Copper Manganese Oxide Catalysts Modified by Gold Deposition: The Influence on Activity for Ambient Temperature Carbon M
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Copper Manganese Oxide Catalysts Modified by Gold Deposition: The Influence on Activity for Ambient Temperature Carbon Monoxide Oxidation Kieran J. Cole • Albert F. Carley • Mandy J. Crudace • Michael Clarke • Stuart H. Taylor • Graham J. Hutchings
Received: 6 May 2010 / Accepted: 4 June 2010 / Published online: 22 June 2010 Ó Springer Science+Business Media, LLC 2010
Abstract The addition of gold, by deposition precipitation, to a mixed copper manganese oxide catalyst (Hopcalite) has been studied for ambient temperature carbon monoxide oxidation. The deposition of gold on the catalyst surface enhanced the activity of the Hopcalite. The catalyst containing 1 wt% gold was the most active and showed higher activity than Hopcalite containing 0.5 and 2 wt% gold. It is expected that the introduction of gold will introduce new active sites to the Hopcalite that are associated with the gold nanoparticles. However, gold addition also increased the reducibility of the catalyst significantly compared to unmodified Hopcalite, and the most easily reduced catalyst was the most active, indicating that the lability of lattice oxygen was an important factor influencing activity. Keywords Hopcalite Carbon monoxide Low temperature oxidation Gold
1 Introduction The use of catalysts for carbon monoxide oxidation at ambient temperature is an important process in a number of applications including respiratory protection. Mixed copper manganese oxide (Hopcalite or CuMn2O4), has long been K. J. Cole A. F. Carley S. H. Taylor (&) G. J. Hutchings Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK e-mail: [email protected] M. J. Crudace M. Clarke Molecular Products Limited, Mill End, Thaxted, Essex CM6 2LT, UK
established as a catalyst of choice for many applications [1]. One of the most effective preparation routes for Hopcalite is by co-precipitation, and there have been attempts to optimise the preparation conditions to enhance the activity of the catalyst [2]. One of the most important parameters for preparing a high activity catalyst is the influence of ageing time, as catalysts aged for short and extended periods were more active than catalysts aged for intermediate times [3]. Furthermore, the surface concentration of residual sodium ions, remaining on the final catalyst due to insufficient washing during preparation, also have a poisoning effect on catalyst activity [4]. In the original formulations of Hopcalite, additional catalyst components, such as silver [5], were included to enhance the oxidation activity. In more recent years there have been few attempts to investigate the incorporation of extra catalyst components to improve activity. However, recently we have shown that Hopcalite promoted by low levels of cobalt demonstrate an improvement in activity for CO oxidation compared to commercially available catalysts [6]. Hopcalite is not the only well-recognised low temperature CO oxidation catalyst, as some 25 years ago Haruta and co-workers d
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