Method for separation and purification of monomethylamine-dimethylamine mixture in methylamine synthesis system

Abstract

The invention relates to a method for separation and purification of monomethylamine and dimethylamine in a methylamine synthesis system. According to the invention, a mixed raw material of monomethylamine and dimethylamine passing through a dehydration tower is fed from the central part of a main separation tower; light and heavy components are separated in a main separation tower; monomethylamine is distilled off from the top of the main separation tower and flows into a monomethylamine product tank for storage via an output pipeline; the heavy components consisting of water, methanol and a mixture of ethylmethylamine and ethylamine flow into a raffinate tank from the bottom of the main separation tower; dimethylamine gas carrying heavy components flows into a side column only having a rectifying section via a connecting pipeline; in the side column, dimethylamine migrates to the top of the side column, and the carried heavy components return to the main separation tower after mass transfer separation and are then discharged from the bottom of the main separation tower; and a dimethylamine product is obtained from the top of the side column. The method provided by the invention can reduce the content of water in the dimethylamine product and improve the purity of the dimethylamine product without increasing the steam consumption of the product, and has the advantages of low investment cost for equipment, low energy consumption and high economic benefits.

Description

technical field [0001] The invention relates to a separation and purification method for a mixture of monomethylamine and dimethylamine in a methylamine synthesis system, and belongs to the field of separation technology. Background technique [0002] Methylamine products include monomethylamine (MMA), dimethylamine (DMA) and trimethylamine (TMA). Methylamine is produced by the reaction of methanol and ammonia. Among the three methylamines, dimethylamine is used in the largest amount. Dimethylamine is mainly used as a raw material for the production of rubber vulcanization accelerators, leather depilatory agents, medicines, and pesticides. The biggest use of dimethylamine lies in the production of high-quality chemical fiber solvents and polyurethane solvents - N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC). The purity of the raw material dimethylamine has a great influence on the product quality and cost of the amide. The heavy component moisture and methylet...

AI Technical Summary

Problems solved by technology

Increase the discharge of the tower kettle, and discharge a large amount of dimethylamine products while draining the water. In the existing process, the discharged heavy components cannot be returned to the previous separation system, otherwise heavy components such as methylethylamine and ethylamine will be released. Accumulated in the system, these components enter the DMF synthesis system with dimethylamine, and other amide by-products will be generated. If they are discharged, more DMF products will be lost, and the problem will become more serious.

The second measure is to further purify by connecting a new tower in series, which not only requires an increase in equipment investment, but more importantly, it consumes steam and increases the energy consumption of the product

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