LAUSR

Abstract In the present work, catalysts based on copper and nickel and obtained from hydrotalcite like-compounds were evaluated in the NO reduction by CO in order to analyze the activity and yield to N2 and N2O. The co-precipitation method was used to obtain catalyst precursors with variable (y = Cu/(Cu + Ni)) molar ratios values (y = 0, 0.3, 0.5, 0.7 and 1). The use of terephthalate as a compensation anion was a novelty in this series of precursors. The formation of layered compound was observed at y values smaller than or equal to 0.7. The X-ray absorption spectroscopy analysis showed that the Cu-catalysts obtained from the calcination of the precursor at 600 °C have only Cu2+ species, and Cu+ and Cu° species were found throughout the reaction as observed by in situ XANES. However, even during pretreatment at 500 °C under helium flow, copper reduced species were observed. According to TPR results, the introduction of a second metal decreased the reduction temperature of the monometallic catalysts. An easier reduction of copper oxide over nickel is also clear. Cu content, calcination temperature, compensation anion of the hydrotalcite and a pre-reduction of the catalysts significantly impact on the activity and selectivity of the catalysts.