(2hu) Carbon Capture and Aerosol Technology for Carbon Dioxide Utilization

Several companies and countries are making net-zero commitments to mitigate climate change by eliminating anthropogenic CO₂ emissions by 2050. There does not exist a single solution to eliminate CO₂ emissions, hence, several technologies including carbon capture and utilization need to be advanced to address the global challenge of climate change¹. My research is focused on developing efficient pressurized oxy-combustion systems for CO₂ capture and the synthesis of advanced catalysts via single-step continuous aerosol-based processes for CO₂ conversion to chemicals and fuels.

To advance pressurized oxy-combustion power plant technology for CO₂ capture, there is a need to understand particle formation at high pressure conditions to ensure minimal particulate matter (PM) emission and reliable performance. To study PM formation of pulverized solid fuels at high pressures, I designed, fabricated and set-up a Lab scale pressurized drop-tube furnace experiment system which consists of a high pressure (HP) drop tube furnace, HP pulverized fuel feed system, and HP particle sampling system.

I also explored catalyst synthesis for CO₂ reforming and DME production. First, to illustrate the significance of CO₂ conversion via reforming processes I performed thermodynamic studies^2,3. The studies showed that up to 45 million tons of CO₂ per annum can be incorporated into methanol, Fischer-Tropsch liquid fuels and butyraldehyde. Consequently, I demonstrated the synthesis of alumina, a conventional catalyst support for reforming, via aerosol process (spray flame aerosol reactor)⁴. Currently, I am studying the synthesis of Rh/Al₂O₃ catalyst using the spray flame aerosol reactor and designing highly dispersed and single atom Rh/Al₂O₃ catalysts for reforming of carbon dioxide.

In addition, I synthesized Cu/ZnO/MgO and Cu/ZnO/ZrO₂ for single-step DME synthesis from CO₂. Hybrid catalysts synthesized using the spray flame aerosol reactor when compared to co-precipitation catalysts were found to be about 15% more active and selective to DME/methanol, hence its potential to increase the yield of DME by 33% and decrease unit cost of DME production by 25% when compared to conventional catalyst⁵.

Finally to accurately describe the evolution of particles in engineered systems in a computationally efficient manner I have, as a first step, developed a hybrid ANN model to describe particle coagulation⁶. I am currently working on developing computationally efficient machine learning models that will incorporate several aerosol dynamics phenomena including nucleation, condensation and sintering.

Overall, based on my PhD research, I have gained experience on material synthesis, material characterization methods and multi-scale modelling. I am presently interested in an post-doctoral fellowship/position where I can continue to develop novel catalysts for carbon dioxide conversion or where I can use my in-depth knowledge of aerosol processes to synthesize nanoparticles for specialized applications.

1. Okonkwo and Biswas (2021), Synthesis of novel catalysts for carbon dioxide conversion to products of value, 527-556.
2. Okonkwo et al, (2020) Journal of CO₂ Utilization 39:101156
3. Okonkwo et al, (2022) Journal of CO₂ Utilization 60:101998
4. Okonkwo et al, (2022) Journal of the American Ceramic Society 105;2 1481-1490
5. Okonkwo et al, (2023) Chemical Engineering Journal (in preparation)
6. Okonkwo et al, (2023) Aerosol Science and Technology (under review)