the invention results in a higher concentration of hydroxide dissolved or capable of dissolving in the liquid phase of the third aqueous mixture than in the liquid phase of the first aqueous mixture. In independent experiments, it has been found that adding said second amount of hydroxide to the second aqueous mixture leads to the most advantageous results in terms of increased yield of pseudoionone and selectivity for its formation using the process according to the invention.

Without being bound by any theory, it is currently assumed that the 4-hydroxy-4-methylpentan-2-one formed in step (P2) contributes to an increase in the solubility of the hydroxide in the second aqueous mixture and/or the third aqueous mixture (compared to the solubility of the hydroxide in the first aqueous mixture), and that this increase in the solubility of the hydroxide contributes to the beneficial results of the process of the invention in terms of the yield and selectivity of the main product (the main product being the pseudoionone). Furthermore, it has been found that the highest solubility of the hydroxide (and therefore the most beneficial effect explained above) is achieved when the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has reached its maximum value or has reached a value close to its maximum value (in particular a value of ≧80%, preferably ≧85% of its maximum value) and before the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture falls again during the reaction, for example by a reverse reaction (as usually occurs in chemical equilibrium reactions).

It is therefore preferred to add the second amount of hydroxide to the second aqueous mixture when the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has reached a value of ≧80%, preferably ≧85% of its maximum value and/or before the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has (again) fallen to a value of ≦80%, preferably ≦85% of its maximum value. Correspondingly, the second amount of hydroxide is added to the second aqueous mixture in step (P3) when the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has a value of ≧80%, preferably ≧85% of its maximum value.

therefore,
the molar concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a value of 70 mmol/l or more;
and/or
before the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a maximum value or when the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a maximum value;
and/or
- the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has a value of ≥ 80%, preferably ≥ 85% of its maximum value,
and/or
- at least 3 minutes, preferably at least 5 minutes, after the first aqueous mixture has been prepared (i.e. when all the components, water, acetone, citral and hydroxide, have been combined in step (P1)) and preferably less than 25 minutes, more preferably less than 20 minutes, even more preferably less than 15 minutes after the first aqueous mixture has been prepared,
and/or
- after 3 minutes or more, preferably 5 minutes or more, of the reaction time of the components of the first aqueous mixture in step (P2), and preferably after less than 25 minutes, more preferably after less than 20 minutes, even more preferably after less than 15 minutes, of the reaction time of the components of the first aqueous mixture in step (P2),
and/or
when the molar ratio of 4-hydroxy-4-methylpentan-2-one:acetone in the second aqueous mixture reaches a value in the range of 1:45 to 1:8;
Preference is given to a process according to the invention as defined herein (or a process according to the invention as described above or below as preferred), wherein in step (P3) a second amount of hydroxide is added to the second aqueous mixture.

In a preferred variant of the method according to the invention, in which a second amount of hydroxide is added to the second aqueous mixture in step (P3) when the molar concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a value of 70 mmol/l or more, the molar concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture is the total molar amount of 4-hydroxy-4-methylpentan-2-one relative to the total amount of water and acetone present in the second aqueous mixture.

In independent experiments, it has been found that a time interval of at least 3 minutes, preferably at least 5 minutes, of the reaction time of the components of the first aqueous mixture in step (P2) before the second amount of hydroxide is added to the second aqueous mixture in step (P3) usually gives a favorable compromise between the desired residence time (as short as possible for reasons of process efficiency) on the one hand and a good conversion rate in step (P2) on the other hand. In independent experiments, it has also been found that said time interval of at least 3 minutes, preferably at least 5 minutes, of the reaction time of the components of the first aqueous mixture in step (P2) before the second amount of hydroxide is added to the second aqueous mixture in step (P3) usually correlates with the time interval (as explained above) in which the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a value of ≥ 80%, preferably ≥ 85% of its maximum value.

In the context of the present invention, the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture and its variants is preferably determined by gas chromatography, more preferably by a calibrated gas chromatography method. For this purpose, a sample of the second aqueous mixture is withdrawn and neutralized (preferably with dilute aqueous acetic acid) and then the concentration of 4-hydroxy-4-methylpentan-2-one is determined in the neutralized sample as known in the art. To determine the maximum concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture or generally the change in the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture over time, samples can be withdrawn from the second aqueous mixture at time intervals and analyzed for their concentration of 4-hydroxy-4-methylpentan-2-one as a function of time. From the results received, reference values can be determined and normalized (for example as a calibration curve) for the prediction of the progression of the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture under various method conditions.

In the context of the present invention, the molar ratio of 4-hydroxy-4-methylpentan-2-one:acetone in the second aqueous mixture and its variants is preferably determined by gas chromatography as described herein above. Alternatively, the molar ratio of 4-hydroxy-4-methylpentan-2-one:acetone in the second aqueous mixture and its variants is determined by ¹ H-NMR spectroscopy and integration of the signals related to the target compounds as is generally known in the art. Both methods give essentially the same results, with deviations that are not significant for practical purposes.

For enhanced performance of the method according to the invention, it is expedient to provide an intimate mixing of the hydroxide in the first and/or second aqueous mixture (preferably at the respective dosing points or locations of dosing the hydroxide into the first and/or second aqueous mixture), e.g. to facilitate as good a dissolution and distribution of the hydroxide in said aqueous mixture as possible.

Therefore, preferred are methods according to the invention as defined herein (or as described above or below as preferred) in which the first aqueous mixture and/or the second aqueous mixture and/or the third aqueous mixture are mechanically mixed or agitated. If the method according to the invention is carried out continuously for at least a part of the method or process time, mixing can be carried out, for example, by integrating a static mixer at the desired position in the reactor. If the method according to the invention is carried out batchwise or semi-batchwise for at least a part of the method or process time, mixing can be carried out, for example, by a mechanical stirrer.

In the context of the present invention, a "part of the method" according to the invention preferably means steps (P1), (P2) and (P3) individually or a combination of two of said steps.

In independent experiments, it has been found that the method according to the invention is particularly suitable for continuous performance, which is most favorable for industrial processes in terms of production efficiency.

therefore,
- at least part of the process, preferably the entire process, is carried out continuously (in flow mode), preferably in a tubular reactor, more preferably in a tubular reactor exhibiting a flow mode as close as possible to plug flow behavior;
and/or
- a second amount of hydroxide is continuously added to the second aqueous mixture;
A method according to the invention as defined herein (or a method according to the invention described as preferred above or below) is preferred.

When at least a part of the process, preferably the entire process, is carried out continuously in a tubular reactor, said tubular reactor preferably exhibits a behavior at least approximating plug flow behavior.

In some cases, it is also preferred that the method according to the invention as defined herein (or the method according to the invention described as preferred above or below) is carried out in which at least part of the method, preferably the entire method, is carried out discontinuously, preferably in batch or semi-batch mode.

In some cases, also preferred are methods according to the invention as defined herein (or methods according to the invention as described above or below as preferred) in which the second amount of hydroxide is added to the second aqueous mixture in one go or in several portions, preferably in one go. This variant of the method according to the invention can be applied in continuous, batch and/or semi-batch mode operation of the method.

