稀土精矿催化剂对选择性催化还原脱硝性能及表面吸附特性的研究

A Study of Selective Catalytic Reduction Denitration Performance and Adsorption Characteristics of Rare Earth Concentrate

采用白云鄂博稀土尾矿富集得到的稀土精矿作为低温脱硝催化剂,借助XRD、SEM、BET、In-situ FT-IR手段,考察焙烧前后催化剂的脱硝性能、表面结构及吸附能力。结果表明,经过500℃焙烧的稀土精矿催化剂的脱硝活性增强,表面出现一定的孔缝隙,比表面积、孔体积明显增大,同时出现CeO2衍射峰,Fe、Nd、La等金属元素在催化剂内部具有较好的分散性,表面晶型结构结果表明各元素之间以共生态结构存在。通过原位红外结果发现,NOx和NH3在催化剂表面存在竞争吸附,NH3的预吸附抑制了NOx的吸附,焙烧后的催化剂出现了只吸附NOx的高选择性活性位点,催化剂表面两种物质的共同吸附才促进催化脱硝,因此稀土精矿低温NH3-SCR反应以L-H反应机理为主。

The rare earth concentrates enriched from Bayan Obo tailings was used as catalyst for low-temperature selective catalytic reduction of NOx. The catalyst sample was investigated by XRD(X-ray diffraction),SEM(Scanning Electron Microscope),Brunauer-Emmett-Teller(BET) and In-situ FTIR methods to investigate the denitrification performance,surface structure and adsorption capacity. The results show that the denitrification activity is enhanced after the rare earth concentrate catalyst calcined at 500 ℃ . The specific surface area and pore volume are increased obviously. At the same time,the diffraction peaks of CeO2 appear and Fe,Nd,La and other metal elements have better dispersion inside the catalyst. All of the elements exist in the form of coexisten from the results of surface crystal structure. It was found that there are competitive adsorption between NOxand NH3 on the surface of catalyst. The pre-adsorption of NH3 inhibits the adsorption of NOx. After catalyst calcined at 500 ℃,a high selectivity active site for adsorbing of nitrogen oxides appeared. And the common adsorption of two substances on the catalyst surface promotes the NOxremoval. The selective catalytic reduction(SCR) reaction over rare earth concentrates catalysts mainly followed the L-H mechanism.