Conversion Of CO₂ Into Carbamate And Cyclic Carbonate Under Low Pressure

Carbon dioxide is an important C1 resource,and the transformation of carbon dioxide into organic compounds is one of the useful ways of carbon dioxide utilization.In recent years,China has put forward the strategic goal of “peak carbon dioxide emissions and carbon neutrality”,and the conversion of carbon dioxide has become more and more important.Among them,the conversion of carbon dioxide to carbamates or cyclic carbonates is the research hotspot of its utilization.Therefore,it is of great significance to develop new and efficient reaction systems for converting carbon dioxide into these two types of compounds.Based on this,the main research content of this thesis includes the following two parts:1.An efficient method for synthesizing carbamate compounds was developed using carbon dioxide,aniline and its derivatives,brominated hydrocarbons as raw materials,1,8-diazabicycloundec-7-ene(DBU)as activator,N,N-dimethylformamide(DMF)as the solvent.The influences of solvent,temperature,initial pressure,base loading and mole ratios of reactants on the reaction were investigated using a template reaction of aniline,1-bromobutane and carbon dioxide.The optimal reaction conditions were obtained as follows: aniline 1.0 mmol,1-bromobutane 2.0 mmol,DBU 2.5 mmol,initial pressure 0.25 MPa,reaction temperature 70℃and DMF 0.5 mL.Under the optimal conditions,24 carbamate compounds were synthesized with the highest yield up to 91%.The reaction system has the characteristics of mild conditions and rapid reaction.2.An efficient method for synthesizing cyclic carbonate compounds was developed using epoxide and carbon dioxide as raw materials and potassium iodide as catalysts.The influences of solvent,temperature,initial pressure,catalyst type and amount,and reaction time on the reaction were investigated using a template reaction of carbon dioxide and 1,2-propylene epoxide.The optimal reaction conditions were obtained as follows: the initial pressure was 0.5MPa,the reaction temperature was 120℃,potassium iodide(2.0 mol%),1,2-propylene oxide was 14.3 mmol,and the solvent was ethanol(71.5 mmol).Under these conditions,five cyclic carbonate compounds were synthesized.Among them,a yield of 99.9% was obtained when ethylene oxide was used as the starting reagent.In order to explore the relationship between the solvent polarity and the reaction yield,the effect of solvent ratio on the cycloaddition reaction of 1,2-propylene epoxide and carbon dioxide catalyzed by tetrabutylammonium iodide was investigated in a mixed solvent of toluene and ethanol.The results show that the polarity of the mixed solvent(Lippert-Mataga polarity parameter Δf)is positively correlated with the reaction yield.