Magnesium oxide as a support material for dehydrogenation catalysts

Abstract

Two commercial preshaped magnesium oxides, viz. pellet-shaped magnesium oxide (Englhard, Mg-0601) and spherical magnesium oxide (Süd-Chemie, T-4403), have been evaluated for use as carrier material in supported dehydrogenation catalysts. The influences of temperature and steam atmosphere on the textures of the support materials have been studied.

The texture of the pellet-shaped support has been found to be well controlled by thermal treatment in air. Upon thermal treatment the B.E.T. surface area of this magnesium oxide decreases, while the average pore radius increases. Typically, a B.E.T. surface area of 6 m² g^–1 and an average pore radius of 1000 Å is obtained upon treatment at 1173 K. Spherical magnesium oxide (Süd-Chemie, T-4403) has a very low surface area of 0.18 m² g^–1 and an average pore radius of 40 000 Å. Calcination in air at temperatures up to 1473 K does not affect the texture. In 4.8 bar of steam at 423 K both magnesium oxides react completely to magnesium hydroxide. This is accompanied by a drastic increase of the B.E.T. surface area and a decrease of the mechanical strength. At 973 K and a steam pressure of 1 bar no reaction with water is observed.