Extraction And Separation Of M/P-cresol Isomer And Study Of Mechanism

Cresol has three isomers:o-,m-,and p-cressol,all of which were important organic chemical raw materials.O-cresol can be separated by rectification,and m/p-cresol will form an azeotrope because the difference in boiling point of m/p-cresol was less than 1~oC,and the existing separation methods were difficult to separate efficiently.Extraction was a green and efficient separation method,which has many applications in the separation of phenolic compounds.Based on this,this topic established a method for extraction and separation of m/p-cresol isomers,and studied the mechanism of extraction and separation,and screened out suitable extractants.The main research contents and results were as follows:(1)Based on the oxalic acid/urea complex separation of m/p-cresol in the previous literature,this paper investigated its used in extraction and separation,and studied the separation mechanism through quantum chemical calculations.The experimental results show that at 25~oC,the molar ratio of oxalic acid and cresol was 0.3:1,oxalic acid can extract and separate m/p-cresol from n-hexane solution,and the purity of p-cresol was 98.0%.Urea can extract m-cresol enriched in the supernatant,the purity was 99.0%.Quantum chemical studies have shown that the hydrogen bond energy and interaction energy between oxalic acid and cresol were greater than the solvent free energy of cresol in n-hexane solvent,and due to the strong repulsion between m-cresol and oxalic acid,the interaction energy between cresol and oxalic acid was much smaller than that between p-cresol and oxalic acid,which was why oxalic acid can selectively extract p-cresol.(2)Based on the understanding of the extraction and separation mechanism,the extractant and its matching solvent were screened out,and the effect of factors such as addition amount,time and temperature were investigated,and the optimal conditions and separation mechanism were determined.By calculating the hydrogen bond energy and interaction energy between the extractant and m/p-cresol,and comparing it with the solvent free energy of m/p-cresol in the solvent,the selective separation in toluene solvent was screened out.The 4-pyridinecarboxamide of m/p-cresol can finally obtain p-cresol with a purity of 95.2%,and the importance of hydrogen bonding for extraction and separation is proposed to further verified the mechanism of extraction and separation.