(630g) Multiscale Design and Synthesis of Power-to-Liquid Process for Sustainable Aviation Fuel from CO2 and Renewable Energy

We present a systematic multiscale process synthesis approach for developing an intensified Power-to-Liquid (PtL) process for the production of liquid hydrocarbons amenable to be used as Sustainable Aviation Fuel (SAF) from intermittent renewable energy sources (such as wind and solar) and carbon dioxide (CO₂). The pressing need for expanded renewable energy deployment underscores the urgency for innovative solutions to circumvent grid interconnection challenges. Current grid interconnection waiting times, which can extend up to four years^[1], underscore the necessity for methods that lessen dependence on the grid, accelerating the adoption of renewable energy sources. Our proposed strategy not only enables cost-effective energy storage but also offers potential solutions for balancing supply and demand in scenarios with high renewable energy penetration, while also addressing land and water constraints for biofuel production. While SAFs and chemicals derived from CO₂ and renewable processes present a promising pathway to meet our energy demands in a decarbonized world, current processes are not product specific and are economically not viable^[2]. Further challenges include the intermittency of renewable energy sources with the continuous operation of the PtL process, the low selectivity for the desired carbon-containing liquid products, the low single-pass conversion of CO₂ and H₂, and the presence of unsuitable shorter-chain olefins and paraffins for aviation fuel.

Our multiscale design approach includes decisions at material, unit operation and process scales. At the material scale, our design starts by incorporating in tandem catalysis that combines two catalyst components for CH₃OH synthesis and methanol-to-hydrocarbons (MTH), namely, a reducible metal oxide such as Cu/ZnO/Al₂O_{3 ­}and a zeolite with high-acidity such as HZSM-5, within a single intensified reactor. At the unit operation scale, we perform detailed design and optimization of an electrified reactor amenable to dynamic process intensification. At the process scale, our design involves decoupling downstream liquid hydrocarbon production from upstream energy storage and hydrogen gas production via electrolysis, along with the storage of nascent gas. This simplifies the downstream process complexity, enabling steady-state operation while allowing upstream H₂ production and energy storage to adapt based on energy availability. This enables a decomposition approach where the optimal scheduling of upstream intermittently available energy supply and the production of renewable hydrogen (H₂) is performed using a linear program (LP), and the synthesis of an optimal PtL process configuration to produce SAF from CO₂ and H₂ is performed using a mixed-integer nonlinear program (MINLP) based on the building block approach^[3-4]. After separately solving both decoupled systems, the energy and materials produced upstream is linked to downstream feed materials using coupling process variables. Additionally, we employ a superstructure for upstream and downstream processes to determine optimal process configurations, aiming to reduce annualized operating and continuous costs. Compositions of single-pass products were determined from existing studies and used to inform heat integration, separation, purge, and recycling downstream processes. We further incorporate oligomerization of short-chain liquid carbon-containing components unsuitable for aviation fuel to enhance SAF yield.

References

[1] Rand, J. “Record Amounts of Zero-Carbon Electricity Generation and Storage Now Seeking Grid Interconnection,” Electricity Markets and Policy Group, Lawrence Berkeley National Laboratory, (2022)
[2] Raksha, T. et. al., “Power-to-Liquids as Renewable Fuel Option for Aviation: A Review” Chemie Ingenieur Technik, 90, 127-140 (2018)

[3] Demirel, S. E.; Li, J.; Hasan, M. M. F. “Systematic Process Intensification using Building Blocks”. Computers & Chemical Engineering, 2017, 150, 2–38.

[4] Demirel, S. E.; Li, J.; Hasan, M. M. F. “Systematic Process Intensification”. Current Opinion in Chemical Engineering, 2019, 25, 108–113.