(489d) Modeling Relaxation Processes for Fluids in Ordered Pore Networks Using Dynamic Mean Field Theory

Recently we have developed a dynamic mean field theory (DMFT) for fluids in porous materials (P. A. Monson, J. Chem. Phys., 128, 084701 (2008)). The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores. DMFT is especially useful for studying mesoporous systems exhibiting adsorption/desorption hysteresis, as well as mass transfer resistances to equilibration for states outside the hysteresis regime. Since the theory describes the evolution of the density distribution in the system it can be used to visualize the evaporation and condensation processes involved in adsorption and desorption.

In this paper we describe the application of the DMFT approach to fluids in ordered pore networks, to model the behavior seen in systems like MCM-48 or hierarchically ordered mesoporous silica materials. We show how the theory can be used study the relaxation time for different points on adsorption and desorption isotherm. We focus especially on the dynamics for states in the hysteresis region. We also discuss the equilibration processes for fluids pore networks relative to those in independent pores.