A method for separating colored impurities in a pentaerythritol production system

Abstract

The application discloses a method for separating colored impurities in a pentaerythritol production system, comprising the following steps: 1) cooling the pentaerythritol mother liquor to 35 degrees with a heat exchanger, then adding it into an extraction mixing kettle and mixing with a n-butanol-methanol compound solvent at a mass ratio of 1:0.5, and the mixing temperature is 30-60 DEG C; 2) after mixing, separating through a horizontal screw centrifuge to obtain filter cake and filtrate; 3) the filter cake enters a 90 pentaerythritol production system to produce pentaerythritol and sodium formate products; 4) the filtrate is subjected to rectification at 130 DEG C, the obtained solvent is returned to the pentaerythritol production system, and the obtained impurities are subjected to waste liquid treatment. The method adopts a n-butanol-methanol compound solvent extraction mode to separate the colored impurities in the pentaerythritol production system, the separated sodium formate and pentaerythritol are returned to the pentaerythritol system after horizontal screw separation, the solvent obtained after rectification of the filtrate is returned to the pentaerythritol production system through a solvent recovery tank, and the accumulation of the colored impurities in the system is reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of pentaerythritol production methods, specifically relating to a method for separating colored impurities in a pentaerythritol production system. Background Technology

[0002] In the production process of pentaerythritol, formaldehyde, acetaldehyde and sodium hydroxide are first used as raw materials for a condensation reaction. After the reaction is completed, formic acid is used to neutralize the condensation liquid. Then, the condensation liquid is passed through a distillation column to remove formaldehyde and is initially concentrated before entering an evaporator. After evaporation and concentration to the predetermined target, it is sent to a crystallization kettle for cooling and crystallization. After centrifugation, the crystallized liquid is separated, and the filter cake is dried to obtain monopentaerythritol. The crystallization mother liquor is separated into dipentaerythritol by sedimentation and filtration. The sedimentation filtrate is concentrated by evaporation, crystallization and centrifugation to obtain pentaerythritol mother liquor and sodium formate.

[0003] However, during the production process, colored impurities accumulate in the pentaerythritol mother liquor, increasing its color and viscosity. These impurities contain polysaccharides, which are readily soluble in water. The "sodium method" for pentaerythritol production primarily utilizes differences in solubility at different temperatures to separate and purify the product; however, colored impurities are difficult to separate from the pentaerythritol mother liquor. The continuous accumulation of these impurities within the production system affects subsequent pentaerythritol crystallization, resulting in poor crystal particle size and increasing the difficulty of separating pentaerythritol from sodium formate. Simultaneously, the increased melting color of the pentaerythritol crystals leads to poor product quality, impacting its application.

[0004] Therefore, there is an urgent need in the existing technology for a method to separate colored impurities in the pentaerythritol production system in order to effectively remove the difficult-to-separate colored impurities from the pentaerythritol mother liquor. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for separating colored impurities in a pentaerythritol production system, so as to effectively remove difficult-to-separate colored impurities from the pentaerythritol mother liquor.

[0006] The objective of this invention is achieved through the following technical solution: a method for separating colored impurities in a pentaerythritol production system, comprising the following steps:

[0007] 1) After cooling the pentaerythritol mother liquor to 35 degrees Celsius using a heat exchanger, add it to the extraction mixing vessel and mix it with the n-butanol-methanol composite solvent at a mass ratio of 1:0.5, with a mixing temperature of 30-60 degrees Celsius.

[0008] 2) After mixing, sodium formate and pentaerythritol precipitate out of the pentaerythritol mother liquor, and colored impurities are extracted into the composite solvent. The mixture is then separated by a horizontal screw centrifuge to obtain filter cake and filtrate.

[0009] 3) The filter cake enters the 90 pentaerythritol production system to produce pentaerythritol and sodium formate products;

[0010] 4) The solvent obtained by distilling the filtrate at 130℃ is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by distillation are treated as waste liquid.

[0011] The n-butanol-methanol composite solvent is a composite solvent obtained by mixing methanol and n-butanol at a volume ratio of 7:3.

[0012] The beneficial effects of this invention are as follows: This method uses n-butanol-methanol composite solvent extraction to separate colored impurities in the pentaerythritol production system. The n-butanol-methanol composite solvent has good extraction efficiency for organic impurities. The precipitated sodium formate and pentaerythritol are returned to the pentaerythritol system after horizontal screw separator separation. The solvent obtained after distillation of the filtrate is returned to the pentaerythritol production system, effectively reducing the accumulation of colored impurities in the system. The impurities obtained from distillation are treated as waste liquid. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings.

[0015] like Figure 1 As shown, a method for separating colored impurities in a pentaerythritol production system includes the following steps:

[0016] 1) After cooling the pentaerythritol mother liquor to 35 degrees Celsius using a heat exchanger, add it to the extraction mixing vessel and mix it with the n-butanol-methanol composite solvent at a mass ratio of 1:0.5, with a mixing temperature of 30-60 degrees Celsius; the n-butanol-methanol composite solvent is a composite solvent obtained by mixing methanol and n-butanol at a volume ratio of 7:3.

[0017] 2) After mixing, sodium formate and pentaerythritol precipitate out of the pentaerythritol mother liquor, and colored impurities are extracted into the composite solvent. The mixture is then separated by a horizontal screw centrifuge to obtain filter cake and filtrate.

[0018] 3) The filter cake enters the 90 pentaerythritol production system to produce pentaerythritol and sodium formate products;

[0019] 4) The solvent obtained by distilling the filtrate at 130℃ is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by distillation are treated as waste liquid.

[0020] After removing colored impurities, the 90-grade pentaerythritol crystals are easier to separate, and the color of the 90-grade pentaerythritol decreases from 150 to 100 (platinum-cobalt color), which is conducive to further improving the purity of the 90-grade pentaerythritol. The purity of the 90-grade pentaerythritol can reach more than 96%.

[0021] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for separating colored impurities in a pentaerythritol production system, characterized by It comprises the following steps: 1) After the pentaerythritol mother liquor is cooled to 35 degrees by a heat exchanger, it is mixed with n-butanol-methanol complex solvent in a mass ratio of 1:0.5 in a mixing kettle, and the mixing temperature is 30-60℃; 2) After mixing, sodium formate and pentaerythritol in the pentaerythritol mother liquor are precipitated, and colored impurities are extracted into the complex solvent, which is separated by a horizontal screw centrifuge to obtain a filter cake and a filtrate; 3) The filter cake enters a 90 pentaerythritol production system to produce pentaerythritol and sodium formate products; 4) The solvent obtained by rectifying the filtrate at 130℃ is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by rectification are treated as waste liquid; The n-butanol-methanol complex solvent is a complex solvent obtained by mixing methanol and n-butanol in a volume ratio of 7:3.

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