Method for purifying dodecanedioic acid

Abstract

The invention discloses a method for purifying dodecanedioic acid, which comprises the following steps of: carrying out demulsification, filtration and decoloration on stop fermentation liquor of dibasic acid and adding pure water to dilute; adding purified water into a crystallization kettle, pumping diluted fermented clear liquid into a crystallizer, simultaneously filling dilute sulphuric acid with the mass concentration of 30 percent into a discharge hole of an external circulating pump and adding the dilute sulphuric acid into the crystallizer, and controlling the PH of reaction materials; ensuring crystal mush to flow to the lower part of a crystallization chamber through a central downcomer and then flow upwards, so that crystals with large granularities are enriched on the bottom layer of the crystallization chamber; and cooling the crystals outflowing from a discharge hole of the crystallizer by a cooler and carrying out filter pressing, washing and drying to obtain the dodecanedioic acid. Due to the adoption of the purifying method, the micro mixing effect is achieved by diluting local concentration of the reaction mass through the material circulating pump, the solution nucleation rate, the crystal growth rate and the aggregation rate are reduced, the moisture percentage and the impurity content of a filter cake are obviously reduced, the dried dibasic acid product has large and uniform particles, good glossy and high purify, and the continuity of the crystallizing process is realized.

Description

technical field [0001] The invention relates to a purification method, in particular to a purification method of dodecanedioic acid. Background technique [0002] At present, the purification methods of long-chain dibasic acids mainly include solvent method and aqueous phase method. Among them, the use of the solvent method is greatly restricted due to large investment in operating equipment, high production costs, residual solvents in the product, environmental pollution and safety issues. Although the traditional aqueous phase method overcomes the defects of the solvent method, the resulting dibasic acid product has low purity, poor color, uneven crystal size, and high content of protein and other impurities. For example, CN95116450.3 discloses a method for treating α, ω dibasic acid fermentation broth, heating the terminated fermentation broth to remove unreacted alkanes, adding perlite, degerming by microfiltration, acidifying and crystallizing the filtrate, and drying ...

AI Technical Summary

Problems solved by technology

Among them, the use of the solvent method is greatly restricted due to large investment in operating equipment, high production costs, residual solvents in the product, environmental pollution and safety issues.

Although the traditional aqueous phase method overcomes the defects of the solvent method, the resulting dibasic acid product has low purity, poor color, uneven crystal size, and high content of protein and other impurities.

For example, CN95116450.3 discloses a method for treating α, ω dibasic acid fermentation broth, heating the terminated fermentation broth to remove unreacted alkanes, adding perlite, degerming by microfiltration, acidifying and crystallizing the filtrate, and drying Obtain dibasic acid, because this method does not carry out decolorization, product purity is low, and color and luster is poor

CN1219530A proposes a double-salt salting-out method for refining dibasic acid, which is cumbersome to operate and difficult to recover the salt

[0003] The dibasic acid crystallization process is a reaction crystallization process, the chemical reaction rate is very fast, and the induction period is extremely short. The crystallization process cannot achieve sufficient micro-mixing by adding concentrated sulfuric acid for acidification crystallization. The chemical reaction rate in the entire reactor is different, resulting in localized If the supersaturation is too high, the nucleation rate and growth rate in the entire reaction crystallizer are not uniform, which eventually leads to the internal inclusion of impurities or solvents during the crystallization and agglomeration, and the rough surface of the agglomeration absorbs more impurities. The impurities contained in the interior and adsorbed on the surface are generally not easy to remove by washing, and the particle size distribution of the product has adverse consequences such as multi-peaks and inconsistent crystal forms. High moisture content of acid filter cake; dibasic acid crystal particle size is small and uneven

The three interact with each other, the more uneven the particle size distribution, the more mother liquor contained in the crystal product, resulting in high moisture content of the filter cake, which will directly lead to slow washing and filtration, high impurity content of the dried product, and low purity of the product , poor color, uneven crystal size, high content of protein and other impurities, which seriously affect the development of downstream technologies