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.

Molybdenum phosphide (MoP) catalyzes the hydrogenation of CO, CO₂, and their mixtures to methanol, and it is investigated as a high-activity catalyst that overcomes deactivation issues (e.g., formate poisoning) faced by conventional transition metal catalysts. MoP as a new catalyst for hydrogenating CO₂ to methanol is particularly appealing for the use of CO₂ as chemical feedstock. Herein, we use a colloidal synthesis technique that connects the presence of MoP to the formation of methanol from CO₂, regardless of the support being used. By conducting a systematic support study, we see that zirconia (ZrO₂) has the striking ability to shift the selectivity towards methanol by increasing the rate of methanol conversion by two orders of magnitude compared to other supports, at a CO₂ conversion of 1.4% and methanol selectivity of 55.4%. In situ X-ray Absorption Spectroscopy (XAS) and in situ X-ray Diffraction (XRD) indicate that under reaction conditions the catalyst is pure MoP in a partially crystalline phase. Results from Diffuse Reflectance Infrared Fourier Transform Spectroscopy coupled with Temperature Programmed Surface Reaction (DRIFTS-TPSR) point towards a highly reactive monodentate formate intermediate stabilized by the strong interaction of MoP and ZrO₂. This study definitively shows that the presence of a MoP phase leads to methanol formation from CO₂, regardless of support and that the formate intermediate on MoP governs methanol formation rate.