SE468559B - Process for preparing monoesters of branched 1,3-glycols - Google Patents

Abstract

The present invention relates to a process for preparing monoesters of branched 1,3-diols of the general formula I <IMAGE> and/or the general formula <IMAGE> where R1 and R2 are identical or different and are lower alkyl having 1-4 carbon atoms, preferably methyl, in which a stream of aldehyde and a stream of an aqueous solution of an alkaline catalyst are subjected to such intensive processing that two phases are brought into such intimate contact with each other that a condensation reaction sets in and takes place spontaneously.

Description

J 468 559 As a by-product, a certain amount of the corresponding diol is formed, which can be obtained either by the hydrotysis of the ester R1 H R1 R1 R1 H R1 5 | | | I Naou I I I H - c - c - c - cuz -o - c - c - H - 9 »H - c - c - c - cH, oH I I I II I I I I I R2 on R2 or R2 R2 on R2 + R1 -cn -cooNa IN R? OR POSSIBLY BY ATHOLIATION OF THE STARTING ALDEHYDE WITH THE 15th reduction according to Canizarro: R1 R1 - CH - CH - C - COH + R1 - CH - COH -P 20 I I I I R2 oH R2 R2 H R1 25 I I R1 - cH - c -c -cH2oH + R1 - cH - coon I I I I R2 oH R2 R2 Although the diol is a technically useful substance, its proximity be in the reaction product undesirable due to SERIOUS SEPARATE ration difficulties from the monoesters. The boiling points of monoest- and glycol can be very close to each other. This is the case when the starting material is isobutyryldehyde. 10 15 25 30 468 559 Background of the invention Autocondensation of aldehydes containing a hydrogen atom in alpha position is of great technical interest. The industrial largest the raw material for this process is isobutyraldehyde, which is formed in significant amounts in the hydroformylation of propylene - the so-called the OX0 processes. Formula I shows that in the case of autocondensing the reaction is formed by two main types of reaction products; mo- noesters (two isomers) and a 1,3-diol. These two types of purifications have a number of technical uses but in the current situation are the monoester which arouses the greatest industrial interest.

The reason for this is firstly that the monoester itself has a number of industrial applications (Ref. 1) and secondly that if necessary the monoester can be easily converted into free glycol respectively diester, while the synthesis of monoester starting from glycol respective diester is very difficult due to small selection and separation difficulties. A number of patents describe ver auto condensation processes. Their common feature is that as catalyst use basic substances, usually sodium hydroxide, and that the optimum temperature of the reaction is in a range between 60-9UoC. What distinguishes these described procedures is above all the process itself - continuous respect tive discontinuous - and the design of the reactor. These two technical parameters are crucial for the selectivity of the reaction, change and reaction time.

From a process point of view, all processes can be divided into three groups: Group 1 comprises procedures according to which the synthesis process only may proceed periodically.

Group 2 comprises procedures which describe in principle batchwise procedures, which may, however, be transformed under certain conditions to continuous procedure.

Group 3 includes procedures which claim to be conti- modern production processes.

hrs 468 559 10 15 20 25 30 35 The first group includes the procedure described in DE-A1 3,024,496. The method is based on a parallel dosing of isobut tanol and an aqueous solution of NaOH in a periodic operation reaction vessel equipped with a stirrer. The reaction time is countries Long, at least 3 hrs. The main requirement states that the process only is batchwise. The same applies to the process according to DE-A1-3,403,696, where synthesis of a crude reaction mixture proceeds on one method as in the above-mentioned DE-A1-3,024,496, aqueous phase, the organic reaction product is hydrogenated in Ni catalyst at 120 ° C and 100 bar (1 x 104) identical but after separation of presence of kPa) pressure. Reactive The product consists of a mixture of three main products: isobutanol. trimethylpentanediol and its monoisobutyric residues (2 isomers). Two discontinuous reactions and the necessary Reversal of expensive high-pressure equipment makes the process hardly is competitive with other methods used low pressure, no hydrogen and no hydrogenation S8t0P.

A typical batch process is described in DE-A1-2,820,518, there the process proceeds in the presence of solid calcium hydroxide and Lower organic acids. At the end of the process, the hydroxide is transferred through effect of CO2 in difficult-to-handle fine-grained calcium carbonate. Difficult rights tied to a 3-phase process, the use of cumbersome separations of precipitates and elimination of organic acids hardly equalizes a certain exchange increase.

