KR19980028460A - How to prepare neopentyl glycol - Google Patents

Abstract

The present invention condensation reaction of isobutylaldehyde and formaldehyde in the presence of tertiary amine catalyst to obtain crude hydrofibaldehyde (HPA), distillation, extraction and purification, and hydrogenation reaction to purified HPA to give crude neopentyl In the method of preparing NPG by purifying the mixture after obtaining a mixture containing glycol (NPG), water is added to the mixture containing the crude NPG to extract NPG into an aqueous solution layer, and the crude NPG-containing aqueous solution. A layer is introduced into the bottom of the multi-stage distillation column to use water in the aqueous solution layer as a droplet entrainer, and a small amount of water is added to the top of the multi-stage distillation column to distill the inorganic salt contained in the aqueous solution layer into contact with water at each end of the distillation column. Thereby providing a method for purifying the NPG, and by the method of the present invention complete the inorganic salt that can be included in the final NPG It can be obtained by separating the high purity of the NPG.

Description

How to prepare neopentyl glycol

The present invention relates to a process for the preparation of neopentyl glycol (2,2-dimethyl-1,3-dihydroxypropane, hereinafter abbreviated as NPG). More specifically, the present invention relates to a method for producing high purity NPG by separating and purifying NPG from inorganic salts such as sodium hydroxy pivalate and sodium formate formed in the NPG production process.

NPG can be prepared by reacting isobutylaldehyde and formaldehyde under a base catalyst to obtain the aldol condensate hydroxyfibaldehyde (hereinafter described as HPA), and then reducing and purifying the HPA obtained. Alkali hydroxide (US Pat. No. 2,400,724) or triethylamine (hereinafter described as TEA) (US Pat. No. 3,808,280) is commonly used as the base catalyst used in the process for obtaining the aldol condensate HPA. Currently, TEA is the most widely used to significantly reduce side reactions in aldol condensation reactants. As a catalyst for reducing the aldol condensate HPA to NPG, a mixed metal oxide of Cu, Ni, Cr, and Zn (US Pat. No. 4,250,337) is commonly used, and in part, precious metals of Pt, Ru, and Rh (European Patent No. 0,343,475). Or Raney-Ni (US Pat. No. 3,920,760). NPG is used as an additive for lubricating oils and plasticizers, and is most often used to obtain polyester which is a raw material of powder coatings. The purity is very important for NPG supplied not only with additives such as lubricating oils and plasticizers, but also with synthetic raw materials of polyester which is a raw material of powder coating. Impurities contained in NPG include trimethylpentanediol (hereinafter referred to as TMPD) with reduced 2,2,4-trimethyl-3-hydroxypentanal produced in the aldol condensation reaction and Kanizaro reaction and T in the aldol condensation reaction. Monoesters such as neopentylglycol hydroxypivalate (hereinafter referred to as HPNE) and neopentylglycol isobutylate (hereinafter referred to as IBNP) produced by the Chenko reaction are typical. In particular, the allowable concentrations of these monoesters, which have been found to affect the physical properties of derivatives produced from NPG as raw materials, are managed very low, less than 0.1%. However, the monoester, which inevitably contains 3 to 5% of HPNE produced by the Tichenco reaction in the aldol reaction step in the NPG manufacturing process, is not reduced under the condition of reducing HPA, but remains in the final product together with NPG. Monoester residues have a boiling point similar to that of NPG, making it difficult to separate them directly by conventional distillation methods.

In German Patent No. 1,014,089, a method for removing the produced monoester was added sodium hydroxide to convert the ester into a high boiling metal salt, which was then achieved by steam distillation. However, simple distillation because metal salts such as hydroxypivalic sodium salt and isobutyric sodium salt produced by conversion of monoester by sodium hydroxide act as a catalyst to decompose NPG when contacted with NPG at a temperature above 150 ° C. Prolonged high temperature heating of the metal salt and NPG mixture during the refining process leads to the decomposition of NPG, which is accompanied by secondary pollution and yield reduction of NPG by low boilers and monoesters.

In US Patent No. 2,895,966, in order to prevent NPG from being decomposed by metal salts, crude NPG is supplied to the submeter at the same time as steam to entrain the NPG by steam, so that most of the upper portion of the tower is processed at 140 ° C. or lower. NPG was obtained in an aqueous solution, and high boiling point metal salts and organics were removed at the bottom. NPG aqueous solution obtained from the top of the tower was removed from the drying column, NPG remaining in the bottom of the drying tower was removed from the TMPD, a impurities contained in the NPG in a simple purification column to obtain a final purified NPG.