In independent experiments, it was found that the average reaction rate for forming pseudoionone and the total amount of pseudoionone formed as a result of the reaction are both higher in the process according to the invention than in a similar process of the prior art, i.e., for the same volume and residence time, more pseudoionone is formed in the process according to the invention than in a similar process of the prior art that does not utilize the present invention.

Therefore, preferred are methods according to the invention as defined herein (or as described above or below as preferred) in which the total amount of pseudoionone formed in the series of steps (P2) and (P3) in a reaction time t [(P2) + (P3)] is greater than the total amount of pseudoionone formed in an equal reaction time t [(P2) + (P3)] in an isolated step (P2).

In the definitions given above, the term "t[(P2)+(P3)]" refers to the reaction time taken to perform steps (P2) and (P3) as defined above and below.

Furthermore, preferred are methods according to the invention as defined herein (or as described above or below as preferred) in which the overall method time is in the range of ≧9 to ≦30 minutes, preferably in the range of ≧12 to ≦25 minutes, more preferably in the range of >12 to ≦20 minutes.

In the context of the present invention, the term "overall process time" means the total time taken to carry out the process according to the invention, i.e. the process comprising steps (P1), (P2) and (P3). If the process according to the invention is carried out continuously, preferably for the entire process time, the entire process time preferably corresponds to the residence time in a continuous reactor, preferably a tubular reactor. If the process according to the invention is carried out batchwise or semi-batchwise, preferably for the entire process time, the entire process time preferably corresponds to the (overall) reaction time in a batch (or semi-batch) reactor.

Also,
- a first concentration of hydroxide in the first aqueous mixture is in the range of 0.0015 to 0.02% by weight, preferably in the range of 0.0015 to 0.0140% by weight, more preferably in the range of 0.0017 to 0.0070% by weight, even more preferably in the range of 0.0020 to 0.0065% by weight relative to the total weight of water and acetone present in the first aqueous mixture,
and/or
- the molar ratio of the first amount of hydroxide present in the first aqueous mixture to the first amount of citral present in the first aqueous mixture is in the range of 1.0 to 30.0 mmol/mol, preferably in the range of 2.0 to 20.0 mmol/mol, more preferably in the range of 2.0 to 12.0 mmol/mol;
and/or
- the molar ratio of the total amount of acetone present in the first aqueous mixture to the total amount of citral present in the first aqueous mixture is in the range of 24.0:1 to 65.5:1, preferably in the range of 31.5:1 to 65.5:1, more preferably in the range of 35.0:1 to 60.0:1, even more preferably in the range of 37.5:1 to 50.0:1;
A method according to the invention as defined herein (or a method according to the invention described as preferred above or below) is preferred.

In a particularly preferred variant of the process of the invention as defined herein (or the process according to the invention as described above or below as preferred), the molar ratio of the total amount of acetone present in the first aqueous mixture to the total amount of citral present in the first aqueous mixture is in the range of 38.0:1 to 47.0:1.

In independent experiments, it has been found that the aforementioned or preferred concentrations of hydroxide in the first aqueous mixture are suitable for allowing complete or substantially complete dissolution of the hydroxide in the first aqueous mixture and for forming 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture at a convenient rate and concentration. In a preferred variant of the method of the invention, the first concentration of hydroxide in the first aqueous mixture is adjusted to the maximum concentration of hydroxide that is soluble in the first aqueous mixture (i.e., the maximum possible concentration of hydroxide that can be completely dissolved in the first aqueous mixture is used in step (P1)).

Independent experiments have also found that the aforementioned ranges and preferred ranges of "first amount of hydroxide present in the first aqueous mixture":"first amount of citral present in the first aqueous mixture" and the aforementioned ratios of "total amount of acetone present in the first aqueous mixture":"total amount of citral present in the first aqueous mixture" contribute to enhanced performance of the method according to the invention. The aforementioned concentration and ratio ranges and preferred ranges can preferably be combined. When the aforementioned preferred ranges of concentrations and ratios are combined with each other, the combination also results in a preferred or even more preferred variant of the method according to the invention.

Also, when the first amount of hydroxide used to prepare the first aqueous mixture (step (P1)) and/or the second amount of hydroxide added to the second aqueous mixture (step (P3)) is provided by one or more metal hydroxides (in each case, as appropriate):
Preferably
- one or more metal hydroxides
- alkali metal hydroxides, preferably LiOH, NaOH and KOH,
- alkaline earth metal hydroxides, preferably Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ and Ba(OH) ₂
is selected from the group consisting of
More preferably, said one metal hydroxide or one of said one or more metal hydroxides is selected from the group consisting of alkali metal hydroxides, even more preferably LiOH, NaOH and KOH;
Most preferably, the one or more metal hydroxides is NaOH.
And/or (preferably "and")
- the one or more metal hydroxides comprise one or more metal hydroxides dissolved in a liquid phase;
Preferably, the one or more metal hydroxides comprise one or more aqueous metal hydroxides;
More preferably, the one or more metal hydroxides are provided in the form of an aqueous solution of one or more metal hydroxides;
Preferably, the aqueous solution has a concentration of hydroxide ions in the range of 0.3 to 1.5% by weight, preferably in the range of 0.35 to 0.65% by weight, more preferably in the range of 0.4 to 0.6% by weight, relative to the total weight of water and metal hydroxide present in the aqueous solution;
A method according to the invention as defined herein (or a method according to the invention described as preferred above or below) is preferred.

In a variant of the process according to the invention as defined above, the one or more metal hydroxides dissolved in the liquid phase can be dissolved in any solvent or mixture of solvents that is suitable for dissolving the amount of one or more metal hydroxides required or preferred for the process according to the invention, is compatible with or does not interfere with the performance of the process. The amount of one or more metal hydroxides required or preferred for the process according to the invention is preferably an amount that results in a concentration of hydroxide ions in the liquid phase in the range of 0.3 to 1.5% by weight, preferably in the range of 0.35 to 0.65% by weight, more preferably in the range of 0.4 to 0.6% by weight, relative to the total weight of the solvent or mixture of solvents and the metal hydroxides present in the liquid phase.

In a preferred variant of the process according to the invention, the one or more metal hydroxides comprise one or more metal hydroxides dissolved in a liquid phase comprising one or more solvents selected from the group consisting of water, acetone, alcohols containing 1 to 3 carbon atoms and mixtures thereof. Solvents or mixtures of solvents already present in the process are preferred, in particular water, acetone and mixtures thereof.

In a preferred variant of the method according to the invention as defined above, aqueous metal hydroxide means a solution of one or more metal hydroxides, preferably with water. Said aqueous metal hydroxide may contain (in addition to water) a water-miscible solvent, preferably selected from the group consisting of methanol, ethanol and acetone. Preference is given to aqueous metal hydroxides which are solutions of one or more metal hydroxides in water or in a mixture of water and acetone.

In a variant of the method according to the invention as defined above, the one or more metal hydroxides may be provided by one or more metal hydroxides of varying purity. One or more metal hydroxides having a purity of ≧70% by weight, preferably ≧85% by weight, more preferably ≧90% by weight, even more preferably ≧95% by weight are preferred. To the extent that impurities present in the metal hydroxide are compatible with or do not interfere with the performance of the method (for example because they are not adequately soluble in the liquid or aqueous phase as defined above and below), metal hydroxides of low grade (for example "technical grade" having a purity of ≦90% by weight) can be used in the method of the invention.

