Elimination Of Air Pollutants CO And NO_X—Synthesis Of Novel Nanostructured And Porous Catalytic Materials

Over recent years, although people’s life standrads have been greatly improved due to the fast development of science and technology, air pollution is becoming more and more severe because of using energy sources in many unclean ways. It is imminent to eliminate the pollution of NOx and CO, the two toxic gases among air pollutants. Selective catalytic reduction and catalytic oxidation have been proved to be the effective methods to remove NOx and CO pollution, respectively. In this thesis, the design and preparation of the catalysts for NOx and CO removal have been systematically investigated.In the first part, the reaction performance of Sn-MFI zeolite catalysts for NOx selective reduction(NOx-SCR) has been studied. It is found that Sn cations have been successfully incorporated into the MFI framework. The as-prepared Sn-MFI catalysts possess uniform morphologies and structures. In addition, both micropores and mesopores have been formed in the bulk. Due to the incorporation of Sn cations into the MFI matrix, a large amount of Lewis acidic sites and active surface oxygen species have been formed. Therefore, Sn-MFI catalysts show high activity and superior resistance to water and sulfur deactivation for NOx-SCR.To further improve the activity of Sn-MFI catalysts, Sn-ZSM-5 zeolite catalysts have been investigated in the second part. Compared with Sn-MFI, the formation of novel acidic sites has been induced by the introduction of Al. In addition, the strength of the acidity has also been improved. As a consequence, Sn-ZSM-5 displays higher NOx-SCR activity than Sn-MFI.In the third part, the reaction performance of lamellar Cu-MFI catalysts(Cu-LMFI) for NOx-SCR has been studied. It is revealed that the as-prepared Cu-LMFI consists of uniform nano-sheets and possesses both micropores and mesopores in the bulk structure. With the increasing of Cu contents, the activity has been improved, and the width of optimal NOx conversion window has been broadened.In the fourth part, nanosized SnO2 catalytic materials with various morphologies have been synthesized and used for CO oxidation, whose activity-structure relationships are investigated. The results demonstrates SnO2 nanosheets have high CO oxidation activity due to their high surface area, abundant loose pores and active surface oxygen species, and the complete CO conversion can be achieved at 260 oC; Although the surface area is only 1 m2g-1, SnO2 nanorods have high catalytic performance for CO oxidation, which is due to the specific exposure of the active(110) crystal planes. For the SnO2 nanorods, the complete CO conversion can be achieved at 280 oC, and the catalytic property is similar to that of the precious metals.In the fifth part, ZnO nanotubes, nanosheeets, nanorods and microstars have been synthesized by facile methods and applied to catalyze CO oxidation. The activity-structure relationships of the as-prepared materials are explored in detail. Compared with regular ZnO nanopowders, the sheet-like ZnO shows relatively high activity for CO oxidation, on which the complete CO conversion can be achieved at 300 oC, due to its high surface area of 41 m2g-1, and the presence of a large amount of loose pores. Although ZnO nanorods have a low surface area of 3 m2g-1, it shows also high activity for the reaction, on which the complete CO conversion can be achieved at 280 oC, Because of the formation of strict single-crystalline structure, which can alter the electron properties and reaction mechanism. In the narrow temperature region of 260-280 oC, quick light-off of the CO conversion can be evidently observed, which is similar to what was observed on noble metal catalysts.In the sixth part, CuO nanoparticles confined on fibrous nano-silica(KCC-1) are successfully synthesized and used for CO oxidation and NOx-SCR. It is revealed that Cu-KCC-1 displays high activity for both reactions. CuO, the active component, is dispersed highly on the surface of fibrous nano-silica, whose particle size is less than 10 nm. As a result, Cu-KCC-1 demonstrates superior activity for the two redox reactions.