A novel route of single step reactive calcination of copper salts far below their decomposition temperatures for synthesis of highly active catalysts

Abstract

A novel route of reactive calcination (RC) of Cu-salts for the synthesis of highly active catalysts was studied for the first time. The route involved feeding a low concentration of a chemically reactive-CO–air mixture over the salts at low temperature (160 °C). The RC of the precursor produced copper species (Cu₂O and CuO) in thermodynamic equilibrium, with the major nano-size Cu₂O phase having a large surface area, while calcinations in stagnant air at 400 °C resulted in a CuO phase of larger crystallites with lower surface area. The optimum concentration of CO in the feed for RC was found to be 4.5%. The amazing activity of the novel catalysts over conventional ones in CO oxidation was associated with the presence of Cu₂O and its unusual morphology as evidenced by N₂ adsorption, XRD, XPS and FTIR characterization. The catalysts obtained by RC of various precursors showed activities for CO oxidation in the following order: acetate > hydroxide > oxalate > ammoniacal oxalate > nitrate between 130–160 °C while traditional route catalysts followed the same activity order but at higher temperatures (175–280 °C). Further, the activity order of the catalysts obtained by various calcination methods is as follows: RC > flowing-air > stagnant-air.