RANEY COPPER-CATALYSTS FOR THE WATER-GAS SHIFT REACTION - II - INITIAL CATALYST OPTIMIZATION

The initial Raney copper WGS activity based on catalyst volume has bee n shown to be comparable to industrial and coprecipitated alternatives under varying reaction conditions, The presence of zinc oxide in the Raney copper structure was shown to be necessary for resisting catalys t deactivation due to copper crystallite sintering. Over long operatin g times, greater stability was maintained by increasing the Raney cata lyst zinc content by leaching precursor Cu-Zn-Al alloys with zinc cont ents 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 zincat e to the caustic solution slowed the leach rate, promoting an increase in copper crystallite size with a corresponding decrease in copper su rface area and WGS activity. Leaching precursor alloys with higher zin c contents was effective for increasing the rim zinc content of the Ra ney catalyst without inhibiting the leach rate and the development of large copper surface areas, A statistically significant correlation wa s observed between the WGS activity of Raney copper catalysts and thei r active metal surface areas, demonstrating that the WGS reaction is a structure insensitive reaction over Raney copper, (C) 1997 Elsevier S cience B.V.