Influence of the preparation method on the surface properties and activity of alumina - supported gallium oxide catalysts

As alumina seems to be the best support for gallium species in terms of activity in the reaction of NOx reduction by hydrocarbons, alumina-supported gallium oxide catalysts presenting similar surface areas were prepared by two different methods, an innovative pseudo sol-gel method and for comparison a conventional impregnation method. The bulk and surface compositions of the samples as well as their structural and textural features confirmed the better dispersion of the pseudo sol-gel sample. The acid-base properties of the samples were determined by adsorption microcalorimetry of ammonia and sulfur dioxide. The sample prepared in non-aqueous mixture showed a more homogeneous distribution of the acid sites, accompanied by an increase of the acid strength and a decrease of the number of basic sites. Moreover the catalytic activity for NOx reduction by ethene in oxygen excess was superior for the sol-gel sample. It is likely that this better activity could be associated with the higher dispersive effect of this synthesis method.