Preparation Of Mn?CeWO_x/TiO₂ Catalyst And Its NH₃-SCR Activity

Selective catalytic reduction?SCR?of NO_x with NH₃ is currently considered to be an effect technique for NO_x removal.Recently,with the constant innovation of NH₃-SCR technology,the low NH₃-SCR technology has become a new research hotspot issues which is known for low energy consumption and high economic benefit.However,low activity and sulfur resistance at low temperature,uncertainty of SCR reaction mechanism and sulfur poisoning mechanism are the main factors that restrict the SCR technology development.In order to solve the above problems,the low-temperature SCR reaction was systematically investigated by W modified Mn and Ce based catalyst respectively in this article.The founction of assistant W not only can stabilize active phase and adjust acid and oxygen vacancies sites,but also improve the sulfur resistance.Thus,W was firstly chosen to be doped into MnO_x catalysts,and then MnWO₄ phase was found in the MnWO_x catalysts.From the activity tests and characterization results,it was found the low-temperature activity was improved with the increment of molar ratio of Mn to W.Under the same condition,the supported MnaWO_x/TiO₂ catalysts were prepared and their activity was tested respectively.Results from supported catalysts activity test that Mn₂WO_x/TiO₂ showed the best low temperature activity and the widest active temperature window.Furthermore,the relationship between activity and MnWO₄ phase was deeply investigated by different preparation methods.Finally,synergistic effect between MnWO₄ and Mn3O₄ was proved to be a key factor to decide Mn₂WO_x/TiO₂ catalyst's excellent activity at low temperature and high selectivity at high temperature.Based on the above research,a series of Ce WTiO_x catalysts with different loading of WO₃ and CeO₂ were synthesized and screened the best activity catalyst.Then,from the characterization of the catalyst by BET,XRD,TPR,TPD,XPS,TEM,it was found that W can reduce CeO₂ crystallite size,increase oxygen vacancy and Bronsted acid,improve the ability of NH₃ activation and the amount of chemical adsorption oxygen.Finally,the sulfur resistance of CeWTiO_x catalyst was also investigated.BET and TG were used to investigate the textural and state of sulfate.Results indicated that the surface deposition NH₄HSO₄ salt and some Ce₂?SO₄?₃ salt was the main reason that lead to catalyst deactivation at low temperature.