Thus, also, the first amount of hydroxide used to prepare the first aqueous mixture (step (P1)) and/or the second amount of hydroxide added to the second aqueous mixture (step (P3)) is provided by one or more metal hydroxides (in each case, as appropriate);
- one or more metal hydroxides
- an alkali metal hydroxide, preferably selected from the group consisting of LiOH, NaOH and KOH;
More preferably, said one metal hydroxide or one of said one or more metal hydroxides is selected from the group consisting of alkali metal hydroxides, even more preferably LiOH, NaOH and KOH;
Most preferably, the one or more metal hydroxides is NaOH.
And/or (preferably "and")
- the one or more metal hydroxides are provided as an aqueous solution of the one or more metal hydroxides;
Preferably, the aqueous solution has a concentration of hydroxide ions in the range of 0.3 to 1.5% by weight, preferably in the range of 0.35 to 0.65% by weight, more preferably in the range of 0.4 to 0.6% by weight, relative to the total weight of water and metal hydroxide present in the aqueous solution;
A method according to the invention as defined herein (or a method according to the invention described as preferred above or below) is preferred.

Preferably, the at least second amount of hydroxide added to the second aqueous mixture (step (P3)) is provided by one or more metal hydroxides as defined herein above.

In a preferred variant of the method according to the invention defined herein above, preferably the aqueous solution of one or more metal hydroxides is a solution in water or in a mixture of water and acetone.

In the preferred variants of the method according to the invention defined herein above, the preferred metal hydroxides and the preferred forms of the aqueous metal hydroxides, in particular the preferred forms of the aqueous solutions of metal hydroxides and the preferred concentrations of hydroxide ions in said aqueous solutions of one or more metal hydroxides, can be combined to result in particularly preferred variants of the method according to the invention.

In one preferred variant of the method of the invention, the second amount of hydroxide added to the second aqueous mixture (step (P3)) is provided by an aqueous NaOH solution, preferably a solution of NaOH in water, having a concentration of hydroxide ions preferably in the range of 0.3 to 1.5% by weight, preferably in the range of 0.35 to 0.65% by weight, more preferably in the range of 0.4 to 0.6% by weight, relative to the total weight of water and NaOH present in said aqueous NaOH solution.

In independent experiments, it has been found that when NaOH (in particular an aqueous NaOH solution having the concentration or preferred concentrations as defined above) is used to provide the second amount of hydroxide (step (P3)), NaOH provides particularly advantageous properties in terms of solubility and reaction performance, such that the process according to the invention provides particularly favorable results in terms of product yields, in particular the yield of pseudoionone.

Furthermore, in order to adequately mix or agitate the second and/or third aqueous mixture (as explained above), especially when the process of the invention is carried out continuously for at least part of the process or process time, it is expedient to add (dosage) the second amount of hydroxide (step (P3)) in the form of an aqueous solution of one or more metal hydroxides (as defined above) in the smallest possible container or pipe diameter and/or by means of a static mixer and/or by means of a sparger and/or by means of a liquid distributor.

the first aqueous mixture, and/or (preferably "and") the second aqueous mixture, and/or (preferably "and") the third aqueous mixture form a liquid phase below their boiling points;
Preferably
the reaction temperature in the first aqueous mixture and/or in the second aqueous mixture and/or in the third aqueous mixture is in the range of from 60 to 110°C, preferably in the range of from 70 to 100°C, more preferably in the range of from 70 to 90°C,
and/or
at least a part of the process, preferably the entire process, is carried out at a pressure in the range of from 150 to 1000 kPa, preferably in the range of from 150 to 700 kPa, more preferably in the range of from 200 to 650 kPa, even more preferably in the range of from 250 to 600 kPa absolute,
and/or
Also preferred is a process according to the invention as defined herein (or a process according to the invention as described above or below as preferred), wherein at least part of the process, preferably the entire process, is carried out under adiabatic conditions.

In a preferred variant of the process according to the invention, the reaction temperature in the first aqueous mixture, in the second aqueous mixture and in the third aqueous mixture is in each case in the range from 60 to 110°C, preferably in the range from 70 to 100°C, more preferably in the range from 70 to 90°C.

In one variant of the invention, a process (or a process according to the invention described above or below as preferred) is preferred, in which the first aqueous mixture and/or (preferably "and") the second aqueous mixture and/or (preferably "and") the third aqueous mixture form a liquid phase below their boiling points and the reaction temperature in the first aqueous mixture and/or in the second aqueous mixture and/or in the third aqueous mixture is in the range of 72-95°C, preferably in the range of 72-92°C.

Also preferred are methods according to the invention as defined herein (or as described above or below as preferred) in which the reaction conditions, preferably the concentrations of acetone, citral and/or hydroxide, are selected or adjusted such that the first aqueous mixture forms a single liquid phase, and/or the second aqueous mixture forms a single liquid phase, and/or the third aqueous mixture forms a single liquid phase. In a preferred variant of the invention, said reaction conditions are selected or adjusted such that the first aqueous mixture, the second aqueous mixture and the third aqueous mixture each form a single liquid phase.

Furthermore, preferred is a method according to the invention as defined herein (or a method according to the invention as described above or below as preferred), in which the total amount of hydroxide present in the third aqueous mixture dissolves in the liquid phase. In independent experiments, it has been found that particularly good results of the method according to the invention in terms of the yield of pseudoionone are achieved when the hydroxide present in the third aqueous mixture is present in as high a concentration as possible that is still present or can be dissolved in the third aqueous mixture.

Preferred is a method according to the invention as defined herein (or as described above or below as preferred) in which the first aqueous mixture comprises water at a concentration in the range of 3-9% by weight, preferably in the range of 4-8% by weight, more preferably in the range of 5-7% by weight, relative to the total weight of water and acetone present in the first aqueous mixture.

In a preferred variant of the process for producing pseudoionones and hydroxypseudoionones according to the invention, the pseudoionones formed in step (P3) are isolated from the reaction mixture, and the remaining residual mixture is recycled - in whole or in part - to the process and used for the preparation of the first aqueous mixture. In a particularly preferred variant of the process according to the invention, the remaining residual mixture is further purified to obtain selected fractions thereof and, if desired, recycled to the process and used for the preparation of the first aqueous mixture.

[Example]
The following examples are intended to further explain and illustrate the present invention without limiting its scope. Examples 1 to 3 were carried out in an experimental apparatus and in a batch mode and serve as model reactions for carrying out the method of the present invention, particularly under the second and/or third aspects in a continuous mode. Additional experiments (in a continuous mode) were carried out (not shown) using an apparatus according to one of the embodiments under the first aspect of the present invention and/or a method according to one of the preferred embodiments under the second and/or third aspects of the present invention. Such additional experiments confirmed the advantageous results obtained in Examples 2 and 3 discussed below.

