Preparation Of Modified Ni-Fe Spinel Catalyst And Its Application In H₂-SCR Denitration

Nitrogen oxides(NOx)are one of the main pollutants in the atmosphere,which can cause photochemical pollution,ozone layer destruction,acid rain and other environmental problems.And NOx effect the living environment and health of human seriously.In this paper,clean and non-polluting H2 was used as reducing agent for selective catalytic reduction of NO.The H2-SCR denitration performance of NiFe1.97Pd0.03O4-δ catalysts doped Zn,Mn and Al and replaced Fe ions was studied.Combined with Various characterization techniques,the mechanism of replaced Fe ions with different positions in NiFe1.97Pd0.03O4-δ catalysts was discussed.Also,the effect on the H2-SCR denitration performance of NiFe1.97Pd0.03O4-δ catalysts was investigated.In addition to,the effects of different parameters,such as preparation method of catalysts,molar ratio of H2/NO,temperature GHSV and concentration of O2 on the denitration performance of catalyst were discussed.The main conclusions are as following:1、Nife1.97Pd0.03O4-δ catalysts were prepared and characterized by sol-gel method,hydrothermal method and biological template method.And the results found that the catalysts prepared by using degreased cotton as template showed the bettest H2-SCR denitration.Therefore,the formation mechanism of NiFe1.97Pd0.03O4-δcatalyst prepared with degreased cotton as template and the removal mechanisation of degreasing cotton template were also investigated.2、NiFe1.97-xMnxPd0.03O4-δ(x=0.00,0.01,0.02,0.05and 0.10)catalysts doped Mn promoter showed that Mn replaced Fe ions in tetrahedral sites of NiFe1.97Pd0.03O4-δcatalysts.Not only was the dispersion of active species Pd on the surface of the catalyst increased,but also the content of total acid on the catalyst surface and reduction ability of the catalyst were significantly increased,thus the H2-SCR denitrification activity of the catalyst were significantly increased.Thus,the H2-SCR denitrification activity of the NiFe1.97Pd0.03O4-δcatalysts at low temperature was improved and the temperature window of catalytic activity was broadened.3、The H2-SCR denitration performance of Zn instead of NiFe1.97Pd0.03O4-δ catalysts in tetrahedral position of Fe ion was investigated.The experimental results showed that the doping of Zn can improve the reduction performance of the catalysts,and promote the reduction of PdO.Thus,H2-SCR denitration activity of NiFe1.97Pd0.03O4-δcatalyst at the low temperature was improved.Different from NiFe1.97Pd0.03O4-δ catalysts doped Mn in tetrahedral Fe ions,the presence of Zn can inhibit the oxidation of precious metal Pd,which promoted the NOx catalytic activity of NiFe1.97-xZnxPd0.03O4-δ at the temperature of 50℃～150℃,and inhibited its NOx catalytic activity at the temperature of 150℃～300℃.4、The H2-SCR denitration performance of NiFe1.97Pd0.03O4-δ catalysts doped and substituted Al in octahedral Fe ion was investigated.The results showed that Al doping can improve the reduction performance of the catalysts,and decreases the particle size of the catalyst,and increases the specific surface area and dispersion of the catalyst.Thus,the H2-SCR denitration activity of NiFe1.97Pd0.03O4-δ catalysts at the temperature of 150℃～300℃ was improved,and its catalytic activity temperature window was broadened.In addition,the doping of Al also promoted the reduction of active species Pd.In conclusion,the H2-SCR denitration activity of spinel type NiFe1.97Pd0.03O4-scatalysts can be improved effectively by doping other metal ions,but the effect of dored metal ions on catalytic performance is related to the position and properties of doped metals.