(600f) Novel Materials for Carbon Capture Utilisation and Storage: Studies Under Relevant Industrial Conditions

Carbon capture utilisation and storage (CCUS) using solid sorbents such as zeolites, activated carbon, Metal Organic Frameworks (MOFs) and Polymers of Intrinsic Microporosity (PIMs) could facilitate the reduction of anthropogenic CO₂ concentration. Developing efficient and stable adsorbents, understanding their transport diffusion limitations, and assessing their performance for industrial CO₂ capture plays a crucial role in CCUS technology development. However, experimental data available under relevant industrial conditions is scarce, particularly for novel materials like MOFs or PIMs.

In this study we evaluate recently developed adsorbents on their capabilities for CCUS under pertinent industrial conditions. Usually, new generation adsorbents are tuned to enhance their adsorption capacity, selectivity, and stability. Here, we explore the modification of MIL-101(Cr) by incorporation of fluorine atoms to enhance the material hydrophobicity. We evaluated its potential use for CCUS by measuring CO₂ adsorption and kinetics in the presence of different water vapour concentrations (0.0, 0.05, 0.10, 0.15 and 0.20) and SO₂ adsorption and stability in the presence of water. All experiments were carried out at ambient pressure and temperature to resemble economically feasible industrial conditions.

Our results show that at low and moderate water loadings the total CO₂ uptake capacity of MIL-101(Cr)-4F(1%) improved, with the best uptake (0.097 CO₂ mmol g-1) at P/P0= 0.15. However, higher partial pressures seem to inhibit CO₂ uptake. As for the pristine material, the highest water loading decreases it’s overall CO₂ capacity by 18% compared to its dry form. Both materials present a stable behaviour in moist environments when compared to other commercial adsorbents with higher CO₂ capacity such as HKUST-1 and MIL-53(Al) under the same conditions. Desorption results of CO₂ with different water loadings at ambient pressure and temperature suggest that the fluorinated material would have a minimum energy penalty during the regeneration step. CO₂ diffusion coefficients at different water partial pressures were extracted from the mass uptake curves of the co-adsorption experiments. For both materials, CO₂ diffusion occurs faster when water is introduced; this is because water is responsible for providing a more homogeneous surface and permits an easier movement for CO₂. For water concentrations from P/P₀ = 0.05 to 0.15 the CO₂ diffusion coefficients of both materials remain stable, however, at the maximum water partial pressure studied P/P₀ = 0.2 a drop in the diffusion coefficient in the fluorinated material can be observed, coinciding with a drop in CO₂ uptake. This data suggests that certain water vapour concentrations of up to 0.15 P/P₀ can promote CO₂ diffusion which coincidentally corresponds to the water concentrations of most industrial importance for CCS. Above these conditions, a compromise between uptake and transport kinetics should be considered. Additionally, MIL-101(Cr)-4F(1%) showed exceptionally high SO₂ capture under humid conditions and an outstanding cycling performance up to 50 cycles with facile regeneration.

We are also investigating other new functionalised materials such as MIL-100 in monolithic form and AO-PIM in film form, considering competition for adsorption sites with other gases present in flue gas streams.