The second process group includes the process according to DE-A1- 2,019,192, according to which metal salts were used as catalyst of various phenols. The inventor confines himself to one statement that the process can also be carried out continuously without giving some details. In addition, the 23 examples given describe only one batch procedure. A flow-through system where catalysts in form of a sludge is transported through different types of devices and wiring causes great difficulties. It should be noted that a continuous system would consist of five units: reactor for the production of catalyst, dewatering plant, heating exchanger, reactor and sludge separator. In addition, one has to 10 15 20 25 30 35 5,468,559 use hazardous and highly corrosive phenols.

The third process group includes continuous processes: US A-3,718,689, US-A-3,291,821, US-A-3,091,632 and DE-A1-3,447,029.

The most important and at the same time most difficult problem in a continuous honest procedure is to provide such a large contact area as possible between the alkaline aqueous phase and the organ phase and with limiting the reaction time and the degree of hydrolysis. The above the said four patents describe four different solutions to this task, but all Solutions are subject to a number of serious Liga disadvantages. At first glance, it seems like it The simplest solution is a flow-through tank reactor consisting of one vessel equipped with an efficient stirrer, heat resp. cooling jacket and return cooler. Dosing tubes pump continuously. aldehyde and an aqueous solution of catalyst (e.g. NaOH) while the reaction mixture leaves the reactor continuously through a drain pipe. The mixture flows to a separator there the phases are separated. Such a process is described in US-A-3,718,689. Ex. 2. The residence time of the reaction mixture is quite long, 1 hr. This means that in the case of large-scale production, a very large reactor - perhaps several reactors - and its except one must expect a large consumption of electrical energy to keep the contents of the reactors in the form of an emulsion. The it should be noted that the density of isobutanol is below 0,8 kg / l, while 50% aqueous solution of NaOH has a density of about 1.5 kg / l. The most important thing, however, is that the process cannot be applied for the production of monoester because an extensive hydrolysis ring to trimethylpentanediol. This serious disadvantage also referred to in 6, 63-66). experiments have also confirmed the negatives described in US-A-3,718689 patent specification (col. r. Implemented ex- experience. Despite the use of different types of conventions no stirrers and different reaction conditions were obtained results, which could be considered suitable for large-scale duction. To avoid difficulties associated with the use of a back-mixing reactor is used by the inventor of said US-A 3,718,689 of the following solutions: first by 6 468 559 10 15 20 25 30 35 intensive stirring mix isobutanal with small amounts (cza 2 Z) of a 50% NaOH solution a stable emulsion is obtained. This emulsion is pumped through a continuously operating tubular reactor. RE- the action time is about 6 min. The reproducibility of the process is great small. So was e.g. according to Table II in US-A-3,718,689 experiments 4, 5, and 6 are obviously performed under identical conditions but nevertheless completely different yields of monoester were obtained: 61%, 45% and 20%, respectively.

According to US-A-3,291,821 a flow-through reactor equipped is used with a concave guide rail, the task of which is to further increase moving turbulence. A stream of cold reactants is pumped into one heat exchanger where it is heated to a temperature at which the condensation reaction begins. From there, the hot re- the action mixture through a vertical conduit into the above the reaction vessel provided with the concave guide rail. Despite all these improvements, the reaction time is quite long: optimum lig- gives between 15-60 min. The sluggish reaction process is probably due to similar to mixing isobutyraldehyde and alkaline aqueous solution with each other at low temperature. Under such conditions, spontaneously raises the isobutyraldehyde to 2,6-diisopropyl-5,5- dimethyl-4-hydroxy-1,3-dioxane. After heating, this is broken trim compound eventually down to the monomeric form but in in this case, it is the degradation kinetics that determine the whole cessens speed.

According to US-A-3,091,632 a continuous condensing can be carried out isobutanal using metal alcohol as catalysts. The reaction environment must be complete free from water and acid (<10 ppm H2O). 'These two purity requirements means that the process can hardly be competitive with the other procedures where the presence of water and technical table content of acid does not constitute an obstacle.

