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

Abstract

AbstractBACKGROUNDThe 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).RESULTSSteady 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 gcat min mol‐1, GHSVmonolith‐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.CONCLUSIONSThe 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 gcat min mol‐1 (GHSVmonolith‐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