The Synthesis Of 2,3,5-Trimethylbenzoquinone From 1,2,4-trimethylbenzene

In industry,2,3,5-trimethylbenzoquinone（TMBQ）,an important intermediate of vitamin E（VE）,is prepared by using expensive 2,3,6-trimethylphenol（TMP）as raw material.The purpose of this article is to seek a kind of high efficiency catalyst for one-step catalytic oxidation of cheaper pseudocumene（TMB）to TMBQ,which can reduce the production cost of VE.Catalytic oxidation activities and technological conditions of kinds of catalyst with TMB as material were studied.Based on catalytic oxidation of a series of modified Al₂O₃,industrial packingγ-Al₂O₃ calcined at high temperature was modified with Ce by the ultrasonic assisted impregnation technique,which was used for catalytic oxidation of TMB.Influences of adding amount of modifier,heating rate,calcination temperature and time of catalyst were studied.TMB conversion of 31.1%,TMBQ yield of 13.1%,selectivity of 42.1%were attained under the optimized conditions.TMBQ selectivity was 40.3%and 37.7%,for industrial packingγ-Al₂O₃ modified with 5wt%A-151 and 25wt%respectively,however,TMB conversion was relative lower.Two modification methods mentioned above had little influence on the macro-morphology of Al₂O₃.The largerdiameter and lower surface area were found,which may be beneficial for the increase of the selectivity.Organic metal-containing compounds,such as organophosphates,metal-organic frameworks and metal phthalocyanines,were applied to the catalytic oxidation of TMB using glacial acetic acid as solvent.These catalysts exhibited poor performance with the structure destroyed.When taking Re（IV）compound as the catalyst,the selectivity of TMBQ reached 49.8%,poor stability of catalyst was also displayed.The results showed that same kinds of Al₂O₃ had relatively good selectivity with smaller specific surface area of catalyst.Al₂O₃ of other crystal phases can catalyze and oxidize TMB,in addition toγ-Al₂O₃ crystal phase.And catalytic effect was not only about crystal phase,but it was about the extent of crystallization and surface area.Influences of adding amount of Al,heating rate,calcination temperature and time of Al-MCM-41 were studied,TMB conversion of 31.1%,selectivity of 35.3%were attained by Al-MCM-41 with a few macropore and massive micropores under the optimized conditions.This article provides directions for research on catalysts for catalytic oxidation of TMB to TMBQ.In future researches,moderate aluminium-based catalysts with the presence of glacial acetic acid,such as modified alumina and aluminium-based zeolite,should be research objects.