Method for separation and purification of p-cresol

Abstract

The invention discloses a method for separation and purification of p-cresol. The method comprises the following steps: 1) complexation: adding toluene and a complexing agent of oxalic acid into a reaction kettle, heating, adding mixed cresol, insulating for reaction, and filtering to obtain a cresol- oxalic acid complex crude product; 2) purification: adding the p-cresol-oxalic acid complex crude product into a purification solvent, stirring and filtering to obtain a p-cresol-oxalic acid complex; 3) decomplexation: adding the p-cresol-oxalate complex into water, insulating for reaction, separating an upper organic phase while hot, extracting the lower aqueous phase by toluene, and merging the extraction liquid into the upper organic phase; and 4) distillation: distilling the upper organic phase to remove solvent so as to obtain p-cresol. Compared with the prior art, a purification step is added to ensure that the final isolated p-cresol has purity of no less than 99%; the amount of organic solvents is reduced, the complexation step employs water, and the organic solvent and water involved in the separation process can be used indiscriminately, thereby saving cost.

Description

technical field [0001] The invention relates to a method for separating industrial p-cresol and m-cresol mixture, in particular to a method for obtaining p-cresol by purifying the industrial p-cresol and m-cresol mixture by selective complexation separation method. Background technique [0002] Phenol and methanol carry out the methylation reaction of phenol under the action of a solid catalyst, and the product is mixed cresol, which mainly contains o-cresol, p-cresol and m-cresol, and a small amount of xylenol. The development of the chemical industry and the development of new products put forward higher requirements for the purity of p-cresol. O-cresol can be separated by rectification, and the residual mother liquor includes p-cresol, m-cresol and a small amount of xylenol. Because the difference between m / p-cresol boiling points at atmospheric pressure is less than 1.0°C, it is difficult to separate them by rectification. At present, the separation methods of m / p-cres...

AI Technical Summary

Problems solved by technology

[0004] 1) The content of p-cresol in mixed cresol is less, only 27.8wt%, and the use of oxalic acid method is limited, and the best effect cannot be brought into play;

[0005] 2) use volatile low-boiling solvents in the reaction process, such as cyclohexane, sherwood oil, thereby increasing the loss of solvent, and the proportion of solvent loss accounts for the largest proportion of process cost;

[0006] 3) The p-cresol-oxalic acid complex is directly decomplexed without purification, and the quality index of the obtained p-cresol is difficult to meet the requirements of relevant standards;

[0007] 4) Two different organic solvents are used in the complexation reaction and decomplexation process, and it is difficult to achieve effective separation between the solvents, thus increasing the complexity of the actual operation