Nitrate reduction with hydrogen in the presence of physical mixtures with mono and bimetallic catalysts and ions in solution

Several physical mixtures with mono and bimetallic catalysts were tested in the catalytic nitrate reduction with hydrogen. It was observed that the physical mixtures of Pd and Cu or Pt and Cu monometallic catalysts are similar or more active than the corresponding bimetallic catalysts. The mixtures with Pd catalysts are the most selective to nitrogen, being the mixtures with Rh catalysts the most selective to ammonium. The addition of a monometallic catalyst to a bimetallic catalyst does not decrease the accumulation of nitrite in solution neither the formation of ammonium. The activity of the mixture of monometallic catalysts is due to the formation of in situ bimetallic catalysts as a result of the adsorption of the leached copper. The noble metal must be already supported, and copper does not need to be in the metallic form. (C) 2010 Elsevier B.V. All rights reserved.