KR820000092B1 - Nydrocarboxylation of vinyl acetate - Google Patents

Abstract

Vinyl esters such as vinyl acetate are hydrocarboxylated to give α-acyloxypropionic acids by reaction with carbon monoxide and water in a liq. reaction medium using a tertiary organophosphine-stabilized Pd catalyst, and by adding the water required for the hydrocarboxylation during the course of the reaction such that the amt. of water present in the reaction medium is always less than the stoichiometric amt. The ready hydrolysis of the α-acyloxypropionic acids affords a convenient route to lactic acid.

Description

Hydrocarboxylation of Vinyl Acetate

The present invention relates to a method for producing l-acetoxypropionic acid by hydroxy carboxylation of vinyl acetate to finally produce lactic acid.

Various Group 8 metal catalysts, in particular iridium and rhodium catalysts which are converted to iodides, palladium catalysts such as the palladium halide phosphine composites described in U.S. Patent No. 3,437,676 and phosphine stabilized platinum described in U.S. Patent No. 3,887,595 Or in the presence of a palladium complex, a process for producing carboxylic acids by reacting olefins with carbon monoxide and water is known. Generally, however, these methods relate to methods of hydrocarboxylating unsaturated compounds or olefin hydrocarbons containing inert or unobstructed components and also include methods unsuitable for hydrocarboxylating active olefins such as vinyl acetate.

The present invention relates to a method for producing α-acetopropionic acid by hydrocarboxylation of vinyl acetate. Other vinyl alkanoates may also be hydroacylated and commercially used α-acyloxypropionates according to the method of the present invention (e.g., vinyl propionate, vinyl butyrate, vinyl hexnoate, etc.). Can be made.)

The present invention also relates to a complete reaction process for hydrolyzing α-acyloxypropionic acid to produce lactic acid and converting vinyl acetate to lactic acid. Under certain conditions, lactic acid is produced in one step by simultaneously carrying out hydrocarboxylation and hydrolysis without separating the catalyst in the whole reaction medium.

The catalyst used in the hydrocarboxylation reaction in the present invention is used in the presence of excess phosphine as a tertiary organophosphine-stabilized palladium complex. Generally, stabilized tertiary organic phosphine ligands are used, which are sufficiently stable catalysts that can be active in the range of 100 to 150 ° C., ie, in the mild temperature range of about 150 ° C. As the tertiary organic phosphine, the compound of formula (I) is used.

R ₃ P (I)

In the above structural formula, R is an organic group and usually has 20 or less carbon atoms. R is sometimes a hydrocarbon group having no other unsaturated than aromatic unsaturation. In practice these phosphine stabilized palladium catalysts containing substituents such as sulfur, oxygen, nitrogen and halogens are known in the art. It is generally preferred to use tri-aryl phosphines as ligands, since phosphines form more stable and reactive catalytic groups, but one or more alkyl or aralkyl groups can also be used in combination with phosphorus. The R groups bound to phosphorus may be the same or different, but the same is usually easier. Phosphines having three aromatic groups such as triphenyl or substituted triphenyl phosphines are preferred ligands if the substituents do not interfere with the action of the catalyst.

Other aryl groups, including alkyl substituted phenyls, include triarylphosphines, such as the LORYL group patents p- and m-toryl (provided that 0-toryl palladium is prone to degradation). Tris- (P-fluorophenyl) phosphine is suitable as ligand, but catalysis is weaker than triphenyl phosphine. Alkyldiarylphosphines (eg methyldiphenylphosphine) are also used with dialkylaryl phosphines. Triarylphosphines are preferred as ligands in the present invention. The catalyst stabilized with phosphine is represented by the following structural formula (II).

Pd (R ₃ P) n (II)

In the above structural formula, R is as described above, n is an integer of 1 to 4.

