Carbonate-based solvents for carbon capture
Time: Thu 2026-04-23 10.00
Location: F3 (Flodis), Lindstedsvägen 26
Video link: https://kth-se.zoom.us/s/67603525238
Language: English
Subject area: Chemical Engineering
Doctoral student: Nima Mirzaei , Processteknologi
Opponent: Professor Hanna Knuutila, NTNU - Norwegian University of Science and Technology, Norge
Supervisor: Universitetslektor Matthäus Bäbler, Processteknologi; Universitetslektor Efthymios Kantarelis, Processteknologi
QC 20260325
Abstract
Carbon dioxide (CO2) emissions from the combustion of fossil fuels and biomass used for energy production drive global warming and climate change. Carbon capture and storage (CCS), involving the removal of CO2 from combustion flue gas and its sequestration in geological formations, is therefore a key strategy for reducing CO2 emissions. Absorption processes based on aqueous potassium carbonate (K2CO3) are among the first-generation carbon capture technologies due to process maturity, benign chemistry, and operational robustness. Owing to its high potential for waste heat recovery, aqueous K2CO3 is considered particularly suitable for applications where low-grade heat is a valuable product. The main limitation of aqueous K2CO3, however, is the slow absorption rate of CO2, which results in a large material footprint and an electricity demand for flue gas compression. To alleviate this limitation, rate promoters are added to enhance the CO2 absorption rate.
This thesis investigates boric acid (B(OH)3) and vanadium pentoxide (V2O5), which are employed as rate promoters in industrial solvent blends. Absorption experiments were conducted using a stirred batch reactor over a broad range of promoter concentrations and solvent loadings. Boric acid exhibited negligible rate enhancement but was found to increase the absorption capacity for CO2 through an additional buffering effect. In contrast, vanadium pentoxide increased the CO2 absorption rate by up to 2–3 times that of unpromoted K2CO3, a performance comparable to that of monoethanolamine (MEA) as promoter. This rate enhancement occurs because the active species, hydrogen monovanadate, catalyzes the hydrolysis of CO2. These results provide a mechanistic understanding of the roles of B(OH)3 and V2O5 in improving CO2 absorption in aqueous K2CO3. The kinetic rate models developed to describe the experimental observations can serve as a sound basis for accurate design of large-scale absorption processes.