The Structure of Catalyst Gauzes After Hydrogen Cyanide Production
The Structure of Catalyst Gauzes J after Hydrogen Cyanide Production A POSSIBLE EXPLANATION FOR THE FACETED FEATURES By A. G. Knapton Group Research Centre, Johnson Matthey and Co Limited During hydrogen cyanide production by the Andrussow process con- siderable redistribution of the surface of the rhodium-platinum gauze catalyst occurs, resulting in the formation of a porous mass of well-faceted metal crystallites. The phenomenon is illustrated in this paper, and some possible mechanisms to account for its formation are discussed. Rhodium-platinum alloy gauzes feature surface that occurs during operation. Much prominently in two important manufacturing has already been written in this journal (3, processes, the catalytic oxidation of ammonia 4, 5) on the surface effects on gauzes used for to nitric oxide in the production of nitric ammonia oxidation, but little attention has acid, and the Andrussow process for making been paid to gauze packs used in hydrogen hydrogen cyanide from methane and ammonia. cyanide production. At the Johnson Matthey Although direct reaction of the latter con- Research Centre we have recently had occa- stituents is possible via: sion to examine in detail gauzes that had been used in long campaigns in the Andrussow CH4 + NH, + HCN -1 3H, 4 100 kcal process. These gauzes showed some unusual and has been employed on a large scale (I), features, not found in those from ammonia the reaction is strongly endothermic, and oxidation and which have not been satisfac- supplying the heat to maintain the reaction torily explained by earlier workers (6, 7, 8, 9) temperature of 1000 to 1200T makes it on rhodium-platinum catalysts.
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