Method for synthesizing pentaerythritol

Abstract

The invention provides a method for synthesizing pentaerythritol, and belongs to the technical field of organic synthesis. The method comprises the following steps: adding a formaldehyde aqueous solution and a formaldehyde glycan inhibitor into a condensation reaction kettle, heating the solution to 48-52 DEG C, dropwise adding liquid caustic soda and acetaldehyde, keeping the temperature after dropwise adding, and then adding acid to adjust the pH value to 6-6.8; and transferring the solution into a dealdehyding tower and a dealcoholizing tower for dealdehyding and dealcoholizing to obtain a condensation liquid, adding acid into the condensation liquid to adjust the pH value to 3-4, feeding the condensation liquid into a hydrolysis tower for hydrolysis, feeding the hydrolysis liquid into a crystallization kettle, and cooling and crystallizing to obtain a pentaerythritol product. According to the method disclosed by the invention, the saccharification reaction of the formaldehyde glycan is effectively inhibited by adding the formaldehyde glycan inhibitor into the reaction liquid, and the conversion rate of the dipentaerythritol is improved. And the condensation liquid after dealdehyding and dealcoholization is subjected to acid addition and pressurized hydrolysis, so that organic impurities are reduced, and the product quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for producing synthetic pentaerythritol. Background Art

[0002] Monopentaerythritol and dipentaerythritol are fine chemical products with high added value, especially dipentaerythritol, whose product price is more than three times that of monopentaerythritol and is widely used in many fields.

[0003] At present, the most common pentaerythritol production technologies in domestic and foreign industries are mainly sodium method and calcium method. The "sodium method" uses sodium hydroxide as an alkaline catalyst to prepare pentaerythritol. This method is divided into low-temperature low-ratio method and high-temperature high-ratio method. The low-temperature method synthesizes pentaerythritol, and the product quality is poor, and many impurities are generated, which seriously affects the stability of the pentaerythritol process system and enriches impurities. Although the high-temperature high-ratio method synthesizes pentaerythritol with fewer impurities than the low-temperature method, the synthesized dipentaerythritol is less, and the economic benefits are poor.

[0004] For example, Chinese patent CN101696158A discloses a method for preparing monopentaerythritol and dipentaerythritol. The method uses formaldehyde, acetaldehyde and sodium hydroxide as raw materials, controls the reaction temperature according to the reaction mechanism, adopts a specific feeding procedure to control the ratio of each raw material for reaction, and neutralizes with formic acid after the reaction is completed; the reaction liquid is cooled and then filtered for tripentaerythritol, and then the reaction liquid is subjected to rectification, dealdehyde removal, pressure hydrolysis, and evaporation concentration, and monopentaerythritol and crude dipentaerythritol are crystallized and separated at a specified temperature, and the crude dipentaerythritol is refined to obtain fine dipentaerythritol. The invention has a simple process, and by accurately controlling the raw material ratio and concentration, reaction temperature and feeding procedure, the generation of tripentaerythritol is reduced as much as possible under the premise of ensuring the dipentaerythritol yield and total yield, the obtained monopentaerythritol and dipentaerythritol are of high quality, especially the dipentaerythritol content is high, the dipentaerythritol content can reach more than 90%, and the ash content is low, which is only 0.01-0.03%.

[0005] The "calcium method" uses Ca(OH) 2 As an alkaline catalyst for the preparation of pentaerythritol, this method is the second most widely used process in the industrial production of pentaerythritol after the sodium method. 2+ It will catalyze the self-polymerization of formaldehyde into formaldehyde polysaccharide, and in the later stage, it will remove Ca 2+ It must go through sedimentation and filtration processes. At the same time, the "calcium ash" remaining in the product at high temperatures will catalyze the decomposition of pentaerythritol, resulting in a decrease in product purity. Therefore, the "calcium method" does not have sustainable development potential.

[0006] For example, Chinese patent CN104672060 A discloses a method for preparing pentaerythritol using a low-ash calcium process, wherein formaldehyde and acetaldehyde are used as raw materials, calcium hydroxide is used as a catalyst and reactant to prepare pentaerythritol, and a formose inhibitor is added during the condensation process to reduce the formose reaction. The main feature of the preparation method of the invention is that an inhibitor is added during the condensation process to inhibit formose, thereby reducing the product color number and improving the product quality.

