Synthesis, Characterization and Catalytic Activity of Ternary Oxide Catalysts Using the Microwave-Assisted Solution Combustion Method.

Kawthar Frikha,Lionel Limousy,Jamel Bouaziz,Kamel Chaari,Simona Bennici

doi:10.3390/ma13204607

Abstract

Ni−Co−Al, Ni−Cu−Al and Co−Cu−Al ternary oxide catalysts, with a fixed 5 wt% transition metal loading, were prepared by the microwave-assisted solution combustion method and tested in CO oxidation. The bulk and surface properties of the catalysts were investigated, using XRD, N2 adsorption–desorption, SEM, XPS and TEM techniques. XRD, XPS and TEM results revealed that nickel and cobalt were present as spinels on the surface and in the bulk. Differently, copper was preferentially present in “bulk-like” CuO-segregated phases. No interaction between the couples of transition metal species was detected, and the introduction of Cu-containing precursors into the Ni−Al or Co−Al combustion systems was not effective in preventing the formation of NiAl2O4 and CoAl2O4 spinels in the Ni− or Co-containing catalysts. Copper-containing catalysts were the most active, indicating that copper oxides are the effective active species for improving the CO oxidation activity.

Highlights

Transition metal oxides are potential catalysts in heterogeneous catalysis
On the surface of the Ni− or Co-containing catalysts, while copper oxides exist in the CuO form on the surface of the Cu-containing catalysts, without interacting with alumina, which is in accordance with the transmission electron microscope (TEM) results
The comparison study between the catalytic activities of the different ternary oxide catalysts showed that 5Ni5CuAl and 5Co5CuAl catalysts were more active than 5Ni5CoAl catalysts, and the 5Ni5CuAl catalyst was the most effective

Summary

Introduction

Transition metal oxides are potential catalysts in heterogeneous catalysis. These metal oxides possess interesting electronic surface properties, which are supposed to be beneficial for their application in catalysis [1,2,3]. These properties include the presence of cationic and anionic vacancies, the ability of transition metal cations to undergo oxidation and reduction, as well as the presence of highly mobile oxygen inside their structure [4]. Co or Cu oxide-based catalysts are among the most commonly used catalysts in heterogeneous catalysis. On the surface of the Ni− or Co-containing catalysts, while copper oxides exist in the CuO form on the surface of the Cu-containing catalysts, without interacting with alumina, which is in accordance with the TEM results

Methods

Results

Conclusion