Method for preparing lactic acid n-propyl ester with low water content, low acidity and high purity

Abstract

The invention relates to a method for preparing lactic acid n-propyl ester with low water content, low acidity and high purity, which is an alcohol ester preparation method belonging to the field of synthesis of fine organic chemicals. The method comprises the following steps of: adding lactic acid, n-propyl alcohol, a water-carrying agent and an esterification catalyst in the mass ratio of 90:(30-300):(45-450):(0.1-50) into a reactor, and reflux-reacting for 0.5-24 h; in situ removing water and low-boiling acid in an azeotropic mixture which is a water-carrying agent in an external circulating water-separating device by using the reactivity of anhydrous magnesium sulfate, anhydrous sodium sulfate and anhydrous zinc sulfate or calcium oxide with water; and removing a little amount of lactic acid remained in reacted material through the salification between an organic amine mixture and the lactic acid remained in the reacted material, wherein the organic amine mixture comprises ethylamine, diethylamine, triethylamine, propylamine, dipropyl amine and tripropyl amine in the mass ratio of (0.001-5):(0.001-8):(0.003-6):(0.0001-7):(0.001-10):(0.003-3). After being treated by an activated 4A and / or 5A molecular sieve, the lactic acid n-propyl ester product has the ester content more than 98.5 percent, the water content less than 0.1 percent, and the acidity (represented by OH<->) less than 0.5.

Description

technical field [0001] A method for preparing high-purity n-propyl lactate with low water content and low acidity involved in the present invention is a method for the preparation of hydroxy acid esters in the field of fine organic synthesis, in particular, it involves a method using benzene and / or toluene and / or di Toluene and / or cyclohexane is the azeotropic water carrier, calcium oxide and / or anhydrous magnesium sulfate and / or anhydrous sodium sulfate and / or anhydrous zinc sulfate is the desiccant and deacidification for in-situ treatment of the water carrier 4A and / or 5A molecular sieves are used as dehydrating agents for ester products, and the process of preparing high-quality n-propyl lactate directly through in-situ dehydration and deacidification of azeotropic water-carrying agents. Background technique [0002] N-propyl lactate is a cheap chiral starting material, and also a non-toxic, biodegradable, good solubility, wide application range and easy recovery organic...

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Problems solved by technology

[0007] The invention of a method for preparing high-purity n-propyl lactate with low water content and low acidity is mainly to solve the problems of long reaction time, complicated post-treatment, low utilization rate of lactic acid, and lactic acid in existing n-propyl lactate preparation methods and processes. The yield of n-propyl lactate is not high, the content of free acid and moisture in the product is high, the purity of the product is difficult to meet the requirements, and it affects the application of n-propyl lactate products in other industrial fields.

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