Intraparticle and interstitial flow in wide-pore superficially porous and fully porous particles

- Models of fully porous and superficially porous particles are constructed.
- Extensive fluid flow is calculated within and around these particles in packed beds.
- Velocities within these wide pore particles show significant internal flow.
- Perfusion chromatography can be performed with these particles.
- Course-grained theory agrees with the fluid velocities.

Using a synthetic particle model, viscous fluid flow through packed beds of porous particles is directly simulated at the pore scale (1000Å) using the lattice Boltzmann method to characterize intraparticle and interstitial flow. Synthetic particle models are derived from synthesis conditions, scanning electron and focused ion-beam microscopy. A fully porous particle (FPP) and a superficially porous particle (SPP), derived from the FPP, both with the same external surface, are studied. Packed beds of random packings and body-centered cubic packings of the SPP and FPP models were generated by a Monte Carlo procedure that employs random translation and rigid-body rotation of the particles.Detailed velocity distributions are presented for the interstitial and intraparticle regions of the packed beds and within the particles. These results confirm that porous particle packed beds are heterogeneous systems which require extensions to classical theory for correctly predicting the resistance to flow. It is shown that SPPs require less pressure than FPPs to maintain the same flow velocity. For the random SPP and FPP packed beds, the particle hull mass flux is ≈10% of the interstitial flux and ≈3% of the total volumetric flux in the flow direction through the SPP hull. The calculated intraparticle pore velocities confirm that an internal flow, characteristic of “perfusion” chromatography, exists within the porous shell that can enhance biomolecular separations.