Method for cooling, crystallizing and separating 4-cyanopyridine by solvent

Abstract

The invention discloses a method for cooling, crystallizing and separating 4-cyanopyridine by a solvent. The method comprises the following steps: (1) performing decoloring treatment on a mixed cyanopyridine raw material containing 3-cyanopyridine and 4-cyanopyridine at high temperature; (2) dissolving the mixed cyanopyridine raw material after decoloring treatment into a preponderant solvent methanol in a crystallizer and preparing a supersaturated solution; and (3) cooling the supersaturated solution at a certain cooling rate to final temperature to separate out the 4-cyanopyridine, discharging the 4-cyanopyridine and mixed cyanopyridine mother liquid out of the crystallizer in a form of slurry, entering a filter, separating the 4-cyanopyridine and the mixed cyanopyridine mother liquid in the filter and drying to obtain a high-purity 4-cyanopyridine product. The method has the advantages of low energy consumption and low cost through cooling, crystallization and separation; furthermore, one-step crystallization is only needed after the raw materials are subjected to decoloring treatment, and the product purity can reach to 99.2 to 99.7 percent. By the method, the production costis low and the economic benefit is good; meanwhile, the problem about recycling of waste is solved.

Description

technical field [0001] The invention relates to a method for separating 4-cyanopyridine by solvent cooling and crystallization. Background technique [0002] Cyanopyridine is widely used in the production fields of pesticides and pesticide intermediates, pharmaceutical products and pharmaceutical intermediates, feed and its raw materials, and spices. The cyanopyridine mixture is mainly derived from the ammoxidative synthesis of alkylpyridines, and the mixture contains two isomers: 3-cyanopyridine and 4-cyanopyridine. Among them, the important use of 3-cyanopyridine is to prepare nicotinic acid or nicotinamide by hydrolysis, which can be used as a feed additive and nutritional additive, and can also be used as an intermediate to synthesize the derivative product chromium nicotinate. 4-cyanopyridine, as an important medicine and dye intermediate, is mainly used in the synthesis of anti-tuberculosis drug remifen. In order to obtain the required high-purity intermediate raw ma...

AI Technical Summary

Problems solved by technology

During the rectification and separation process of cyanopyridine mixture system, fumalonitrile is easy to polymerize. The polymer produced not only affects the change of material components in the rectification tower, but also easily blocks the rectification device. Equipment affects its normal operation, resulting in unsatisfactory separation effect of 4-cyanopyridine in industrial production, and high operating costs

Based on economic cost considerations, manufacturers usually treat 3 / 4-cyanopyridine homologous mixtures containing 4-cyanopyridine as waste, or directly incinerate them as chemical waste, resulting in a low recycling rate of cyanopyridine homologous mixtures. cause great waste and environmental pollution