Magnetic catalyst bodies

After a discussion about the importance of the size of the catalyst bodies with reactions in the liquid-phase with a suspended catalyst, the possibilities of magnetic separation are dealt with. Deficiencies of the usual ferromagnetic particles are the reactivity and the clustering of the particles. A procedure to produce more suitable magnetic particles is to deposit a nickel-iron precursor on a support and to obtain small metal particles by reduction. Subsequently the metal particles are encapsulated in layers of graphitic carbon by exposure to methane at 700 degrees C. Exposure to methane at lower temperature leads to growth of carbon fibrils, which can be controlled by raising the temperature. The alumina support is dissolved in hydrochloric acid. The magnetic properties of nickel-iron alloys prevent clustering of the ferromagnetic particles. (C) 1999 Elsevier Science B.V. All rights reserved.