Study On Separation Of M-cresol And P-cresol By Alkylation

P-cresol（PC）and m-cresol（MC）are important fine chemical intermediates,which are widely used in engineering plastics,medicine,spices,dyes and other fields,and their demand is increasing day by day.In the process of cresol production,PC and MC usually coexist at the same time,so the separation of these two substances is very important.However,the boiling points of PC and MC are 202.3℃and 203.0℃respectively,and the temperature difference is less than 1.0℃.In this paper,the extractive distillation method（diethanolamine as extractive distillation agent）is used to separate PC and MC cresol to verify the separation method proposed in the literature.The results show that the intermolecular forces of diethanolamine on PC and MC are similar,and the effect of relative volatility improvement is not obvious.Therefore,diethanolamine may not be used as an extractive distillation agent for separating PC and MC.In this paper,the idea of separating PC and MC by alkylation is used to synthesize attapulgite catalysts modified by different metal oxides.The catalytic performance of attapulgite catalysts is studied and characterized（1）Attapulgite catalysts modified with different metal oxides（Fe,Cu,Mo,W）were prepared by impregnation method with acid attapulgite（ATP）as support.It was found that the addition of metal oxides can increase the number of L-acid sites on the surface of ATP,and increase the total acid content of the catalyst,so as to effectively improve the catalytic effect of metal oxide supported ATP catalyst,and ATP loaded with WO₃ has the best effect.（2）The effects of different loading of MoO₃ and WO₃ on the alkylation of PC were investigated.The best catalytic effect was obtained when the loading of WO₃ was 16%.The conversion and selectivity of 2-tert-butyl-p-cresol reached 78.8%and 81.9%.The catalyst was characterized and analyzed.SEM characterization showed that w element was successfully loaded on ATP;XRD analysis showed that the pore structure of ATP did not change,indicating the successful preparation of ATP catalytic material loaded with WO₃;furthermore,NH₃-TPD characterization showed that WO₃ loading increased the total acid content,and with the increase of loading,the total acid range increased,and the reaction activity was improved;however,N₂-BET characterization showed that WO₃ loading increased the total acid content with the increase of loading It was the interaction of these two factors that makes the change of catalytic effect and loading amount from the increasement to the d ecreasement then.（3）The alkylation performance of MC with modified ATP supported on 14%MoO₃ and 16%WO₃ was investigated.It was found that the modified ATP supported on 16%WO₃ had better catalytic effect.The selectivity of mono alkylation product was 78.7%and the yield was 57.7%.The results showed that the conversion of PC and MC reached 74.4%and71.3%,respectively;the yield of 2-p-cresol was 59.2%,the selectivity was79.6%,the yield of 6-m-cresol was 54.6%,the selectivity was 76.5%.The repeatability test showed that the catalyst remained good catalytic activity after three times of continuous usaque.