Direct Synthesis Of Diethyl Carbonate From Ethanol And Carbon Dioxide Over Basic Ionic Liquid Catalysts

Diethyl carbonate(DEC),a dicarbonate of ethanol,is an important organic intermediate.It has been widely used in textile printing-dyeing and plastic processing.The basic ionic liquids(BILs)are kinds of liquid salts composed by anion and cation,and can be used as new catalysts.They have many advantages,such as,environmental friendly,low toxicity,well thermal stability and so on.Therefore,in this work,BILs catalysts have been designed and synthesized to catalyze the reaction from CO2 and ethanol to DEC.It has important theoretic significance and research prospect for this work.Firstly,three BILs,benzylmethyldihydroxyethylammonium methoxide(BzMDM),benzylmethyldihydroxyethylammonium hydroxide(Bz MDH),and benzyltrihydroxyethylammonium hydroxide(BzTH)were synthesized by the modified of the cation group of the choline hydroxide(CH)and choline methoxide(CMe).The BzMDM showed higher catalytic activity in the direct synthesis of DEC than other catalysts.Under the optimal conditions,that the amount of BzMDM is 8.0 g(33.2 mmol),ethanol volume is 20 ml,reaction temperature is150 ?,reaction time is 3 h and CO2 initial pressure is 6.0 MPa,the yield of DEC reaches to1.82%(3.12 mmol)with the selectivity of 93.2%.Secondly,benzylmethyldihydroxyethylammoniumtert pentoxide(BzMDTa)and benzylmethyldihydroxyethylammoniumtert butoxide(BzMDT)were synthesized by the modifying the anion group of BzMDM.The results showed that the catalytic activities of BzMDTa and BzMDT were higher than Bz MDM,but the selectivity of DEC was poorer.The optimal conditions were that the amount of catalyst was 9.0 g,ethanol volume as 20 ml,reaction temperature was 150 ?,reaction time was 3 h and CO2 initial pressure was 6.0 MPa.The yields of DEC were 2.5%(4.30 mmol)and 3.12%(5.35 mmol),and the selectivity were20.1% and 30.3% by using Bz MDTa and BzMDT as the catalysts respectively.In addition,BzMDTa and Bz MDT also showed well catalytic activity in the synthesis of dimethyl carbonate(DMC)from CO2 and methanol.In addition,the structure and properties of these BILs was characterized by FT-IR,1HNMR and UV-Hammett methods.The catalytic mechanism of the BILs in direct synthesis of DEC from CO2 and ethanol was also researched.