The oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) is a key step both in NOx abatement technologies as well as in the Ostwald process for nitric acid production. A 1 wt.% Pt/Al2O3 catalyst was used to study oxidation of nitric oxide at two different concentrations of NO; 400 ppm NO (representative of engine exhaust treatment) and 10% NO (nitric acid plant). The catalyst was characterised using N2 adsorption and CO chemisorption. The effect of temperature and feed concentration on catalytic activity was investigated.For a feed comprising of 10% NO and 6% O2, Pt/Al2O3 exhibits significant catalytic activity above 300 o C. Addition of 15% H2O in the feed had an insignificant effect on activity of the catalyst. We report for the first time the kinetics for oxidation of NO to NO2 under nitric acid plant conditions.An apparent activation energy of 33 kJ/mol was observed. The rate equation for the overall reaction was determined to be r=kfKG(PO2) 0.5 , where kf is the forward rate constant. The reaction is independent of NO concentration while it has half order dependency on oxygen. The reaction mechanism which fits our experimental observation consists of dissociative adsorption of oxygen, associative adsorption of nitric oxide with desorption of nitrogen dioxide as the rate limiting step.

Eight different silanes with chloro or methoxy active ligands have been examined to modify the surface of a standard γ-alumina support to investigate the effect of surface acidity and hydrophobicity in Fischer-Tropsch synthesis (FTS) at common operating conditions (210 °C; 20 bar; H2/CO=2.1). Silanes were impregnated prior to cobalt (Pre) or after cobalt impregnation and calcination (Post). Samples were characterized by standard techniques (FTIR, XRD, TPD, TPR, TGA, BET). In the Post series, cobalt crystallite size is maintained, while it is reduced when cobalt impregnation is performed on a partly hydrophobic surface. Both series of catalysts have FTS performances that deviate significantly from a reference catalyst and, in combination with characterization data, the silanes have modified all the 15 examined catalysts. The Pre series offer options for improved selectivity to higher hydrocarbons in FTS. The effects of silylation on FT performance mechanisms are discussed in terms of gas diffusion limitations, strain on cobalt particles and partial blocking of CO activation sites.

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 LaCo1−xMnxO3 (x = 0, 0.25, 0.5 and 1) and LaCo1−yNiyO3 (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.