The Synthesis Of Cyclic Carbonates Catalyzed By Nitrogen-Containing Compounds

Insertion of CO₂ into epoxides to synthesize cyclic carbonates is one of the effectual means of CO₂ fixation.In present,some of the catalysts still have certain corrosion resistance and environmentally hazardous problems.From the view point of green and safty,two kinds of nitrogen-containing catalysts with good catalytic activity were developed in this work.Firstly,An eco-friendly and efficient binary catalyst system of superbases and amino acids was developed for synthesis of cyclic carbonates from epoxides and CO₂under solvent-free,metal-free and halide-free condition.Various amino acids and superbasessystemswereinvestigated,andtheL-histidine/1,8-diazabicyclo[5.4.0]undec-7-ene?DBU?system was found to have better catalytic activity than others.The influence of reaction conditions?temperature,pressure,amount of catalyst,and reaction time?on the fixation of CO₂ to propylene oxide?PO?were studied,and found that under the conditions of 120 ?,2 MPa,2 h,L-distidine?2%mol?,DBU?10%mol?,the L-histidine/DBU system achieved the maximum conversion of PO of 97%and the selectivity of propylene carbonate?PC?of 99%.The L-hisditine/DBU binary catalyst system also had a good catalytic activity in the cycloaddition reaction of other epoxides.A possible catalytic mechanism for the cycloadditon of epoxides and CO₂ catalyzed by L-hisditine/DBU system was proposed.This catalyst system of L-histidine and DBU played a synergetic catalysis role in making the reaction proceed smoothly.In addition,mesoporous silica?FDU?-supported ionic liquids composites were synthesized and used as catalyst in the synthesis of cyclic carbonates.It was found that the FDU immobilized 1-ethyl-2,3-dimethylimidazolium bromide?[EMIM]Br?material has better catalytic activity among different FDU immobilized ionic liquids?ILs?materials.In order to investigate the effect of ionic liquid loading on the catalytic activity of FDU-[EMIM]Br,the catalysts with different[EMIM]Br loadings were synthesized.It was found that FDU-[EMIM]Br with an ionic liquid loading of 30%wt had better catalytic activity.The results also showed that under the optimal reaction conditions of 120 ?,2 MPa,catalyst?12%wt?,3 h,FDU-[EMIM]Br-30%had better activity and achieved the maximum of 99%PO conversion and 98%PC selectivity.The FDU-[EMIM]Br-30%also had a good catalytic activity for the cycloaddition of other epoxides.