Separation And Purification Of Phenolic Compounds From Medium And Low Temperature Coal Tar In Northern Shaanxi Province

There exist abundant coal deposits in the northern region of Shaanxi Province, and the mining and processing of these resources are accompanied by the generation of considerable amounts of medium and low temperature coal tar. For a long term, the medium and low temperature coal tar is either sold without further processing, at a low price off course, or burn as a fuel,which results in severe pollution. The medium-and low-boiling coal tar is rich in phenolic compounds, a class of important raw materials in chemical industry. They, as fine chemicals of high added value, have found extensive applications in areas such as synthetic fibre, engineering plastics, pesticides, pharmaceuticals, explosives, plasticizers, preservatives, perfumes and dye intermediates, etc. The syntheses of these phenolics cost a lot,both economically and environmentally. As a result, research into the extraction of phenols from medium and low temperature coal tar has quite important economical and social benefits.In the present work, data concerning the physical properties of some typical samples from Northern Shaanxi were acquired, and by analysis, specific research was targeted. Soda-washing process is improved, the effictiveness of extraction can reach up to 98%. GC-MS analyses were performed on the extracted phenolic compounds, and its composition was determined.Refining process of raw phenols is also improved. Meanwhile high-content raw phenols are obtained. Multi-tower sequential fractional distillation was studied and corresponding experimental parameters were acquired. Computer modelling was performed, and factors concerning equipment investment and energy consumption were considered. Optimum process and parametres were acquired. Pure compounds such as phenol and o-methyl phenol can be isolated and fairly enriched fractions of mixed phenols are also obtained. Research into optimum separation of mixtures of m- and p-methyl phenols were done. Such methods as urine-complexation, oxalic acid-complexation and recrystallization can be employed to obtain m-methylphenol, p-methylphenol,2,6-dimethylphenol and 2-ethylphenol. Fusion crystallization of dimethyl-substituted phenols was studied, and by using the optimum separation process,2,4-dimethylphenol and 2,5-dimethylphenol were isolated respectively. As a conclusion, a process of isolation and purification of raw phenols of medium and low temperature coal tar is obtained and eight phenolic compounds are obtained as well.