KR20000001825A - Method of manufacturing high purity veltol - Google Patents

Abstract

PURPOSE: A veltol manufacturing process is relatively superior in yield than that of conventional processes and enables high purity above 99%. CONSTITUTION: The manufacturing process of veltol comprises two steps of: oxidation by using oxidizing agent; and hydrolysis and followed by neutralization, extraction, removal of extracting solvent, removal of tar residue, crystallization, filtration, washing, and drying. The yield of high purity veltol(I, ethyl maltol) obtained from alpha-ethylfurfuryl alcohol is 63-66%.

Description

Process for producing high purity veltol

The present invention relates to a method for producing high purity veltol. More specifically, the present invention relates to a high-purity Veltol from alpha-ethylperfuryl alcohol, that is, a method of preparing ethyl maltol represented by the following structural formula.

The synthetic route differs from the present invention in Tetrarahedron Letters No. 17, 1363-1364 (1976) shows that the yield of veltol from alpha-ethylperfuryl alcohol is less than 10%, and US Pat. No. 4,342,697 (1982) describes a similar route through the synthesis. , Mainly examples for maltol, and no synthetic yield for veltol is given.

The synthetic route is the same as the present invention, according to US Pat. No. 4,082,717 (1978) and International Patent No. PCT / IB94 / 00432, although the synthetic yield of veltol is significantly improved, the distillation of solids is included in the purification process to make high purity products. It is not an advantageous process for commercialization.

Beltol is said to be about 6 times higher than maltol in terms of product flavor or efficacy as a food enhancer or aroma enhancer, according to US Pat. No. 3,446,629 (1969).

It is an object of the present invention to provide a process for the production of high purity veltol of 99% or more, which is not only relatively superior in terms of yield compared to existing processes but also advantageous for commercialization.

1 is a block diagram showing a manufacturing process of veltol according to the present invention.

Method for producing high purity veltol according to the present invention comprises the steps of reacting the alpha-ethylperfuryl alcohol and the oxidizing agent in a liquid medium by a gas recycle method to obtain a reaction product veltol intermediate intermediate;

Performing a hydrolysis reaction by heating until no reaction product remains;

neutralizing the reaction with a strong base such that the pH is between 2 and 4;

Extracting veltol from the neutralized reactant using a first solvent;

Dissolving the residue from which the first solvent is removed from the extract in a second solvent of dipropylene glycol or ethylene glycol to remove tar residue;

Filtering the veltol solid obtained by first crystallizing the liquid from which the tar residue was removed to remove the second solvent to obtain a filter cake;

Removing the third solvent by filtration of the solid cake obtained by dissolving the filter cake in a third solvent and then again crystallizing it; And

It is characterized in that the method for producing a high purity veltol by vacuum drying the veltol cake obtained by washing the solid cake and removing impurities.

Hereinafter, the present invention will be described in more detail.

The production method of high purity veltol of the present invention is composed of two steps, which are performed by oxidation and hydrolysis reaction with an oxidizing agent, followed by neutralization, extraction, extraction solvent removal, tar residue removal, crystallization, filtration, washing and drying, etc. It consists of.

In the present invention, the oxidation reaction is first prepared by reacting alpha-ethylperfuryl alcohol and 2 equivalents of an oxidizing agent in a liquid medium to produce a veltol intermediate.

As the oxidizing agent, chlorine, bromine, bromine chloride (Br-Cl), hypochlorous acid (HOCl), hypobromic acid (HOBr) or a mixture thereof may be used. As the liquid medium, water, alkanol having 1 to 4 carbon atoms and a mixture thereof are preferable.

For example, the reaction scheme of the oxidation reaction using chlorine as the oxidant and methanol / water as the liquid medium is as follows.

