Recovery of Noble Metals in the Production of Nitric Acid and Ammonium Nitrophosphate Fertilizer

摘要

Ammonia is known to decompose into nitrogen and water in the homogeneous oxidation by atmospheric oxygen (catalyst-free combustion). The technology for the heterogeneous oxidation of ammonia to NO_2, necessary for the synthesis of weak nitric acid (WNA), was first devised by W. Ostwald (Germany) in 1902 and put into industrial practice in 1907. Platinum was suggested as a catalyst for this process [1]. Later on, alloys of platinum with rhodium (3.5–10%), and sometimes with the addition of palladium (now up to 23%), came to be used to increase the strength and service life of the catalyst.