(51a) Theoretical Calculating the Thermodynamic Properties of Solid Sorbents for CO2 Capture Applications


for 2012 AIChE Annual Meeting                                    Oct.28-Nov.2,
2012 Pittsburgh, PA


Theoretical calculating the thermodynamic properties
of solid sorbents for CO2 capture applications


US Department of Energy,
National Energy Technology Laboratory, Pittsburgh, PA 15236



Since current technologies for capturing CO2to fight global climate change are still too energy intensive, there is a
critical need for development of new materials that can capture CO2
reversibly with acceptable energy costs. Accordingly, solid sorbents have been
proposed to be used for CO2 capture applications through a
reversible chemical transformation. 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 CO2 sorbent candidates from the vast array of possible
solid materials has been proposed and validated. The calculated thermodynamic
properties of different classes of solid materials versus temperature and
pressure changes were further used to evaluate the equilibrium properties for
the CO2 adsorption/desorption cycles. According to the requirements
imposed by the pre- and post- combustion technologies and based on our
calculated thermodynamic properties for the CO2 capture reactions by
the solids of interest, we were able to screen only those solid materials for
which lower capture energy costs are expected at the desired pressure and
temperature conditions. Only those selected CO2 sorbent candidates
were further considered for experimental validations. The ab initio
thermodynamic technique has the advantage of identifying thermodynamic
properties of CO2 capture reactions without any experimental input
beyond crystallographic structural information of the solid phases involved.
Such methodology not only can be used to search for good candidates from
existing database of solid materials, but also can provide some guidelines for
synthesis new materials. In this presentation, we first introduce our screening
methodology and the results on a testing set of solids with known thermodynamic
properties to validate our methodology. Then, by applying our computational
method to mixed solid systems of Li2O and SiO2 with
different mixing ratios and to substituted solid systems of XnY2-nZrO3,
where X and Y = Li, Na, K, we show that increasing the Li2O/SiO2
ratio in lithium silicates increases their corresponding turnover temperatures
for CO2 capture reactions and that a small portion of Li substituted
by Na or K in Li2ZrO3 could increase the CO2
absorption capacity.


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