According to DE-A1-3,447,029, isobutanol is pumped and concentrated NaOH solution cocurrently through a vertical tubular reactor. To increase the contact surface between the phases, the aldehyde is introduced through a porous 'fl 10 15 20 25 30 35 * 468 559 porcelain body and in addition the reactor can be filled with couple. The process described has a number of disadvantages.

Thus, the reaction time is quite long. In the three described examples len, the residence times were 0.83, 0.54 and 0.86 hrs. It was impossible to avoid extensive hydrolysis of the monoester. In the three above- mentioned examples were the molar ratio of diol to monoester equal to 19.8: f5.5; 15.3: 74.8: 14.0: 76.1, respectively.

Description of the present invention The difficulties and disadvantages described above can be significantly reduced or completely eliminated by applying the procedure according to the present invention, which method is characterized by exposing a stream of aldehyde and a stream of an aqueous solution of an alkaline catalyst for such an intensive work that the two phases are brought into such intimate contact with each other that a spontaneous reaction takes place: usually within the course of a few seconds.

Additional characteristics are set forth in the appended claims.

During the intensive processing of the two phases, one is obtained microemulsion, which comprises such a fine distribution of the phases that they are still transparent unlike macroemulsions where opacity is present.

According to a preferred embodiment, the present invention is implemented as a continuous process, preferably uses a centrifugal pump to achieve the intended intensive grazing. J The stirring in e.g. the rotor chamber of a centrifugal pump causes that the two immiscible phases are brought into such intimate contact with the water that at the output of the pump system the reaction has time to run spontaneously with a relatively high yield during a short reaction time.

The process has also been studied with the help of one 468 559 1D 15 20 25 30 35 reactor calorimeter invented and described by Nilsson, H., Silvegren, Ch., And Törnell, B., Angeuandte Makromol Chemie, 113, (1983), p.12S, equipped with a turbine stirrer with speed 800 rpm. One could thereby establish that it is the intensity of the stirring, or the processing of the phases with each other, which, in technically available conditions, determines the reaction rate.

Thus, various stirring and processing methods have been further studied. such as inert gas stirring, rotary stirring cylinder (votator) and different types of agitators placed in round piston. However, none of these stirring methods yielded a sufficiently intensive processing to achieve a con- densification reaction at the same rate as obtained in a reactor calorimeter. Only in the use of efficient agitation, thereby producing a microemulsion and / or phase degrading shear forces, e.g. by means of a centrifugal pump the problem was solved.

Use of different types of homogenizers, static mixers and arrangements for the production of ultrasound also work well for causing a spontaneous reaction.

In such intensive processing, very short reaction times are obtained. der, <2D p. and good yields of monoester. Use of such intensive processing, such as a pump reactor, allows large investments savings, as a standard rotary pump can replace many costly periodic and continuous vascular and tubular reactors. Table 1 below compares different types of procedures. and reactors with regard to reaction time, yield and lectivity of monoester synthesis. In this context, the the parameters by which the process can be controlled and timeras: -catalyst type catalyst concentration catalyst amount reaction temperature residence time -x 10 15 20 25 30 35 q 468 559 Of various types of basic catalysts, sodium hydroxide is the most useful. It is strongly alkaline, well water-soluble and re- relatively cheap. Other Suitable hydroxides which, however, are also preferred are potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide and magnesium hydroxide. As pointed out in our conti- patent application "Process for the production of branched 1,3- glycols and their monoesters (I) "obtain an excellent catalytic system by using an alkaline substance and a solid transfer catalyst.

