Improving the efficiency of the catalytic hydrogenation of CO2 via intensified process concepts and novel catalysts
Το πλήρες κείμενο είναι δεσμευμένο από το συγγραφέα εώς 2027-01-13.
Ημερομηνία
2025-01-13
Συγγραφείς
Koidi, Vasiliki
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Παραπομπή
Παραπομπή
Άδεια Creative Commons
Εκτός εάν σημειώνεται διαφορετικά, η άδεια αυτού του αντικειμένου περιγράφεται ως Attribution-NonCommercial CC BY-NC
Περίληψη
Περίληψη
The on-going use of fossil fuels leads to the persistent increase of carbon dioxide emissions, which in turn contribute to global warming and climate change. To mitigate this threat, a substantial part of research has been devoted to CO2 conversion into value-added products such as methanol or dimethyl ether. Methanol synthesis via CO2 hydrogenation reaction is exothermic, favored at high pressures and low temperatures. However, CO2 is a fully oxidized, thermodynamically stable, and chemically inert molecule that requires relatively high activation temperature. The reaction is therefore limited due to thermodynamics at high temperature and due to kinetics at low temperature. The purpose of the present thesis is to improve the efficiency of CO2 hydrogenation to value-added products, such as methanol or dimethyl ether, by developing novel catalysts and intensified process concepts with special emphasis on the experimental development of the sorption-enhanced (SE) methanol synthesis process.
On the catalyst side, Mo₂C-based catalysts were systematically studied to address kinetic constraints, revealing that both the catalyst preparation method and Cu promotion significantly affect the catalytic performance, while Cu addition was also shown to increase methanol selectivity at temperatures below 275 °C. Additionally, the stability of a commercial CuO/ZnO/Al₂O₃ catalyst exposed to typical off-gases impurities was investigated, showing that activity loss is primarily due to a reduction in exposed Cu surface area caused by the poisons.
To address thermodynamic limitations, the SE methanol synthesis concept was experimentally validated using zeolite-based sorbents for continuous water removal, enhancing methanol yield by up to 115%. The impact of different zeolites on performance and stability was evaluated, revealing that zeolite 4A offers the highest stability. Another route to circumvent thermodynamic limitations is to further convert the methanol produced to dimethyl ether. To that end, 3D-printing technology was employed to prepare structured acidic supports for methanol dehydration and bifunctional catalysts for the one-step CO₂-to-DME conversion, achieving high stability and selectivity.