A method for improving the crystallization yield of dipentaerythritol

Abstract

The application discloses a method for improving the crystallization yield of dipentaerythritol, which comprises the following steps: 1) mixing the pentaerythritol mother liquor sedimentation filter cake with water according to the weight ratio of 1:5, and controlling the specific gravity of the mixture to be 1.01-1.10; 2) adding formic acid to adjust the pH value to 4.5, and heating to 90 DEG C; 3) heating to 140 DEG C, and staying for 2h; 4) adding activated carbon to perform turbidization and decolorization; 5) entering a crystallization tank, adjusting the pH value to 7.0, deprotonating the dipentaerythritol, and changing the pH value to neutral in the temperature reduction crystallization; 6) further reducing the temperature to 80-90 DEG C, adding 200-mesh dipentaerythritol crystalline powder, and inducing crystallization; 7) reducing the temperature to 40-45 DEG C, and after crystallization, centrifugal washing, drying and crushing to obtain the finished dipentaerythritol product. The application improves the crystallization yield of dipentaerythritol and improves the purity of the finished product.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dipentaerythritol production method, and particularly relates to a method for improving dipentaerythritol crystallization yield. BACKGROUND

[0002] In the production process of pentaerythritol, formaldehyde, acetaldehyde and sodium hydroxide are used as raw materials for condensation reaction, and after neutralization, a condensate is obtained. The condensate is removed from the formaldehyde by the rectifying column and is preliminarily concentrated, and then the concentrated liquid enters the evaporator, and after the evaporation concentration reaches the index, it enters the crystallization kettle for cooling crystallization. The crystallization liquid is separated by centrifugation to obtain filter cake and filtrate. The filter cake is dried to obtain monopentaerythritol. The filtrate is filtered by cooling and settling, and the settled filtrate is evaporated and crystallized, and after centrifugation of the crystallization liquid, pentaerythritol mother liquor and sodium formate are obtained. The settled filter cake is dissolved, decolorized and crystallized to obtain dipentaerythritol. Dipentaerythritol is the main by-product in the production process of pentaerythritol, and has high economic value.

[0003] However, the existing dipentaerythritol production process has low crystallization yield, which needs to be further solved. There is an urgent need in the prior art for a production method for improving the crystallization yield of dipentaerythritol. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for improving the crystallization yield of dipentaerythritol.

[0005] The purpose of the present application is achieved by the following technical scheme: a method for improving the crystallization yield of dipentaerythritol, comprising the following steps:

[0006] 1) The pentaerythritol mother liquor settled filter cake is mixed with water according to a weight ratio of 1:5, and the specific gravity of the mixture is controlled to be 1.01-1.10 to ensure the composition of the raw materials;

[0007] 2) Add formic acid to adjust the pH value to 4.5 to protonate the dipentaerythritol, and heat to 90℃;

[0008] 3) Heat to 140℃ and stay for 2h to decompose the polyether macromolecular impurities in the dipentaerythritol;

[0009] 4) Add activated carbon for turbidity decolorization;

[0010] 5) Enter the crystallization tank, add liquid alkali to adjust the pH value to 7.0 to deprotonate the dipentaerythritol, and add liquid alkali to change the pH value to 7.0-7.4 in the cooling crystallization, which is beneficial to improve the crystallization efficiency of dipentaerythritol;

[0011] 6) Further cool to 80-90℃, and add 200 mesh dipentaerythritol crystalline powder to induce crystallization;

[0012] 7) cooling to the crystallization temperature of dipentaerythritol 40-45℃, after crystallization, centrifugal washing to obtain dipentaerythritol wet material, drying by bundle pipe, crushing to obtain dipentaerythritol finished product.

[0013] In step 1), the specific gravity of the mixture is controlled to be 1.10.

[0014] In step 5), liquid alkali is added in the cooling crystallization to change the pH value to 7.4.

[0015] In step 6), cooling to 90℃.

[0016] In step 7), cooling to the crystallization temperature of dipentaerythritol 45℃.

[0017] The beneficial effects of the present application are: the present application adjusts the pH value to be acidic by formic acid, so that the dipentaerythritol is protonated, thereby adjusting the solubility of dipentaerythritol, improving the crystallization yield of dipentaerythritol, and obtaining 0.5 tons of dipentaerythritol finished product per 10 tons of dipentaerythritol crystallization liquid. The present application decomposes the polyether macromolecular impurities in dipentaerythritol at high temperature to improve the purity of the finished product, and the content of dipentaerythritol in the finished product reaches more than 90%. DETAILED DESCRIPTION

[0018] The present application is described in detail below. Example 1

[0019] 1) The pentaerythritol mother liquor settling filter cake (formaldehyde and acetaldehyde are condensed under the condition of liquid alkali to obtain a condensation liquid, the condensation liquid is subjected to rectification to remove aldehyde, evaporation to concentrate, cooling crystallization, and centrifugal separation to obtain crude pentaerythritol and pentaerythritol mother liquor, and the pentaerythritol mother liquor is subjected to cooling and settling separation to obtain the pentaerythritol mother liquor settling filter cake) is mixed with water at a weight ratio of 1:5, and the specific gravity of the mixture is controlled to be 1.01 to ensure the composition of the raw material.

