Catalytic transformations of CO₂ into fine chemicals can be used to reduce the reliance on fossil resources and mitigate carbon emissions. The conversion of CO₂ into diethyl carbonate (DEC), for example, is useful because of DEC’s applications in batteries and polymer synthesis. However, the direct DEC synthesis via a reaction of ethanol and CO₂ is limited by its chemical equilibrium. Water is produced as a byproduct in this reaction and an effective combination of catalyst and dehydrating agent is necessary.

Jun-Chul Choi, Norihisa Fukaya, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, and colleagues have developed a sustainable synthesis of DEC from CO₂ using ethoxysilane derivatives and Zr(OEt)₄ (pictured). The team used tetraethyl orthosilicate (TEOS) as a reactant to avoid the formation of water. Instead, a disiloxane byproduct is created, which can be converted back to TEOS with ethanol, using molecular sieves as a dehydrating agent. Zr(OEt)₄ acts as the catalyst for DEC formation.

 

With this approach, the team achieved a record turnover number for DEC synthesis of 43. The regenerable disiloxane byproduct points to a new direction for the development of waste-free syntheses of DEC according to the researchers.

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• Sustainable Catalytic Synthesis of Diethyl Carbonate,
  Wahyu S. Putro, Akira Ikeda, Shinji Shigeyasu, Satoshi Hamura, Seiji Matsumoto, Vladimir Ya. Lee, Jun-Chul Choi, Norihisa Fukaya,
  ChemSusChem 2020.
  https://doi.org/10.1002/cssc.202002471