Effect of flue gas impurities on performance of monolithic MOFs (Flexible Funding 2023)

Dr Ali Nabavi, Cranfield University, was awarded funding through the UKCCSRC’s Flexible Funding 2023 call to investigate, in collaboration with Immaterial Ltd., the performance of their novel monolithic metal-organic frameworks (MOFs) for industrial carbon capture applications.

Adsorption separation using porous solid sorbents has been considered a promising CO₂ capture and removal approach to curbing the deleterious effect of anthropogenic CO₂. Cyclic adsorption processes using nanoporous sorbents are the key building blocks in deriving industrial carbon capture, fuel switching and negative emission technologies. Aligned with the UK climate ambition, the cost and energy penalty of the existing carbon capture technologies must be reduced to be widely deployed.  Porous solid adsorbents, including metal organic frameworks (MOFs), when optimised, offer a substantial cost reduction for CO₂ capture due to lower energy requirements for regeneration, compared to the conventional approaches.

MOFs offer high surface area, tuneable pore structures and exceptional adsorption properties. Their porosity and adjustable chemistry enable them to exhibit a significantly higher CO₂ adsorption capacity compared to conventional sorbents. Despite their versatility and tunable properties, conventional MOFs face several challenges that hinder their widespread implementation in carbon capture from industrial flue gases. These challenges include issues related to their stability in the presence of water, steam and flue gas, difficulties in scaling up production and low volumetric adsorption capacity. Furthermore, although there have been advancements in the performance and stability of MOFs, their powder form is impractical for direct use in separation columns. To address these challenges, Immaterial has developed monolithic MOFs (m-MOFs) that benefit from production scalability and a form factor that targets the drawbacks of conventional MOFs. Therefore, owing to better material packing, the volumetric adsorption performance has been shown to increase significantly.

Recognising the potential of m-MOFs for carbon capture, the UKCCSRC has in-part funded a collaborative project between Immaterial Ltd and Cranfield University, to investigate the effect of water, steam and flue gas impurities (i.e. SOx, and NOx) on adsorption characteristics and hydro-chemical stability of m-MOFs, to explore their feasibility for carbon capture from industries.

To assess the feasibility, Cranfield University upgraded one of its bench-scale facilities to conduct fixed-bed breakthrough analysis under various scenarios to determine CO₂ adsorption-desorption kinetics. The assessment covered CO₂ adsorption properties, CO₂ concentration in flue gas, flue gas relative humidity, and the impact of flue gas impurities under various conditions, including short- and long-term exposure to dry and wet gas streams with or without O₂, NO₂ and SO₂. In addition, Dynamic Mechanical Analysis (DMA) was used to assess the mechanical stability of the material, providing insights into its structural integrity under different operating conditions.

The findings from these assessments demonstrated the hydrothermal stability of m-MOFs under flue gas impurities. Moreover, the material demonstrated excellent robustness, maintaining its structural integrity and performance despite prolonged exposure to industrial gas streams or mechanical attrition. Such features will be crucial in ensuring the commercial viability and widespread implementation of m-MOF for carbon capture from industries.

As global demand for viable carbon capture solutions increases, research partnerships like the collaboration between Immaterial and Cranfield University through this project are vital for advancing net-zero commitments. This project highlights the potential of m-MOFs as promising CO₂ sorbents, offering a scalable and cost-effective alternative to conventional carbon capture approaches and paving the way for the adoption of adsorption-based CO₂ capture processes for industrial decarbonisation.

Cranfield University research team working on the breakthrough rig

Cranfield Principal Investigator: Dr Ali Nabavi, Reader in Low Carbon Energy Systems

Cranfield Researchers: Mr Fayez Qureshi, Mr Sunera Athauda, and Dr Ziqi Shen

Industrial Sponsor: Immaterial Ltd.

Read more on Ali’s Flexible Funding 2023 project page.