Study On SCR Denitration Catalyst Regeneration Method By Wide Temperature Range Modification

Selective catalytic reduction（SCR）technology is currently the most widely used and most research-oriented flue gas denitrification technology.The regeneration of deactivated catalysts and the development of low and medium temperature catalysts have attracted extensive attention of researchers because they can solve the problems of easy deactivation and difficult recovery after deactivation in the actual production process.In this work,the deactivated catalyst is in situ regenerated without destroying the original structure of the deactivated catalyst.At the same time,based on the preparation technology of low and medium temperature denitrification catalyst,a low and medium temperature SCR denitrification catalyst with high activity and wide activity temperature window based on regenerated denitrification catalyst was developed.During the regeneration process,the catalysts were studied as follows:First,the deactivated catalyst was pretreated with different concentrations of acid and base solutions,and the cleaned catalyst was used as the substrate to in situ construct the titanium dioxide film by sol-lift method combined with freeze drying.It was found that the denitrification activity of the catalyst could be effectively recovered by immersing with 0.2mol/L Na OH solution.Furthermore,the constructed titanium dioxide film has a smooth and porous surface with less particle agglomeration,and the crystal phase is mainly anatase Ti O₂,which can be used as a good substrate for the subsequent supporting active components.Then,the active components,manganese oxide and cerium oxide,were respectively loaded on the titanium oxide film by solution impregnation.It was found that the catalytic activities of manganese oxide and cerium oxide were exhibited at low temperature（200oC）and medium temperature（200～300oC）respectively,indicating that there is a difference in the denitrification mechanism between the two.Combined with X-ray diffraction analysis to analyze the physical and chemical properties of the catalyst,and based on in-situ diffuse reflection infrared spectroscopy（DRIFTS）and other means to explore the denitrification mechanism,it was proposed that the surface of the catalyst regenerated by loading Mn O_xcontained a higher content of Mn³⁺and chemical adsorption oxygen（O_α）,which plays an important role in low temperature denitrification activity,and the denitrification reaction follows the Langmuir-Hinshelwood mechanism.The presence of Ce O_x makes the regenerated catalyst have a certain amount of Ce³⁺and a high content of chemical adsorption oxygen（O_α）,which is conducive to denitrification reaction at medium temperature.The denitrification process follows both Eley-Rideal and Langmuir-Hinshelwood mechanisms.Finally,Mn O_x and Ce O_x were co-loaded on the titanium oxide film by solution impregnation.The denitrification performance of the regenerated catalyst at low temperature was significantly improved.Due to the synergistic effect of Mn O_x and Ce O_x,the surface of the regenerated catalyst has a higher content of Mn³⁺and a certain amount of Ce³⁺and chemical adsorption oxygen（O_α）.The SCR reaction process simultaneously follows Eley-Rideal and Langmuir-Hinshelwood mechanisms.