Study On The Vapor Phase Synthesis Of 3,5-dimethylphenol From Acetone On A Solid Base Catalyst

Acetone as material of preparating 3,5-xylenol in gas-solid condensation is a reasonable routing.In this paper this complex reaction was studied by one and two stage fixed bed,analysed catalysts,conditions and mechanism of this routing which laid the groundwork for the route of industrialization.Based on ?-Al2O3 support,many solid base catalysts are prepared by equivalent-volumetic impregnation methods in this thesis.These catalysts were tested for reaction of synthesis of 3,5-xylenol in vapor-phase condensation of acetone with one-stage fixed bed reactor,and catalytic performances had been investigated by CO2-TPD to analyze the base property of catalysts.The results show that 0.5wt%NiO-9wt%CaO/?-Al2O3 was found to be preferred for this reaction system.Finally explored the preferred reaction condition of fixed bed including reaction temperature,pressure of system,acetone flow velocity.Using two different catalysts for two reaction stages in the two-stage fixed bed to explore catalysts.The results show that 5wt%CaO/?-Al2O3 was found to be preferred for the upper section of reactor,7wt%CaO/?-Al2O3 was preferred for the under section of reactor.Finally detemined the optimal reaction condition of each stage.Thermodynamic analysis of vapor-phase condensation of acetone to 3,5-xylenol system has been carried out.The reaction process was divided into three systems according to the result and reaction mechanism in this paper:acetone aldol condensation,1,6-Michael addition reaction of acetone and mesityl,isophorone aromatization.By using Benson group contribution method,partial unknown parameters of thermodynamics were estimated,the enthalpy changes,Gibbs free energy changes and equilibrium constant of each reaction system were calculated in detail as a function of temperature.The results show that in the temperature investigated,three reactions are spontaneous and the process of making mesityl oxide into isophorone is exothermic reaction;the reaction of making acetone into mesityl oxide is virtually irreversible but isophorone into 3,5-xylenol is limited by thermodynamic equilibrium.