Cobalt Oxide Catalysts in the Form of Thin Films Prepared by Magnetron Sputtering on Stainless-Steel Meshes: Performance in Ethanol Oxidation

Květa Jirátová,Martin Čada,Pavel Topka,Roman Perekrestov,František Kovanda,Zdeněk Hubička,Martin Koštejn,Jana Balabánová,Michaela Dvořáková,Jiří Olejníček

doi:10.3390/catal9100806

Abstract

Catalytic total oxidation is an effective procedure to minimize emissions of volatile organic compounds (VOC) emissions in industrial gases. Catalysts in the form of meshes are remarkable as they minimize the internal diffusion of reactants during the reaction as well as the need of expensive active components. In this paper, various conditions of radio frequency magnetron sputtering of cobalt on stainless-steel meshes was applied during catalyst preparation. Properties of the supported Co3O4 catalysts were characterized by SEM, XRD, temperature programmed reduction (H2-TPR), FTIR, XPS, and Raman spectroscopy. Catalytic activity was examined in deep oxidation of ethanol chosen as a model VOC. Performance of the catalysts depended on the amount of Co3O4 deposited on the supporting meshes. According to specific activities (the amounts of ethanol converted per unit weight of Co3O4), smaller Co3O4 particle size led to increased catalytic activity. The catalyst prepared by sputtering in an Ar+O2 atmosphere without calcination showed the highest catalytic activity, which decreased after calcination due to enlargement of Co3O4 particles. However, specific activity of this catalyst was more than 20 times higher than that of pelletized commercial Co3O4 catalyst used for comparison.

Highlights

Catalytic total oxidation is an effective procedure to minimize emissions of volatile organic compounds (VOC) emissions in industrial gases [1,2]
The following cobalt oxide catalysts were prepared on stainless-steel meshes: Three catalysts differing in Co3 O4 layer thickness were prepared by radio frequency (RF)
Magnetron sputtering of Co in 90% N2 and 10% H2 forming gas, two catalysts were prepared by RF magnetron sputtering of Co in an oxidation Ar+O2 atmosphere, and a catalyst prepared by conventional impregnation of meshes (Co-I) was included for comparison

Summary

Introduction

Catalytic total oxidation is an effective procedure to minimize emissions of volatile organic compounds (VOC) emissions in industrial gases [1,2]. We have demonstrated a high catalytic activity of cobalt oxide catalysts in oxidation of ethanol [3], which is very often emitted from pharmaceutical plants or printing works. High activity of cobalt oxide catalysts was observed in total oxidation of other organic compounds, like propane [4,5,6], toluene [5,7], CO [8], or formaldehyde [9]. Catalysts intended for fast chemical reactions have to work at short residence times, i.e., at high throughputs of reaction mixture. Under such conditions, pelletized catalysts show high pressure drops, and catalysts bed of high free volume is necessary. The well-known application of a metal gauze catalyst is the oxidation of ammonia with air to nitric oxide used in the production of nitric acid and Catalysts 2019, 9, 806; doi:10.3390/catal9100806 www.mdpi.com/journal/catalysts

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