Transition metal oxide catalysts as an alternative for the oxidation of nitrogen monoxide to nitrogen dioxide: kinetic modelling at high space velocity.

BACKGROUND The oxidation of NO to NO₂ is a key step in environmental pollution abatement techniques, such as 'fast- SCR' or diesel engine catalytic traps. In both cases, the conversion of an important fraction of NO into NO₂ is a key step. In this work, two commercially available transition metal oxide catalysts, CuMn and CuCr-based, are studied as an alternative to noble metal catalysts (a Pt/ Al₂O₃ catalyst is used as reference catalyst). RESULTS Steady NO conversion is obtained after the first 1-2 h of operation. The experiments, carried out in an isothermal fixed-bed reactor operating at high space velocities (5.60 g_cat min mol^-1, GHSV_monolith-eq. = 83 000 h^-1) with 500 ppm NO and 20% oxygen, showed that the optimum operating temperature is 380 °C for the CuMn catalyst, 430 °C for the CuCr catalyst and 366 °C for a 0.5% Pt/ Al₂O₃ catalyst. CONCLUSIONS The CuMn catalyst performed very similarly to the 0.5% Pt/ Al₂O₃ catalyst in the vicinity of 380 °C, being a good and cheaper alternative to noble metal catalysts. Kinetic measurements obtained under different conditions, e.g. 3.73-5.60 g_cat min mol^-1 ( GHSV_monolith-eq. = 83 000-125 000 h^-1), 300-900 ppm NO, 1-20% oxygen concentration and 330-480 °C, have been found to fit a mechanistic kinetic model based on the reaction between gas nitrogen oxide and adsorbed oxygen. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]