Basic Researches For Direct Hydration Of Dihydromyrcene

Dihydromyrcenol(DHMOL)is one of the most popular perfumes nowadays and is widely applied in soaps and detergents due to its powerful citrus and lime-like aroma and excellent stability.The direct hydration of dihydromyrcene(DHM)is the main method to synthesize DHMOL.The reaction between DHM and water is usually carried out heterogeneously in a fixed bed with ion exchange resin as catalyst and suffers from low reaction rate and poor conversion per pass.Many improvements on the catalysts and reaction processes have been done to accelerate the reaction.However the hydration is still hindered since the theoretical basis of the heterogeneous hydration is insufficient and the main cause of the low rate is still unrevealed.In this thesis,the basic of the heterogeneous hydration of DHM was studied.The effects of the micro-solution inside the resin on the hydration were investigated,the reaction-phase equilibrium of the liquid-liquid reaction mixture was predicted,and the mass transfer and reaction rates in a fixed bed were evaluated.The limitations of the multiphase hydration on reaction rate and converstion were summarized,which provides the theoretical foundation for the design and improvement of the hydration process of DHM and other olefins.The following chapters are contained:The hydration of DHM was investigated and the reaction mechanisms were revealed as well as the surface reaction process on the resin catalyst.The components in the DHM material and the reaction mixture were qualitatively and quantitatively analyzed,the mechanisms of the subreactions were deduced,and the main subreaction of the hydration is the ismerizaion of DHM.The adsorption of reactive components on the resin was determined by FTIR and the surface reaction on the resin follows the modified Eley-Rideal kinetics model.The composition of the micro-solution in the resin was experimentally determined,the effects of solvents and resin parameters on the reaction were compared,and the influences of the micro-environment inside the resin were discussed.The results show that the distribution of the reactive components(mainly DHM and DHMOL)over the resin and the bulk mixture will greatly affect on the equilibrium conversion,while the low accessibility of the sulfonic groups is responsible for the slow reaction rate.The liquid-liquid equilibriums(LLE)of three ternary systems(water-acetone-DHM,water-acetone-DMOL and water-DHM-DHMOL)and the hydration kinetics of DHM with acetone and 1,4-dioxane as solvent were measured.The NRTL model was applied to correlate the LLE data and the binary interaction parameters of each component pairs were attained;the pseudo-homogeneous(PH)model and the modified Eley-Rideal(mER)model were used to correlate the measured data,and the reaction rate constants of each model were obtained.The reaction-phase equilibrium of the multiphase hydration was predicted,a mathematical model of the liquid-liquid-solid hydration was set up to calculate the mass transfer and the reaction rates in the fixed bed,and the conversion limitation of the hydration was revealed.The biphasic conversion of the hydration is affected by the distribution of DHM and DHMOL over the organic and aqueous phases,and the mass transfer rate between the phases is significantly lower than the reaction rate in the aqueous phase,which contributes to the poor conversion per pass.In this thesis,the main limitations of the hydration of DHM are the accessibility of the sulfonic group in the resin and the mass transfer between the organic and aqueous phases.And the selection for the proper intensification method should be based on the actual industrial process.