Pd(아세틸 아세토네이트[(알킬)PdCl]₂, PdCl₂(트리페닐포스핀)₂및 Pd(트리페닐포스핀)₄들이다. 복합체는 하나 이상의 파라듐 원자를 포함하는 복합체의 아량체 또는 다른 형태를 포함한다. 포스핀은 본 발명에서 사용되는 촉매를 안정화시킬 목적으로 사용되나 반드시 촉매의 배위자로 족재하여 하는 것은 아니다. 따라서 과잉의 포스핀 존재하에서는 포스핀과 함께 존재하는 다른 배위자로 인하여 충분히 안정화될 수 있다.Normally, palladium in the complex is present at zero valence and sometimes L is present as a ligand, such as triphenyl phosphine, PdL ₄ , but palladium changes to various forms during the reaction, especially in the palladium (II) state. do. Furthermore, when paradium is added to the reaction medium in salt form and converted into PdL ₄ , the intermediate acts as a catalyst or affects the action of the catalyst. The first form of catalyst used in the palladium introduction, for example

Pd (acetyl acetonate [(alkyl) PdCl] ₂ , PdCl ₂ (triphenylphosphine) ₂ and Pd (triphenylphosphine) _{4 The} complex is a dimer or other form of a complex comprising one or more palladium atoms Phosphine is used for the purpose of stabilizing the catalyst used in the present invention but is not necessarily co-catalyzed as a ligand of the catalyst, so that in the presence of excess phosphine it is sufficiently stabilized due to other ligands present with the phosphine. Can be.

The palladium form used in the present invention is completely converted to PdL ₄ via hydrocarboxylation, but this conversion reaction is not constant since some palladium compounds which are relatively difficult to reduce to PdL ₄ are also effective as catalysts. The ligand L is generally R ₃ P. In some cases, however, all L or parts of L are CO days, which can be represented by the following structural formula (III):

Pd (R ₃ P) _X (CO) _4-X (III)

Due to the excess of phosphine present in the reaction process, the palladium catalyst is stabilized with phosphine regardless of the particular form. The amount of phosphine in the reaction medium is therefore (from about 10 to 150 moles per palladium / atom and a value of about 15 to 30 moles per palladium atom is preferred. It is generally the same as phosphine, but it is preferable to use a mixture of phosphines, in order to expect the desired stabilizing effect and action there should be a sufficient amount of phosphine and the amount should usually be at least 10 moles per palladium atom.

Excess phosphine, however, promotes side reactions, lowering the reaction selectivity of the desired α-acetoxy propionic acid. The amount of phosphine for the desired effect is about 20 moles per palladium atom.

The catalyst is degraded when used or recycled, but stabilizing the catalyst in the present invention does not mean protecting the catalyst from degradation.

The stabilized catalyst used in the present invention has sufficient stability to be effective for the hydrocarboxylation reaction under the reaction conditions, but this does not necessarily mean that the life of the catalyst has been extended or the life of the particular catalyst has changed significantly.

In the reaction of hydrocarboxylating unsaturated olefin hydrocarbons with various noble metal catalysts, arsine, styrene, and potite have similar effects to phosphine ligands and thus can be used as catalyst ligands. However, such other ligands are not effective in the hydrocarboxyl reaction process of the present invention.

Hydrocarboxylation reaction conditions and procedures are known in the art and specific conditions of the reaction process according to the process of the present invention may be applied. This reaction is carried out under relatively mild conditions with very good catalytic action.

This is particularly important because the reactant of the present reaction is vinyl acetate, which may inhibit reactions other than the desired hydrocarboxylation and such undesirable reactions are generally promoted at high temperatures.

Thus, in the presence of water, vinyl acetate is hydrolyzed to vinyl alcohol and acetic acid and vinyl alcohol is again acetaldehyde. The reaction at low temperature precisely leads to the carbonylation of the α-carbon of vinyl acetate. Sometimes decomposition or other by-products cause the β-carbon to react.

High pressure is not necessary in this reaction and the range of 8.1 to 71.3 kg / cm 2 is easy. Higher forcing is used at 1000 or more atmospheres, and suitable reaction conditions include water pressures up to 1000 degrees or more at relatively weak pressures.

