Industrially Produced Fe- and Mn-Based Perovskites: Effect of Synthesis on Reactivity in Three-Way Catalysis: Part 2.

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

doi:10.1021/acsomega.1c02132

Abstract

Mn-based perovskites obtained by two different industrial procedures [flame spray pyrolysis (FSP) and co-precipitation (COP)] have been extensively compared in terms of chemical, structural, and morphological properties with the aim of evaluating how the upscale of complex catalysts can affect the functionality. The transition between laboratory and production scale is, in fact, usually not straightforward. The catalytic activity was tested focusing on reactions of relevance in the abatement of pollutants. In particular, CO-assisted NO reduction (which could be also considered as a model reaction) and reactions with a synthetic automotive exhaust mixture, including 10% steam and oxygen, were carried out. The development of three-way catalysts is still a relevant question: noble metal-free, efficient catalysts are even more necessary in hybrid vehicles. For this purpose, the catalytic activity of the samples has been correlated with the characterization results and thus with the peculiar aspects of the production method. Relevant differences have been observed between COP and FSP catalysts, in terms of the specific surface area, surface composition, and presence of surface-active sites. Also, the different efficiencies of inserting dopants in the perovskite unit cell and thus in reducibility and ion mobility are relevant. Despite having the same composition and crystalline structure, the catalytic activity and the effect of pre-treatments are observed to depend on the production procedure.

Highlights

This paper should be considered as a direct continuation of part 1; the aim is to evaluate if the effect of preparation procedure described and discussed in part 1 is to be intended for ferrites or it can be considered more generally a problem of upscaling of perovskite oxides
The literature data suggest that good activities can be obtained, considering Fe, Co, and Mn in the B site.[1−3] Cobalt is very active in the abatement of pollutants, with particular reference to oxidation[4−6] and activity in reduction can be enhanced through doping and tuning of the nanocomposition.[7,8]
Besides lattice oxygen, a significant contribution due to other surface oxygen species can be observed. This is evident for the flame spray pyrolysis (FSP) sample, in which surface oxygen species contribute with a broad signal centered at 532−533 eV; the peak position and shape are attributed to surface active oxygen species

Summary

INTRODUCTION

This paper should be considered as a direct continuation of part 1; the aim is to evaluate if the effect of preparation procedure described and discussed in part 1 is to be intended for ferrites or it can be considered more generally a problem of upscaling of perovskite oxides. Work is in course in our laboratories to test the behavior of K-doped manganites with respect to soot oxidation. For these materials, the commonly accepted mechanism is based on structural defects and vacancies which affect oxygen uptake and release. Coprecipitation (COP) technique is not efficient in allowing Ca. inclusion in the lattice and seems less attractive for industrial application, while flame spray pyrolysis (FSP) synthesis allows Ca to enter the structure, and this causes the formation of species like Fe(IV) and oxygen vacancies, an active site for molecule oxidation in the gas phase

Synthesis

RESULTS AND DISCUSSION

CONCLUSIONS

■ REFERENCES