The use of CO2 as a fracturing fluid for enhanced gas recovery is receiving increased attentionas it could accomplish the dual purpose of sequestering CO2 in mineral formations, and recovering CH4 as a source of energy. Isotherms for CO2 and CH4 adsorbed to mineral surfaces have been determined experimentally and are available in the literature. While these experimental isotherms allow one to infer the affinity of the adsorbates for the substrates, computational chemistry can provide a molecular level interpretation of the interactions between CO2 and CH4 and the substrate, necessary for the development of first-principle models of these complex systems. Recently progress has been made with a variety of computational approaches. In this work we use first principles Density Functional Theory with the b3lyp/6-311++G(d,p) functional  to model CO2, CH4, and their respective interactions with montmorillonite surfaces to determine surface complexes and adsorption energies. The effect of water on the adsorption is addressed with implicit solvation models and the inclusion of explicit water molecules.  Models were developed with GaussView, energy minimized with Gaussian 09, and analyzed with Molden in order to get an array of data representing a variety of experimental conditions.    The free energy of adsorption ?Gads was determined from the theoretical calculations and compared to the values extracted from the experimental isotherms. Similarly, the vibrational frequencies for infrared and Raman active modes were calculated and compared to experimental determinations.

Atomistic level computation of CH<sub>4</sub> and CO<sub>2</sub> with clay mineral surfaces: Adsorption and vibrational frequencies

248th National Meeting (2014)

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Atomistic level computation of CH4 and CO2 with clay mineral surfaces: Adsorption and vibrational frequencies

Atomistic level computation of CH₄ and CO₂ with clay mineral surfaces: Adsorption and vibrational frequencies