Process for biphenyl purification by rectification-emulsification crystallization method

Abstract

The present invention relates to a technology for purifying biphenyl by means of distillation-emulsion crystallization comprising: (1) distillation pretreatment: the solution containing rich biphenyl is get by distilling the raw material in a distillation device with a theoretical plate number of 30-60 and a column pressure of 20-60KPa; (2) emulsion and crystallization: emulsifying the rich biphenyl solution with water (the weight ratio of biphenyl solution and water is between 1:20 and 1:4) and 0.02-4wt% of emulsifier in an emulsator for 10-90 minutes at 60-100 DEG C with an emulsion pH value of 4-12, then cooling the emulsion to 5-20 DEG C; (3) separation and drying: preparing the biphenyl products after separation, washing and drying. The technology of the invention has advantages of strong adaptability to raw materials, convenient operation, simple device, mild technology condition and high product purity. At the same time the costs of material and energy consumption are greatly reduced by using water as solvent with little dosage of emulsifier and auxiliary agent, which is also useful for environmental protection.

Description

technical field

[0001] The invention belongs to the field of coal fine chemical industry, and relates to a method for purifying biphenyl, in particular to a method for extracting high-purity biphenyl from coal tar. Background technique

[0002] Biphenyl is an important organic chemical raw material, and its value is constantly being discovered and utilized. Biphenyl derivatives synthesized with biphenyl molecules as the skeleton can be widely used in medicine, pesticides, polymer liquid crystals, pigments, emulsifiers, fluorescence Brighteners, fabric dyes and other fields. Natural biphenyl is mainly contained in coal tar, and its mass fraction is about 0.2-0.4%. After coal tar is processed, most of the biphenyl contained in it is enriched in the oil washing fraction, and the enriched fraction contains biphenyl. Benzene varies from 7 to 10%. At present, the methods for extracting high-purity biphenyl from coal tar at home and abroad are mainly azeotropic distillation and h...