Molecular simulation of carbon dioxide adsorption in chemically and structurally heterogeneous porous carbons

Capture of carbon dioxide from fossil fuel power plants via adsorption and sequestration of carbon dioxide in unmineable coal seams are achievable near-term methods of reducing atmospheric emissions of this greenhouse gas. To investigate the influence of surface heterogeneity upon predicted adsorption behavior in activated carbons and coal, isotherms were generated via grand canonical Monte Carlo simulation for CO 2 adsorption in slit-shaped pores with underlying graphitic structure and several variations of chemical heterogeneity (oxygen and hydrogen content), pore width, and surface functional group orientation. Adsorption generally increased with increasing surface oxygen content, although exceptions to this trend were observed on structurally heterogeneous surfaces with holes or furrows that yield strongly adsorbing preferred binding sites. Among the heterogeneous pore structures investigated, those with coal-like surfaces adsorbed carbon dioxide more strongly than planar, homogeneous graphitic slit pores of comparable width. Electrostatic adsorbate–adsorbent interactions significantly influenced adsorption onto model surfaces. © 2006 American Institute of Chemical Engineers Environ Prog, 25: 343–354, 2006Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55883/1/10168_ftp.pd

Molecular dynamics simulations of simple fluids confined in realistic models of nanoporous carbons

We present molecular dynamics simulations in the micro-canonical ensemble of a Lennard-Jones model of nitrogen confined in realistic models for saccharose-based carbons developed in our previous work. We calculate the velocity autocorrelation function and mean-squared displacement, and the self-diffusivities from the latter. We observe that the self-diffusivity increases with temperature and exhibits a maximum with loading or adsorbate density. To the best of our knowledge, a maximum in self-diffusivities has not been observed in molecular dynamics simulations of fluids confined in slit pores

Shape factors and interaction parameters in equations of state -- Part I. Repulsion phenomena in rigid particle systems

An equation of state for the fluid phase of nonattracting rigid particles of arbitrary shape is presented. A particle shape factor is defined and its dependence on the packing fraction is evaluated from Monte Carlo and molecular dynamics simulation results for a variety of nonattracting asymmetric rigid particles, e.g., rigid-sphere polymers, ellipsoids, star particles, spherocylinders

The use of molecular probes for the characterization of nanoporous adsorbents

Molecular probes can be employed in three different ways for the characterization of nanoporous adsorbents. The simplest approach is to use a range of globular nonpolar molecules of different diameter in order to assess the effective size of the pore entrances in a molecular sieve. For this purpose, conventional gas adsorption (static or dynamic measurements) or gas chromatographic techniques can be used. The aim of the second approach is to characterize the nanopore structure with the aid of nitrogen adsorption at 77 K together with isotherm and adsorption energy measurements with a variety of adsorptives of different molecular size, shape and polarity. The third approach is to make use of polar probe molecules (notably water and alcohols) to investigate the surface chemistry and stability of the adsorbent