Low-density catalysts and catalyst supports part II : the preparation of strong, low-density pellets of alumina / G.T. Shaw and B.I. Parsons, Fuels Research Centre. : M38-1/230-1970E-PDF

"The preparation and properties of pellets from highly porous forms of alumina gel are described. Considerable modification in both apparatus and technique is required to form pellets of low density reproducibly. A continuous-type pelleting press has been adapted to function as a constant-pressure apparatus, and a lubricating system has been developed to minimize friction between the walls of the punches and dies. In general terms, the pellet strength and density are a function of a) the pore volume initially present in the granular gel, and b) the pelleting pressure. Under all the conditions investigated, pellet strength and density increased systematically with the pelleting pressure. At equal pelleting pressures, the larger the pore volume (and the average pore size) present in the granular gel, the lower the pellet density and the greater the pellet strength. It has also been found that the particle size distribution in the powder mixtures increases in importance with increasing porosity. In the case of the gel with the highest porosity, the pellet density decreased as the concentration of fine particles (minus 200 mesh) increased. A mechanism is proposed to explain the improved pelleting characteristics observed with the highly porous aluminas"--Abstract, page i.

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