Study On The Promoters And The Disproportionation Behavior Of Fe_1-xO For Fused Iron Ammonia Synthesis Catalyst

Ammonia industry is the pillar one of chemical industries,ammonia(NH3)is an important chemical product and chemical raw material,which promotes the development of the national agriculture and industry.Meanwhile,the ammonia industry is a high-energy consumption and low-efficiency industry.Fe1-xO-based catalyst,which Developed by Zhejiang University of Technology,was proved to be a highly efficient catalyst for ammonia synthesis,and has been used widely in chemical industry.The main factors that affect catalyst's performance are:type of promoters,Fe1-xO stability,iron surface and pore structure of the catalyst.Therefore,we have studied in this paper on different types of promoters and disproportionation behavior of Fe1-xO for fused iron ammonia synthesis catalysts,and also have studied on the addition of activated carbon(AC)on the pore and iron catalyst surface area structure.The main results are as follows:Firstly,activated carbon(AC)has some influence on the catalyst's pore structure.The catalyst's specific surface area increased by about 11%attribute to the addition of AC.However,the addition of carbon decreased the catalyst's activity,mainly due to a small amount of S,P and other impurities in AC,which made the catalyst poisoning.High-temperature and H2-treated activated carbon can effectively reduce the amount of poisons,which lead to catalyst's activity increasing than the one added AC without hydrogen treatment.Secondly,influence of different promoters on reduction and catalytic performance for Fe1-xO-based catalysts were studied.CuO or Nb2O5 promoted the catalyst's reduction performance,but decreased the catalyst's activity.BaO can promote the reduction performance and activate the catalyst,and the best content of BaO is 0.5wt%.TiO2 can improve the heat resistance but decreased the catalyst's activity.And then we investigated the important structural promoters Al2O3 and MgO by orthogonal test,and results showed that,the best content of Al2O3 is 1.5wt%,and the best content of MgO is 0.55wt%.Thirdly,mixed rare earth oxide and its interplay with other promoters were investigated.The results showed that:mixed rare earth oxide promoted catalyst activity,which was in accordance with the promotion to the reduction performance of the catalyst.Orthogonal test showed that,ERE2O3 obviously interplayed with K2O.The activity increased with CaO and ?RE2O3 content.The interplay between TiO2 and?RE2O3 was not obvious,and added both TiO2 and ?RE2O3 activated the catalysts.Finally,disproportionation reaction of Fe1-xO was investigated by means of Differential Scanning Calorimetry(DSC).The results showed that:disproportionation reaction of Fe1-xO occurs from 250 to 420?.Promoters(especially the CaO,MgO and ZrO2)can effectively inhibit the disproportionation reaction.