Thermodynamic Analysis For Systhesis Of Veratrole From Catechol And Methanol Or Dimethyl Carbonate

Veratrole is an important synthetic intermediate.They are widely use in medicine,pesticides and chemicals.At present,the method for synthesis veratrole has not met the requireents of green environental protection.The synthesis of veratrole from catechol and methanol or dimethyl carbonate is one of the competitive routes.This route is more clean more economical and more environmentally friendly.In this paper,the thermodynamic calculation and analysis for the synthesis veratrole of from catechol and methanol or dimethyl carbonate are done.And compare the advantage of the reaction between two methylating agents.In order to provide a basis for process research,process simulation and production plant.First of all,the standard molar enthalpy,standard molar entropy and heat capacity value and molar latent heat of vaporization of each component in the reaction are estimated by some group contribution methods.such as Benson method,Joback method,Rozicka-Domalski method,etc.and the enthalpy change value,gibbs free energy and equilibrium constant of the reaction in the gas phase,liquid phase and gas-liquid coexistence system and different temperature were calculated and analyzed.The optimal methylation reagent and optimal experimental conditions for the synthesis of veratrole were analyzed from the thermodynamic point of view.Main conclusions are as follows:(1)The reaction of methanol or dimethyl carbonate to synthesis veratrole ethers can occur spontaneously in the range of 298~800 K.(2)As the methylating agent methanol or dimethyl carbonate with catechol for the synthesis of veratrole at in the range of 480~518 K.In the first step,the Gibbs free energy is the smallest and the equilibrium constant is the largest.It is beneficial to synthesis of the guaiacol,not conducive to synthesis of veratrole.(3)Methanol as a methylating agent,The minimum Gibbs free energy is easy to spontaneously in the temperature range of 373~480 K.The heat released is the least and the equilibrium constant is the largest at 298~337 K,which is beneficial to synthesis of veratrole.At this temperature,Methanol/Catechol molar ratio=3:1,The conversion of catechol reached 100%,and the yield of veratrole was 99.86%.Therefore,in order to generate the target product as much as possible,the selected temperature range is 298 to337 K.(4)Dimethyl carbonate as methylating agent,the yield of veratrole can reach 99.99%at 298~800 K,The reaction is easily carried out spontaneously at 518~800 K,the absorbed heat is the smallest.But when the temperature above 673 K,the reaction will be difficult to control,so the best temperature range for the synthesis of veratrole is 518~800 K.(5)Compared with dimethyl carbonate and methanol,it is found that dimethyl carbonate as a methylating agent has a larger equilibrium constant,higher conversion rate and better reaction effect.Therefore,it is more advantageous to choose dimethyl carbonate as a methylating agent.(6)Reactive distillation is used to solve the problem of water inhibition on the reaction and improve the yield of veratrole.