Thermal Stability Of FeO Based Catalysts For Ammonia Synthesis

Iron-based catalyst will be the main catalysts in the recent decades due to its low price and mature techniques.Thermal stability is one of iron catalyst stability and has the enormous influence to the industrial application of iron catalyst.The thermal stability of Fe₃O₄,FeO,Fe₃O₄ based A110-2 catalyst,FeO based ZA-5 catalyst at atmospheric pressure and high temperature,and the effects of promoters and Fe²⁺/Fe³⁺ on the thermal stability of iron catalyst was studied in present work.The following results were obtained:1、Thermal stability of Fe₃O₄ and FeO is not good and the latter is slightly inferior to the former.The activity of pure Fe₃O₄ and FeO is low and drops greatly after thermal treatment.And the change of SEM、the crystal grain size、the surface area、pore volume and pore size is great.2、FeO based ZA-5 catalyst has good thermal stability.The change of the activity,SEM,the crystal grain size,the surface area,pore volume and pore size is little after thermal treatment under 550℃.3、The thermal stability of FeO based catalyst is weakened by electronic promoter K₂O and CaO.And constitutive promoter Al₂O₃ and MgO can significantly improve its thermal stability.4、When Fe²⁺/Fe³⁺ is about 0.5 or varies within the range of 5.33～8.64,precursor phase composition of iron catalyst is Fe₃O₄ or FeO.And the thermal stability of iron catalyst is good.When Fe²⁺/Fe³⁺ varies within other ranges,the precursor phase composition of iron catalyst is two phase andα-Fe is easy to grow up at high tempreture.And thermal stability of iron catalyst reduces.