Wall coating behavior of catalyst slurries in non-porous ceramic microstructures

We report the use of the gas-displacement technique to generate wall coatings of catalyst slurries in fused silica capillaries, as well as ceramic microreactors. The non-porous and glassy surfaces make it difficult to prepare adherent coatings within ceramic structures. In the fused silica capillaries, we were able to show adherent catalyst coats up to 20μm thick and found that the maximum fraction coated decreased as the capillary diameter decreased. We developed a model for the various diameters showing the relationship of the fraction coated versus the capillary number, Ca. It was determined that the coating behavior was controlled by the coupled effects of the fluid rheology and the dramatic increase in the Reynold's number as the diameters decreased. For the ceramic microreactor, we determined that the coatings were adherent and tests showed the wall-coated catalyst in these structures to be catalytically active for the steam reforming of methanol.