Nickel-alumina catalyst activity data

There is little data available to quantify these factors. The loss of catalyst surface area with high temperatures is well-known (136). One hundred hours of dry heat at 900°C are usually sufficient to reduce alumina surface area from 120 to 40 m2/g. Platinum crystallites can grow from 30 A to 600 A in diameter, and metal surface area declines from 20 m2/g to 1 m2/g. Crystal growth and microstructure changes are thermodynamically favored (137). Alumina can react with copper oxide and nickel oxide to form aluminates, with great loss of surface area and catalytic activity. The loss of metals by carbonyl formation and the loss of ruthenium by oxide formation have been mentioned before. 

The single crystal results are compared in Fig. 2 with three sets of data taken from Ref. 13 for nickel supported on alumina, a high surface area catalyst. This comparison shows extraordinary similarities in kinetic data taken under nearly identical conditions. Thus, for the Hj-CO reaction over nickel, there is no significant variation in the specific reaction rates or the activation energy as the catalyst changes from small metal particles to bulk single crystals. These data provide convincing evidence that the methanation reaction rate is indeed structure insensitive on nickel catalysts. 

Table I shows the results of catalytic activity in the WG5 reaction, expressed as the reaction rate constants, for the series of nickel-free and nickel enriched molybdenum loaded Y-zeolites. The data concerning alumina based Co-Mo industrial catalysts are presented only for comparison reasons.

---