RANEY COPPER-CATALYSTS FOR THE WATER-GAS SHIFT REACTION - CATALYST OPTIMIZATION USING STATISTICAL-METHODS

Statistically designed experiments were used to optimise a Raney coppe r catalyst system for the water-gas shift reaction by assessing a larg e number of variables which contribute towards catalytic activity and stability. A 2(IIII)(I-7) fractional factorial design was employed to screen eleven preparation and four reaction process variables, of whic h the CO:H2O ratio, alloy particle size, caustic/soluble metal ratio a nd zincate leach concentration were found to significantly influence t he long term final catalyst activity and the overall change in activit y. A composite factorial design together with response surface methodo logy was used to optimise the three preparation variables with respect to maximum final activity and minimum change in activity. The results of these experiments showed that the interaction between alloy partic le size and caustic/soluble metal ratio was significantly responsible for final activity. Catalyst deactivation, as measured by change in ac tivity, was significantly influenced by the interaction of zincate con centration and the caustic/soluble metal ratio. At an operating temper ature of 200 degrees C, the optimum Raney copper catalyst of compositi on 48.8 weight percent Cu, 15.9 weight percent Zn and 33.1 weight perc ent Al demonstrated a higher specific activity than an industrial low temperature shift catalyst over 960 hours-on-stream under the same con ditions. The above example of catalyst optimisation thus provides an e xcellent example of the advantages associated with this approach to ca talyst experimentation.