Method and device for preparing high-purity pyridine series products from crude pyridine by refining

Abstract

The invention discloses a method for preparing high-purity pyridine series products from crude pyridine by refining. The method comprises following steps: (1), drying: a crude pyridine raw material and an entrainer are mixed and preheated to enter a drying tower for azeotropic distillation, water phase and the entrainer are obtained at the top of the drying tower, the entrainer is recycled or extracted for standby application, and a crude pyridine material is obtained at the bottom of the drying tower; (2), heavy component removal: the crude pyridine material obtained in step (1) enters an evaporation kettle and is subjected to the heavy component removal treatment, part of gas phase at the top of the evaporation kettle returns to the drying tower, and the other part enters a pre-fractionation tower and is subjected to light and heavy material fractionation; (3), distillation of the pyridine series products. The pyridine series products with high added value are separated out with adoption of azeotropic distillation, atmospheric and vacuum distillation and heat integration technologies, purity of pyridine, o-methylpyridine, methylpyridine, dimethyl pyridine and trimethyl pyridine reaches 96wt% or higher, and one energy-saving and high-efficiency technical method for preparing the high-purity pyridine series products from crude pyridine by refining is obtained.

Description

technical field [0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a method and a device for refining high-purity pyridine series products from crude pyridine. Background technique [0002] Coal tar is a very valuable chemical raw material, and medium and low temperature coal tar contains a certain amount of crude pyridine and crude phenolic raw materials, such as pyridine, o-picoline, lutidine, collidine and other crude pyridine compounds and Crude phenolic compounds such as phenol, o-cresol, m-cresol, p-cresol, xylenol, ethylphenol, tricresol, etc. Although the content of these compounds is not very high, they are all high value-added fine chemical products, and synthetic Such substances need to pay higher environmental costs or economic costs. [0003] Current research mainly focuses on the simple separation of phenolic compounds or the simultaneous separation of phenolic compounds and pyridine compounds. For examp...

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Problems solved by technology

[0003] Current research mainly focuses on the simple separation of phenolic compounds or the simultaneous separation of phenolic compounds and pyridine compounds. For example, the domestic patent CN102731264 discloses a continuous distillation to obtain two high-purity phenolic products and one high-content mixed phenolic product. A method for separating crude phenols from medium and low temperature coal tar, and CN107721826 further discloses a method and device for separating various phenols from crude phenols from medium and low temperature coal tar. The crude phenol products are mainly obtained through a pretreatment system, and the crude phenol products are then processed through continuous Four kinds of high-purity phenol series products are obtained by the rectification system; and the domestic patent CN104893750 discloses a method for extracting pyridine compounds from coal tar. Phenolic compounds and dephenolized oil, and then use solvent extraction to extract all the crude pyridine compounds in the phenolic compounds and dephenolized oil, and finally obtain pyridine compounds through dehydration, slag removal and rectification; although there are many studies, but There is no specific method on how to refine high-purity pyridine series products from pyridine compounds. Therefore, it is of great significance to separate and refine high-purity pyridine series products from medium and low temperature coal tar crude pyridine

[0004] The existing process of producing pyridine from coal tar has the disadvantage of not being able to remove trace moisture, but the existence of trace moisture will greatly affect product quality

In addition, coal tar crude pyridine raw materials generally contain residues with a mass percentage of about 3%. In addition to high boiling point components (boiling point more than 225 ° C), it also contains Na2SO4, Na2CO3 and other inorganic salts. If it is not removed first, it will be directly used If the continuous tower is used, the packing and reboiler will inevitably be blocked, and the production process cannot be carried out smoothly.

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