Example 1: Preparation of pseudoionone and hydroxypseudoionone (comparative experiment not according to the present invention)
A 50 ml glass autoclave (maximum pressure load 1.2 MPa) fitted with ports for dosing under pressure (aqueous solution of sodium hydroxide) and for withdrawing samples under pressure (from the reactor), equipped with a magnetic stirrer, an oil bath, temperature measurement of the oil bath, and temperature measurement of the reactor was used for the following experiments (hereafter referred to as the "autoclave").

34.18 g of acetone with a water content of 5.9% (wt./wt.) and 2.005 g of citral (mixture of isomers, purity 97.0% determined by gas chromatography) were placed in an autoclave at room temperature under nitrogen atmosphere. The resulting mixture was heated to a temperature of 75°C (reactor; oil bath temperature: 80°C) and vigorously stirred at internal pressure. Then, 0.426 g of a 1.22% (wt./wt.) aqueous solution of sodium hydroxide (equivalent to 140 ppm NaOH, "first amount of hydroxide") was added by syringe through a port for dosing under pressure, and the syringe was purged several times with the mixture from the reactor (T=0, preparation of the first aqueous mixture).

After addition of the aqueous sodium hydroxide solution, samples were withdrawn from the reactor (through a port for withdrawing samples under pressure) at t=0.25 min (i.e. immediately after addition of the aqueous sodium hydroxide solution), and then at 5, 15, 30 and 60 min, and in each case the samples were immediately neutralized with dilute aqueous acetic acid. The neutralized samples were analyzed by weight-calibrated gas chromatography for (i) citral conversion, (ii) selectivity for pseudoionone formation, and (iii) selectivity for hydroxypseudoionone formation.

Table 1 below shows the results from these analyses.

In this table (and in Tables 2 and 3 below), "citral conversion [%]" means the percentage of citral that was converted after each period of time, "pseudoionone selectivity [%]" means the percentage of citral that was converted to pseudoionone after each period of time (where "pseudoionone" is as defined above), and "hydroxypseudoionone selectivity [%]" means the percentage of citral that was converted to hydroxypseudoionone after each period of time (where "hydroxypseudoionone" is as defined above).

"n.d." in this case means that no data points were sought.

[Example 2] Preparation of pseudoionones and hydroxypseudoionones (method according to the present invention) An experiment according to Example 1 (above) was carried out, except that an additional amount of hydroxide ("second amount of hydroxide") was added 5 minutes after administration of the first aqueous solution of sodium hydroxide ("first amount of hydroxide"). As the second amount of hydroxide, 105 mg of a 1.2% (wt./wt.) aqueous solution of sodium hydroxide (equivalent to 35 ppm NaOH) was added by syringe in a manner similar to that described in Example 1 above (see addition of "first amount of hydroxide").

Samples were again withdrawn from the reaction vessel in the manner described in Example 1 above at t=0.25 minutes (i.e., immediately after the addition of the first dose of the aqueous solution of sodium hydroxide, i.e., the addition of the "first amount of hydroxide"), 5 minutes (i.e., immediately after the addition of the second dose of the aqueous solution of sodium hydroxide, i.e., the addition of the "second amount of hydroxide"), 10 minutes, 15 minutes, 30 minutes, and 60 minutes after the addition of the first dose of the aqueous solution of sodium hydroxide. Samples were again immediately neutralized and analyzed by gas chromatography as described in Example 1 above.

The results from these analyses are shown in Table 2 below.

From the results in Table 2 above, it can be seen that the process according to the invention, when compared to a similar process not according to the invention (see Example 1 above), shows an increase in the reaction rate (see, for example, a value of 96.3% citral conversion after 15 minutes for the process according to the invention compared to 94.7% for the comparative process according to Table 1), an increase in the yield of the main product pseudoionone (see, for example, a value of 86.8% selectivity for pseudoionone formation after 15 minutes for the process according to the invention (corresponding to a yield of 83.6% of pseudoionone) compared to 85.6% for the comparative process according to Table 1 (corresponding to a yield of 81.1% of pseudoionone)) and a beneficial decrease in the selectivity for the formation of hydroxypseudoionone (see, for example, a value of 2.2% after 15 minutes for the process according to the invention compared to 2.6% for the comparative process according to Table 1, respectively).

[Example 3] Preparation of pseudoionones and hydroxypseudoionones (method according to the invention) An experiment according to Example 2 (above) was carried out, except that an additional amount of hydroxide ("second amount of hydroxide") was added 10 minutes after the dose of the first aqueous solution of sodium hydroxide ("first amount of hydroxide"). A sample was withdrawn at t=10 minutes after the addition of the second dose of the aqueous solution of sodium hydroxide, i.e. immediately after the addition of the "second amount of hydroxide".

Table 3 below shows the results from this Example 3:

From the results in Table 3 above, it can be seen that the process according to the invention also shows, when compared to a similar process not according to the invention (see Example 1 above), an increase in the reaction rate (see, for example, a value of 96.5% citral conversion after 15 minutes for the process according to the invention compared to 94.7% for the comparative process according to Table 1), an increase in the yield of the main product pseudoionone (see, for example, a value of 85.7% selectivity for pseudoionone formation after 15 minutes for the process according to the invention (corresponding to a yield of 82.7% of pseudoionone) compared to 85.6% for the comparative process according to Table 1 (corresponding to a yield of 81.1% of pseudoionone)) and a beneficial decrease in the selectivity for the formation of hydroxypseudoionone (see, for example, a value of 2.2% after 15 minutes for the process according to the invention compared to 2.6% for the comparative process according to Table 1, respectively).

Preferred embodiments of the present invention, particularly the first and second aspects of the present invention, will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an apparatus for producing pseudoionone and hydroxypseudoionone according to a preferred embodiment. FIG. 2 is a detailed schematic diagram of the reactor of the apparatus of FIG. 1.

Figure 1 depicts an apparatus 1 for producing pseudoionones and hydroxypseudoionones according to the invention as described in the general section above. The apparatus 1 comprises a feed line 3 producing a first component feed _C1 . The feed line 3 comprises a first mixer 5 configured to receive and combine a first starting material feed _S1 and a second starting material feed _S2 . The first starting material feed _S1 preferably comprises citral and the second starting material feed _S2 preferably comprises acetone.

Downstream of the first mixer 5, the feed line 3 comprises a heat exchanger 7 configured to heat the combined first and second starting material feeds _S1 + _S2 to a predetermined temperature. Downstream therefrom, the feed line 3 comprises a second mixer 9 configured to combine the first and second starting material feeds _S1 + _S2 with a third starting material feed _S3 , preferably comprising a hydroxide. The temperature of the third starting material feed _S3 is preferably lower than the temperature of the first and second starting material feeds _S1 + _S2 downstream of the heat exchanger 7. Therewith, the first component feed _C1 leaving the second mixer 9 can preferably be controlled to have a predetermined set point temperature.

The apparatus 1 comprises a reactor 11, which in a preferred embodiment is a double-tube reactor. The reactor 11 comprises a first reaction vessel 13 having an inlet 15 and an outlet 16. The outlet 16 is at the same time at the outlet part of a mixing device 17 arranged at the outlet end of the first reaction vessel 13. The first reaction vessel 13 is delimited by the inner tube 14 of the reactor 11.

