Method for improving crystallization yield of dipentaerythritol

Abstract

The invention discloses a method for improving the crystallization yield of dipentaerythritol, which comprises the following steps: 1) mixing a pentaerythritol mother liquor sedimentation filter cake and water according to the weight ratio of 1: 5, and controlling the specific gravity of the mixed material 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 2 hours; 4) adding activated carbon for turbid decoloration; the invention discloses a method for preparing dipentaerythritol, which comprises the following steps of 1, adding dipentaerythritol into a reaction kettle, 2, adding dipentaerythritol powder into the reaction kettle, 3, adding the dipentaerythritol powder into the reaction kettle, 4, adding the dipentaerythritol powder into the reaction kettle, 5, feeding into a crystallizing tank, adjusting the pH value to 7.0, deprotonating the dipentaerythritol, and changing the pH value to be neutral during cooling crystallization, 6, cooling to 80-90 DEG C, adding 200-mesh dipentaerythritol crystal powder, and inducing crystallization, and 7, cooling to 40-45 DEG C, crystallizing, centrifugally washing, drying and crushing to obtain a dipentaerythritol finished product.

Description

Technical Field

[0001] The invention belongs to the technical field of dipentaerythritol production methods, and particularly relates to a method for improving the crystallization yield of dipentaerythritol. Background Art

[0002] In the production process of pentaerythritol, formaldehyde, acetaldehyde and sodium hydroxide are used as raw materials for condensation reaction, and condensation liquid is obtained after neutralization. After the condensation liquid is removed from formaldehyde by a distillation tower and initially concentrated, the concentrated liquid enters the evaporator, and after evaporation and concentration reaches the target, it enters the crystallization kettle for cooling and crystallization. The crystallization liquid is centrifuged to obtain filter cake and filtrate. The filter cake is dried to obtain monopentaerythritol. The filtrate is filtered by cooling and sedimentation. The sedimentation filtrate is evaporated and crystallized, and the crystallization liquid is centrifuged to obtain pentaerythritol mother liquor and sodium formate. The sedimentation 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 production process of dipentaerythritol has a low crystallization yield, which needs to be further solved. A production method for improving the crystallization yield of dipentaerythritol is urgently needed in the prior art. Summary of the invention

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

[0005] The object of the present invention is achieved through the following technical scheme: A method for improving the crystallization yield of dipentaerythritol, comprising the following steps: 1) The pentaerythritol mother liquor sedimentation filter cake is mixed with water in a weight ratio of 1:5, and the specific gravity of the mixed material is controlled to be 1.01-1.10 to ensure the raw material composition; 2) Add formic acid to adjust the pH to 4.5 to protonate dipentaerythritol, and raise the temperature to 90°C; 3) Heat to 140°C and hold for 2 hours to decompose the polyether macromolecular impurities in dipentaerythritol; 4) Add activated carbon for turbidity decolorization; 5) Enter the crystallization tank, add liquid alkali to adjust the pH value to 7.0, deprotonate the dipentaerythritol, and add liquid alkali to change the pH value to 7.0-7.4 during the cooling crystallization, which is beneficial to improve the crystallization efficiency of dipentaerythritol; 6) Cool down to 80-90°C and add 200-mesh dipentaerythritol crystalline powder to induce crystallization; 7) Cooling to the crystallization temperature of dipentaerythritol 40-45°C, after crystallization, centrifugation and washing to obtain dipentaerythritol wet material, drying in a bundle tube, and crushing to obtain the finished dipentaerythritol.

[0006] In step 1), the specific gravity of the mixed material is controlled to be 1.10.

[0007] In step 5), liquid alkali is added during the cooling crystallization to change the pH value to 7.4.

[0008] In step 6), the temperature is lowered to 90°C.

[0009] In step 7), the temperature is lowered to 45° C., the crystallization temperature of dipentaerythritol.

[0010] The beneficial effects of the present invention are as follows: the present invention adjusts the pH value to acidity by formic acid to protonate dipentaerythritol, thereby adjusting the solubility of dipentaerythritol and improving the crystallization yield of dipentaerythritol, and 0.5 tons of dipentaerythritol finished product is obtained for every 10 tons of dipentaerythritol crystal liquid. The present invention decomposes the polyether macromolecular impurities in dipentaerythritol by 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

