Method for purifying acetyl citrate

Abstract

A method for purifying the acetyl citrate relates to the purification technique and comprises the following steps: (1) the citrate reacts with an excessive amount of acetic anhydrides and then is preliminarily dehydrated in a reaction vessel on the vacuum condition after being deacidified, neutralized and washed so as to obtain the crude products of the acetyl citrates; (2) the crude products are subject to the secondary treatment utilizing a film evaporator, the vacuum degree is controlled to range from 100Pa to 13300Pa and the flow of the film evaporator ranges from 2kg / m<2> h to 200kg / m<2> h; the film evaporator and the preheater are heated by the steam or heat conduction oil; when the steam is used for heating, the heating steam pressure of the preheater is controlled to range from 0.5kgf / cm<2> to 1.5kgf / cm<2> and the steam pressure of the evaporator ranges from 2.0 to 5.0kgf / cm<2>; when the heat conduction oil is used for heating, the temperature of the heat conduction oil ranges from 100 to 140 DEG C. The method is very effective for reducing the purities in the acetyl tri-n-butyl citrate and lowering the water and acid value so as to enhance the quality purity of the acetyl citrate.

Description

technical field [0001] The invention belongs to the separation and purification technology of the chemical industry, in particular to a method for purifying acetyl citrate by using a thin film evaporator. Background technique [0002] As plasticizers, citric acid esters mainly include triethyl citrate (TEC), tributyl citrate (TBC), tri-n-hexyl citrate (THC) and triisooctyl citrate (TOC). The acylated citrate has better performance as a plasticizer. Citrate and acetyl citrate are green, recyclable, non-toxic and environmentally friendly non-toxic and environmentally friendly plasticizers. And other advantages, has partially replaced petroleum plasticizers. [0003] Acetyl tributyl citrate is the most commonly used of all citrates and the most produced variety. The traditional manufacturing method of acetyl tributyl citrate (ATBC) is to react with tributyl citrate (TBC) and acetic anhydride, after deacidification, neutralization, washing with water and then put in a sealed ...

AI Technical Summary

Problems solved by technology

The products prepared by this method generally contain a small amount of low-boiling substances such as acetic acid, butanol and butyl acetate in addition to high-boiling impurities such as tributyl citrate (TBC) and tributyl propylene tricarboxylate. , not only reduces the content of the main component, but also makes the smell of the finished ATBC finished product heavier, especially in the process of PVC processing, the smell becomes significantly larger, which affects the workshop environment; and when such low boiling substances enter PVC products Not only can it not play the role of plasticizer, but it is easy to escape from the product, aggravating the oil leakage of the product, and affecting the quality of the produced PVC product

[0004] In order to improve the quality of the obtained acetyl tributyl citrate, generally speaking, the method of increasing neutralization and washing times in the neutralization and water washing section after acylation can be adopted to remove acetic acid, Low boiling substances such as butyl acetate and butanol, but this will increase the loss of acetyl tributyl citrate, reduce production and increase costs, and will increase the generation of waste water and cause environmental protection treatment pressure, so this method Not suitable for large-scale industrial production

If a high vacuum degree is maintained during the dehydration process, the temperature is increased and the time is prolonged, low boiling substances such as acetic acid, butyl acetate and butanol can also be removed, but since citrate is a heat-sensitive compound, if the temperature is too high and the time is too long If it is long, it will lead to the deepening of the color of the finished product, promote the decomposition of acetyl tributyl citrate, and generate acetic acid and tributyl propylene tricarboxylate. Sometimes it will increase the acid value of the finished product, and the so-called acid return phenomenon will occur. In the production process of butyl ester, the process is difficult to control, so this method is not conducive to large-scale industrial production

[0005] In the production of high-purity acetyl triethyl citrate, acetyl tri-n-hexyl citrate, acetyl tri-isooctyl citrate or alcohols with different carbon numbers and In the production process of acetylated mixed esters produced by citric acid reaction, there are also similar problems such as excessive impurities, high acid value, difficult process control, and unfavorable for large-scale production.

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