The reactor 11 further comprises a second reaction vessel 23 bounded by the outer tube 25 and the inner tube 14 of the reactor 11, and having a substantially annular shape in the area where the inner tube 14 and the outer tube 25 overlap. The outlet 16 of the first reaction vessel 13 is at the same time an inlet to the second reaction vessel 23. The second reaction vessel 23 further comprises an outlet 18 configured to withdraw material from the reactor 11. In the embodiment shown here, the second reaction vessel comprises just one main outlet 18, but it is understood that the second reaction vessel may be designed to comprise at least one outlet 18, and in preferred embodiments may comprise multiple outlets 18, meaning 2, 3, 4, 5, 6, 7, 8 or more outlets 18.

The inlet 15 attached to the bottom end of the first reaction vessel 13 is a first inlet, and the reactor 11 further comprises a second inlet 19 upstream from the mixing device 17, the second inlet 19 configured to receive the second component feed _C2 and distribute the second component feed _C2 to the mixing device 17. To accomplish this, the second inlet 19 comprises a feed pipe 20 located upstream of the inlet to the mixing device 17, preferably within a distance _H0 of less than 50 cm. The feed pipe 20 comprises several - i.e., one or more - distribution outlets 21, each having an orifice 27 oriented towards the mixing device 17.

Upstream of the mixing device 17, the first reaction vessel 13 includes a tapered section 26 that tapers at an angle α toward the mixing device 17, which is effective to increase the flow rate of the first component feed material C1 through the first reaction vessel 13.

In the embodiment shown in Figures 1 and 2, the first reaction vessel 13 is a vertical upflow column and the second reaction vessel 23 is a substantially annular, vertical downflow column. The flow rate in the first reaction vessel 13 is significantly higher than the flow rate in the second reaction vessel 23 due to the dimensions of the reactor 11, which is shown in more detail in Figure 2. Below the first inlet 15, the first reaction vessel 13 is equipped with a sump 28 for collecting liquids, in particular water and/or hydroxides, and a drain 30 for fast removal of materials from the first reaction vessel 13, if necessary.

2 shows the reactor 11 of the apparatus 1 in more detail. Inside the reactor 11, the first reaction vessel 13 is equipped with a number of mixing elements 29, preferably stationary X-type mixing elements. The mixing elements 29 are distributed over the column height H _1. Downstream from the number of mixing elements 29, the first reaction vessel 13 tapers along a length H _2. In between, the mixing elements 29 and the tapered section 26, the first reaction vessel 13 and its part including the inner tube 14 are fixed to the outer tube 25, preferably by corresponding fixing means 33, e.g. a number of spokes.

The first reaction vessel 13 is provided with a perforated cover sheet 31. The cover sheet 31 is configured to promote uniform flow distribution across the vessel diameter, i.e., to promote the breakup of the directed flow ("jet") coming from the inlet tube due to pressure loss.

The first reaction vessel 13 has a diameter _{D1 that} is larger than the diameter D0 of the mixing device 17 but smaller than the diameter _D2 of the outer tube 25 and defines the second reaction vessel 23. Preferably, the diameter _D2 of the outer tube 25 is 1.5x to 3.0x the size of the diameter _D1 of the inner tube 14. The diameter _D1 of the inner tube 14 is preferably in the range of 3.0x to 5.0x the diameter _D0 of the mixing device.

The column height H ₁ is preferably defined as a function of the diameter D ₁ of the first reactor. Preferably, the ratio H ₁ /D ₁ is in the range of 15:1 or more, more preferably in the range of 25:1 or more.

The mixing device 17 has a length _H3 in the direction of flow. _H3 is preferably defined as a function of the diameter _D0 of the mixing device. Preferably, the ratio _H3 / _D0 is in the range of 3:1 or more, more preferably 5:1 or more.

Above the outlet 16 of the mixing device 17, i.e. the first reaction vessel 13, the second reaction vessel 23, is preferably provided with a head chamber having a height _H4 , _which is preferably defined as a function of the diameter _D2 of the outer tube 25. Preferably the ratio _H4 / _D2 is in the range of 3:2 or more, more preferably in the range of 5:2 or more.

The second reaction vessel 23 has at least one side port 35 for taking samples. In addition, the second reaction vessel 23 preferably has a side opening 39 that can be reversibly opened and closed for inspection of the second reaction vessel 23 and/or for placing loose filler material into the annular portion of the second reaction vessel 23. The opening 39 may be a hand hole or a manhole.

The reactor 11 comprises several - i.e. one or more - perforated sheets, for example indicated by reference sign 41, in the annular portion of the second reaction vessel 23 that delimit the volume in which the packing material can be placed. Furthermore, the reactor 11 comprises at least one cover sheet 37 configured to promote a uniform flow distribution over the diameter of the annular portion.

At the outlet end of the second reactor, downstream of the outlet 18, the apparatus 1 includes an inspection glass 43 that allows visual inspection of the material withdrawn from the reactor 11. Additionally, the reactor 11 may include a sensor assembly 45 to determine at least one of the temperature, pressure, and concentration of the material in the outlet feed.

Furthermore, the reactor 11 may comprise a sensor assembly 47 arranged in the region of the liquid reservoir 28 and configured to determine the liquid level and/or temperature and/or hydroxide concentration in the first reaction vessel in the region of the liquid reservoir 29. The drain line 30 may further comprise a sensor assembly 49 configured to determine the hydroxide concentration and/or flow parameters.

The second reaction vessel 23 may also be equipped with several - i.e., one or more - temperature sensors 53, possibly within the area for filling with the filling material.

Below are summarized preferred embodiments 1 to 15 of the method for producing pseudoionones and hydroxypseudoionones under the third aspect of the present invention. It is to be understood that each of these embodiments is also an embodiment of the present invention under the first and second aspects described above and claimed below.

Embodiment 1. A method for producing pseudoionones and hydroxypseudoionones, comprising:
(P1) preparing a first aqueous mixture containing a first concentration of acetone, citral, and hydroxide by combining a first amount of water, acetone, citral, and hydroxide; (P2) combining the components of the first aqueous mixture with
reacting for a reaction time such that pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one are formed and acetone, citral and hydroxide are consumed to produce a second aqueous mixture, the second aqueous mixture comprising:
- 4-hydroxy-4-methylpentan-2-one in a concentration higher than its concentration in the first aqueous mixture,
- acetone, citral and hydroxide in a second concentration less than the first concentration; and
- comprising pseudoionone and hydroxypseudoionone;
(P3) generating a third aqueous mixture by adding a second amount of hydroxide to the second aqueous mixture, such that an additional amount of pseudoionone is formed in the third aqueous mixture.

In the second embodiment, step (P3)
- the second amount of hydroxide added to the second aqueous mixture is in the range of 5% to 50% by weight, preferably in the range of 10% to 40% by weight, of the first amount of hydroxide in the first aqueous mixture;
and/or
2. The method of embodiment 1, wherein the concentration of dissolved hydroxide present in the third aqueous mixture is higher than the concentration of dissolved hydroxide present in the second aqueous mixture at the end of the reaction period.

