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Espinal, Laura

Publications and source records attributed to Espinal, Laura.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

First-principles study of carbon capture and storage properties of porous MnO 2 octahedral molecular sieve OMS-5

Based on the experimentally determined framework structure of porous MnO 2 octahedral molecular sieve (OMS)-5, we used density functional theory-based calculations to evaluate the effect of Na + cation on pore dimensionality and structural stability, and the interaction between CO 2 and OMS-5. Furthermore, we quantified the formation energy of one CO 2 /unit tunnel and two CO 2 /unit tunnel, and projected the electronic density of states on the OMS-5 framework, CO 2 molecules, and Na+ cations to reveal their individual contributions and bonding nature. Partial charge densities were also calculated to investigate CO 2 adsorption behavior in the OMS-5. Our studies predict the initial stage and driving force for the adsorption of CO 2 in the OMS-5, guiding the OMS material design for carbon capture and storage applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Time-Dependent CO[subscript 2] Sorption Hysteresis in a One-Dimensional Microporous Octahedral Molecular Sieve

The development of sorbents for next-generation CO{sub 2} mitigation technologies will require better understanding of CO{sub 2}/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO{sub 2} sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO{sub 2} sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a 'gate-keeping' role of the cation in the tunnel, only allowing CO{sub 2} molecules to enter fully into the tunnel via a highly unstable transient state when CO{sub 2} loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO{sub 2} is responsible for the observed hysteretic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