Free-standing monolithic catalyst with micro-scale channel dimensions

Abstract

A monolithic catalyst with micro-scale flow channels and methods of making such a monolithic catalyst are provided. The monolithic catalyst includes a plurality of thin catalyst walls. The walls have a set thickness in a range from 1 to 150 &mgr;m. The thin catalyst walls define a plurality of flow channels. A fugitive material is used to form the flow channels. The flow channels have a set width in a range from 1 to 200 &mgr;m. The flow channels are formed by an organic fugitive material, which burns off during processing. By using the thin catalyst walls and flow channels having a set width in a range from 1 to 200 &mgr;m, a reduced diffusion path length that molecules travel between the bulk gas and the active site is provided. Accelerating the mass transport thus improves the overall reaction rate, which allows processing of more reactants. Thus, the volume of the required catalyst is reduced, allowing more compact reactors. Fabrication methods involve simple, low-cost and scaleable procedures, allowing the flow channel and catalyst dimensions to be easily scaled to a requisite size for a given application. One fabrication method involves tape casting successive layers of fugitive and catalyst materials, and then firing to remove the organic binders and partially sinter the catalyst particles. The slurries can also be cast into thin layers using various processes, including screen printing, wet spraying and spin casting. Another fabrication method for fabricating a supported catalyst involves dipping a pre-shaped metal foil into a slurry containing an active catalyst powder, allowing the catalyst slurry to coat the foil evenly and allowing the catalyst slurry coated foil to dry. The catalyst slurry coated foil is dipped into a solution to form a fugitive coating layer, next the coated metal foil is cut into strips and formed into a selected shape.