Haber-Bosch process catalyst poisons

While for the early demonstration units, osmium and uranium had been used, it was the promoted iron (magnetite) catalyst developed by Mittasch that opened the door to commercialization of the Haber-Bosch process. Osmium had to be ruled out for cost and availability reasons, uranium is impracticable due to its sensitivity for permanent oxygen compound poisoning. Emphasizing the outstanding work of Haber, Bosch, and Mittasch, magnetite-based catalysts are still state of the art today. 

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