ABSTRACT
Ammonia synthesis catalysts at this time are very similar in composition and form to that first used by Haber in the early 1900s. It was a natural magnetite, which fortuitously contained the promoters of almost the identical type and quantity used. The fusion operation is one that is contrary to the basic concepts of catalyst preparation and use. Fusion is more severe than sintering, which is usually considered one of the major causes of catalyst failure during use. Some very effective catalysts have, however, been made by sintering, which can be initiated at a temperature about 60% below the fusion point (500–600°C). Spent ammonia synthesis catalyst is pyrophoric when it is removed from the unit unless it has been reoxidized before discharge from the unit. Even though it is “reoxidized,” there may be pockets or lumps of catalyst that are in a reduced condition. Extreme caution is required.
