(276a) Multi-Scale Screening of Porous Materials for Carbon Capture

Carbon capture and storage (CCS) has been identified as the near term solution for mitigating climate change effects with the simultaneous use of fossil fuels for the production of energy. Power plants have been identified as the major sources of CO₂ emissions and the flue gas typically contains 4% CO₂ in case of a natural gas fired power plant and 15% in case of a coal-fired power plant. Adsorption separation process has been identified as a potential candidate for carbon capture applications. The backbone of an efficient adsorption process is the adsorbent, which should possess a very high capacity for CO₂ and high selectivity. The benchmark material for adsorption based carbon capture is Zeolite 13X and several published literature studies are available on this material ^1-5. Recent developments include new materials such as metal organic frameworks (MOFs) and Zeolite imidazolate frameworks (ZIFs). A large number of these new materials are computationally screened using molecular simulations and ranked based on their capacity, despite the limited availability of accurate force fields. Furthermore, optimal behaviour of a material in a real process will also depend on the specifics of process configurations. Therefore, it seems a comprehensive way to screen the materials for CO₂ adsorption applications is to use a multi-scale approach and rank them based on their performance in an actual process, such as four or six step PSA.

In this study, a 4-step vacuum swing adsorption (VSA) cycle described in earlier publications^4,5 was employed in this work to evaluate the performance of two adsorbents namely zeolite 13X and CPO-27-Ni metal organic framework. The information on adsorption equilibrium and kinetics were obtained from lab scale volumetric experiments as well as molecular dynamics simulations. Detailed optimization of the 4-step VSA cycle was carried out using non-dominated sorting genetic algorithm (NSGA-II) to arrive at operating conditions that satisfy 95% CO₂ purity and 90% CO₂ recovery with minimum energy consumption and maximum productivity. The performance of the VSA process was evaluated using both the actual experimental data and predictions from molecular simulations and we demonstrate the differences in the performance of the materials in a VSA process in the two cases.

1. Krishnamurthy, S., et al., CO₂ capture from dry flue gas by vacuum swing adsorption: A pilot plant study. AIChE J, 2014. 60(5): p. 1830-1842.

2. Li, G., et al., Competition of CO₂/H₂O in adsorption based CO₂ capture. Energy Procedia, 2009. 1(1): p. 1123-1130.

3. Liu, Z., et al., Onsite CO₂ Capture from Flue Gas by an Adsorption Process in a Coal-Fired Power Plant. Ind Eng Chem Res, 2012. 51(21): p. 7355-7363.

4. Haghpanah, R., et al., Cycle synthesis and optimization of a VSA process for postcombustion CO₂ capture. AIChE J, 2013. 59(12): p. 4735-4748.

5. Khurana, M. and S. Farooq, Simulation and optimization of a 6-step dual-reflux VSA cycle for post-combustion CO₂ capture. Chem Eng Sci, 2016. 152: p. 507-515.