Industrially Produced Fe- and Mn-Based Perovskites: Effect of Synthesis on Reactivity in Three-Way Catalysis: Part 1

Elena Brusamarello,Cristina Salazar-Castro,Andrea Eva Pascui,Paolo Canu,Cataldo Blonda,Antonella Glisenti

doi:10.1021/acsomega.1c02133

Abstract

La0.6Ca0.2Fe0.8Cu0.2O3, undoped (LF) and Ca, Cu-doped (LCFC), powders, obtained by different industrial procedures, are compared to evaluate reproducibility and scale-up in different industrial synthetic approaches: flame spray pyrolysis (FSP) and coprecipitation (COP). Also the effects of varying composition (doping) and FSP process variability are considered as comparative studies on morphological, crystallographic, redox and compositional properties, and functional activity. A model reaction (CO + NO) and reactions with an automotive exhaust mixture were carried out. Unexpected results on the effectiveness of doping for catalytic activity emerged. Samples with the same compositions proved to be significantly affected by the synthesis, with variability within the same process. The activity of LCFC COP is comparable to the FSP analogue, at stoichiometric conditions, notwithstanding differences highlighted by characterization. In an oxygen-deficient mixture, LCFC-COP yields higher NO reduction and CO oxidation activity than LCFC-FSP. The absence of Ca in the lattice was unexpectedly beneficial. The doping effectiveness must be carefully checked for large-scale production.

Highlights

The development of innovative catalysts for pollutant control focused on perovskites as versatile materials, which allows the incorporation of different cations in their structure to tune activity and selectivity.[1]
The catalytic activity of the samples in three-way catalysis (TWC) reactions is correlated with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2-TPR), Brunauer−Emmett−Teller (BET) surface area measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) results
To help understand the effect of Ca-doping, La0.6Ca0.2Fe0.8Cu0.2O3 was compared with the Ca-free La0.7Fe0.8Cu0.2O3 (LFC flame spray pyrolysis (FSP)) both obtained by FSP

Summary

INTRODUCTION

The development of innovative catalysts for pollutant control focused on perovskites as versatile materials, which allows the incorporation of different cations in their structure to tune activity and selectivity.[1]. The first reports of perovskite synthesis using FSP were by Brewster and Kodas in 1997 who prepared BaTiO3 by spraying an aqueous Ba acetate/Ti lactate feed into a H2/air flame.[14] This was followed by Leanza et al who prepared La1−xMxCoO3 (M = Ce, Eu) by spraying an aqueous metal acetate/nitrate/citrate feed into a H2/O2 flame.[15] This is the first part of the article, which comprises a second one and whose aim is to investigate the effects of industrial scale-up on functional properties of the catalysts, and two different materials are considered: Fe-based Cu-doped and Mn-based K-doped perovskites to shine light on the differences and similarities between different compositions when subjected to different synthetic approaches. The catalytic activity of the samples (both in the first and second parts of the paper) in TWC reactions is correlated with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2-TPR), Brunauer−Emmett−Teller (BET) surface area measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) results

EXPERIMENTAL SECTION

RESULTS AND DISCUSSION

CONCLUSIONS

■ REFERENCES