Study On The Mechanism Of Guaiacol Derivative-Ca²⁺ Coordination Reaction And Its Application In Extracting High Purity Phenols

In this research,the mechanism and application of coordination reaction between guaiacol derivatives and Ca2+under alkaline conditions were studied.The mechanism of coordination reaction between 4-methylguaiacol,4-ethylguaiacol and eugenol and Ca(OH)2 was studied.Based on this mechanism,a new purification method of guaiacol derivatives was developed.The coordination mechanism of phenol-calcium was studied by various characterization methods,including in-situ FTIR,thermogravimetric analysis,elemental analysis,ICP-OES,GC/MS,GC/FID and NMR spectrum.In the course of studying the mechanism of the coordination reaction between Ca2+and MMP,it was found that the coordination reaction between Ca2+and MMP experienced three stages.When excessive 4-methylguaiacol(MMP)was slowly dropped into Ca(OH)2 saturated solution,three consecutive different reaction stages were found.The first stage is the neutralization reaction between acid and alkali to form the intermediate calcium phenolate,whose chemical formula is Ca(OH)(MMPo).In the second stage,Ca(OH)(MMPo)reacts with MMP to form intermediate Ca(MMPO)[MMPo].At the third stage of the reaction,the two MMP molecules further coordinate with Ca(MMPO)[MMPo]on the hydrogen atoms at positions 3 and 6 of the benzene ring to form the final product Ca(MMPo)[MMPo][MMPH]2.Based on the study of MMP,it was proved that the coordination reaction between Ca2+with 4-ethylguaiacol(EMP)and eugenol(EUG)were also carried out in three stages.In addition,the proportion of HA,HB and He in the total integration of the three hydrogen atoms was discussed by using the VT-NMR technique,while the coordination position was further determined.It was confirmed that the coordination site of the third stage was located on the hydrogen atom of the benzene ring.In addition,the mechanism of coordination reaction between eugenol and Ca2+was also studied,which was the same as that of MMP and EMP.Finally,the product Ca(EGO)[EGO][EGH]2 with coordination number 4 was formed.Thermogravimetric analysis showed that the complexes of the three guaiacol derivatives decomposed at about 200℃.Combined with the results of GC/MS,it was found that the liquid product of thermal decomposition was high purity phenolic(corresponding to guaiacol derivative in the complex).Based on this phenomenon,a new purification method of phenolic compounds was developed,which was called complex extraction method.The method has the advantages of simple operation,low energy consumption and high purity of pure product.Using 4-methylguaiacol,4ethylguaiacol and eugenol as model compounds,the purity of purified product was increased to more than 99%.Furthermore,by discussing the influence of temperature and light on the product,the extraction method was modified to avoid light and reduce temperature.Finally,the purity of 4-Ethylguaiacol was improved to 99.6%.In order to further expand the application scope of the combined extraction method,we mixed EMP with ethanol and phenol,and discussed the extraction effect of the combined extraction method in three component mixed system of EMP/phenol/ethanol.The results showed that the purity of EMP was still more than 99.62%when 80%(n/n,the content of EMP in total phenols)of EMP/phenol mixture was extracted with Ca2+.Then the purity of EMP in three component system of EMP/phenol/ethanol was always more than 99.5%,which proved that the combined extraction method had great extraction effect in this system.