[0011] The present invention is described in detail below. Example 1

[0012] 1) Pentaerythritol mother liquor sedimentation filter cake (formaldehyde and acetaldehyde undergo condensation reaction under the condition of liquid alkali to obtain condensation liquid, the condensation liquid is subjected to rectification to remove formaldehyde, evaporation concentration, cooling crystallization, centrifugal separation to obtain crude pentaerythritol and pentaerythritol mother liquor, the pentaerythritol mother liquor is subjected to cooling sedimentation separation to obtain pentaerythritol mother liquor sedimentation filter cake) is mixed with water at a weight ratio of 1:5, and the specific gravity of the mixed material is controlled to be 1.01 to ensure the raw material composition; 2) Add formic acid to adjust the pH to 4.5 to protonate dipentaerythritol, and raise the temperature to 90°C; 3) Heat to 140°C and hold for 2 hours to decompose the polyether macromolecular impurities in dipentaerythritol; 4) Add activated carbon for turbidity decolorization; 5) Enter the crystallization tank, add liquid alkali to adjust the pH value to 7.0, deprotonate dipentaerythritol, and add liquid alkali to change the pH value to 7.0 during the cooling crystallization, which is beneficial to improve the crystallization efficiency of dipentaerythritol; 6) Cool down to 80°C and add 200-mesh dipentaerythritol crystalline powder to induce crystallization; 7) Cooling to the dipentaerythritol crystallization temperature of 40°C, after crystallization, centrifugation and washing to obtain dipentaerythritol wet material, drying in a bundle tube, and crushing to obtain the dipentaerythritol finished product.

[0013] The 30,000 tons / year pentaerythritol device is used, and the dipentaerythritol output is 4.5 tons / day. Every 10 tons of dipentaerythritol crystal liquid can obtain 0.45 tons of dipentaerythritol finished product. The dipentaerythritol purity is 91.0%, and the dipentaerythritol content in the dipentaerythritol mother liquor is 3.1%. The dipentaerythritol content in the mother liquor is relatively high, and the system circulation volume is large. Example 2

[0014] 1) Pentaerythritol mother liquor sedimentation filter cake (formaldehyde and acetaldehyde undergo condensation reaction under the condition of liquid alkali to obtain condensation liquid, the condensation liquid is subjected to rectification to remove formaldehyde, evaporation concentration, cooling crystallization, centrifugal separation to obtain crude pentaerythritol and pentaerythritol mother liquor, the pentaerythritol mother liquor is subjected to cooling sedimentation separation to obtain pentaerythritol mother liquor sedimentation filter cake) is mixed with water at a weight ratio of 1:5, and the specific gravity of the mixed material is controlled to be 1.10 to ensure the raw material composition; 2) Add formic acid to adjust the pH to 4.5 to protonate dipentaerythritol, and raise the temperature to 90°C; 3) Heat to 140°C and hold for 2 hours to decompose the polyether macromolecular impurities in dipentaerythritol; 4) Add activated carbon for turbidity decolorization; 5) Enter the crystallization tank, add liquid alkali to adjust the pH value to 7.0, deprotonate the dipentaerythritol, and add liquid alkali to change the pH value to 7.4 during the cooling crystallization, which is beneficial to improve the crystallization efficiency of dipentaerythritol; 6) Cool down to 90°C and add 200-mesh dipentaerythritol crystalline powder to induce crystallization; 7) Cooling to the dipentaerythritol crystallization temperature of 45°C, after crystallization, centrifugation and washing to obtain dipentaerythritol wet material, drying in a bundle tube, and crushing to obtain the dipentaerythritol finished product.

[0015] Using a 30,000 tons / year pentaerythritol device, the output of dipentaerythritol is 4.8 tons / day. For every 10 tons of dipentaerythritol crystal liquid, 0.55 tons of dipentaerythritol finished product is obtained. The purity of dipentaerythritol is 91.5%, and the content of dipentaerythritol in the mother liquor is 2.5%.

[0016] In the above two embodiments, 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.

[0017] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for improving the crystallization yield of dipentaerythritol, characterized in that The following steps are involved: 1) The pentaerythritol mother liquor sedimentation filter cake is mixed with water in a weight ratio of 1:5, and the specific gravity of the mixed material is controlled to be 1.01-1.10 to ensure the raw material composition; 2) Add formic acid to adjust the pH to 4.5 to protonate dipentaerythritol, and raise the temperature to 90°C; 3) Heat to 140°C and hold for 2 hours to decompose the polyether macromolecular impurities in dipentaerythritol; 4) Add activated carbon for turbidity decolorization; 5) Enter the crystallization tank, add liquid alkali to adjust the pH value to 7.0, deprotonate the dipentaerythritol, and add liquid alkali to change the pH value to 7.0-7.4 during the cooling crystallization, which is beneficial to improve the crystallization efficiency of dipentaerythritol; 6) Cool down to 80-90°C and add 200-mesh dipentaerythritol crystalline powder to induce crystallization; 7) Cooling to the crystallization temperature of dipentaerythritol 40-45°C, after crystallization, centrifugation and washing to obtain dipentaerythritol wet material, drying in a bundle tube, and crushing to obtain the finished dipentaerythritol.

2. A method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized in that: In step 1), the specific gravity of the mixed material is controlled to be 1.

10.

3. A method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized in that: In step 5), liquid alkali is added during the cooling crystallization to change the pH value to 7.

4.

4. A method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized in that: In step 6), the temperature is lowered to 90°C.

5. A method for improving the crystallization yield of dipentaerythritol according to claim 1, characterized in that: In step 7), the temperature is lowered to 45° C., the crystallization temperature of dipentaerythritol.