Embodiment 3.
the molar concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a value of 70 mmol/l or more;
and/or
before the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a maximum value or when the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture reaches a maximum value;
and/or
- the concentration of 4-hydroxy-4-methylpentan-2-one in the second aqueous mixture has a value of ≥ 80%, preferably ≥ 85% of its maximum value,
and/or
- at least 3 minutes, preferably at least 5 minutes, after the first aqueous mixture has been prepared, and preferably less than 25 minutes, more preferably less than 20 minutes, even more preferably less than 15 minutes, after the first aqueous mixture has been prepared,
and/or
- after 3 minutes or more, preferably 5 minutes or more, and preferably after less than 25 minutes, more preferably after less than 20 minutes, even more preferably after less than 15 minutes of reaction time of the components of the first aqueous mixture in step (P2),
and/or
when the molar ratio of 4-hydroxy-4-methylpentan-2-one:acetone in the second aqueous mixture reaches a value in the range of 1:45 to 1:8;
3. The method of any one of the preceding claims, wherein in step (P3) a second amount of hydroxide is added to the second aqueous mixture.

Embodiment 4. The method of any one of embodiments 1 to 3, wherein the first aqueous mixture, and/or the second aqueous mixture, and/or the third aqueous mixture are mechanically mixed or agitated.

Embodiment 5. - At least a part of the process, preferably the entire process, is carried out continuously, preferably in a tube reactor, more preferably in a tube reactor exhibiting a flow regime as close as possible to plug flow behavior;
and/or
- a second amount of hydroxide is continuously added to the second aqueous mixture;
5. The method of any one of embodiments 1 to 4.

Embodiment 6. The method according to any one of embodiments 1 to 5, preferably any one of embodiments 1 to 4, wherein at least a part of the method, preferably the entire method, is carried out discontinuously, preferably in batch or semi-batch mode.

Embodiment 7. The method of any one of embodiments 1 to 6, wherein the second amount of hydroxide is added to the second aqueous mixture in one portion or in several portions, preferably in one portion.

Embodiment 8. The method according to any one of embodiments 1 to 7, wherein the total amount of pseudoionone formed in the series of steps (P2) and (P3) in a reaction time t [(P2) + (P3)] is greater than the total amount of pseudoionone formed in an equal reaction time t [(P2) + (P3)] in an isolated step (P2).

Embodiment 9. The method of any one of embodiments 1 to 8, wherein the overall method time is in the range of ≧9 to ≦30 minutes, preferably in the range of ≧12 to ≦25 minutes, more preferably in the range of >12 to ≦20 minutes.

Embodiment 10. - A first concentration of hydroxide in the first aqueous mixture is in the range of 0.0015 to 0.02% by weight, preferably in the range of 0.0015 to 0.0140% by weight, more preferably in the range of 0.0017 to 0.0070% by weight, even more preferably in the range of 0.0020 to 0.0065% by weight, relative to the total weight of water and acetone present in the first aqueous mixture.
and/or
- the molar ratio of the first amount of hydroxide present in the first aqueous mixture to the first amount of citral present in the first aqueous mixture is in the range of 1.0 to 30.0 mmol/mol, preferably in the range of 2.0 to 20.0 mmol/mol, more preferably in the range of 2.0 to 12.0 mmol/mol;
and/or
- the molar ratio of the total amount of acetone present in the first aqueous mixture to the total amount of citral present in the first aqueous mixture is in the range of 24.0:1 to 65.5:1, preferably in the range of 31.5:1 to 65.5:1, more preferably in the range of 35.0:1 to 60.0:1, even more preferably in the range of 37.5:1 to 50.0:1;
10. The method of any one of embodiments 1 to 9.

Embodiment 11. The first amount of hydroxide used to prepare the first aqueous mixture and/or the second amount of hydroxide added to the second aqueous mixture is provided by one or more metal hydroxides;
Preferably
- one or more metal hydroxides
- alkali metal hydroxides, preferably LiOH, NaOH and KOH,
- alkaline earth metal hydroxides, preferably Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ and Ba(OH) ₂
is selected from the group consisting of
More preferably, said one metal hydroxide or one of said one or more metal hydroxides is selected from the group consisting of alkali metal hydroxides, even more preferably LiOH, NaOH and KOH;
Most preferably, the one or at least one of the one or more metal hydroxides is NaOH.
and/or
- the one or more metal hydroxides comprise one or more metal hydroxides dissolved in a liquid phase;
Preferably, the one or more metal hydroxides comprise one or more aqueous metal hydroxides;
More preferably, the one or more metal hydroxides are provided in the form of an aqueous solution of one or more metal hydroxides;
Preferably, the aqueous solution has a concentration of hydroxide ions in the range of 0.3 to 1.5% by weight, preferably in the range of 0.35 to 0.65% by weight, more preferably in the range of 0.4 to 0.6% by weight, relative to the total weight of water and metal hydroxide present in the aqueous solution;
11. The method of any one of embodiments 1 to 10.

Embodiment 12. The first aqueous mixture, and/or the second aqueous mixture, and/or the third aqueous mixture form a liquid phase below their boiling points;
Preferably
the reaction temperature in the first aqueous mixture and/or in the second aqueous mixture and/or in the third aqueous mixture is in the range of from 60 to 110°C, preferably in the range of from 70 to 100°C, more preferably in the range of from 70 to 90°C,
and/or
at least a part of the process, preferably the entire process, is carried out at a pressure in the range of from 150 to 1000 kPa, preferably in the range of from 150 to 700 kPa, more preferably in the range of from 200 to 650 kPa, even more preferably in the range of from 250 to 600 kPa,
and/or
- at least a part of the process, preferably the entire process, is carried out under adiabatic conditions;
12. The method of any one of embodiments 1 to 11.

Embodiment 13. The method of any one of embodiments 1 to 12, wherein the reaction conditions, preferably the concentrations of acetone, citral and/or hydroxide, are selected or adjusted such that the first aqueous mixture forms a single liquid phase, and/or the second aqueous mixture forms a single liquid phase, and/or the third aqueous mixture forms a single liquid phase.

Embodiment 14. The method of any one of embodiments 1 to 13, wherein the total amount of hydroxide present in the third aqueous mixture dissolves in the liquid phase.

Embodiment 15. The method of any one of embodiments 1 to 14, wherein the first aqueous mixture comprises water at a concentration in the range of 3 to 9% by weight, preferably in the range of 4 to 8% by weight, more preferably in the range of 5 to 7% by weight, relative to the combined weight of water and acetone present in the first aqueous mixture.

