(629h) Atomic Layer Deposition for In-Situ Fabrication of Catalyst Supports

Microchannel catalytic reactors exhibit improved mass and heat transfer properties and are thus often chosen for highly exothermic or endothermic reaction conditions.  In conventional microchannel reactors, catalyst is deposited within channels either by wash coating or by packing channels with particles prior to bonding.  Both methods exhibit challenges: washcoating can result in poor channel volume usage, while channel packing techniques often result in the crushing and subsequent flaking of particles and clogging or fluid channeling due to differences in the thermal expansion of the materials.  A novel in-situ fabrication method is presented for the customizable manufacture of microstructured reactor substrates made from ceramics/cermets for use in highly exothermic or endothermic catalytic reaction applications.    

Microstructured supports were fabricated by atomic layer deposition on sacrificial polymer templates of polystyrene-divinylbenzene with a surface area of 700 m²/g, pore size of 30 nm and particles sizes of 50-100 μm and 80-160 μm.  Atomic layer deposition produces conformal films by two sequential self-limiting surface half reactions of Al(CH₃)₃ and H₂O for alumina and similarly for other materials.  Reactions were performed at temperatures below 100°C; once the desired film thickness was achieved the polymer template was volatilized at temperatures above 400°C.  The resulting thermal, fluid flow and structural characteristics of these structures are presented.  A heat transfer model was developed and is compared to a conventional packed bed of ceramic particles.