改性SCR催化剂对逃逸氨的催化分解作用

摘要

为减少烟气氨法选择性还原催化脱硝(NH3-SCR)过程氨的逃逸问题，提出了在SCR催化单元尾部增设对氨具有高效分解作用的改性SCR催化剂的方法。分别考察了Cu及Ru等金属元素对W/V/Ti型SCR催化剂的改性效果。结果表明，Cu、Ru 两种金属元素改性后的催化剂对逃逸氨均有较好的脱硝还原效果及强化氨的催化分解作用。对氨分解产物分析表明，Cu改性催化剂对氨的分解产物中NOx转化率较高，而Ru改性SCR催化剂不仅具有非常高的氨催化氧化活性，同时其分解产物对N2的选择性能够达到90%以上。另外，考察了温度、催化剂预硫化处理、NO等因素对逃逸氨的分解作用的影响，催化剂在300~400℃具有最好的活性，预硫化对氨的分解作用具有抑制作用,尤其对Cu系催化剂。Ru/SCR催化剂具有很好的抗硫性能，经过预硫化处理后，在NO存在的条件下，NH3去除率能够达到80%以上，在逃逸氨控制方面具有应用前景。%In order to reduce the ammonia (unreacted reductant) slipped from ammonia selective catalytic reduction of NOx (NH3-SCR) in the coal-fired power plants flue gas, catalysts which can be used at the tail-end of a SCR unit were put forward and investigated. Cu and Ru were employed as the main dopants to modify commercial SCR catalyst and the modified catalysts display outstanding catalytic activity on both NOx reduction and NH3 abatement. NOx is the main product of NH3 oxidation over Cu modified catalysts, while the selectivity of N2 as the product of catalytic oxidation of NH3 over Ru/SCR catalyst is as high as 90%. The results suggest that the optimal temperature window is 300~400℃ and presulfurization of the catalyst can inhibit the NH3 conversion, especially for the Cu modified catalysts. However, high NH3 conversion was still obtained at 350℃ with 100 ppm NO over Ru/SCR presulfurized with SO2, therefore the Ru modified SCR catalyst should be promising for the selective oxidation of NH3 to N2.