Ostwald Process Intensification by Catalytic Oxidation of Nitric Oxide

The Ostwald process is one of the commercial pathways for the production of nitric acid (HNO₃), a key component in the production of nitrate fertilizers. The Ostwald process is a mature, extensively studied, and highly optimized process, and there is still room for further intensification. The process can be further intensified by catalyzing the homogeneous oxidation of nitric oxide to nitrogen dioxide. In this work, we explore the NO to NO₂ oxidation capacity of ruthenium on γ-Al₂O₃ support wash-coated on to a cordierite monolith. In a lab-scale setup with simulated feed comprising 10% NO, 6% O₂, 15% H₂O and rest Ar, and 8% NO, 2% NO₂ 5% O₂, 15% H₂O and rest Ar, the ruthenium and γ-Al₂O₃ wash-coated monoliths attained a steady conversion of 72 and 56%, respectively. A remarkable steady conversion of 20% more than the gas phase for 65 h over 4 days was presented by the Ru_{Wc,γ-Al₂O₃,Cordierite} catalyst in one of the pilot plants at Yara, a Norwegian fertilizer company. The results presented in this work clearly provide evidence to support the idea that ruthenium on a gamma-alumina catalyst support can oxidize NO to NO₂ under industrial nitric acid production conditions and mark an important step in the intensification of the Ostwald process.