This method is characterized in that the reaction can be carried out at a temperature of relatively mild, 100 ° C to 150 ° C or 170 ° C. As the temperature range increases, undesirable side reactions tend to increase, but even at high temperatures of 200 ° C. or higher, good results can be obtained.

Water is a reactant in this reaction and must be present. However, since vinyl acetate contains not a simple olefin but a group which is susceptible to hydrolysis, it is necessary to suppress the reaction with undesirable water. In order to select the preferred α-acetoxy propionic acid well, good conditions that can lead to the desired hydrocarboxylation reaction should be devised even if undesirable hydrolysis and dislocation reactions occur.

High concentrations of water should be avoided for the desired hydrocarboxylation reaction in this reaction. Of course there must be enough water (1 mole per mole of vinyl acetate carboxylate) to perform the reaction at some stage. However, if the reaction proceeds continuously or incrementally to provide the required amount, much less than the chemical equivalent will be present during the reaction. In normal reaction termination, the concentration of water is kept low, about 3% by weight or less of the reaction medium, and only the amount necessary to replace the reacted water is added. For example, in a batch reaction, vinyl acetate is initially present with solvent and slightly less than 1% water. Carbon monoxide at a temperature of about 100 to 150 ° C. is carried out under pressure, and water is added over several hours to replenish the water consumed in the reaction. CO uptake for pressure measurement combines the reaction to determine the required amount of water. This is determined according to the stoichiometric amount because the required mole per 1 mole of carbon monoxide depending on the reaction dimer. At the beginning of the in-batch reaction, vinyl acetate is present in excess in water and the amount of water usually approaches stoichiometric amounts as the conversion of vinyl acetate is close to 100%. Regardless of this ratio, however, the presence of low concentrations of water tends to limit the amount of hydrolysis or associated side reactions. In a continuous reaction, such as a flowing stream, water can be added at various stages, or other reaction processes may be applied to avoid high concentrations of water. Unless excess water is supplied to the hydrocarboxylation reaction, the ratio of water to vinyl acetate is in some cases varied from the rate applied to the usual batch reaction. Therefore, in the present invention, water is supplied to the reaction at the rate used for the hydrocarboxylation reaction. The amount of water involved in the side reactions is an approximation and there should be limitations in fine tuning the reaction.

The catalyst used in the present invention works without the aid of a halide propellant. Therefore, the iridium and rhodium catalysts propelled with excess iodide are effective olefin hydrocarboxylation catalysts, but are unsuitable for hydrocarboxylation of the present vinyl acetate because they produce many ethylidene esters and acetic acid. The palladium catalyst used in this reaction contains, in some cases, halide ligands or ions (halides are never required). Halides used with iridium and rhodium catalysts activated with halogen in the form of HI, CH ₃ I, etc. Does not need to be used in excess, especially halides do not need to be used in excess.

Example 1

In a 300 ml autoclave 0.110 g of [(C ₃ H ₅ ) PdCl] ₂ (0.6 mmol Pd), 3.15 g Ph ₃ P (12 mmol), 83 ml acetic acid (solvent) and 37 ml vinyl acetate (0.4 Mole). The autoclave was flooded with nitrogen, 3.1 kg / cm 2 pressure with carbon monoxide, and heated to 150 ° C. After reaching 150 ° C., 1 mm of water from the Jugenson Gauge was introduced into the reaction solution by a pump, and the pressure was maintained at 50.2 kg / cm 2 with carbon monoxide.

The reaction begins to absorb gas at the same time as the pressure drop in the autoclave pressure. Fill the carbon monoxide with a high pressure tank to keep the autoclave pressure at 50.2 kg / cm 2. In addition, for every 10.2 kg / cm 2 dropping in the high pressure tank, 1 milliliter of water is added from the Jugenson Guage to maintain the water concentration in the reaction solution.