The reaction temperature of the oxidation reaction is carried out at -50 to 50 ℃, preferably -10 to 10 ℃, the reaction pressure is preferably carried out at atmospheric pressure to 5 atm, preferably at atmospheric pressure to 3 atm. Under temperature and pressure conditions outside of the above range, the yield decrease due to side reactions is severe.

According to the present invention, the reaction may be performed by injecting an oxidant through a tube into a liquid reactant or by recycling a reaction gas, that is, allowing a reaction gas on top of the reaction liquid in the reactor to be recycled into a small bubble in the reaction liquid. It is also preferable to manufacture a special stirrer to improve the contact efficiency of the gas and liquid. This special stirrer is empty inside the shaft. By utilizing Bernoulli's principle, the gas at the top of the reaction liquid flows through the upper hole of the stirrer shaft due to the pressure difference due to the difference in the fluid flow rate near the tip of the stirring blade in the semi-solution during stirring. It flows into the gap between the agitator blades along the inside of the stirring shaft, and is broken into small bubbles by the rotating agitating blades and dispersed into the reaction liquid.

The advantage of this gas recirculation method is that the reaction time is considerably shortened, which not only improves productivity but also suppresses the yield decrease due to side reactions. After the injection of the oxidizing agent may be aged under stirring at room temperature for about 30 minutes to 1 hour.

After completion of the oxidation reaction, the temperature of the reactant is raised to the boiling point for hydrolysis, and the gas evaporated through the reflux condenser is refluxed into the reaction solution and maintained for 2 to 8 hours, preferably 2 to 4 hours. The alkanol is then removed by raising the temperature to 150 ° C, preferably 100 to 110 ° C, to remove the alkanol from the reaction.

The end point of this hydrolysis process is when no veltol synthesis intermediate, the product of the oxidation reaction, remains. The acid, which is a catalyst of the hydrolysis reaction, is used as it is generated by the hydrolysis, but may be further added if necessary. For example, the hydrolysis equation using methanol / water as the liquid medium is as follows:

The neutralization process is to adjust the pH of the reactants to 2 to 4, preferably 3 to 4 using a strong base. Outside this range, the separation of the layers is not easy, and the extraction efficiency is also lowered, which causes a decrease in yield.

On the other hand, the extraction is methyl isobutyl ketone, dichloromethane, dichloroethane, toluene, dioxane, benzene, halobenzene, any O-, M- or P-xylene, any isomeric aliphatic (C ₅ -C ₁₀ ) alkanes , Veltol in the reaction solution using a suitable solvent such as cyclohexane, tetrahydrofuran, any di (C ₁ -C ₆ ) alkyl ether, (C ₂ -C ₄ ) alkyl acetate or (C ₃ -C ₁₀ ) ketone. To extract. Extraction temperature is performed at room temperature to 100 ℃, preferably room temperature to 80 ℃ 1 to 5 times, preferably 2 to 4 times to minimize the product loss during extraction.

The extractant used is distilled off and the residue is dissolved in dipropylene glycol or ethylene glycol which is used as a solvent for the next tar residue removal process.

The tar residue removal process was performed in two ways, the first method being a thin film evaporation method and the other method using a simple distillation method. In the thin film evaporation process, the temperature of the thermal medium is 100 to 180 占 폚, preferably 120 to 150 占 폚, the temperature of the refrigerant body is 30 to 80 占 폚, preferably 40 to 60 占 폚, and the vacuum is 200 torr or less. , Preferably 100 torr or less.

As a process condition of the simple distillation method, the temperature of the thermal medium is 100 to 180 ° C, preferably 110 to 150 ° C, and the vacuum is 200 torr or less, preferably 100 torr or less. Comparing these two methods, the thin film evaporation method is more advantageous because it has less product loss than the simple distillation method.

Crystallization is a process for obtaining high purity products. In the first crystallization step, the veltol solid is formed through crystallization at a suitable time at -20 to 50 ° C, preferably -10 to 10 ° C, from the pale yellow liquid obtained through the tar residue removal process, and the solid formed Filtration to separate from solvent. If it is performed at a temperature above this range, there is a disadvantage in that productivity is lowered due to a problem of increased solubility in a solvent. The filtrate is then reused as a solvent for the tar residue removal process.

