The origin and types of pores in some alumina catalysts

Abstract

By converting detailed nitrogen desorption isotherm data to pore-volume distributions, as many as three different pore systems have been distinguished in a single calcined catalyst. Dehydration pores are observed to be formed by the loss of water from larger crystals of alumina hydrates, either alumina trihydrates or alumina monohydrate (boehmite). These pores are small and sensitive to sintering conditions. Interparticle pores are found which appear to be developed from the packing of the ultimate particles. The volume and sizes of the interparticle pores are shown in some cases to be directly dependent on the size of the ultimate particles. When the particles are small (about 35 Å) the interparticle pore size is sensitive to the method of drying of the alumina hydrate. The size and volume of pores formed by larger particles (greater than 100 Å) can be affected by extrusion and tableting techniques.