However, the problem with this method is that since the inorganic salt is included in the composition of the NPG solution obtained from the column top to 60 to 310 ppm, it was necessary to install a subsequent purification process to obtain a NPG product suitable for the final NPG application. Therefore, the NPG was separated into a column by a subsequent step to obtain a final product.

The methods described above are undesirable due to the complexity of the process and therefore require an improved process for purifying NPG from the crude reaction product.

Accordingly, an object of the present invention is to provide a method for preparing NPG by simply and economically purifying NPG solution by removing inorganic salts and the like from the crude NPG aqueous solution.

In order to achieve the above object, in the present invention, isobutylaldehyde and formaldehyde are condensed in the presence of a tertiary amine catalyst to obtain crude hydrofibaldehyde (HPA), which is distilled, extracted and purified, and hydrogenated to purified HPA. In order to obtain a mixture containing crude neopentyl glycol (NPG), and then to purify the mixture to prepare NPG, NPG is extracted into an aqueous layer by adding water to the mixture containing the crude NPG and Injecting the crude NPG-containing aqueous solution layer below the multi-stage distillation column to use water in the aqueous solution layer as the entrainment agent, and adding a small amount of water to the upper stage of the multi-stage distillation tower, and the inorganic salts contained in the aqueous solution layer at each end of the distillation column. Provided is a method for purifying NPG by distillation in contact with moisture.

Hereinafter, the present invention will be described in detail.

In the present invention, a multi-stage distillation column is a generic term for a form of a packed cap, a perforated cap, a bubble cap, and the like.

In the present invention, the inorganic salts are separated from the crude reaction product mixed with the inorganic salts and NPG by using a water entrainer, and a small amount of the inorganic salts that can contaminate the separated NPG aqueous solution is distilled using a multi-stage distillation column. It is advantageous to remove inorganic salts by continuously contacting with water in each stage of the separation column. According to this process, high purity NPG can be obtained even using a conventional distillation column.

Isobutylaldehyde, formaldehyde and TEA were charged to a continuous reactor and reacted for 1 to 6 hours at a temperature of 60 to 90 ° C. and a pressure of 10 to 50 psig. In the HPA mixture from the aldol condensation reactor, low boilers (eg, isobutylaldehyde, TEA and methanol) are removed and higher alcohols such as octanol are added to remove water and amine salts. An octanol solution containing 40-50% HPA is hydrogenated under a Ranickel catalyst to give a mixture comprising NPG. In order to selectively isolate NPG contained in the hydrogenation product, first, an aqueous solution of 10 to 20% sodium hydroxide is added to convert HPNE to sodium hydroxide, and water is added to add 1 to 10 times the weight ratio to the NPG mixture. Components metal salt and NPG are extracted into the water layer. The extraction selectively removes the TMPD and organic components from the octanol layer. The aqueous layer leaving the final extraction process tower has a composition of 20 to 23% NPG, 1 to 2% sodium salt, 50 to 95% water, 2 to 3% octanol, and other 0.01 to 0.02%.

The composition of the initial residue of the separation column is composed by adding pure NPG, maintaining a temperature of 100 to 140 ℃ and a pressure of 130 to 400 millibar. When the condition of the separation column is normalized, an aqueous solution layer containing crude NPG is supplied to the bottom of the distillation column after extraction. The aqueous solution layer is preheated and supplied at 60 to 140 ° C. in a heater installed at the front of the distillation column.

The sodium salt accumulated in the column bottom is continuously removed, and the aqueous layer separated into the top of the separation column is cooled through a condenser to obtain a liquid phase. The composition of the liquid phase of the obtained columnar portion is 20 to 25% of NPG, 1 to 4 ppm of sodium salt, 60 to 80% of water, and other 0.01 to 0.02%. NPG aqueous solution separated from the sodium salt is fed to the drying tower to remove water. The composition obtained at the bottom of the drying tower has a composition of at least 99% NPG and 5 to 14 ppm sodium. NPG obtained from the bottom of the drying tower is transferred to the final purification tower to obtain the final product at the top of the purification tower.

The present invention will be described in more detail with reference to the following examples.

