Effect of Small Molecular Organic Acids on the Structure and Catalytic Performance of Sol–Gel Prepared Cobalt Cerium Oxides towards Toluene Combustion

Jianmeng Chen,Jiade Wang,Jinghuan Chen,Junhong Lin

doi:10.3390/catal9050483

Jianmeng Chen, Jiade Wang + Show 2 more

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https://doi.org/10.3390/catal9050483

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Abstract

Cobalt cerium oxide catalysts with small molecular organic acids (SOAs) as chelating agents were prepared via the sol–gel method and investigated for the complete oxidation of toluene. Four kinds of natural SOAs, i.e. malic acid (MA), citric acid (CA), glycolic acid (GA), and tartaric acid (TA), were selected. The effect of organic acids on the composition, structure, morphology and catalytic performance of metal oxides is discussed in details. The cobalt cerium oxides catalysts were characterized by various techniques, including TG–DSC, XRD, SEM–EDS, N2–adsorption and desorption, XPS, and H2–TPR analyses. The results show that the nature of organic acids influenced the hydrolysis, condensation and calcination processes, as well as strongly affected the textural and physicochemical properties of the metal oxides synthesized. The best catalytic activity was obtained with the CoCe–MA catalyst, and the toluene conversion reached 90% at 242 °C. This outstanding catalytic activity could be related to its textural, redox properties and unique surface compositions and oxidation states. In addition, the CoCe–MA catalyst also showed excellent stability in long–time activity test.

Highlights

Volatile organic compounds (VOCs), as the main precursors of ozone and smog [1], do harm to the environment, and endanger human health [2,3,4]
Cobalt cerium oxide catalysts were prepared via the sol–gel method, and four natural carboxylic acids were chosen as chelating agents in the preparation process
The effects of small–molecule organic acids as chelating agents on the composition, structure, and morphology of the CoCe–X catalysts synthesized are discussed in detail

Summary

Introduction

Volatile organic compounds (VOCs), as the main precursors of ozone and smog [1], do harm to the environment, and endanger human health [2,3,4]. One of the most effective control technologies for VOCs, has been widely studied in the past decade [5,6]. VOCs total oxidation catalysts mainly include transition metal oxides and noble metals [9]. In recent years, transition metal oxide catalysts [12,13], such as Mn, Cu, Cr, Fe, and Co oxides, are becoming increasingly popular [14,15]. Among these catalysts, Co3 O4 is one of the most powerful oxides for VOCs oxidation [16]. CeO2 , a typical rare earth oxide, has excellent redox property and oxygen transfer ability [17], it is widely used as a catalyst promoter in VOCs oxidation reaction [18]

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