The Effect Of Cl On Ce-Ti Metal Oxide Catalysts For Selective Catalytic Reduction Of No_x

Because of its high efficiency of NOx removal,selective catalytic reduction?SCR?as a mature technology has widely used in flue gas denitrification.With the large-scale development of waste incineration power generation technology,NOx emitted from waste incineration cannot be ignored.Futhermore,there is Cl which is in the same order of magnitude as NOx in exhaust gas of MSW incinerator,and it will inevitably affect the activity of SCR catalyst.As the commercial vanadium SCR catalyst has some shortcomings,such as narrow active temperature window and biological toxicity of vanadium,the environmental friendly Ce-Ti oxide catalyst has become a hot spot in recent years.In order to further promote the industrial application of Ce-Ti oxide catalysts,the effect of Cl on the denitrification performance of Ce-Ti oxide catalysts were studied.The following main research results were obtained:The influence of HCl gas on the activity of Ce-Ti oxide catalyst was studied.HCl has varying degrees of inhibiting effects on the activity of CeO₂/TiO₂ and CeO₂-MoO₃/TiO₂ catalysts.The reaction of HCl gas and catalyst makes the ratio of chemical adsorbed oxygen on the surface increases which promote the activity of the catalyst to a certain extent,but it also leads to the decrease of the specific surface area,the increase of the crystallinity,the decrease of the redox ability and the decrease of the acid content of the surface.Combined with the above factors,the activity of CeO₂/TiO₂ and CeO₂-MoO₃/TiO₂ catalysts decreased.The effect of HCl and H₂O on the denitrification activity of Ce-Ti oxide catalysts was investigated.The interaction of HCl and H₂O have different effects on the activity of the two catalysts,that is,the activity of CeO₂/TiO₂ catalyst was improved in the range of 150-400°C,and was suppressed in the range of 400-500°C,while the activity of CeO₂-MoO₃/TiO₂ catalyst decreased in the range of 150-500°C.As for the CeO₂/TiO₂ catalyst,the increase in the ratio of chemical adsorbed oxygen and the increase of the surface acid are the main reasons for the increase of the activity of the catalyst,and the decrease of the specific surface area and the total pore volume,the increase of the crystallinity and the decrease of the redox ability are the main reasons for the decrease of the activity.Under the combined action of these factors,the activity of CeO₂/TiO₂ catalyst increased first and then decreased.For the CeO₂-MoO₃/TiO₂ catalyst,the specific surface area and the total pore volume decreased,the crystallinity increased,the ratio of the chemical adsorbed oxygen decreased,the redox ability and the surface acid content decreased.These changes,to a certain extent,produced the inhibition effect on the denitrification activity of the CMT catalyst,thus leading to the activity of CeO₂-MoO₃/TiO₂ catalyst decreased in the whole test interval.The effect of NH₄Cl on the denitration performance of Ce-Ti oxide catalysts was studied.NH4Cl inhibited the activity of two kinds of catalysts,CeO₂/TiO₂ and CeO₂-MoO₃/TiO₂,and the inhibition effect increased with the increase of NH₄Cl concentration.The deposition of NH₄Cl on the surface of the catalyst leads to the reduction of the specific surface area and the total pore volume,the increase of the crystallinity,the decrease of the redox capacity and the surface acid.These changes lead to the reduction of the activity of the CeO₂/TiO₂ and CeO₂-MoO₃/TiO₂ catalysts.