Preparation Of Novel Titanium-based Core-shell Anti-sulfur Catalyst And Study On Low-temperature Denitration Performance

Nitrogen oxide (NOx) is one of the major sources of atmospheric pollution. Low temperature selective catalytic reduction (SCR) denitration technology is an emerging flue gas denitration technology in recent years and is also a hotspot of the research in the domestic flue gas denitration field. But low-temperature SCR denitration technology are still a distance away from the large-scale industrial application, for that the catalysts under low temperature conditions can easily be poisoned by SO2.Although the SO2 concentration in flue gas is very low after the desulfurization system, the catalyst can also be deactivated. This has seriously hindered the popularization and application of low-temperature SCR denitration technology.Therefore, preparation of high active catalyst with sulfur resistant performance is the key to promote the use of low-temperature SCR denitration technology. In recent years, TiO2-based core-shell nanomaterials have received many researchers' attention for their excellent properties. The core-shell nanomaterials can both have the properties of the core and the shell, but different from each of them. The core-shell nanomaterials have operability and their properties can be regulated and controlled according to the need. In this study, high active TiO2-based core-shell structure catalysts with sulfur resistant performance have been prepared by a two-step method.The physical and chemical properties of the prepared catalysts and their performance in the low-temperature SCR reaction were studied through different characterization methods.Firstly, CeO2@TiO2 core-shell nanostructure catalyst was prepared by a two-step hydrothermal method. The catalyst presented the obvious core-shell structure, and the shell was amorphous TiO2 which could protect the active center from the SO2 erosion.The catalyst showed high activity and stability, excellent N2 selectivity and superior SO2 resistance as well as H2O tolerance. When 200 ppm SO2 was added to the system,the NOx conversion over CeO2@TiO2 could maintain 100% for 2.25 hours, after being cut off of the SO2, the NOx conversion over CeO2@TiO2 gradually recovered to 96.2% and tended to be stable in 2 hours. Characterizations such as TEM, HR-TEM,XRD and BET were carried out. The results indicated that the catalyst had large surface area and the active sites were well dispersed on the surface. The NH3-TPD,H2-TPR and XPS results implied that its increased SCR activity might be due to the enhancement of NH3 chemisorption and the increase of active oxygen species.Secondly, MnOx@TiO2 core-shell nanorod catalyst was prepared by a two-step method. The catalyst showed obvious core and shell structure, and TiO2 shell were distributed evenly on MnOx nanorod core. The catalyst performed high activity, high stability and excellent N2 selectivity. Furthermore, it exhibited better SO2 and H2O resistance than those of MnOx,TiO2 and MnOx/TiO2 nanomaterial counterparts. The catalytic activity of MnOx@TiO2 remained 100% when temperature was reached 130?. The prepared catalysts have been characterized systematically by some methods.BET results indicated that the catalyst had abundant mesopores and the active sites were well dispersed on the surface. NH3-TPD and H2-TPR results implied that its enhanced SCR activity might be due to the increase of Lewis acid sites and high redox capability.Finally, MnOx-CeO2@TiO2 core-shell structure catalyst was prepared by a two-step method,using the Mn-Ce composite oxides as the core. The catalyst showed obvious core and shell structure. The catalyst also showed high activity and stability,excellent N2 selectivity and superior SO2 resistance as well as H2O tolerance. The catalytic activity of MnOx-CeO2@TiO2 remained 100% when temperature was reached 160?. According to a series of characterization analysis, its superior SCR activity might be due to the increase of Lewis acid sites and high redox capability.Through the systematic study of this paper, clearing the performance in the low-temperature SCR denitration reaction of TiO2-based core-shell structure catalysts and preliminarily obtaining the sulfur resistant mechanism of the core-shell structure catalyst. It could provide a theoretical basis for the further study in the preparation of high active catalyst with sulfur resistant performance in the future. It could make a step closer to the large-scale industrial application of the low-temperature SCR catalyst.Moreover, it could have important environmental, economic and social significance.