Synthesis Of Ceria-based Materials And Its Performance In Photocatalytic Removal Of Nitric Oxide

Nitrogen oxides (NO, NO2) emitted from industrial sources are harmful atmospheric pollutants that are major causes of atmospheric haze, photochemical smog and acid rain. Therefore, it is very urgent to develop Low temperature, especially below 200℃ catalysts for selective catalytic reduction of NOx from flue gas of coal-fired power plants and exhaust of diesel engines. The objective of this work is to develop novel photoassisted intelligent-orientated catalysts for reduction of NOx at low temperature. The research will be focused on preparation of CeO2-based materials with gradient electron energy levels as photocatalyst. Multiple gradient electron energy levels will be created into CeO2 band gap by introducing oxygen vacancies, and semiconductors to extend the absorption to visible light range. The effects of biomimicking concentration will be obtained from the biotemplate which contains hierarchical porous structure. The synergic combination of electron-hole pairs and the dual redox cycles between the doping semiconductor and ceria increases the number of oxygen vacancies. Virtually, oxygen vacancies are usually the most active centers which enhance the selectivity of the reaction for N2 formation. The feasibility of simultaneous orientated removal of NOx with the novel CeO2-based materials with gradient electron energy levels will be investigated systematically. The different mechanisms derived from the different reducing agents and active centers will also be studied. This program will provide experimental and theoretical basis for the design and application of CeO2-based coupling photocatalyst for inhibiting atmospheric haze.The biomorphic CeO2-CuO catalyzer was prepared by impregnation method with Cucumber and lotus root as the template. Under the conditions of 550℃ Calcination temperature and calcination rate of 2℃/min, the catalyst showed the most complete material morphology and the most abundant pore structure. Characterized by XRD, BET, SEM, TEM, UV-VIS, XPS, it’s shown that CeO2-CuO prepared with the cucumber has more excellent comprehensive performance, with more uniform pore structure and small grain size, and has larger specific surface area and higher absorption rate of visible light.The effect of transition metal doping on the catalytic properties of materials was investigated, when the cerium oxide was loaded with copper, the copper oxide was mixed into the crystal lattice of cerium oxide in the form of replacement solution, which led to the deformation of cerium oxide crystal lattice, the decrease of the material grain size and increase in the specific surface area. At the same time, on one hand, the content of copper oxide reduced the energy gap of cerium oxide by gradient coupling method, which make it response to the visible light. On the other hand, when the Ce4+is replaced by Cu2+, the oxygen vacancies in the material will increase, which will introduce another impurity energy level in the band of the semiconductor, and which will further promotes the visible light catalytic activity of the catalytic material. With the increase of the amount of copper loading, the particle size of the material increases, the specific surface area decreases, and the visible light catalytic activity also decreases gradually. When the copper content is 0.2, the material has the best catalytic performance.Optimal reaction conditions were obtained by repeated tests as following: catalyst material is the biomorphic CeO2-CuO prepared with the cucumber, copper loading is 0.2, catalyst volume is 6 mL, NO concentration is 600 ppm, NH3 concentration is 600 ppm and N2 is the carrier gas, reaction temperature is about 140 degrees Celsius, space velocity is 2000 h-1. under such circumstances, the denitration efficiency of the catalyst is the highest, and the conversion rate of NO is 85%.