Study On Mechanical Properties Of Iron Catalysts For Ammonia Synthesis

The whole manipulation of catalyst bed could be well done in the case that the catalyst has enough high mechanical strength. Mechanical strength is one of the key parameters for the industrial equipment in order working. Furthermore, the catalyst life of application is directly affected by thermal stability. The iron catalyst for ammonia synthesis has a near 100 years history, but so far the study of its mechanical strength has not been reported. The determination methods of abrasion and BCS are applied in this thesis, and the mechanical strength of fused iron catalyst has been studied for the first time. The influences of the precursor composition of catalyst, Fe²⁺/Fe³⁺,the promoter, the method of preparation and reduction and the correlative theory model and explanations are all investigated. In addition, the influence of supports to the thermal stability of Fe_1-xO-based catalyst is discussed by "accelerating deactivation process". The major results are drawn as the foliowings:1. The mechanical strength of catalyst is closely related to Fe²⁺/Fe³⁺, The mechanical strength of oxidized catalyst increases with Fe²⁺/Fe³⁺, so the mechanicalstrength of oxidized Fe_1-xO based catalyst is superior to that of Fe₃O₄ based catalyst, however, Fe²⁺/Fe³⁺ has little effect on the mechanical strength of pre-reduced catalyst, pre-reduced Fe_1-xO and Fe₃O₄ based catalysts have a near mechanical strength.2. The effect of promoters on the mechanical strength was studied. The electronic promoter K₂O hardly increases macro- lacuna of catalyst, which has a little effect on strength of Fe_1-xO based catalyst. The structural promoter Al₂O₃ and CaO can make catalyst precursor form compact oxide, its mechanical strength increases significantly and have near mechanical strength. Al₂O₃ and CaO are important structure promoters for Fe_1-xO and Fe₃O₄ based catalysts respectively, but Al₂O₃ and CaO have different effect...