276002 Molecular Simulation Studies of CO2 Adsorption From Mixtures of N2, CH4, and H2O by Microporous Carbon

Wednesday, October 31, 2012: 9:58 AM
405 (Convention Center )
Yangyang Liu and Jennifer Wilcox, Department of Energy Resources Engineering, Stanford University, Stanford, CA

Carbon capture combined with CO2 utilization and sequestration offers the possibility to reduce CO2 emissions in the near future, while allowing for a continued use of fossil fuels. Adsorption of CO2/CH4, CO2/N2, and CO2/H2O mixtures has been studied in the current work. In the case of carbon capture, our studies show that functionalized carbon-based sorbents may be competitive with other sorbents in terms of the pure CO2 adsorption capacity by modifying the surface functionality. The separation of CO2 from CO2/N2 and CO2/H2O gas mixtures is involved in carbon capture for flue gas applications. In the case of carbon storage in coal and the organic matrix of gas shale, CO2 injection into coalbeds and gas shale reservoirs may enhance subsequent methane (CH4) recovery while simultaneously storing CO2; therefore, the adsorption mixtures of CO2/CH4 is involved in CO2 enhanced coalbed methane recovery (CO2-ECBM) and shale gas productions. In this work, complex pore structures for general carbon-based porous materials and natural organic materials were modeled as a collection of independent, non-interconnected, functionalized graphitic slit pores with surface heterogeneities. Together with Bader charge analysis, electronic structure calculations coupled with van der Waals-inclusive corrections can provide the initial framework comprising both the geometry and corresponding charge information required to carry out statistical-based molecular simulations. Grand canonical Monte Carlo simulations are carried out to determine the adsorption isotherms and selectivity of CO2 from CO2/N2 and CO2/CH4 gas mixtures at temperature/pressure conditions relevant to carbon capture and storage applications. The polarity induced by the surface functionalities and the interactions between the surface and the non-polar/polar molecules have been investigated. Molecular simulations of the adsorption of CO2/CH4 and CO2/N2 mixtures show that CO2 preferentially adsorbs on oxygen-containing functionalized graphitic surfaces with an induced polarity due to the strong quadrupole moment of CO2 compared with that of N2 and the weak octupole moment of CH4. For the mixtures where CO2 has a stronger polarity, the difference in the quadrupole moment of the mixture component results in a different surface occupancy on the same surface, and the oxygen-containing functionalized surfaces not only increase the total adsorption of CO2, but also enhance the separation selectivity of a given gas mixture. The investigation of different polar surfaces also shows that surface chemistry is tunable thereby influencing the selectivity and allowing for control of CO2 separation based upon adsorption processes.

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See more of this Session: Molecular Simulation of Adsorption I
See more of this Group/Topical: Separations Division