UC Irvine

Among the various strategies for mitigating CO2 emissions, carbon capture and utilization (CCU) offers dual benefits of greenhouse gas reduction and productive use of captured carbon. Ammonia-based CO2 capture represents a promising CCU pathway for post-combustion applications, enabling both carbon sequestration and the formation of nitrogen-rich compounds suitable for fertilizer production.This dissertation investigates the gas-phase reaction between CO2 and NH3 at low temperatures and atmospheric pressure, under concentrations representative of flue gas. The study integrates kinetic simulations, laboratory-scale continuous-flow reactor experiments and product characterization; with the objective of measuring CO2 capture, capture efficiency, and product composition. CO2 capture is quantified using a nondispersive infrared (NDIR) analyzer, suspended particles are measured and quantified using a light scattering particle analyzer (ORION), and the collected solids are characterized by nuclear magnetic resonance (NMR) spectroscopy.Results reveal that the presence of water vapor markedly enhances CO2 capture, achieving efficiencies that exceed literature-based kinetic predictions, without altering the predominance of ammonium carbamate in the solid phase. Experimentally obtained CO2 capture efficiencies reach 60% within studied residence times (<3 min), highlighting the slow kinetics of the chemical process. The NH3/CO2 molar ratio was identified as a key variable, with a ratio near 2:1 yielding high capture efficiency while minimizing unreacted ammonia.These findings provide experimental validation that gas-phase ammonia can effectively sequester CO2 under flue-gas conditions while producing ammonium carbamate—a compound with potential as a nitrogen fertilizer. This work establishes a foundation for future studies aimed at integrating gas-phase ammonia-based CO2 capture into industrial processes with co-benefits for carbon mitigation and fertilizer production.