Method for separating and purifying m-cresol and p-cresol through complexation crystallization

Abstract

The invention relates to a method for separating and purifying m-cresol and p-cresol by a complex crystallization method; first, triethylenediamine is used as a complexing agent to obtain high-purity p-cresol through complex crystallization, and then the filtrate in this operation is As a reactant, sodium acetate is used as a complexing agent to purify m-cresol through complex crystallization. In order to improve the overall yield, the filtrate in the sodium acetate method is recycled back to the first step as a reactant to continue to use. The method can simultaneously obtain m-cresol and p-cresol products with a purity of more than 99.5%, and recycles the filtrate after rectification to maximize the use of raw materials, so that the overall yield of the process can reach more than 99%. The organic solvents and complexing agents used in the reaction process can be recycled in the process, without the discharge of "three wastes", achieving the goal of environmental protection. In addition, compared with the prior art, the complexing agent selected in the present invention requires milder temperature conditions for reaction and cooling crystallization, which greatly reduces energy consumption.

Description

technical field [0001] The invention belongs to the field of separation and purification of chemical industry. More specifically, it relates to the method of separating and purifying m / p-cresol mixture by complex crystallization, thereby obtaining high-purity m-cresol and p-cresol products simultaneously. Background technique [0002] Both high-purity m-cresol and p-cresol are important fine chemical intermediates, so the separation of m / p-cresol has been a hot topic in the chemical industry for a long time. m-cresol is an important raw material for the production of pesticides, antioxidants, fragrances, phenolic resins, vitamin E, dyes, fluorescent whitening agents, solvents, plasticizers and flame retardants. Since the downstream products produced using m-cresol as raw material have broad development prospects, the demand for m-cresol in my country maintains a high-speed growth at an annual growth rate of 8-10%. And p-cresol is widely used in the synthesis of drugs, herb...

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Problems solved by technology

Among them, the selection and preparation of high-efficiency adsorbents in the adsorption separation method are difficult, the adsorption capacity is limited and a large amount of desorbent is required; the extraction method needs to use a large amount of organic solvents, which is easy to pollute the environment; the high-pressure crystallization method and recrystallization method will produce harmful The problem of high equipment requirements or the use of a large amount of organic solvents; the technical process of the membrane permeation method is not mature enough to be applied to large-scale industrial production; although the alkylation method can achieve high-purity separation of m / p-cresol, it is also There are disadvantages of complicated process, expensive equipment and operating costs; while the complex crystallization method has the advantages of high product purity, easy operation, green environmental protection, etc., and has high research and application prospects in the field of separation / p-cresol

[0004] Currently published techniques for separating m / p-cresol mixtures by complex crystallization, such as "Jiangsu Chemical Industry", 1997, 05, 21; "Modern Chemical Industry", Volume 17, No. 6, 28; JP2010059137 etc. mainly focus on the purification of p-cresol by piperazine method and m-cresol by urea method, not only rarely involves the exploration of new complexing agents, but also can only obtain a single product, resulting in waste of raw materials, which is not economical and environmental protection

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