Raney copper catalysts for the water-gas shift reaction - II. Initial catalyst optimisation

Abstract

The initial Raney copper WGS activity based on catalyst volume has been shown to be comparable to industrial and co-precipitated alternatives under varying reaction conditions. The presence of zinc oxide in the Raney copper structure was shown to be necessary for resisting catalyst deactivation due to copper crystallite sintering. Over long operating times, greater stability was maintained by increasing the Raney catalyst zinc content by leaching precursor Cu-Zn-Al alloys with zinc contents of up to a nominal 40 wt% for 1 h, Achieving a high catalyst zinc concentration by leaching alloys with a higher zinc content proved to be more beneficial than by increasing the catalyst zinc concentration by the zinc impregnation process, The addition of concentrated zincate to the caustic solution slowed the leach rate, promoting an increase in copper crystallite size with a corresponding decrease in copper surface area and WGS activity. Leaching precursor alloys with higher zinc contents was effective for increasing the rim zinc content of the Raney catalyst without inhibiting the leach rate and the development of large copper surface areas, A statistically significant correlation was observed between the WGS activity of Raney copper catalysts and their active metal surface areas, demonstrating that the WGS reaction is a structure insensitive reaction over Raney copper.