Catalytic Oxidation of NO over LaCo_1−xB_xO₃ (B = Mn, Ni) Perovskites for Nitric Acid Production

Nitric acid (HNO₃) is an important building block in the chemical industry. Industrial production takes place via the Ostwald process, where oxidation of NO to NO₂ is one of the three chemical steps. The reaction is carried out as a homogeneous gas phase reaction. Introducing a catalyst for this reaction can lead to significant process intensification. A series of LaCo_1−xMn_xO₃ (x = 0, 0.25, 0.5 and 1) and LaCo_1−yNi_yO₃ (y = 0, 0.25, 0.50, 0.75 and 1) were synthesized by a sol-gel method and characterized using N₂ adsorption, ex situ XRD, in situ XRD, SEM and TPR. All samples had low surface areas; between 8 and 12 m²/g. The formation of perovskites was confirmed by XRD. The crystallite size decreased linearly with the degree of substitution of Mn/Ni for partially doped samples. NO oxidation activity was tested using a feed (10% NO and 6% O₂) that partly simulated nitric acid plant conditions. Amongst the undoped perovskites, LaCoO₃ had the highest activity; with a conversion level of 24.9% at 350 °C; followed by LaNiO₃ and LaMnO₃. Substitution of LaCoO₃ with 25% mol % Ni or Mn was found to be the optimum degree of substitution leading to an enhanced NO oxidation activity. The results showed that perovskites are promising catalysts for NO oxidation at industrial conditions. View Full-Text