(283e) Molecular Simulation of Supercritical Fluid Solvent Effects on CO Chemisorption

While supercritical fluids (SCFs) have been employed in heterogeneous catalysis for decades across a range of chemistries (oxidation, pyrolysis, amination, Fischer-Tropsch synthesis), there is little fundamental, molecular-level information regarding the role of the SCF on elementary heterogeneous catalytic steps.  In this investigation, we use molecular dynamics (MD) simulations to probe the role of supercritical hexane on the adsorption of carbon monoxide on cobalt, as a first step in catalytic Fischer-Tropsch synthesis.  The free energy (potential of mean force) landscape for CO adsorption is calculated using umbrella sampling and the weighted histrogram analysis method (WHAM), for a range of bulk hexane densities, ranging from ideal gas conditions (no SCF hexane) to various near- and super-critical hexane densities and pressures.  These results allow for the first commentary on SCF solvent effects on the energetic and entropic aspects of chemisorption, and provide improved kinetic and thermodynamic parameters for subsequent microkinetic modeling.