Promoters potash-alumina

Iron promoted with potash, alumina, calcium oxide. 

Fuse magnetite, such as mill-scale, with potash, alumina, silica, and other promoters at 1500°C. 

Amonia synthesis Iron promoted with potash and alumina... 

Catalyst is carbided during reaction with some reoxidation by water produced during the reaction. Potash promotes carburization and retards oxidation. Alumina increases surface area and activity. 

Despite the problems at Sheffield, the Atmospheric Nitrogen Corporation, a subsidiary of the General Chemical Company, had built and operated a second plant with the same design at Syracuse, New York by 1921.The original capacity was 15 tonnes per day anunonia but it was later increased to 40 totmes per day. This plant eventually used a fused iron oxide catalyst, promoted with alumina and potash, developed at the Fixed Nitrogen Research Laboratory by A T Larson. It had first test a catalyst developed by de Jahn of the General Chemical Company. 

Alumina is incorporated as a sohd solution of the iron aluminate spinel, hercynite, in the crystal lattice. The alumina concentration should be less than the solubility of alumina in magnetite. This corresponds to a maximiun content of about 3% alumina. Any excess of alumina does not go into solid solution, and leads to a reduction in catalytic activity, particitlarly when using catalysts promoted with alumina. The presence of alumina as a structural promoter also leads to the formation of wustite and stabihzes the reduced catalyst. Small amounts of magnesia can also dissolve into magnetite and act as a promoter. The calcium component exists in the form of ferrites or alirminates by neutrahzing acidic components—such as silica—and protects the potash that activates the catalyst. 

The potassium ferrites form during catalyst production increase catalyst activity np to about 0.8% potash but above this level activity falls. Ammonia catalysts are said to be doubly-promoted. This is because alumina—a structural promoter—helps control and stabilize both the porosity and surface area of the reduced catalyst on the other hand, potash— an electronic promoter—increases the catalyst activity. Other promoters may have similar effects but usually interact with poisons or impurities to protect the catalyst. 

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