In the last 20 years, the research and development of catalysts for ammonia synthesis have attracted again much attention with the invention of Ru catalysts by BP company in England and with the creation of a non classical molten Fe catalyst by Zhejiang University of Technology in China, which marks that the unique classical technique route has been developed into three routes, making their important progress respectively. The main research results for and the development trend of the classical Fe 3O 4 ...