Efficient Theoretical Screening of Solid Sorbents for CO₂ Capture Applications

Abstract

By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO 2 sorbent candidates from the vast array of possible solid materials has been proposed and validated. The ab initio thermodynamic technique has the advantage of allowing identification of thermodynamic properties of CO 2 capture reactions without any experimental input beyond crystallographic structural information of the solid phases involved. For a given solid, the first step is to attempt to extract thermodynamic properties from thermodynamic databases and the available literatures. If the thermodynamic properties of the compound of interest are unknown, an ab initio thermodynamic approach is used to calculate them. These properties expressed conveniently as chemical potentials and heat of reactions, which obtained either from databases or from calculations, are further used for computing the thermodynamic reaction equilibrium properties of the CO 2 absorption/desorption cycles. Only those solid materials for which lower capture energy costs are predicted at the desired process conditions are selected as CO 2 sorbent candidates and are further considered for ex- perimental validations. Solid sorbents containing alkali and alkaline earth metals have been reported in several previous studies to be good candidates for CO 2 sorbent applications due to their high CO 2 absorption capacity at moderate work- ing temperatures. In addition to introducing our computational screening procedure, in this presentation we will sum- marize our results for solid systems composed by alkali and alkaline earth metal oxides, hydroxides, and carbonates/bicarbonates to validate our methodology. Additionally, applications of our computational method to mixed solid systems of Li 2 O with SiO 2 /ZrO 2 with different mixing ratios, our preliminary results showed that increasing the Li 2 O/SiO 2 ratio in lithium silicates increases their corresponding turnover temperatures for CO 2 capture reactions. Overall these theoretical predictions are found to be in good agreement with available experimental findings.