The Study On The Extraction Of Phenol Oil And The Separation Of M-cresol And P-cresol

At present,the domestic coal chemical enterprises is in the construction and development stage.The low-temperature tar oil,which is from a by-product of coking industry,will be more in the next years,the mass concentration of phenolic compounds is about from 20% to 35%.Industrial separation of phenolic compounds is alkaline elution method,but this approach has some flaws.For example,the process will consume large amounts of acid and alkali,the cost is higher,and the acid and alkali corrosion of equipment needs certain investment for equipment maintenance protection,the pollution is very serious.Every one ton crude phenol oil was extracted,there will be about three tons waste water containing phenol.A lot of waste water containing phenol is difficult to dispose in a short time because that phenols is mutually soluble with water.Pickling reduction process of phenolic compounds will produce a by-product of sodium sulfate,with a pungent stench of smell,which is difficult to find an outlet in the market.Therefore,this article will adopt the method of double-solvent extraction in the extraction and separation of phenol oil phenolic compounds.Every phenolic components,contained in the extracted crude phenol oil,must be separated to achieve the maximization of its value.Being big different from other components on the boiling point,phenol and o-cresol can be separated by traditional distillation method.The boiling point difference of m-cresol and p-cresol is too small,not suitable for distillation separation methods,and other separation methods are also to be optimized,such as alkylation catalyst used in separation is constantly being optimized.In this paper,we will adopt the method of crystallization for separation and purification.This article will start from the following aspects:(1)To avoid the use of acid and alkali,double solvent extraction method is adopted in this project to the extraction and separation of phenol compounds.The effects of different solvents,the amount of solvents,the number of back-extraction,etc,are studied.In addition,theremoving effect of neutral oil and alkaline substance is also discussed.The results showed that the double-solvent extraction method can improve the mass concentration of phenol to more than 99%,reduce natural oil content to 0.5% below,alkanline substance content to about 0.5% while sulfolane as polar solvents and n-octane as non-polar solvents.(2)Accessory ingredient A crystallization is used to the separation of m-cresol.The effects of dosage of accessory ingredient A,the type of solvents,the terminal temperature of crystallization,etc,are studied.Later,accessory ingredient A crystallization in constant temperature is used to separate m-cresol.The results showed that isothermal crystallization separation m-cresol have more advantages,simple operation and low energy consumption,which can make the material containing 70% m-cresol to reach more than 95%,the yield is over 60%.(3)Accessory ingredient B crystallization is used to the separation of p-cresol.The effects of dosage of solvents,the terminal temperature of crystallization,the reaction time,cooling rate,etc,are studied.The results show that when using the optimized separation conditions of 1h reaction time,crystallization terminal temperature 4? and 3 times dosage of solvent as the quality of a raw material,the p-cresol content in raw materies can be enhanced from 42.5% to above 95% after purification,and the yield can reach over 78%.