| abstract |
Catalytic devices employing novel multiple-layer support coatings in combination with known base and noble metal catalysts are described. The devices are generally useful as supported catalyst systems and particularly suitable for use in the treatment of automotive exhaust and other waste gases. The multiple-layer support coatings typically comprise a base oxide layer composed of alumina, silica or mixtures thereof and at least one covering layer of a different composition composed of an oxide selected from the group consisting of silica, titania, zirconia, tin oxide and manganese oxide; these multiple coatings are found to enhance and/or stabilize the activity of known catalysts to a degree not demonstrated by either single-oxide or mixed-oxide support coatings used in the prior art. Also disclosed are novel deposition methods, generally useful in the deposition of the coatings of the present invention, comprising the alkoxide impregnation of a support structure and the subsequent in situ hydrolysis of the alkoxide to form an adherent hydrous oxide coating. |