Study And Comparison Of Three Preparation Methods For 2-imidazolidinone

2-imidazolidinone is widely used in the fields of medicine,chemical industry and agriculture.Therefore,the preparation of 2-imidazolidinone is of great significance.This study mainly investigates three synthetic methods for 2-imidazolidinone including the product separation;after comparison,the suitable preparation route could be decided.When urea was used as the carbon source,the effect of different solvents on the synthesis of 2-imidazolidinone was studied.Experimental results showed that,at the reaction pressure of 1 MPa(N2),the reaction temperature of 180℃(with 6℃/min)and reaction time of 3 h with the molar ratio 1.1:1.0 for ethylenediamine and urea,when 1-methyl-2-pyrrolidone(NMP)was used as the solvent,the yield of 2-imidazolidinone could reach 78%;when methanol was the solvent,the yield of 2-imidazolidinone could achieve 84%;when the methanol-NMP mixture(molar ratio of 1.2:1.0)was used as the solvent,the yield of 2-imidazolidinone could reach 89%.When the product was separated by vacuum distillation,2-imidazolidinone product with a purity of 90.1%was obtained.When CO2 was used as the carbon source,the influence of reaction pressure,time,and temperature on the non-solvent,non-catalytical synthesis of 2-imidazolidinone was explored.Experimental results showed that when the reaction pressure was 5 MPa,the reaction temperature was 200℃(6℃/min)for 3 h,the yield of 2-imidazolidinone reached 94%.After specific sublimation or recrystallization,2-imidazolidinone with purity larger than 96%was obtained,which meets the industrial grade product.When CO2 was used as the carbon source,the effect of different solvents and base catalysts on the catalytical synthesis of 2-imidazolidinone was explored.Experimental results showed that when ethanol was used as a solvent,carboxylation was promoted accompanied by side reactions;when NMP was the solvent,the yield of 2imidazolidinone through tautomerization was improved;when the ethanol-NMP mixture was used,the product yield could reach 90%.It further found that when the cesium carbonate catalyst was applied,at the reaction pressure of 5 MPa(N2),the reaction temperature of 200℃(6℃/min)and reaction time of 3 h with the molar ratio 1.1:1.0 for ethylenediamine,ethanol and NMP,the yield of 2-imidazolidinone reached 95%.The reaction product was separated by vacuum distillation,and 2-imidazolidinone with a purity of 95.5%was obtained.After comprehensive comparison of the three methods,we conclude that using CO2 as the carbon source,non-solvent,non-catalytic synthesis of 2-imidazolidinone with the sublimation or recrystallization procedure is the suitable preparation path.