Catalyst supports based on encapsulated magnetic metal particles

Catalyst bodies considerably smaller than 1 mm are attractive for liquid phase reactions, but they cannot be readily separated from the liquid. Small magnetic particles, however, can be magnetically separated from the liquid, even when they are very small, e.g., 30 nm. The main drawbacks of the currently used ferromagnetic particles are their high chemical reactivity and clustering due to the hard magnetic nature. In this article, a procedure is described to produce small nickel-iron and cobalt-iron alloy particles. Exposure of these particles to methane or carbon monoxide, at 725 degrees C, leads to the encapsulation in graphitic carbon, which make them chemically inert. It is demonstrated that the final coercive force and remanence of the encapsulated iron-nickel and iron-cobalt particles are low and the saturation magnetization is elevated, as is required for successful application as a support for catalysts suspended in liquids.