The concentration of the catalyst in an aqueous solution may vary within a fairly large range from 52 to a saturated solution. Valet of catalyst concentration depends on the requirement of the product purity. Of Table 2, exp. 49. it appears, for example, that a 152-ig NaOH solution gives a 16.22 yield of monoester, but at the same time The diol content is only 0.22. Such a reaction product is suitable excellent for the production of pure monoester. If you use in a 302 .mu.g NaOH solution (Exp. 117) gives a yield of noester which is 43.32 but at the same time the content of diol grows to 3.52. 468 559 10 15 30 TABLE 1. / 0 Comparison of different procedures for the preparation of 2,2,4- trimethyl-1,3-pentanediol monoisobutyric ester Process Type of Reaction-Exchange of Relationship according to process time resp reo monoester monoester: patent tenure weight-Z diol (w / H) DE-A1- 3,703,541 batch 2 hrs 77.8 77.8: 3.9 <19.9: 1) DE-A1f 3,4Û3,696 batchwise 3 hrs 48 48: 6.1 (7.9: 1) DE-A1- 3,447, D29 continuous- 0.54 hrs 37 75:15 honest (S: 1) USA- 3,291,821 continuous- 15 min? 78: 8.3 honest (9.4: 1) USA- 3,718,689 continuous- 6 min SD 50: 3.2 honest (15.6: 1) USA- 3,091,632 continuous- 1 hr 71 71:14 honest (5.1: 1) according to continuous 15.5 49.5 49.5: 3.6 present electricity. (13.8: 1) in batches invention Such a monoester can find use both in its preparation of pure monoester and in the preparation of isobutyr diester. One important parameter is the amount of catalyst be for s tor, , whereby this shall not because the degree of hydrolysis then increases a lot quickly and the reaction product is strongly contaminated 10 15 20 25 30 35 ”468 559 hydrolysis product, i.e. diol. Is the amount of catalyst too small, å on the other hand, the reaction can be stopped completely. Weight ratio the aldehyde: catalyst, expressed as NaOH 100%, may be present between 100: 0.1-15, preferably 100: 0.5-5.

The reaction temperature may be between 30-200 ° C, preferably between 50-15006, with an optimum between 60-8006. The temperature can be controlled either by recirculation of the reaction product or by changing the temperature of the constituent substances or by diluting the aqueous solution of catalyst. Obvious two or all three of these procedures can be used if necessary. the one for temperature control.

The residence time can be changed by changing the dosing rate respectively by changing the type of pump. It is interesting that an increase The residence time only gives a limited increase in the yield.

When the residence time is increased from 15 s. To 60 s. Then the yield of increases monoester from 28.22 (exp. 109) to 4S, 1% (exp 115) but at the same time The diol content increases from 0.62 to 7.12. For example, it is difficult to point to any optimal reaction time if As you can see from these as it depends not only on plant characteristics but also by the planned use of reaction product. Up- holding time assume that can also be affected by heat exchange problems. Man though the residence time in the intensive processing shall not ra shorter than 1 s. but not longer than 2 min.

The reaction mixture leaving the intensive processing consists of two phases: the organase and the aqueous phase. They can be separated either in a gravity separator or by means of a centrifuge. Ask- action of the separated organ phase is due to degradation of trimerized aldehyde with hot water, resp. water vapor and des- tillation. Recovered aldehyde can usually be recycled immediately to the reactor without any preliminary treatment. Separation of diol from monoester is done by vacuum distillation.

Example 1 Experimental setup is shown in FIG. 1. Using a pump 3 468 559 10 15 20 25 30 35 12 isobutyraldehyde is transported from a container 1 through a heater 5 to a centrifugal pump 7, which is driven by a rotating speech of 2,800 rpm and which has a rotor diameter of 40 mm. IN the same centrifugal pump is introduced by means of a pump 4 by preheating a stream of an aqueous solution of sodium hydroxide, or other an alkaline catalyst. In the rotor chamber of the centrifugal pump 7 the aldehyde stream is contacted with the aqueous solution of the during intensive processing. The reaction mixture is trans- ported to a separator 8 where the phases are separated.

To initiate the reaction, the two reactant streams are preheated to about 60 ° C. When the reaction begins, the heating is switched off away and on the outlet side of the centrifugal pump, the temperature depending on the amount and concentration of the catalyst to one level between 70-75 ° C, where the reaction proceeds spontaneously. When the temperature is stable is introduced for half an hour product in a container 10. An average sample is analyzed. Result of a a number of typical experiments are reported in Table 2 below.

Example 2 In the previous example, only the average yield of a synthesis was determined. which lasted for 30 minutes without taking into account any changes during the course of the synthesis. In addition, it is needed proof that the reaction is actually taking place in the rotor chamber, during intensive processing, and not substantially during e.g. storage in the separator. For this purpose, a sampler was mounted into the outlet pipe as close to the centrifugal pump as possible. This device enabled many samples to be taken taken during the course of the synthesis. The reaction in the samples was stopped by bringing them down in a cooling bath and then analyzed.

Some typical results are found in Table 3 below.

