Alkaline ionic liquid/Brønsted acid synergistic catalytic system and its regulatory mechanism on ethylene carbonate synthesis
LOU Xiying
WANG Peng
FANG Bing
WANG Haiyue
Abstract：[Objective]With the increasing global attention to climate change and the implementation of the"dual carbon"goals,the resource utilization of CO2 has become a pivotal research focus worldwide.However,the inherent chemical stability of CO2 poses significant challenges for its chemical fixation and conversion under mild conditions,where catalyst design plays a decisive role.While the carboxylation of ethylene oxide(EO)with CO2 to synthesize ethylene carbonate(EC)is recognized as an effective approach for energy conservation and low-carbon development,substituting EO with bio-based ethylene glycol(EG)offers a safer,eco-friendly,and renewable alternative.To address the thermodynamic limitations and low conversion rates in the direct synthesis of EC from EG and CO2,this study aims to construct a synergistic catalytic system combining alkaline ionic liquids with Brønsted acids,thus developing a bifunctional catalyst for efficient CO2 activation and EG conversion under mild conditions.[Methods]Three alkaline ionic liquid catalysts,including[DBUH]PHY,[TBDH]PHY,and[DBUH]TBD,were synthesized using 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU),1,5,7-triazabicyclo[4.4.0]dec-5-ene(TBD),and phenol as precursors.Their chemical structures and thermal stability were verified through Fourier transform infrared spectroscopy(FT-IR)and thermogravimetric analysis(TGA).The synergistic catalytic performance was evaluated in a high-pressure autoclave using various Brønsted acids(H2SO4,H3PO4,CH3COOH)under optimized conditions.[Results]When used individually,either the ionic liquids or Brønsted acids show low catalytic activity(less than 10.54％yield).However,the combined[DBUH]PHY and H2SO4 system achieves a remarkable EC selectivity of 97.80％and a yield of 20.89％,outperforming single-component systems.Density functional theory(DFT)calculations reveal that H2SO4 protonates EG to form carbocation intermediates,while the[DBUH]+cation activates CO2 via a strong binding energy(-61.94 kJ/mol),forming DBU-carboxylate(DBUH-CO2).The PHY-anion facilitates dehydrogenation to generate oxyanions,synergistically driving EC formation and catalyst regeneration.Compared to conventional CeO2-based catalysts(conversion rate is no more than 2％),this synergistic catalytic system demonstrates superior atomic efficiency under mild conditions(120 ℃,3.0 MPa).[Conclusion]This study constructed a synergistic ionic liquid/Brønsted acid catalytic system,offering a novel strategy for the green conversion of CO2 and diols.The developed bifunctional catalyst integrates CO2 activation and EG protonation capabilities,with the proposed mechanism validated by experimental and computational insights.This sustainable synthesis route aligns with green chemistry principles,providing a viable pathway to mitigate greenhouse effects and enhance resource utilization.The findings hold significant implications for advancing the green transformation of the chemical industry,supporting carbon peak and neutrality goals,and fostering the development of circular economy.
Keywords：alkaline ionic liquidcarbon dioxide activationethylene glycolethylene carbonatecollaborative catalysisBrønsted acidgreen chemistryresource utilization
Publication Date：2025-07-25
Online Publishing Date：2025-09-18(First online date of this platform, not the publication date of the document)
Pages：7( 538-544 )