Screening investigations into the effect of cryptomelane doping with 3d transition metal cations on the catalytic activity in soot oxidation, NO2 formation and SO2 resistance

Monika Fedyna,Piotr Legutko,Joanna Gryboś,Janusz Janas,Xuehua Yu,Zhen Zhao,Andrzej Kotarba,Zbigniew Sojka

doi:10.1016/j.apcata.2021.118302

Abstract

The cryptomelane catalysts containing transition metal (M/K-OMS-2, M = Cu, Ni, Co, Cr and Fe) was synthesized and characterized by XRD, TEM/EDX, XRF, XPS, Raman, H2-TPR corroborated by potassium thermal desorption measurements. The catalysts were tested for soot oxidation in tight and loose contact modes in various conditions: O2, O2 + NO, O2 + SO2, O2 + NO + SO2. The alterations in the soot oxidation activity were discussed in terms of manganese average oxidation number, NO2 formation during the combustion and potassium release, which are modified by the dopants. It was shown that the strong effect of dopants on the NO2 formation is different in absence and presence of soot, and varies with the type of the sot-catalyst contact, being well corelated with the concurrent CO2 formation. Sulphur resistance can be enhanced by doping of the cryptomelane. The most efficient is the catalyst containing segregated mixed cobalt-manganese spinel phase.

Highlights

A massive part of achievable energy that is vitally needed for development of modern societies is accumulated in fossil fuels
Cryptomelane catalysts doped Cu, Ni, Co, Cr and Fe were charac terized by XRD, TEM/EDX, X-ray Fluorescence technique (XRF), XPS, Raman, H2-temperature programmed reduction (H2-TPR) and potassium thermal desorption measurements
The catalytic were accounted for in terms of the manganese average oxidation number, NO2 formation during the soot combustion and potassium release which are modified by the dopants

Summary

Introduction

A massive part of achievable energy that is vitally needed for development of modern societies is accumulated in fossil fuels. Catalysts based on metal oxides or mixed metal oxides are more stable, cheaper and easier to synthesize when compared to the above-mentioned materials, they are the most frequently tested group of soot combustion catalysts [26] Main types of those catalytic materials exhibit particular structures such as layered K2Fe22O34 [27,28], birnessite [2,29,30] and cobaltate [31], or tunnelled KFeO2 [28,32] and cryptomelane [33,34,35,36]. The catalytic activity of the doped catalyst in presence of O2, NO and O2, as well as the resistance to SO2 were screened and discussed

Catalyst preparation

Catalyst characterization

Catalytic activity

Results and discussion

Conclusions