The influence of structural promoters on the surface properties of reduced magnetite catalysts

Abstract

Several series of fused magnetite samples promoted with, respectively, Al 2O 3, TiO 2, Cr 2O 3, MgO, MnO, CaO, SiO 2, and BeO were prepared, reduced with hydrogen, and the surface area, CO, and CO 2 chemisorptive capacity of each reduced sample determined. The effectiveness of the additives as BET area promoters decreased in the order given above. For each individual promoter the area increased with promoter content. The amount of free iron area (CO chemisorption) in general paralleled the total BET area except in the case of TiO 2-promoted samples, where an actual loss of total iron area occurred with increasing TiO 2 content. On a percentage basis MgO is the best iron surface promoter. CO 2 chemisorptions are clearly influenced by the structural promoters, the more basic the latter the higher the CO 2 chemisorption coverages obtained. This was confirmed by studying the CO 2 chemisorptive capacity of some of the above promoters by themselves.