oa Ammonia Oxidation Catalysts

Rhodium-platinum gauzes used as catalysts in nitric acid plants operating at various pressures have been examined by microscopy and by X-ray diffraction. Some gauzes possess low conversion efficiency and these are usually covered with deposits that can frequently be traced to sources of contamination. Gauzes operated at pressures of four or more atmospheres also possess coatings of rhodium oxide that are difficult to remove by fusion or pickling. The suggested cause of formation of this oxide shows that it cannot be avoided but that methods exist for cleaning gauzes from higher pressure plants.