[0007] However, the methods in the prior art have problems such as unstable yield of dipentaerythritol and generation of impurities during the production process. Therefore, there is an urgent need for a new process for synthesizing pentaerythritol, which can not only improve the yield of dipentaerythritol, but also reduce the generation of impurities and stabilize the production process. Summary of the invention

[0008] Based on the technical deficiencies of the prior art such as poor pentaerythritol production quality and low dipentaerythritol yield, the present invention provides a novel and efficient method, which can not only effectively improve the product quality of pentaerythritol, but also increase the yield of dipentaerythritol, and is a process with obvious benefits.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for synthesizing pentaerythritol comprises the following steps:

[0011] (1) adding a formaldehyde aqueous solution and a formose inhibitor into a condensation reaction kettle to obtain a solution 1;

[0012] (2) heating solution 1 until the temperature reaches 48-52° C., adding liquid alkali and acetaldehyde, keeping the temperature after the addition is complete, and then adding acid to adjust the pH value to between 6 and 6.8 to obtain solution 2;

[0013] (3) transferring solution 2 into a dealdehyde tower and a dealcohol tower for dealdehyde and dealcoholization to obtain a condensation liquid, adding acid to the condensation liquid to adjust the pH value to between 3 and 4, to obtain solution 3;

[0014] (4) The solution 3 is pumped into a hydrolysis tower for hydrolysis, and then pumped into a crystallization kettle for cooling and crystallization to obtain the pentaerythritol product.

[0015] The step (1) of adding the formaldehyde aqueous solution into the condensation reaction kettle is to add all the formaldehyde aqueous solution into the condensation reaction kettle.

[0016] The formose inhibitor described in the above step (1) is sodium carboxymethyl cellulose.

[0017] The added concentration of the formose inhibitor in the above step (1) is 200ppm-500ppm based on the volume of the formaldehyde aqueous solution.

[0018] The dripping time of the liquid alkali and acetaldehyde in the above step (2) is 35min-40min.

[0019] When the dripping time of the liquid alkali and acetaldehyde in the above step (2) reaches 15min-20min, the temperature of the reaction liquid is controlled to rise; the heating rate is 0.5-1°C / min; and the temperature of the reaction liquid is 70-75°C when the dripping is completed.

[0020] The insulation time in the above step (2) is 5-10 minutes.

[0021] The alkali solution described in the above step (2) is a sodium hydroxide solution, and the mass fraction of sodium hydroxide is 32%.

[0022] The volume ratio of the formaldehyde, acetaldehyde and alkali solution is 30-45:1.2-2:2.5-4.

[0023] Preferably, the volume ratio of formaldehyde, acetaldehyde and alkali solution is 35:1.4-1.5:2.85.

[0024] The hydrolysis in the above step (4) is pressurized hydrolysis, and the pressurized pressure is 0.02MPa-0.08MPa.

[0025] A pentaerythritol prepared by the above method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] By adding a formaldehyde polysaccharide inhibitor to the reaction solution, the saccharification reaction of formaldehyde polysaccharide is effectively inhibited, and the conversion rate of dipentaerythritol is improved. The condensation liquid after dealdehyde and dealcoholization is hydrolyzed by acidification and pressure to reduce organic impurities and improve product quality. The content of monopentaerythritol in the finished product is increased from about 90% to about 95%, and the yield of dipentaerythritol is increased from less than 4.5% to about 8.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Reference Figure 1 The flow chart of pentaerythritol was used for the preparation of pentaerythritol.

[0031] Example 1 A method for synthesizing pentaerythritol

[0032] The steps include:

[0033] (1) 35m 3 The prepared 150g / L bottom water formaldehyde was injected into the condensation kettle at one time, and 7Kg of sodium carboxymethyl cellulose was added to obtain solution 1;

[0034] (2) When the temperature of solution 1 reaches 50°C, sodium hydroxide and acetaldehyde are added simultaneously, wherein the amount of sodium hydroxide (content is 32%) added is 2.85 m 3 , the amount of acetaldehyde (content> 99.8%) added was 1402L; sodium hydroxide and acetaldehyde were dripped at a relatively uniform speed for 40 minutes; during the addition of liquid alkali and acetaldehyde, the temperature rise rate of the reaction solution was controlled at 0.5°C / min, and when the sodium hydroxide and acetaldehyde were added, the temperature of the reaction solution was 73.6°C. After keeping warm for 10 minutes, formic acid was added to adjust the pH to 6.5 to obtain solution 2; the component content of solution 2 was analyzed, wherein the content of monopentaerythritol was 7.34%, and the content of dipentaerythritol was 0.86%;

[0035] (3) After removing the aldehyde and alcohol from solution 2, formic acid was added to adjust the pH to 3.5 to obtain solution 3;

[0036] (4) Solution 3 was placed in a pressure hydrolysis kettle for pressure hydrolysis, and then concentrated by a single-effect evaporator. After the specific gravity of solution 3 was concentrated to 1.265, the solution was transferred to a crystallization kettle and cooled to 30° C. for crystallization to separate mono- and di-pentaerythritol, and finally 3.05 t of mono-pentaerythritol (content 95.12%) and 283 kg of di-pentaerythritol (content 86.73%) were obtained.

