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This paper studies the effect of addition of Zn and ultrasound-assisted co-precipitation on Cu-Mn oxide catalysts for the oxidation of CO. Cu-Mn-Zn oxide catalysts were synthesised at different molar ratios and characterised and evaluated for CO oxidation performance. Scanning electron microscopy (SEM) imaging showed that the morphologies and textural properties of the catalysts were markedly affected by the different synthesis conditions, notably the formation of different geometries of various sizes depending on the Zn loading used. Characterisation results also revealed that both the addition of Zn and the use of ultrasound-assisted synthesis improved the dispersion of metal constituents in the mixed oxide phase, evident from the lower peak intensity and smaller crystallite sizes and more dispersed particles as seen in SEM imaging. Gas adsorption results revealed that Zn loading influences the porosity and adsorption capability of the catalyst. Zn-loaded samples exhibited a H3 hysteresis loop, which suggests the presence of slit-like pores. Temperature-programmed reduction results indicate that sonicated samples exhibit improved reduction capabilities which can increase overall catalytic activity. Results showed that Cu/Mn/Zn = 2:1:0.5 displayed the highest activity, showing 76.0% and 82.8% for CO and SO2 at 130 °C, respectively. This work has confirmed that the addition of 0.5 molar ratio of Zn and the presence of ultrasonic treatment during the catalyst synthesis have improved the overall catalytic performance, while further addition in Zn concentrations resulted in an adverse effect on the catalyst. [ABSTRACT FROM AUTHOR]

This present work investigates the novel method of synthesising copper manganese oxide (Hopcalite) catalysts with a Cu:Mn ratio of 1:2 by using a facile ultrasound-assisted co-precipitation synthesis technique. The CuMnO x catalysts were synthesised using an ultrasonic bath or an ultrasonic probe with varying ultrasonic powers. The catalysts were further characterised and evaluated for the oxidation of carbon monoxide (CO). Characterisation results revealed that samples prepared using the ultrasonic method exhibited enhanced physical properties, such as highly dispersed particles with a larger surface area and pore size. Besides, the presence of mixed copper and manganese oxide phases was detected, which provided synergistic interactions to facilitate and enhance CO oxidation. The amorphicity and reducibility of the catalysts were also improved, thus indicating the presence of more active sites. Furthermore, the catalyst prepared using the ultrasonic probe at a power of 23.3 W with a 15 min sonication time was found to be the most active, with the capability of oxidising CO to CO 2 to completion (100 %) at ambient conditions. It also possessed high catalytic stability, in which catalytic activity was not compromised for as long as 200 min. On the whole, this work has ascertained that by incorporating a simple ultrasonic irradiation step into the synthesis procedure of copper manganese oxide catalysts, the overall performance of the catalyst can be greatly improved compared to those already found in the literature, which demonstrates the potential application of this new method on a wider, commercial scale for carbon monoxide removal. • Copper Manganese Oxide synthesized in the presence of ultrasonication improved overall catalytic properties. • Mixed oxides of CuO, MnO2 and Cu2MnO4 were essential in the enhancement of copper manganese oxide catalytic activity. • Ultrasound synthesized copper manganese oxide showed complete removal of CO at ambient conditions. [ABSTRACT FROM AUTHOR]