With a total of 5 milliliters of water added, the reaction consumes 48.5 kg / cm 2 of carbon monoxide from the high pressure tank.

At this point the reaction is terminated. The production of α-acetoxypropionic acid can be known by gas chromatography and nuclear magnetic resonance of the concentrated reaction solution. Fractional distillation separates pure α-acetoxypropionic acid. Mass fractionation of the other fractions shows that ethylidene diacetate (mostly), propionic acid (small amount) and acrylic acid (small amount) are by-products.

Example 2

Hydrovinylation of vinyl acetate by the method of Example 1 under various palladium complexes and conditions shown in Table 1 below yields α-acetoxypropionic acid (α-APA) in the following degree of separation.

TABLE 1

Hydrocarboxylation of vinyl acetate with various palladium complexes

[Pd] = 0.005 mol / l, [Ph ₃ P] ₀ = 0.01 mol, body vinyl acetate = 37 ml (0.392 mol), solvent = butyric acid (83 ml), temperature = 150 ° C., total pressure = 50.2 kg / cm ² , Reaction time = 3 hours, the water is maintained at about 0.9% by pump.

Remove 4 ml of reaction solution at the beginning of the reaction. Conversion and separation takes place based on 0.379 moles of vinyl acetate.

ㆍ 30 minutes introduction.

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid by a scaled internal standard GC (gas chromatography) method.

ㆍ Pd (Acetate) ₂

ㆍ Pd (acetylacetonate) ₂

Example 3

Hydrocarbide the vinyl acetate using the various ligands listed in Table 2 below.

TABLE 2

Hydrocarboxylation of Vinyl Acetate: Influence of Ligands

Pd precursor = [(allyl) PdCl] ₂ , [Pd] ₀ = 0.05 mol / l, [ligand] = 0.1 mol / l, body temperature vinyl acetate = 37 ml (0.392 mol), solvent = butyric acid (83 ml), temperature = 150 ℃, total pressure = 50.2kg / cm ² , reaction time = 3 hours, the water is maintained at about 0.9% with a pump.

Remove 4 ml of reaction solution at the beginning of the reaction. Conversion and separation takes place based on 0.379 moles of vinyl acetate.

All reactions occur during the initial 10 minutes.

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid with a scaled internal standard GC (Gas Chromatography) method.

Example 4

Hydrovinylation of vinylacetate is carried out using various temperatures, pressures and acid solvents as described in Table 3 below.

TABLE 3

Hydrocarboxylation of Vinyl Acetate: Effect of Temperature, Pressure and Solvent

Pd precursor = [(allyl) PdCl] ₂ , [Pd] ₀ = 0.05 mol / l, [Ph ₃ P] ₀ = 0.1 mol / l, body temperature vinyl acetate = 37 ml (0.392 mol), volume of solvent = 83 ml, reaction At time = 3 hours, the water is maintained at about 0.9% with a pump.

Remove 4 ml of reaction solution at the beginning of the reaction. Conversion and separation takes place based on 0.379 moles of vinyl acetate.

ㆍ After 5 hours, the amount of water increases 7 times. Triple speed

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid with a scaled internal standard GC (Gas Chromatography) method.

ㆍ 5 hours continuous

ㆍ 3.4 hours continuous

ㆍ Not analyzed using the grading method

It is fast at first, but decreases a lot after the first 10 minutes. Gas absorption is very large. For 23.7 hours, the reaction solution is black. Reaction solution (gas chromatography) on SP-2401 shows boiling lactylactate at high temperatures.

Example 5

Carboxylation of vinyl acetate with different ligand concentrations, ie triphenylpostin (Ph ₃ P), gives the results in Table 4 below.

TABLE 4

Hydrocarboxylation of Vinyl Acetate, Influence of Ph ₃ P Concentration

Pd precursor = [(allyl) PdCl] ₂ , [Pd] ₀ = 0.005 mol / l, body vinyl acetate = 37 ml (0.39 2 mol), solvent = butyric acid (83 ml), temperature = 150 ° C., total pressure = 50.2 kg / cm ² , reaction time = 3 hours, the water is maintained at about 0.9% by pump.