[0037] Example 2 A method for synthesizing pentaerythritol

[0038] The steps include:

[0039] (1) 35m 3 The prepared 150 g / L bottom water formaldehyde was injected into the condensation kettle at one time, and 10.5 kg of sodium carboxymethyl cellulose was added to obtain solution 1;

[0040] (2) When the temperature of solution 1 reaches 50°C, sodium hydroxide and acetaldehyde are added simultaneously, wherein the amount of sodium hydroxide (content is 32%) added is 2.85 m 3, the amount of acetaldehyde (content> 99.8%) added was 1403L; sodium hydroxide and acetaldehyde were dripped at a relatively uniform speed for 40 minutes; during the addition of liquid alkali and acetaldehyde, the temperature of the reaction solution was controlled to be 1°C / min, and when the sodium hydroxide and acetaldehyde were added, the temperature of the reaction solution was 72.4°C. After keeping warm for 10 minutes, formic acid was added to adjust the pH to 6.4 to obtain solution 2; the component content of solution 2 was analyzed, wherein the content of monopentaerythritol was 7.28%, and the content of dipentaerythritol was 0.84%;

[0041] (3) After removing the aldehyde and alcohol from solution 2, formic acid was added to adjust the pH to 3.6 to obtain solution 3;

[0042] (4) Solution 3 was placed in a pressure hydrolysis kettle for pressure hydrolysis, and then concentrated by a single-effect evaporator. After the specific gravity of solution 3 was concentrated to 1.261, solution 3 was transferred to a crystallization kettle and cooled to 28° C. for crystallization to separate mono- and di-pentaerythritol, and finally 2.98 t of mono-pentaerythritol (content 95.73%) and 276 kg of di-pentaerythritol (content 85.94%) were obtained.

[0043] Example 3 A method for synthesizing pentaerythritol

[0044] The steps include:

[0045] (1) 35m 3 The prepared 150 g / L bottom water formaldehyde was injected into the condensation kettle at one time, and 17.5 kg of sodium carboxymethyl cellulose was added to obtain solution 1;

[0046] (2) When the temperature of solution 1 reaches 50°C, sodium hydroxide and acetaldehyde are added simultaneously, wherein the amount of sodium hydroxide (content is 32%) added is 2.85 m 3 , the amount of acetaldehyde (content> 99.8%) added was 1401L; sodium hydroxide and acetaldehyde were dripped at a relatively uniform speed for 40 minutes; during the addition of liquid alkali and acetaldehyde, the temperature rise rate of the reaction solution was controlled to be 1°C / min, and when the sodium hydroxide and acetaldehyde were added, the temperature of the reaction solution was 74.1°C. After keeping warm for 10 minutes, formic acid was added to adjust the pH to 6.5 to obtain solution 2; the component content of solution 2 was analyzed, wherein the content of monopentaerythritol was 7.31%, and the content of dipentaerythritol was 0.85%;

[0047] (3) After removing the aldehyde and alcohol from solution 2, formic acid was added to adjust the pH to 3.5 to obtain solution 3;

[0048] (4) Solution 3 was placed in a pressure hydrolysis kettle for pressure hydrolysis, and then concentrated by a single-effect evaporator. After the specific gravity of solution 3 was concentrated to 1.267, the solution was transferred to a crystallization kettle and cooled to 29° C. for crystallization to separate mono- and di-pentaerythritol, and finally 3.02 t of mono-pentaerythritol (content 95.88%) and 281 kg of di-pentaerythritol (content 85.86%) were obtained.

[0049] Comparative Example 1 A method for synthesizing pentaerythritol

[0050] The steps include:

[0051] (1) 35m 3 The prepared 150g / L bottom water formaldehyde is injected into the condensation kettle at one time to obtain solution 1;

[0052] (2) When the temperature of solution 1 reaches 50°C, sodium hydroxide and acetaldehyde are added simultaneously, wherein the amount of sodium hydroxide (content is 32%) added is 2.85 m 3 , the amount of acetaldehyde (content> 99.8%) added was 1401L; sodium hydroxide and acetaldehyde were dripped at a relatively uniform speed for 40 minutes; during the addition of liquid alkali and acetaldehyde, the temperature rise rate of the reaction solution was controlled to be 1°C / min, and when the sodium hydroxide and acetaldehyde were added, the temperature of the reaction solution was 73.7°C. After keeping warm for 10 minutes, formic acid was added to adjust the pH to 6.4 to obtain solution 2; the component content of solution 2 was analyzed, wherein the content of monopentaerythritol was 7.35%, and the content of dipentaerythritol was 0.42%;

[0053] (3) Solution 2 was concentrated in a single-effect evaporator. After the specific gravity of Solution 2 was concentrated to 1.263, it was transferred to a crystallization kettle and cooled to 30° C. for crystallization to separate mono- and di-pentaerythritol, and finally 3.15 t of mono-pentaerythritol (content 90.12%) and 162 kg of di-pentaerythritol (content 81.33%) were obtained.