Example 1

The crude HPA obtained by condensing isobutylaldehyde and formaldehyde under a triethylamine catalyst at a molar ratio of 1.2: 1.0: 0.5 was passed through a low boiling point removal tower and an extraction column using octanol to remove organic salts. Into a high pressure reactor filled with a hydrogenated Raney-Nickel reduction catalyst at atmospheric pressure to obtain crude NPG through a reduction reaction. The ester contained in the crude NPG is converted into a metal salt through a saponification reaction by adding an appropriate amount of sodium hydroxide. Remove The composition of the obtained crude NPG is shown in Table 1 below:

TABLE 1

ingredient Composition (weight ratio) NPGTMPD Octanol low boiling point material (BuOH, TEA, MeOH) Water Other (ester, high boiling point) Sodium salt 47.20.441.71.16.61.02.0

Continuously add 26.9 g / min of water to the top of the 30 stage extraction tower and 30.1 g / min of crude NPG to the bottom. The temperature of the extraction column is maintained at 10 ℃, the pressure is carried out at atmospheric pressure. After extraction, the flow rate of the octanol layer separated and coming out of the top of the extraction column is 14.0 g / min, and the flow rate of the aqueous solution layer coming out is 44.0 g / min. Only a small amount of TMPD remained in the aqueous solution layer where 96.3% of NPG was recovered, and over 98% of TMPD contained in the crude NPG was removed by the octanol layer. The aqueous solution layer coming out of the bottom of the extraction column was distilled by continuous feeding to the column bottom of the 10-stage porous distillation column maintained at a temperature of 115 to 120 ℃ and a pressure of 210 mmHg. The composition of the aqueous solution obtained at the top of the distillation column is shown in Table 2 below:

TABLE 2

ingredient Composition (weight ratio) NPGTMPD Octanol low boiling point material (BuOH, TEA, MeOH) Water Other (ester, high boiling point) Sodium salt Water layer after extraction Distillate at the Top of Separation Tower 31.8 trace 0.20.366.3 trace 1.4 32.3 traces 0.20.367.2 traces 4.5 ppm or less

Example 2

The crude NPG-containing aqueous solution obtained in the extraction step of Example 1 was fed to the bottom of a five stage porous distillation column maintained at a temperature of 115 to 120 ° C. and a pressure of 133 mmHg, followed by distillation. The composition of the aqueous solution obtained at the top of the separation column is shown in Table 3 below:

TABLE 3

ingredient Composition (weight ratio) NPGTMPD Octanol low boiling point material (BuOH, TEA, MeOH) Water Other (ester, high boiling point) Sodium salt Water layer after extraction Distillate at the Top of Separation Tower 31.8 trace 0.20.366.3 trace 1.4 32.3 traces 0.20.367.2 traces less than 15 ppm

Example 3

The NPG aqueous solution purified in Example 1 was removed from the drying tower maintained at 140 ° C. atmospheric pressure to obtain NPG having a composition as shown in Table 4 below at the bottom of the drying tower.

TABLE 4

Item unit value Hydroxyl Group Water (Catalyzed Method) Ash Component Color (50% in Water) Water Purity (HPLC) mg KOH / gppm ° C %% 107368130200.499.7

As described above, the present invention simplifies the multistage purification process of the purification process and, depending on the intended use, it is possible to obtain the desired NPG purity only by the drying step in the subsequent purification process.

High purity neopentylglycol can be produced continuously and economically.

Claims (4)

Condensation reaction of isobutylaldehyde and formaldehyde in the presence of a tertiary amine catalyst to obtain crude hydrofibaldehyde (HPA), distillation, extraction and purification, and hydrogenation of the purified HPA to give crude neopentyl glycol (NPG). In the method for preparing NPG by purifying the mixture, and then mixing the mixture, water is added to the mixture containing the crude NPG to extract NPG into an aqueous solution layer, and the crude NPG-containing aqueous solution layer is multistage. Into the bottom of the distillation column, the water in the aqueous solution layer is used as a splash entrainer, and a small amount of water is added to the upper stage of the multi-stage distillation column so that the inorganic salts in the aqueous solution layer are contacted with water at each end of the distillation column to distill NPG. Purifying. The method of claim 1, The water contained in the crude NPG-containing aqueous solution layer is 50-95%. The multi-stage distillation column is maintained at a pressure of 130 to 400 millibars and a temperature of 100 to 140 ℃. The method of claim 1, The crude NPG-containing aqueous solution layer is preheated to 60 to 140 ℃ and characterized in that the feed to the multi-stage distillation column.