Remove 4 ml of reaction solution at the beginning of the reaction. Conversion and separation takes place based on 0.379 moles of vinyl acetate.

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid by a scaled internal standard GC (gas chromatography) method.

TABLE 5

Hydrocarboxylation of Vinyl Acetate: Effect of H ₂ O Content

Pd = precursor [(allyl) PdCl] ₂ , [Pd] ₀ = 0.005 mol / l, [Ph ₃ P] = 0.1 mol, body temperature vinyl acetate = 37 ml (0.392 mol), solvent = butyric acid (83 ml), temperature = 150 ℃, total pressure = 50.2kg / cm ² , reaction time = 3 hours, the water is maintained in the desired amount by a pump.

Remove 4 ml of reaction solution at the beginning of the reaction. Conversion and separation takes place based on 0.379 moles of vinyl acetate.

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid by a scaled internal standard GC (gas chromatography) method.

• Most of the reaction solution is water because it does not contain water during analysis.

Example 7

Hydrovinylation of vinyl acetate to determine the degree of conversion and separation at specific time intervals is shown in Table 6 below.

TABLE 6

Hydrocarboxylation of Vinyl Acetate: Conversion and Separation versus Time

Catalyst used: [(allyl) PdCl] ₂ , [Pd] ₀ = 0.005 mol / l, [Ph ₃ P] = 0.1 mol / l, body vinyl acetate = 37 ml (0.392 mol), solvent = butyric acid (83 ml), Temperature = 150 ° C., total pressure = 50.2 kg / cm ² , maintain water at about 0.9% with a pump.

Transformation and separation occur based on the vinyl acetate concentration of 0 hours.

Analyze acetaldehyde, acetic acid, vinyl acetate, propionic acid, butyric acid and α-acetoxypropionic acid by a scaled internal standard GC (gas chromatography) method.

Similar results are obtained by replacing with vinyl propionate or other vinyl alkanoates in the above examples.

The hydrocarboxylation process of the invention is carried out in an inert solvent according to the process of the invention or according to the general conditions used for homogeneous hydrocarboxylation reactions. In general, liquid carboxylic acids (eg lower alkanoic acid) are useful as solvents of the invention, in particular liquid carboxylic acids having 2 to 6 carbon atoms. Sometimes it is easy to use vinylalkanoate equivalent acids (eg acetic acid when using vinyl acetate), but it is preferable to use other acids for increased selectivity or for other reasons. The product (e.g., α-acetoxypropionic acid) dissolves tertiary organic spins, which is undesirable but can be used as a solvent.

A preferred route from vinylacetate to lactic acid is the transfer of Harold Bernan Linker, filed May 27, 1975, and is described in US Patent Application No. 4,072,709, issued February 7, 1978. However, this patent relates to a process for producing lactic acid by hydroformylation to produce α-acyloxypropion aldehyde, which is then oxidized and hydrolyzed.

This reaction process includes hydrocarboxylation and hydrolysis reactions. The hydrolysis methods described and exemplified in U.S. Patent No. 4,972,709 are suitable for the present invention and used by reference in the present invention.

In the present invention, lactic acid is prepared by hydrolyzing α-acyloxypropionic acid with a mixture of lactic acid and carboxylic acid (if the starting material is vinyl acetate, this carboxylic acid acetic acid). This ester hydrolysis step is carried out in the presence of an acid or base catalyst. However, hydrolysis proceeds well without a catalyst. The use of inorganic acids, sulfonic acids and their resins or various acid ion exchange resins, sodium hydroxide, potassium hydroxide and the like increases the hydrolysis reaction rate. The ester is heated to hydrolyze in the presence of water. Hydrolysis can be carried out while varying the temperature from 0 ° C to 300 ° C and the preferred temperature is 40 ° C to 220 ° C. When hydrolysis is performed in the separation step, a very large amount of water is generally used, but the ratio of water to acyloxypropionic acid is 1: 1 to 1000: 1 or more. Although less than the chemical equivalent of water can hydrolyze acyloxypropionic acid, usually sufficient water is used for hydrolysis.

