The Influence of Residual Sodium on the Catalytic Oxidation of Propane and Toluene over Co3O4 Catalysts

Guangtao Chai,Yanglong Guo,Jose Luis Valverde,Weidong Zhang,Anne Giroir-Fendler

doi:10.3390/catal10080867

Abstract

A series of Co3O4 catalysts with different contents of residual sodium were prepared using a precipitation method with sodium carbonate as a precipitant and tested for the catalytic oxidation of 1000 ppm propane and toluene at a weight hourly space velocity of 40,000 mL g−1 h−1, respectively. Several techniques were used to characterize the physicochemical properties of the catalysts. Results showed that residual sodium could be partially inserted into the Co3O4 spinel lattice, inducing distortions and helping to increase the specific surface area of the Co3O4 catalysts. Meanwhile, it could negatively affect the reducibility and the oxygen mobility of the catalysts. Moreover, residual sodium had a significant influence on the catalytic activity of propane and toluene oxidation over the synthesized Co3O4 catalysts. The catalyst derived from the precursor washed three times presented the best activity for the catalytic oxidation of propane. The origin was traced to its better reducibility and higher oxygen mobility, which were responsible for the formation of active oxygen species. On the other hand, the catalyst obtained from the precursor washed two times exhibited better performance in toluene oxidation, benefitting from its more defective structure and larger specific surface area. Furthermore, the most active catalysts maintained constant performance in cycling and long-term stability tests of propane and toluene oxidation, being potentially applicable for practical applications.

Highlights

Volatile organic compounds (VOCs), mainly released from transportation and industrial processes, cause serious environmental pollution, and have toxic effects on human health [1,2]
Thermogravimetric and Differential Scanning Calorimeter (TG-DSC) analyses were carried out to investigate the thermal decomposition of cobalt oxide precursors
It was proved that both the physicochemical properties of the synthesized Co-CO3catalysts and their catalytic activities for propane and toluene oxidation were influenced by the residual xT catalysts and their catalytic activities for propane and toluene oxidation were influenced by the sodium in the catalysts

Summary

Introduction

Volatile organic compounds (VOCs), mainly released from transportation and industrial processes, cause serious environmental pollution, and have toxic effects on human health [1,2]. They contribute to the formation of photochemical smog and further promote the production of ozone. The degradation of VOCs is usually difficult and produces secondary pollutants, resulting in long-lasting pollution and impacting the ecosystem. Research has focused on developing different efficient techniques to degrade VOCs. One of the most promising and economical techniques to remove these pollutants is the catalytic oxidation method, which allows VOC removal from dilute streams at a Catalysts 2020, 10, 867; doi:10.3390/catal10080867 www.mdpi.com/journal/catalysts

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