[0054] Comparative Example 2 A method for synthesizing pentaerythritol

[0055] The steps include:

[0056] (1) 35m 3 The prepared 150g / L bottom water formaldehyde is injected into the condensation kettle at one time to obtain solution 1;

[0057] (2) When the temperature of solution 1 reaches 50°C, sodium hydroxide and acetaldehyde are added simultaneously, wherein the amount of sodium hydroxide (content is 32%) added is 2.85 m 3, the amount of acetaldehyde (content> 99.8%) added was 1399L; sodium hydroxide and acetaldehyde were dripped at a relatively uniform speed for 40 minutes; during the addition of liquid alkali and acetaldehyde, the temperature rise rate of the reaction solution was controlled to be 1°C / min, and when the sodium hydroxide and acetaldehyde were added, the temperature of the reaction solution was 74.2°C. After keeping warm for 10 minutes, formic acid was added to adjust the pH to 6.5 to obtain solution 2; the component content of solution 2 was analyzed, wherein the content of monopentaerythritol was 7.33%, and the content of dipentaerythritol was 0.41%;

[0058] (3) Solution 2 was concentrated in a single-effect evaporator. After the specific gravity of Solution 2 was concentrated to 1.265, it was transferred to a crystallization kettle and cooled to 28° C. for crystallization to separate mono- and di-pentaerythritol, and finally 3.12 tons of mono-pentaerythritol (content 90.21%) and 162 kg of di-pentaerythritol (content 81.04%) were obtained.

[0059] It can be seen from the above examples and comparative data that before the pentaerythritol reaction begins, the addition of sodium carboxymethyl cellulose is beneficial to increasing the output of dipentaerythritol, and the output of dipentaerythritol in a single kettle can be increased by about 120 kg. By hydrolyzing the reaction solution with acid and pressure, organic impurities in the product can be effectively removed, and the content of monopentaerythritol in the finished product increases from about 90% to more than 95%, and the content of dipentaerythritol increases from about 80% to more than 85%, which greatly improves the conversion rate of dipentaerythritol, improves the quality of the product, and increases the added value.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for synthesizing pentaerythritol, characterized in that: The steps include: (1) adding a formaldehyde aqueous solution and a formose inhibitor into a condensation reaction kettle to obtain a solution 1; (2) heating solution 1 until the temperature reaches 48-52° C., adding liquid alkali and acetaldehyde, keeping the temperature after the addition is complete, and then adding acid to adjust the pH value to between 6 and 6.8 to obtain solution 2; (3) transferring solution 2 into a dealdehyde tower and a dealcohol tower for dealdehyde and dealcoholization to obtain a condensation liquid, adding acid to the condensation liquid to adjust the pH value to between 3 and 4, to obtain solution 3; (4) The solution 3 is pumped into a hydrolysis tower for hydrolysis, and then pumped into a crystallization kettle for cooling and crystallization to obtain the pentaerythritol product.

2. The method according to claim 1, characterized in that: The step (1) of adding the formaldehyde aqueous solution into the condensation reaction kettle is to add all the formaldehyde aqueous solution into the condensation reaction kettle.

3. The method according to claim 1, characterized in that: The formose inhibitor described in step (1) is sodium carboxymethyl cellulose.

4. The method according to claim 1, characterized in that: The added concentration of the formose inhibitor in step (1) is 200ppm-500ppm based on the volume of the formaldehyde aqueous solution.

5. The method according to claim 1, characterized in that: The dripping time of the liquid alkali and acetaldehyde in step (2) is 35min-40min.

6. The method according to claim 1, characterized in that: When the dripping time of the liquid alkali and acetaldehyde in step (2) reaches 15min-20min, the temperature of the reaction liquid is controlled to increase; the temperature increase rate is 0.5-1°C / min; and the temperature of the reaction liquid is 70-75°C when the dripping is completed.

7. The method according to claim 1, characterized in that: The insulation time described in step (2) is 5-10 minutes.

8. The method according to claim 1, characterized in that: The alkali solution described in step (2) is a sodium hydroxide solution, and the mass fraction of sodium hydroxide is 32%.

9. The method according to claim 1, characterized in that: The volume ratio of the formaldehyde, acetaldehyde and alkali solution is 30-45:1.2-2:2.5-4.

10. Pentaerythritol prepared by the method according to any one of claims 1 to 9.

Images