As noted herein, the amount of water defined to reduce side reactions is generally used to hydrocarboxylate vinylacetate. Therefore, there is not enough water left to hydrolyze simultaneously with the hydrocarboxylation reaction. In this case, hydrolysis of the acyloxypropionic acid does not occur until the vinylalkanoate is completely converted. It is usually preferred to distill the acyloxypropionic acid product by distillation from the reaction medium and catalyst before diluting with water for hydrolysis for the purpose of regenerating and recycling the hydrocarboxylation catalyst. In some cases, however, it is also possible to synthesize lactic acid in one step by simultaneously performing hydrocarboxylation of vinylalkanoate and hydrolysis of the resulting acyloxypropionic acid.

This method requires the addition of additional water at the rate at which no large side reactions occur.

Sometimes substances having high boiling points are produced when hydrocarboxylating vinylacetate and lactyllactate containing acid anhydrides of α-acetoxypropionic acid. Since these materials are hydrolyzed to α-acetoxypropionic acid or lactic acid, it is also suitable to hydrolyze together high boiling materials upon hydrolysis of α-acetoxypropionic acid after or in isolation from the original reaction medium.

The present invention describes a particular method of hydrocarboxylating vinylalkanoate with α-acyloxypropionic acid and hydrolyzing back to lactic acid.

However, hydrocarboxylation by other means yields good results and is also considered a suitable method of converting vinylalkanoate to lactic acid.

Example 8

Lactic acid is synthesized by hydrolyzing α-acetoxypropionic acid (66 g, 550 mmol) at a temperature of 150 ° C. and steam (150 ml) in a 300 ml autoclave. Acetic acid and most of the water are distilled off.

Example 9

α-Ethoxypropionic acid (33 g, 250 mmol) is dissolved in water (150 mL). Fill the solution into the autoclave and heat to 200 ° C. By distilling acetic acid and water off, lactic acid is obtained.

Example 10

0.692 g of Pd (Ph ₂ P) ₄ (0.6 mmol Pd): 3.15 g of Ph ₃ P (12 mmol): 83 ml of butyric acid (solvent) and 37 ml of vinyl acetate (0.4 mol) were placed in a 300 ml autoclave. Fill it.

Pour the autoclave and proceed in a similar manner to Example 1. A total of 9 ml of 1 ml of water is added and the reaction is continued overnight.

After reacting at 150 ° C. and 50.2 kg / cm 2 for 23 hours, the reaction was terminated and analyzed by gas chromatography. The resulting mixture contains both α-acetoxypropionic acid and lactic acid and the amount of lactic acid is 67 to 100% of α-acetoxypropionic acid.

Presence of lactic acid in mixtures can be determined by nuclear magnetic resonance and mass spectrometry. Therefore, lactic acid is produced in one step from vinyl acetate in this experiment.

In the present invention, when vinyl alkanoate (such as vinyl acetate) is hydrocarboxylated under a paradium catalyst stabilized with a tertiary organic phosphine, the selectivity and conversion of α-acyloxypropionic acid are increased (for example, based on vinyl acetate). 60 or 70% or more).

Furthermore, the high boiling point materials generally produced can be hydrolyzed to increase selectivity. This method is a promising method for producing lactic acid with an efficient and easy hydrolysis step.

Claims (1)

The reaction of vinyl alkanoate with carbon monoxide was carried out using a paradium catalyst stabilized with a tertiary organic phosphine in a liquid reaction medium, while adding less water than the stoichiometric amount based on vinyl alkanoate. A method of hydrocarboxylating vinylalkanoate, characterized in that.