Preparation And Activity Evaluation Of Pd-based NPCs Regeneration Catalyst For Complex Denitrification Solution

With the acceleration of industrialization,a series of problems caused by the excessive emission of nitrogen oxides（NO_x）have attracted strong attention.It is found that the complex denitrification method is undoubtedly a simple and efficient solution,but the difficult regeneration of the absorbed Fe（Ⅱ）EDTA-NO complex solution hinders the further development of the process.Aiming at this problem,selected NH₄HCO₃as nitrogen source,and nitrogen doped porous activated carbons（NPCs）support was prepared by foaming method,and then Pd-based NPCs catalysts were prepared by loading active components.In order to promote the industrialization of this denitrification method,the denitrification performance of the prepared catalysts for the catalytic reduction of Fe（Ⅱ）EDTA-NO complex solution with formic acid as reducing agent was tested.The main research contents are as follows:（1）The effect of nitrogen doped support on Pd-based catalysts were studied.NPCs was prepared by foaming method with ammonium bicarbonate as nitrogen source,and then Pd/NPCs catalyst was prepared by loading Pd nanoparticles（NPs）.XRD,XPS,TEM,BET and H₂-TPD confirmed that the introduction of nitrogen atoms could improve the dispersion of Pd NPs and reduced the amount of Pd NPs falling off,and Pd/NPCs exhibited superior performances.Under appropriate conditions,the denitrification rate of 90.4%with the N₂ selectivity was 99.6%could be achieved in 5min,and turnover frequency（TOF）of 1916 h^-1.In addition,the study of kinetic and reaction mechanism derivation provided a new idea for the preparation of high-efficiency complex denitrification catalyst.（2）The denitrification performance of core-shell bimetallic Ag-Pd/NPCs catalyst was studied.Because the manufacturing cost of pure Pd catalyst was too expensive,it was still a challenge to improve the regeneration rate of complex solution and reduce the preparation cost by changing the structure of catalyst.Ag-Pd NPs with core-shell structure was prepared by loading Ag NPs on NPCs support and then partially replaced by Pd.XRD,XPS,TEM,BET,H₂-TPD and other characterization confirmed that Ag-Pd/NPCs has well core-shell structure,stronger electron exchange capacity,appropriate NPs particle size,and the introduction of Ag atoms could greatly improve the catalytic activity of the catalyst.Under appropriate conditions,the denitrification rate of 91.04%with the N₂ selectivity was 98.51%could be achieved in 5 min,and TOF of 1995 h^-1.（3）The pilot scale experiment of continuous catalytic reduction denitration under simulated flue gas was studied.A set of continuous denitration device suitable for the evaluation system in this chapter was built,and the prepared granular Pd/NPCs catalyst was placed in the fixed bed mode.Under the condition of high oxygen content of 16%,the appropriate conditions were reaction p H of 5,reaction temperature of 60℃and system liquid gas ratio of 6.At this time,the overall denitrification rate could be maintained at more than 92%within 180 min under simulated flue gas is 200 L/h with NO inlet gas content of 1000 ppm.It provides basic continuous experimental data for industrial amplification.The innovation of this paper lies in:A new idea of catalytic reduction of Fe（Ⅱ）EDTA-NO denitrification complex solution was proposed.Nitrogen doped carbons was used as support,so that Pd-based catalysts have high dispersion and small particle size.Bimetallic catalysts were studied to make the catalysts more economical under the premise of high performance and high selectivity.A fixed bed pilot plant using packed catalyst was built,and the process parameters were tested to promote the industrialization process of complex denitrification.