Characterization and catalytic investigation of NO + CO reaction on perovskites of the general formula La xM 1 − xFeO 3 (M = Sr and/or Ce) prepared via a reverse micelles microemulsion route

Abstract

Four different perovskite type solids with nominal composition LaFeO 3 (LFOr), La 0.85Sr 0.15FeO 3 (LSFOr), La 0.8Sr 0.1Ce 0.1FeO 3 (LSCFOr) and La 0.8Ce 0.2FeO 3 (LCFOr) were prepared via a reverse micelles microemulsion route. The aim of this work was to investigate the effect of doping with Sr and Ce in the structural properties, surface area and catalytic properties of final solids in comparison with the undoped reference solid LaFeO 3. The microemulsion system which was used is composed of cetyl-trimethyl-ammonium-bromide (CTAB), 1-butanol, n-octane and nitrate salts of the metals. XRD measurements combined with Rietveld analysis helped us to identify the % quantity of structural phases which were formed. Scanning electron microscopy (SEM) images showed that the obtained solids consist of nanoparticles in the range of 20–80 nm. BET experiments showed that the final solids achieve much higher specific surface area (ssa) (30–61 m 2/g) than similar solids which have been prepared by other methods. Catalytic tests in NO + CO reaction were made with the use of gases He/NO/CO in the ratio 96/2/2 with a total flow rate of 100 cm 3/min. The full sequence of catalytic activity of tested solids is LCFOr > LSCFOr > LSFOr ≥ LFOr and this sequence is in full agreement with the sequence of increment of ssa of the solids.