Computational Insights of Catalytic Carbon Dioxide Valorization and Circular Recycling Processes

Identifier:  TDX:4447

Handle: https://hdl.handle.net/20.500.11797/TDX4447

Authors:  Villar Yanez, Alba

Abstract:
Two of the major environmental challenges in today’s society are CO2 emissions and waste management surrounding plastics. The inability to properly recycle plastic materials (polymers) not only creates pollution issues related to microplastics present in our eco-systems, but also directly relates to the carbon emitted causing a major impact on global warming and climate change. It is thus essential to create new strategies to reduce these negative effects, and chemistry offers a tool to access polymers using circular economy principles, which utilize CO2 as a reactant. This minimizes our dependency on fossil fuels, while new types of monomers can be made from CO2 (cyclic carbonates) used to produce degradable polymers within a circular economy approach. This thesis focuses on computational analysis (DFT) of CO2 valorization/recycling processes through homogeneous catalysis, and creating a predictive reactivity model. In each chapter, I studied a specific part of process circularity or CO2 recycling, starting with the conversion of CO2 into five-membered cyclic carbonates from alkyne-1,2-diols using a Ag catalyst. Then, the creation of larger-ring carbonates (six-membered) from smaller ones is presented via a unique organocatalytic strategy. As these cyclic carbonates can be used as monomers, though not in all cases, I conducted an extensive study of the Ring-Opening Polymerization (ROP) reaction of cyclic carbonates using BnOH as initiator and an organocatalyst. This exploration led to defining a main ROP pathway for a wide range of monomers and model that can predict the polymerization ability of a monomer. Finally, I studied the organocatalyzed depolymerization of a polycarbonate, that selectively breaks down the polymer into a trans-cyclic carbonate, or an epoxide and CO2. This ultimate study provides deep insights for CO2 valorization, complemented by experimental results offering a more complete view on how to effective convert and recycle CO2 within a circular approximation.