The present invention includes, for example, the following embodiments.
[Item 1]
An apparatus (1) for producing pseudoionone and hydroxypseudoionone, comprising:
- a vertically oriented first reactor (13) arranged to flow components through the first reactor in a first flow direction;
- a vertically oriented second reactor (23) in fluid communication with the first reactor (13), the second reactor (23) being oriented such that the components flow through the second reactor (23) in a second flow direction different from the first flow direction;
- a first reaction vessel (13) configured to receive a first component feed (C1) containing a first aqueous mixture through an inlet (15) and to produce a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time;
- the apparatus (1) comprises a mixing device (17) located downstream of the first component feed inlet (15) and configured to add the second component feed (C2) to the first component feed (C1) when the second aqueous mixture is formed,
- a second reaction vessel (23) configured to receive the first and second component feeds combined at the mixing device (17) from the first reaction vessel (13) and to produce a third aqueous mixture from the first and second aqueous mixtures of the apparatus (1).
[Item 2]
Item 1. The device (1) according to item 1, wherein the first flow direction is oriented upwards and the second flow direction is oriented downwards, or vice versa.
[Item 3]
3. The apparatus (1) according to claim 1 or 2, wherein the mixing device (17) is located at the outlet end of the first reaction vessel (13).
[Item 4]
the inlet (15) to the first reactor (13) for receiving the first component feed (C1) is a first inlet, the first reactor (13) further comprising a second inlet (19) for receiving the second component feed (C2) located upstream from the mixing device (17);
Preferably, the second inlet (19) is located immediately upstream of the mixing device (17) or at a distance upstream of the mixing device (17), the distance being preferably selected such that the entire second component feed (C2) is drawn into the mixing device (17) without any preceding backflow inside the first reaction vessel (13).
[Item 5]
- the first reaction vessel (13) is provided with a tapered section (26) upstream of the inlet of the mixing device (17), preferably immediately upstream of the second inlet, in order to accelerate the flow rate of the second aqueous mixture;
and/or
- the first reactor (13) comprises upstream of the mixing device (17) several further mixing elements (29) configured to match the residence time of the first component feed (C1) between the inlet (15) to the first reactor and the mixing device (17),
and/or
- the second reaction vessel (23) is adapted to be reversibly opened and closed by means of a corresponding cover and is provided with an opening (39) dimensioned for introducing a packing material, preferably comprising or consisting of a loose packing material, into the second reaction vessel (23);
5. The device (1) according to any one of items 1 to 4.
[Item 6]
an inlet for a first component feed (C1) in fluid communication with a feed line (3) configured to produce the first component feed (C1) from a plurality of starting materials;
Preferably, the supply line (3) comprises a first mixer (5) and a second mixer (9), the first mixer (5) being configured to combine the first starting material feed (S1) and the second starting material feed (S2), and the second mixer (9) being located downstream of the first mixer (5) and configured to combine the combined first and second starting feeds (S1+S2) coming from the first mixer (5) with a third starting material feed (S3) to form a first component feed (C1).
[Item 7]
the feed line (3) comprises at least one heating device (7), preferably at least one heat exchanger, configured to heat the first and second starting material feeds (S1, S2) to a predetermined temperature higher than the temperature of the third starting material feed (S3), the at least one heating device (7) being preferably configured to heat the first and second starting materials such that the first component feed (C1) reaches a predetermined set point temperature before entering the first reaction vessel (13) as a function of the first, second and third starting material feed rates and the temperature of the third starting material feed; and/or
- located between the first and second mixers (5, 9),
Item 6. The device (1) according to item 6.
[Item 8]
8. The apparatus (1) according to any one of items 1 to 7, wherein at least one of the first and second reaction vessels (13, 23) is a reaction tube.
[Item 9]
9. The apparatus (1) according to any one of the preceding claims, wherein the second reaction vessel (23) is at least partially formed as an annular vessel.
[Item 10]
10. The apparatus (1) according to paragraph 8 or 9, wherein the first reaction vessel (13) and the second reaction vessel (23) are part of one common reactor (11) having an inner tube (14) and an outer tube (25), the first reaction vessel (13) being delimited by the volume of the inner tube (14) and the second reaction vessel (23) being delimited by the volume of the outer tube (25) minus the volume of the inner tube (14).
[Item 11]
A method for producing pseudoionones and hydroxypseudoionones, preferably in an apparatus (1) according to any one of claims 1 to 10, comprising:
- feeding a first component feed (C1) containing a first aqueous mixture comprising a first concentration of acetone, citral and hydroxide into a first reaction vessel (13) through an inlet (15);
- producing a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time such that pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one are formed and acetone, citral and hydroxide are consumed, the second aqueous mixture comprising 4-hydroxy-4-methylpentan-2-one in a concentration higher than its concentration in the first aqueous mixture, acetone, citral and hydroxide, and pseudoionone and hydroxypseudoionone in a second concentration lower than the first concentration;
- adding a second component feed (C2) containing a second amount of hydroxide to the first component feed (C1) downstream of the inlet (15), in particular when a second aqueous mixture has been formed;
- producing a third aqueous mixture by feeding the first and second component feeds (C1+C2) to a second reaction vessel (23) and reacting the second aqueous mixture and the second component feed (C2) in the second reaction vessel (23) for a reaction time such that an additional amount of pseudoionone is formed in the third aqueous mixture in the second reaction vessel (23).
[Item 12]
- accelerating the flow rate of the second aqueous mixture prior to adding the second component feed ; and/or
- combining a first starting material feed (S1) with a second starting material feed (S2) and then combining the combined first and second starting feeds with a third starting material feed (S3) to form a first component feed (C1), thereby producing a first component feed (C1); and/or
- heating the first and second starting material feeds (S1, S2) to a predetermined temperature higher than the temperature of the third starting material feed (S3) prior to entering the first reaction vessel (13), preferably by heating the first and second starting materials as a function of the first, second and third starting material feed rates and the temperature of the third starting material feed , such that the first component feed (C1) reaches a predetermined set point temperature.
[Item 13]
- controlling the feed rate of the first component feed (C1) so that the first component feed (C1) has a predetermined residence time in the first reaction vessel (13) before reaching the second reaction vessel (23), preferably in the range of 3 minutes or more, more preferably 5 minutes or more, and/or
- matching the residence time of the first component feed (C1) in the first reactor (13) by providing several mixing elements (29), and/or
- providing a charge in the second reaction vessel (23); and/or
- determining a pressure difference between the first reaction vessel (13) and the second reaction vessel (23), preferably at a location upstream and downstream of the mixing device (17).
[Item 14]
b1) The following:
- the amount of hydroxide that accumulates unnecessarily inside the first reaction tank (13)
- the amount of citral entering the first reaction vessel (13)
- the amount of citral at the outlet or downstream of the first reactor (13),
- the amount of citral at the outlet or downstream of the second reactor (23),
- the amount of water at the outlet or downstream of the second reaction vessel (23),
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the first reactor (13),
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the second reactor (23);
- the reactor feed temperature of at least one of the first or second component feeds (C1, C2);
- the reactor residence time of at least one of the first or second component feeds (C1, C2); or
- determining at least one of the feed rates of a first component feed (C1);
b2) If the quantity or value determined or calculated in b1) falls outside the respective predetermined threshold range:
the feed rate of the second component feed (C2) relative to the first component feed (C1), or
- increasing or decreasing at least one of the feed rates of said starting material feed comprising hydroxide, preferably the third starting material feed (S3), relative to the first component feed (C1) so that the amount determined in b1) is returned inside the threshold range.
[Item 15]
Use of the system according to any one of claims 1 to 10 for producing pseudoionones and hydroxypseudoionones.

