Method for separating colored impurities in pentaerythritol production system

Abstract

The invention discloses a method for separating colored impurities in a pentaerythritol production system, which comprises the following steps: 1) cooling pentaerythritol mother liquor to 35 DEG C by using a heat exchanger, adding the pentaerythritol mother liquor into an extraction mixing kettle, and mixing the pentaerythritol mother liquor with an n-butanol-methanol composite solvent according to the mass ratio of 1: 0.5 at the mixing temperature of 30-60 DEG C; 2) after mixing, separating through a horizontal screw centrifuge to obtain a filter cake and filtrate; 3) feeding the filter cake into a 90 pentaerythritol production system for producing pentaerythritol and sodium formate products; and 4) returning a solvent obtained by rectifying the filtrate at 130 DEG C to a pentaerythritol production system, and performing waste liquid treatment on impurities obtained by rectifying. According to the method, colored impurities in a pentaerythritol production system are separated by adopting an n-butyl alcohol and methanol composite solvent extraction mode, separated sodium formate and pentaerythritol are subjected to horizontal screw separation and then returned to the pentaerythritol system, a solvent obtained after filtrate is rectified is returned to the pentaerythritol production system through a solvent recovery tank, and the pentaerythritol is obtained. And accumulation of colored impurities in the system is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of pentaerythritol production methods, and particularly relates to a method for separating colored impurities in a pentaerythritol production system. Background Art

[0002] In the production process of pentaerythritol, formaldehyde, acetaldehyde and sodium hydroxide are first used as raw materials for condensation reaction. After the reaction is completed, formic acid is used to neutralize the condensation liquid. The condensation liquid is then removed from the formaldehyde by a distillation tower and initially concentrated before entering an evaporator. After the evaporation concentration reaches a predetermined index, it enters a crystallization kettle for cooling and crystallization. After the crystallization liquid is centrifuged, the filter cake is dried to obtain monopentaerythritol. The crystallization mother liquor is filtered by sedimentation to separate dipentaerythritol. The sedimentation filtrate is evaporated and concentrated, and then crystallized and centrifuged to obtain pentaerythritol mother liquor and sodium formate.

[0003] However, during the production process, colored impurities in the production system are enriched in the pentaerythritol mother liquor, which increases the chromaticity and viscosity of the pentaerythritol mother liquor. Colored impurities contain polysaccharides and are easily soluble in water. The "sodium method" production process of pentaerythritol mainly uses the difference in solubility at different temperatures to separate and purify products. Colored impurities are not easy to separate from the pentaerythritol mother liquor. The continuous enrichment of colored impurities in the production system will affect the subsequent recovery of pentaerythritol crystals, resulting in poor crystal particles and increasing the difficulty of separating pentaerythritol from sodium formate. At the same time, the chromaticity of the crystal melting of the pentaerythritol product increases, resulting in poor product quality and affecting the application of the product.

[0004] Therefore, there is an urgent need in the prior art for a method for separating colored impurities in a pentaerythritol production system to effectively remove the difficult-to-separate colored impurities in the pentaerythritol mother liquor. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for separating colored impurities in a pentaerythritol production system so as to effectively remove the colored impurities that are difficult to separate in the pentaerythritol mother liquor.

[0006] The object of the present invention is achieved through the following technical scheme: A method for separating colored impurities in a pentaerythritol production system comprises the following steps: 1) Cool the pentaerythritol mother liquor to 35 degrees with a heat exchanger, add it into the extraction mixing kettle and mix it with the n-butanol methanol composite solvent in a mass ratio of 1:0.5, and the mixing temperature is 30-60°C; 2) After mixing, sodium formate and pentaerythritol in the pentaerythritol mother liquor are precipitated, and colored impurities are extracted into the composite solvent and separated by a horizontal screw centrifuge to obtain a filter cake and a filtrate; 3) The filter cake enters the 90 pentaerythritol production system to produce pentaerythritol and sodium formate products; 4) The solvent obtained by distillation of the filtrate at 130°C is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by distillation are treated as waste liquid.

[0007] The n-butanol-methanol composite solvent is a composite solvent obtained by mixing methanol and n-butanol in a volume ratio of 7:3.

[0008] The invention has the beneficial effects that: the method adopts the n-butanol-methanol composite solvent extraction mode to separate the colored impurities in the pentaerythritol production system; the n-butanol-methanol composite solvent has good organic impurity extraction efficiency; the precipitated sodium formate and pentaerythritol are returned to the pentaerythritol system after being separated by horizontal screw; the solvent obtained by distillation of the filtrate is returned to the pentaerythritol production system, the accumulation of colored impurities in the system is effectively reduced; the impurities obtained by distillation are used as waste liquid for waste liquid treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0010] The present invention is described in detail below in conjunction with the accompanying drawings.

[0011] like Figure 1 As shown, a method for separating colored impurities in a pentaerythritol production system comprises the following steps: 1) After the pentaerythritol mother liquor is cooled to 35 degrees by a heat exchanger, it is added into an extraction mixing kettle and mixed with a n-butanol-methanol composite solvent at a mass ratio of 1:0.5, and the mixing temperature is 30-60°C; the n-butanol-methanol composite solvent is a composite solvent obtained by mixing methanol and n-butanol at a volume ratio of 7:3; 2) After mixing, sodium formate and pentaerythritol in the pentaerythritol mother liquor are precipitated, and colored impurities are extracted into the composite solvent and separated by a horizontal screw centrifuge to obtain a filter cake and a filtrate; 3) The filter cake enters the 90 pentaerythritol production system to produce pentaerythritol and sodium formate products; 4) The solvent obtained by distilling the filtrate at 130°C is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by distillation are treated as waste liquid.

[0012] After the colored impurities are removed, the 90-grade pentaerythritol crystals are easier to separate, and the chromaticity of the 90-grade pentaerythritol is reduced 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%.

[0013] 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 separating colored impurities in a pentaerythritol production system, characterized in that The steps include: 1) Cool the pentaerythritol mother liquor to 35 degrees with a heat exchanger, add it into the extraction mixing kettle and mix it with the n-butanol methanol composite solvent in a mass ratio of 1:0.5, and the mixing temperature is 30-60°C; 2) After mixing, sodium formate and pentaerythritol in the pentaerythritol mother liquor are precipitated, and colored impurities are extracted into the composite solvent and separated by a horizontal screw centrifuge to obtain a filter cake and a filtrate; 3) The filter cake enters the 90 pentaerythritol production system to produce pentaerythritol and sodium formate products; 4) The solvent obtained by distillation of the filtrate at 130°C is returned to the pentaerythritol production system through a solvent recovery tank, and the impurities obtained by distillation are treated as waste liquid.

2. The method for separating colored impurities in a pentaerythritol production system according to claim 1, characterized in that: The n-butanol-methanol composite solvent is a composite solvent obtained by mixing methanol and n-butanol in a volume ratio of 7:3.

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