Beyond net-zero carbon emissions in industrial processes through catalyst-aided amine solvents for the indirect co-combustion of natural gas and biomass

Abstract

This thesis investigates the application of absorber catalysts developed and optimized for effective CO₂ capture in a power production process involving the indirect co-combustion of biomass and natural gas, addressing a crucial case study challenge of carbon emissions from large. By employing a novel bi-blend amine solvent system, improved by heterogeneous solid base catalysts, the study explores the synthesis of various super basic catalysts in a bid to optimize CO₂ absorption rates, solvent loading, and overall process efficiency A series of heterogeneous catalysts which include PEI modified catalysts, K/MgO, K/MgO-CaO, and activated carbon blends, were synthesized and tested using a semi-batch apparatus. The initial CO₂ absorption rates of these catalysts were thoroughly analyzed against a non-catalytic baseline (control experiment). The results obtained revealed that catalysts such as AC Hydrothermal and K/MgO-CaO (5-35-60) significantly increased CO₂ absorption rates by up to 46% and 21%, respectively, over the baseline. Contrarily, despite characterized by high basic strength, some PEI-modified catalysts, exhibited lower performance due to reduced surface area and electron transfer limitations. However, further analysis was conducted on the K/MgO-CaO (5-35-60) catalyst over the activated carbon catalyst considering its superior chemical, thermal and mechanical stability, as well as the ease of preparation and reduced waste. The screening of the catalysts was carried out at a gas composition of 4.5% CO2 (balance N2, an absorption temperature of 40℃ ± 2, and a gas flow rate of 200± 5 ml/min). Additionally, extensive catalyst characterization test, including Powder X-ray Diffraction (XRD), CO₂ Temperature Programmed Desorption (TPD), and BET surface analysis, were conducted to understand how catalyst properties such as basic site strength, surface area, and pore structure influence CO₂ capture rates observed. The environmental impact and potential cost savings of catalyst-aided carbon capture were then evaluated in a simulated power generation process, where an LCA, life cycle assessment, model was applied based on the ReCiPe methodology. From comparing traditional MEA benchmark solvent, the novel AMP-PRLD amine bi-blend, and the AMP-PRLD solvent enhanced with a K/MgO-CaO catalyst, the results demonstrated that the catalyst-enhanced system achieved superior carbon dioxide reductions across various gas compositions, underscoring its potential for net-zero emissions. Conclusively, this catalyst-solvent system provides a promising pathway for the power and energy sectors to significantly reduce emissions while enhancing cost-effectiveness and sustainability.