In the second crystallization step, the filter cake obtained in the first crystallization step is dissolved in an appropriate amount of water, alkanol having 1 to 4 carbon atoms, or a mixture thereof. In order to completely dissolve the beltol, the liquid temperature is raised to 50 to 100 ° C, and then cooled to perform crystallization under the same process conditions as the first crystallization step.

In order to further remove impurities remaining in the filtered solid cake, the washing liquid may be water, alkanol or a mixture thereof, and the washing liquid may have a temperature of 20 to 50 ° C, preferably -10 to 10 ° C. Less product loss should be done at

The vacuum drying process is carried out to remove the washing liquid from the beltol cake obtained by washing. As process conditions, temperature is 20-80 degreeC, Preferably it is 30-50 degreeC. Below this range, the drying speed is slow and a long time is required, and above this range, the loss due to sublimation is large. The vacuum is 600 to 1 Torr, preferably 200 to 5 Torr.

The structural analysis of the beltol was confirmed by NMR, and the analysis for yield calculation was performed using GC. A schematic block diagram for the synthesis of high purity veltol described above is illustrated in FIG. 1.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following Examples.

Example

Example 1

43.9 g of alpha-ethylperfuryl alcohol (purity 97.0%), 130 g of methanol (purity 95.0%), and 65.0 gr of distilled water were added and stirred in a 1 L high pressure glass reactor, and the reactor temperature was lowered to -10 ° C or lower. 53 g of chlorine gas was injected and the reaction temperature was maintained at -5 to 0 ° C through cooling. At the initial stage of the oxidation reaction, the reaction rate is fast and the atmospheric pressure is maintained, and after about 30 minutes, when the reaction pressure reaches 1.5 bar at the end of the reaction, the chlorine injection is terminated, the reaction pressure is depressurized, and nitrogen is added to the reaction solution to excess. Chlorine was removed.

The reaction was transferred to a 500 ml glass reactor and the temperature was slowly raised to a boiling point of about 80 ° C. over 1 hour and then refluxed at that temperature for 4 hours. At this time, hydrochloric acid gas was generated as a by-product. The temperature of the reaction was lowered to room temperature and 60 g of 40% caustic soda was added to adjust the pH to 3-4. 200 g of methyl isobutyl ketone was added thereto, and the mixture was heated to 80 ° C. under strong stirring, and the layers were separated. 200 g of fresh methyl isobutyl ketone was added to the separated aqueous layer, and the layer separation process was repeated two more times. The methyl isobutyl ketone layer obtained by layer separation was collected and the methyl isobutyl ketone was removed through a rotary evaporator.

After removing the extraction solvent, 150 g of dipropylene glycol was dissolved in the remaining residue and co-distilled through a vacuum thin film evaporator. At this time, the temperature was 140 ° C and the vacuum degree was 40 Torr. The dipropylene glycol layer thus obtained was crystallized at 0 deg. C and filtered to obtain a veltol cake. The veltol cake was recrystallized from the water layer and dried to obtain 30.6 g of a high purity veltol white solid having a purity of 99.5% with a total yield of 64.7%.

Example 2

It was carried out under the same conditions as in Example 1, but the temperature of the chlorine oxidation reaction was carried out in the range of 0 ~ 5 ℃. The purity of the obtained beltol was 99.1%, and the yield was 60.1%.

Example 3

Ethylene glycol was used instead of dipropylene glycol under the same conditions as in Example 1. The resulting beltol had a purity of 99.3% and a yield of 62.3%.

Example 4

The reaction was carried out under the same conditions as in Example 1 except that the chlorine gas at the top of the reactor was recycled into the reaction solution during the chlorine oxidation reaction. The resulting beltol had a purity of 99.5% and a yield of 66.5%.

