Rotating foam stirrer reactors have a promising application in multiphase reactions. In this reactor, highly porous open-celled materials, solid foams, are used both as a catalyst support and as stirrer blades. One of the advantages of such a foam stirrer is easy catalyst handling. This paper presents a preparation method for catalysts on solid foam supports. The performance of the alumina foam catalysts is tested in the hydrogenation of a functionalized alkyne. A stable and homogeneous catalytic coating was deposited on aluminum foams by a combination of anodization and wash coating using the slurry method. Anodization produced a rough and porous material that improved the adhesion of the catalytic coating. The use of a slurry with a bimodal particle size distribution increased the catalytic coating stability. The mass loss of the catalytic coating after applying ultrasonic vibrations was less than 10 wt %, which indicates a good adhesion. A high specific surface area was achieved by increasing the foam cell density, that is, the number of pores per linear inch (ppi), and the catalytic coating thickness. With the wash-coating method, catalytic coatings were produced having a thickness between 10 and 40 µm, a porosity of around 50%, and a specific surface area up to 28.5 m2/gfoam. The hydrogenation of 3-methyl-1-pentyn-3-ol was chosen as the test reaction. Internal and external mass transfers limit the reaction rate of this fast reaction. High activity and selectivity were reached by combining a high specific surface area with a thin catalytic coating on the foam. Increasing the foam cell density up to 20 ppi led to enhanced liquid-solid mass transfer because of the high specific surface area combined with the fast refreshment of the catalyst surface. Coating thicknesses of less than 20 µm led to improved internal mass transfer due to shorter diffusion paths.
Leon Matheus, M. A., Tschentscher, R., Nijhuis, T. A., Schaaf, van der, J., & Schouten, J. C. (2011). Rotating foam stirrer reactor: Effect of catalyst coating characteristics on reactor performance. Industrial and Engineering Chemistry Research, 50(6), 3184-3193. https://doi.org/10.1021/ie101962g