A method for purifying C4-C6 dibasic acid monomers from adipic acid by-product mixed dibasic acids

Abstract

The invention discloses a method for purifying C4 to C6 dibasic acid monomers from an adipic acid byproduct mixed dibasic acid. The method disclosed by the invention comprises the following steps: firstly, carrying out esterification reaction on the adipic acid byproduct mixed dibasic acid and methanol at pre-set temperature in the presence of a catalyst; distilling and separating out mixed dibasic acid dimethyl ester; rectifying to obtain dimethyl succinate, dimethyl glutarate and dimethyl adipate; carrying out hydrolysis reaction on the dimethyl monomers in a rectifying reactor in the presence of a hydrolysis catalyst by two sections; at the first section of the reaction, controlling the conversion ratio of a hydrolysis ester group to be 80 percent to 95 percent and directly utilizing tower top methanol to esterify; at the second section of the reaction, controlling the conversion ratio of the hydrolysis ester group to 99.9 percent or more and directly utilizing a mixture of the tower top methanol and water to hydrolyze raw materials. According to the method disclosed by the invention, the conversion ratio of the ester group and the reaction efficiency are improved; no waste liquid is generated in a hydrolysis process so that the method is a green and environment-friendly production process.

Description

technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a method for purifying C4-C6 dibasic acid monomers from adipic acid by-product mixed dibasic acids. Background technique [0002] With the continuous development of polyurethane and nylon industries, the production capacity and product quality of adipic acid as the main raw material have been greatly improved. A certain amount of C is by-produced in the industrial production process of adipic acid 4～6 The output of mixed dibasic acid (also known as nylon acid, DBA for short) is about 3% to 5% of that of adipic acid. Due to different manufacturers and batches of products, the composition of DBA and the purity of products are also different. Generally, C 4～6 The total dibasic acid content in the mixed dibasic acid is 95%-97%, of which succinic acid (C4) accounts for 20-30wt%, glutaric acid (C5) accounts for 50-65wt%, adipic acid (C6) accounts for 10% ~20wt%, and copp...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that succinic acid and adipic acid still have a certain solubility at 15-20°C, resulting in a low yield, and this method needs to consume a large amount of magnesium oxide and sulfuric acid, and the composite solvent used for extraction is in use. there will be losses

In addition, this process requires a large amount of catalyst, and the catalyst needs to be regenerated every time the raw material is replaced. The process is complicated, the catalyst is easily broken, and the hydrolysis reaction is incomplete, which limits the commercial application of this process.

[0012] In summary, the existing patent literature and journal literature report the method of using physical methods to purify the C4-C6 dibasic acids in the by-product mixed dibasic acids of adipic acid, which has the problems of poor product quality and low yield; In the process of esterification and hydrolysis by chemical methods, the solid catalyst used for esterification is easy to block pores and deactivate, the amount of resin catalyst used for hydrolysis is large, the hydrolysis is not complete, the product purity and yield are low, the single-pot reaction efficiency is low, and the reaction time is too long Long-term problems, high operating costs for separation and purification

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