W: 10 15 20 25 30 35 'ß 468 559 TABLE 2 Synthesis of 2,2,4-trimethyl-1,3-pentanediotic monoisobutyrate residues according to Ex. 1 Attempt Catalyst Residence Time Yield no conc. amount) sec. mono- diolb) weight-Z Z esterb) Z Z 49 15 2.5 15 16.2 0.2 59 15 2.5 71 22.8 1.2 109 20 "2.5 15 28.2 0.6 115 20 2.5 60 45.1 7.1 117 30 2.5 15 43.3 3.5 118 30 y 0.45 15 17.1 0.3 120 40 1.8 15 49.5 3.6 a) amount of NaOH (1002-μg) expressed as weight-Z of aldehyde used b) weight-Z in crude reaction mixture c) under the described reaction conditions, the aldehyde stream is the same at 37 ml / min TABLE 3 Synthesis peak in stable conditions Try Na0H Medium Magnifier Yield no conc. amount of shelf life monoester diol weight-Z weight-Z sec. weight-Z weight-Z 111 15 2.5 15 16.5 0.1 116 30 2.5 15 56.5 3.0 120 40 2.5 15 57.0 1.8 It is clear from the above reported attempts to Lying procedure gives a very fast reaction and an excellent 468 559 10 15 20 30 35 IH yield, partly with high yields of monoester, but also with low yields of diol.

The present process can be carried out as a batch process. they or as a continuous process. In those cases one batch large-scale process is carried out, the reactant is suitably processed. the mixture in a flow-through line placed to a larger one reaction vessel. Thus mixing of the reactants can take place in one such a line provided with an intensive processing device above.

In the appended FIG. a test set-up is shown, in which 1 and 2 draws storage containers for isobutanal resp. NaOH solution, 3 gives a piston pump, and 4 indicates a hose pump. Respective solution passes a preheating S with to and from the heating medium.

Each reactant line is equipped with a thermometer. the aunts are combined in an impeller pump 7 and the reaction solution temperature is checked with an additional thermometer 6. Reactor The ion mixture is then transferred to a settler 8 equipped with a cooler 9. The crude product is taken out to a collecting vessel 10 for crude product and the aqueous phase is taken out to a collecting vessel 11 for water phase. 3,)

Claims (11)

10 115 20 25 30 35/5 468 559 CLAIMS. Process for the preparation of monoesters of branched 1,3-diols of the general formula I 1 'I 1 IIIH - C - C - C - CH2 - OH IIII' R2 0 R2 IC = 0 I R1 - CH - R2 and / or the general formula II R1 H R1 R1 R1 IIIIH - c - c - c - cH2 -o - c + c - H 11 III 'II I R2 OH R2 0 R2 wherein R1 and R2 are the same or different and are Lower alkyl with 1 -4 carbon atoms, preferably methyl, characterized in that a stream of aldehyde and a stream of an aqueous solution of an alkaline catalyst are subjected to such intensive processing that two phases are brought into such intimate contact with each other that a spontaneous reaction takes place , wherein the reaction mixture is intensively processed to form a microemulsion and / or phase degrading shear forces for a period of 1-120 sec, preferably 2-60 s and at a temperature below 20006, preferably below 150 ° C, more preferably below 120 ° C, wherein the weight ratio of the alkaline catalyst component to aldehyde is 0.1-1S: 100, preferably 0.5-5: 100 .. Method according to Claim 1, characterized in that the intensive processing takes place in the rotor chamber of a centrifugal pump. / 6 468 559 10 15 20 25 30 35 Process according to Claim 1, characterized in that the intensive processing takes place in a homogenizer. Method according to Claim 1, characterized in that the intensive processing takes place by means of ultrasound. Method according to one of Claims 1 to 3, characterized in that the intensive processing takes place in a static mixer. Process according to one of Claims 1 to 5, characterized in that the aldehyde is isobutanal. Process according to one of Claims 1 to 6, characterized in that the alkaline catalyst consists of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide and / or barium hydroxide. Process according to one of Claims 1 to 7, characterized in that the reaction proceeds at a temperature of at least 3000. Process according to Claims 1 to 8, characterized in that the reaction mixture obtained is separated into organ phase and aqueous phase in a gravity separator or a centrifuge. Process according to one or more of Claims 1 to 9, characterized in that the process is carried out as a batch process. Process according to one or more of Claims 1 to 10, characterized in that the process is carried out as a continuous process.