Example 5

It was carried out under the same conditions as in Example 1, but was carried out by a simple vacuum evaporation method instead of a vacuum thin film evaporation process. The resulting beltol had a purity of 99.5% and a yield of 64.7%.

Comparative Example 1

The reaction was carried out under the same conditions as in Example 1, but the chlorine oxidation reaction was performed for 3 hours in an atmospheric pressure glass reactor. The resulting beltol had a purity of 97% and a yield of 53.9%.

Comparative Example 2

Under the same conditions as in Example 1, but the chlorine oxidation reaction temperature was carried out at 15 ~ 20 ℃. The resulting beltol had a purity of 95% and a yield of 33%.

Comparative Example 3

Under the same conditions as in Example 1, but the pH was adjusted to 7. The purity of the obtained beltol was 96% and the yield was 40.1%.

The present invention is a process developed to favor commercialization from a technical and economical point of view. Existing patents and literature methods use a purification process, which is disadvantageous for commercialization such as solid distillation, but according to the present invention, a high purity white veltol of 99% or more can be synthesized in a yield of 63-66% by a relatively simple process. .

In addition, by using a gas recirculation method during the oxidation reaction can significantly shorten the reaction time. Ethylene glycol or dipropylene glycol is used as a tar residue removal solvent, and the thin film evaporation or simple evaporation method is used using such a solvent, and the tar residue can be efficiently removed while minimizing product loss.

Claims (9)

A method for preparing veltol, comprising: reacting alpha-ethylperfuryl alcohol and an oxidizing agent in a gaseous recycle method in a liquid medium to obtain a veltol synthetic intermediate which is a reaction product; Performing a hydrolysis reaction by heating until no reaction product remains; neutralizing the reaction with a strong base such that the pH is between 2 and 4; Extracting veltol from the neutralized reactant using a first solvent; Dissolving the residue from which the first solvent is removed from the extract in a second solvent of dipropylene glycol or ethylene glycol to remove tar residue; Filtering the veltol solid obtained by first crystallizing the liquid from which the tar residue has been removed and removing the second solvent to obtain a filter cake; Removing the water by filtration of the solid cake obtained by dissolving the filter cake in water and then again crystallizing it; And A method for producing high purity veltol, characterized in that the veltol cake obtained by washing the solid cake and removing impurities is vacuum dried. The method of claim 1, wherein the liquid medium is selected from the group consisting of water, alkanols having 1 to 4 carbon atoms, and mixtures thereof. The method of claim 1, wherein the oxidizing agent is selected from the group consisting of chlorine, bromine, bromine chloride, hypochlorous acid, hypobromic acid, and mixtures thereof. The method of claim 1, wherein the oxidation reaction is carried out under a temperature condition of -50 to 50 ℃ and a pressure of atmospheric pressure to 5 atm. The method of claim 1, wherein the first solvent is methyl isobutyl ketone, dichloromethane, dichloroethane, toluene, dioxane, benzene, halobenzene, any O-, M- or P-xylene, any isomeric aliphatic Group consisting of (C ₅ -C ₁₀ ) alkane, cyclohexane, tetrahydrofuran, any di (C ₁ -C ₆ ) alkyl ether, (C ₂ -C ₄ ) alkyl acetate and (C ₃ -C ₁₀ ) ketone Method for producing a high purity veltol, characterized in that selected from. The method of claim 1, wherein the extraction conditions are carried out in a range of 1 to 5 times at room temperature to 100 ℃. The method of claim 1, wherein the tar residue is removed by a thin film evaporation method or a simple distillation method. The method of claim 1, wherein the primary crystallization step is carried out under a temperature condition of -20 to 50 ℃. The method of claim 1, wherein the washing liquid in the washing step is selected from the group consisting of water, alkanol having 1 to 4 carbon atoms, and a mixture thereof.