CO2 atmosphere enables efficient catalytic hydration of ethylene oxide by ionic liquids/organic bases at low water/epoxide ratios

The development of an efficient and low-cost strategy for the production of monoethylene glycol (MEG) through hydration of ethylene oxide (EO) at low H2O/EO molar ratios is an important industrial challenge. We have established that by using CO2 as the reaction atmosphere, hydration of EO can be achieved at a low H2O/EO ratio of 1.5 : 1 along with high yields (88-94%) and selectivities (91-97%) of MEG catalyzed by binary catalysts of ionic liquids and organic bases. The results are significantly better than those of experiments conducted under an atmosphere of N-2. Isotope labeling experiments revealed that CO2 had altered the reaction pathway and participated in the reaction, in which cycloaddition of EO with CO2 occurred first followed by the hydrolysis of ethylene carbonate (EC) to generate MEG and recover CO2. The ionic liquids and organic bases synergistically catalyzed the one-pot two-step reaction. DFT calculations confirmed that this route is more kinetically favorable compared to the pathway of direct epoxide hydration.