Abstract
Mitigating CO₂ emissions is a critical global challenge, particularly from fossil fuel power plants, which remain the predominant energy source. While renewable energy adoption is growing, fossil fuels will continue to play a key role, making efficient CO₂ capture essential for achieving climate targets and minimizing environmental impact.
This PhD research focuses on evaluating amine-based adsorbents as alternatives to conventional liquid amine solutions for post-combustion CO₂ capture in natural gas combined-cycle (NGCC) power plants. NGCC flue gases typically contain 3–5 % CO₂, lower than the 10–15 % found in coal-fired plants, which reduces adsorption efficiency and overall capacity. To advance solid sorbents toward commercial deployment, it is necessary to provide a complete set of properties: high adsorption capacity, fast adsorption and desorption kinetics, good thermal and chemical stability under relevant operating conditions, and low regeneration energy to reduce the energy penalty associated with liquid amines.
This thesis investigates two classes of amine-based adsorbents: Class 1, silica impregnated with polyamines, and Class 2, siliceous supports functionalized with chemically bonded aminosilanes. Different polyamine and aminosilane structures were systematically explored to assess the effects of structural configuration, molecular weight, deposition method, and amine type on CO₂ adsorption capacity, adsorption and desorption kinetics, and thermal and chemical stability under relevant desorption techniques. Complementary Clausius–Clapeyron and microcalorimetry work was conducted to evaluate the true adsorption heat, highlighting the critical role of amine mobility in the responsiveness of adsorption heat to temperature changes.
This thesis identified a potential adsorbent that combines high CO₂ adsorption capacity, even at ppm concentrations, with fast adsorption and desorption kinetics, and excellent thermal and chemical stability under practical regeneration conditions, such as temperature swing adsorption (TSA) with CO₂ as the purge gas. Additionally, experimentally determined regeneration heat is significantly lower than that of conventional MEA, highlighting the material’s potential for energy-efficient CO₂ capture in NGCC power plants.