Claims (19)

An apparatus (1) for producing pseudoionone and hydroxypseudoionone, comprising:
- a vertically oriented first reactor (13) arranged to flow components through the first reactor in a first flow direction;
- a vertically oriented second reactor (23) in fluid communication with the first reactor (13), the second reactor (23) being oriented such that the components flow through the second reactor (23) in a second flow direction different from the first flow direction;
- a first reaction vessel (13) configured to receive a first component feed (C1) containing a first aqueous mixture through an inlet (15) and to produce a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time;
- the apparatus (1) comprises a mixing device (17) located downstream of the first component feed inlet (15) and configured to add the second component feed (C2) to the first component feed (C1) when the second aqueous mixture is formed,
- a second reaction vessel (23) configured to receive the first and second component feeds combined at the mixing device (17) from the first reaction vessel (13) and to produce a third aqueous mixture from the first and second aqueous mixtures of the apparatus (1). The device (1) of claim 1, wherein the first flow direction is oriented upward and the second flow direction is oriented downward, or vice versa. The apparatus (1) according to claim 1 or 2, wherein the mixing device (17) is located at the outlet end of the first reaction vessel (13). 4. The apparatus (1) according to any one of claims 1 to 3, wherein the inlet (15) to the first reaction vessel (13) for receiving the first component feed (C1) is a first inlet, the first reaction vessel (13) further comprising a second inlet (19) for receiving the second component feed (C2) located upstream from the mixing device (17). 5. Apparatus (1) according to claim 4, wherein the second inlet (19) is located immediately upstream of the mixing device (17) or at a distance upstream of the mixing device (17). 6. The apparatus (1) according to claim 5, wherein the second inlet (19) is located at a distance upstream of the mixing device (17), said distance being selected such that the entire second component feed (C2) is drawn into the mixing device (17) without any preceding backflow inside the first reaction vessel (13). - the first reaction vessel (13) is provided with a tapered section (26) upstream of the inlet of the mixing device (17) and tapering towards it;
and/or
- the first reactor (13) comprises upstream of the mixing device (17) a number of further mixing elements (29) configured to match the residence time of the first component feed (C1) between the inlet (15) to the first reactor and the mixing device (17);
and/or
- the second reaction vessel (23) is adapted to be reversibly opened and closed by means of a corresponding cover and is provided with an opening (39) dimensioned for introducing a filler material into the second reaction vessel (23);
7. Apparatus (1) according to any one of claims 1 to 6 . 8. The apparatus (1) according to any one of claims 1 to 7, wherein the inlet for the first component feed (C1) is in fluid communication with a supply line (3) configured to produce the first component feed (C1) from a plurality of starting materials . 9. Apparatus (1) according to claim 8, wherein the supply line (3) comprises a first mixer (5) and a second mixer (9), the first mixer (5) being configured to combine the first starting material feed (S1) and the second starting material feed (S2), and the second mixer (9) being located downstream of the first mixer (5) and configured to combine the combined first and second starting feeds (S1+S2) coming from the first mixer (5) with a third starting material feed (S3) into a first component feed (C1). 10. Apparatus (1) according to claim 8 or 9, wherein the supply line (3) comprises at least one heating device (7) configured to heat the first and second starting material supplies (S1, S2) to a predetermined temperature higher than the temperature of the third starting material supply (S3). At least one heating device (7)
- configured to heat the first and second starting materials such that the first component feed (C1) reaches a predetermined set point temperature before entering the first reaction vessel (13) as a function of the first, second and third starting material feed rates and the temperature of the third starting material feed; and/or
- located between the first and second mixers (5, 9),
11. Apparatus (1) according to claim 10. 12. The apparatus (1) according to any one of the preceding claims, wherein at least one of the first and second reaction vessels (13, 23) is a reaction tube. 13. Apparatus (1) according to any one of the preceding claims, wherein the second reaction vessel (23) is at least partially formed as an annular vessel. 14. Apparatus (1) according to claim 12 or 13, wherein the first reaction vessel (13) and the second reaction vessel (23) are part of one common reactor (11) having an inner tube (14) and an outer tube (25), the first reaction vessel (13) being delimited by the volume of the inner tube (14) and the second reaction vessel (23) being delimited by the volume of the outer tube ( 25 ) minus the volume of the inner tube ( 14 ). 1. A method for producing pseudoionones and hydroxypseudoionones, comprising the steps of:
- feeding a first component feed (C1) containing a first aqueous mixture comprising a first concentration of acetone, citral and hydroxide into a first reaction vessel (13) through an inlet (15);
- producing a second aqueous mixture by reacting the components of the first aqueous mixture for a reaction time such that pseudoionone, hydroxypseudoionone and 4-hydroxy-4-methylpentan-2-one are formed and acetone, citral and hydroxide are consumed, the second aqueous mixture comprising 4-hydroxy-4-methylpentan-2-one in a concentration higher than its concentration in the first aqueous mixture, acetone, citral and hydroxide in a second concentration lower than the first concentration, and pseudoionone and hydroxypseudoionone;
- adding a second component feed (C2) containing a second amount of hydroxide to the first component feed (C1) downstream of the inlet (15), in particular when a second aqueous mixture has been formed;
- producing a third aqueous mixture by supplying the first and second component feeds (C1+C2) to a second reaction vessel (23) and reacting the second aqueous mixture and the second component feed (C2) in the second reaction vessel (23) for a reaction time such that an additional amount of pseudoionone is formed in the third aqueous mixture in the second reaction vessel (23). - accelerating the flow rate of the second aqueous mixture prior to adding the second component feed ; and/or
- combining a first starting material feed (S1) with a second starting material feed (S2) and then combining the combined first and second starting feeds with a third starting material feed (S3) to form a first component feed (C1), thereby producing a first component feed (C1); and/or
- heating the first and second starting material feeds (S1, S2) to a predetermined temperature higher than the temperature of the third starting material feed (S3) such that the first component feed ( C1) reaches a predetermined set point temperature before entering the first reaction vessel ( 13) . - controlling the feed rate of the first component feed (C1) so that the first component feed (C1) has a predefined residence time in the first reactor (13) before reaching the second reactor (23); and/or
- matching the residence time of the first component feed (C1) in the first reactor (13) by providing several mixing elements (29), and/or
- providing a charge in the second reaction vessel (23); and/or
The method according to claim 15 or 16 , further comprising one, some or all of the steps of: - determining a pressure difference between the first reaction vessel (13) and the second reaction vessel (23). b1) The following:
- the amount of hydroxide that accumulates unnecessarily inside the first reaction tank (13)
- the amount of citral entering the first reaction vessel (13)
- the amount of citral at the outlet or downstream of the first reactor (13),
- the amount of citral at the outlet or downstream of the second reactor (23),
- the amount of water at the outlet or downstream of the second reaction vessel (23),
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the first reactor (13),
- the amount of at least one of pseudoionone or hydroxypseudoionone at the outlet or downstream of the second reactor (23);
- the reactor feed temperature of at least one of the first or second component feeds (C1, C2);
- the reactor residence time of at least one of the first or second component feeds (C1, C2); or
- determining at least one of the feed rates of a first component feed (C1);
b2) If the quantity or value determined or calculated in b1) falls outside the respective predetermined threshold range:
the feed rate of the second component feed (C2) relative to the first component feed (C1), or
- Increasing or decreasing at least one of the feed rates of said starting material feed containing hydroxide relative to the first component feed (C1) so that the amount determined in b1 ) is returned inside the threshold range. 15. Use of the device (1) according to any one of claims 1 to 14 for producing pseudoionones and hydroxypseudoionones.