[0020] 2) Formic acid is added to adjust the pH value to 4.5, so that the dipentaerythritol is protonated, and the temperature is raised to 90℃;

[0021] 3) Heating to 140℃ for 2h to decompose the polyether macromolecular impurities in dipentaerythritol;

[0022] 4) Activated carbon is added for turbidity decolorization;

[0023] 5) Into the crystallization tank, liquid alkali is added to adjust the pH value to 7.0, so that the dipentaerythritol is deprotonated, and liquid alkali is added in the cooling crystallization to change the pH value to 7.0, which is beneficial to improve the crystallization efficiency of dipentaerythritol;

[0024] 6) Further cooling to 80℃, adding 200 mesh dipentaerythritol crystallization powder to induce crystallization;

[0025] 7) cooling to the dipentaerythritol crystallization temperature 40℃, after crystallization, centrifugal washing to obtain dipentaerythritol wet material, drying by bundle pipe, crushing to obtain dipentaerythritol finished product.

[0026] Using 30,000 tons / year pentaerythritol device, the obtained dipentaerythritol yield is 4.5 tons / day, 0.45 tons of dipentaerythritol finished product is obtained from every 10 tons of dipentaerythritol crystallization liquid, the purity of dipentaerythritol is 91.0%, and the content of dipentaerythritol in the mother liquor is 3.1%. The content of dipentaerythritol in the mother liquor is relatively high, and the system circulation amount is large. Example 2

[0027] 1) The pentaerythritol mother liquor sedimentation filter cake (formaldehyde and acetaldehyde are condensed under the condition of liquid alkali to obtain condensation liquid, the condensation liquid is subjected to de-aldehyde rectification, evaporation concentration, cooling crystallization, and centrifugal separation to obtain crude pentaerythritol and pentaerythritol mother liquor, and the pentaerythritol mother liquor is subjected to cooling sedimentation separation to obtain the pentaerythritol mother liquor sedimentation filter cake) is mixed with water according to a weight ratio of 1:5, and the specific gravity of the mixture is controlled to be 1.10 to ensure the composition of the raw material;

[0028] 2) Formic acid is added to adjust the pH value to 4.5 to protonate the dipentaerythritol, and the temperature is raised to 90℃;

[0029] 3) Heating to 140℃ for 2h to decompose the polyether macromolecular impurities in the dipentaerythritol;

[0030] 4) Activated carbon is added for turbidity decolorization;

[0031] 5) Into the crystallization tank, liquid alkali is added to adjust the pH value to 7.0 to deprotonate the dipentaerythritol, and the pH value is changed to 7.4 in the cooling crystallization to improve the crystallization efficiency of the dipentaerythritol;

[0032] 6) The temperature is further reduced to 90℃, and 200 mesh dipentaerythritol crystallization powder is added to induce crystallization;

[0033] 7) Cooling to the dipentaerythritol crystallization temperature 45℃, after crystallization, centrifugal washing to obtain dipentaerythritol wet material, drying by bundle pipe, crushing to obtain dipentaerythritol finished product.

[0034] Using 30,000 tons / year pentaerythritol device, the obtained dipentaerythritol yield is 4.8 tons / day, 0.55 tons of dipentaerythritol finished product is obtained from every 10 tons of dipentaerythritol crystallization liquid, the purity of dipentaerythritol is 91.5%, and the content of dipentaerythritol in the mother liquor is 2.5%.

[0035] In the above two examples, the degree of deprotonation of dipentaerythritol is different, and the yield of dipentaerythritol is different, the method improves the crystallization yield of dipentaerythritol in a single kettle, and reduces the content of dipentaerythritol in the circulating dipentaerythritol centrifugal mother liquor.

[0036] It should be pointed out finally that the above is only used to explain the technical solutions of the present application, and is not a limitation on the protection scope of the present application, and simple modifications or equivalent replacements of the technical solutions of the present application by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method of improving the crystallization yield of dipentaerythritol characterized in that The method comprises the following steps: 1) The pentaerythritol mother liquor settling filter cake is mixed with water at a weight ratio of 1:5, and the specific gravity of the mixture is controlled to be 1.01-1.10 to ensure the raw material composition; 2) Formic acid is added to adjust the pH value to 4.5 to protonate the dipentaerythritol, and the temperature is raised to 90°C; 3) The temperature is raised to 140°C, and the residence time is 2h to decompose the polyether macromolecular impurities in the dipentaerythritol; 4) Activated carbon is added for turbidification and decolorization; 5) The mixture is introduced into a crystallization tank, and liquid alkali is added to adjust the pH value to 7.0 to deprotonate the dipentaerythritol, and the liquid alkali is added to change the pH value to 7.0-7.4 during the temperature reduction crystallization, which is beneficial to improve the crystallization efficiency of the dipentaerythritol; 6) The temperature is further reduced to 80-90°C, and 200-mesh dipentaerythritol crystalline powder is added to induce crystallization; 7) The temperature is reduced to the crystallization temperature of the dipentaerythritol, which is 40-45°C, and after crystallization, centrifugal washing is performed to obtain dipentaerythritol wet material, which is dried by a pipe bundle and crushed to obtain dipentaerythritol finished product.

2. The method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized by: In step 1), the specific gravity of the mixture is controlled to be 1.

10.

3. The method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized by: In step 5), the liquid alkali is added to change the pH value to 7.4 during the temperature reduction crystallization.

4. The method of increasing the crystallization yield of dipentaerythritol according to claim 1, characterized by: In step 6), the temperature is reduced to 90°C.

5. The method of increasing the crystallization yield of dipentaerythritol according to claim 1, characterized by: In step 7), the temperature is reduced to the crystallization temperature of the dipentaerythritol, which is 45°C.