EFFECT OF INCORPORATION OF AL+3 ION ON THE STRUCTURE OF CU-ZN COPRECIPITATE

Ternary catalysts containing oxides of copper, zinc, and aluminum have been widely used as catalysts for water-gas shift reactions and methanol synthesis. Although many studies have been carried out with the calcined mixed oxides, very little information is available regarding the effect of Al3+ On the structure of the copper-zinc hydroxycarbonate which is the precursor of the catalyst. On the basis of the findings of the present investigation it has been suggested that Al3+ partially replaces Cu2+ and Zn2+ ions in the aurichalcite structure during coprecipitation, and this process of replacement causes appreciable changes in X-ray and electron diffraction patterns, infrared spectra, and the thermal stability of the precursor. These changes occur due to distortion of the aurichalcite structure of the coprecipitate by Al3+, which has a higher charge and a stronger acid character than Cu2+ or Zn+2 ions. (C) 1995 Academic Press, Inc.