【作者】 史乐萌；

【导师】 王新平；

【作者基本信息】 大连理工大学 ， 物理化学， 2010， 硕士

【摘要】 本文在反应气组成为1000 ppm NO,1000 ppm正丁烯,5000 ppm H2,10% O2,N2作平衡气,气体流量为200 ml/min的条件下,考察了Ag/Al2O3(0-5%)催化剂选择催化还原氮氧化物(NO_x)的性能和H2对正丁烯-SCR反应的影响。结果表明,H2的加入对低温范围内正丁烯还原NO_x的反应起到了明显的促进作用。当GHSV从48000h-1降低到9600h-1时,在200-250℃反应温度范围内NO_x的转化率明显提高,尤其是在1.5%Ag/Al2O3和2%Ag/Al2O3催化剂上。在GHSV= 9600 h"1的条件下,考察了Ag担载量对催化剂活性的影响。结果表明,在所研究的催化剂中2%Ag/Al2O3活性最高,250℃时该催化剂上NO_x的转化率达到了88%。此外,2%Ag/Al2O3催化剂还具有较高的选择性和稳定性。因此,可以认为,对于低温(250℃)下的正丁烯-H2-SCR反应,2%Ag/Al2O3是最佳的催化剂。对于2%Ag/Al2O3催化剂,本文还研究了250℃下正丁烯和H2的浓度对NO_x转化率的影响。结果发现,在正丁烯浓度为0～1000 ppm, H2浓度为0～5000 ppm的范围内,NO_x的转化率随二者浓度的增大而增大,但当H2的浓度超过5000 ppm后,NO_x转化率的增加趋势显著变缓。更多还原

【Abstract】 Selective catalytic reduction (SCR) of nitrogen oxides (NOx) by n-C4H8 in the assistance of H2 (n-C4H8-H2-SCR) was investigated over Ag/Al2O3 catalysts (0-5 wt.% Ag). The n-C4H8-H2-SCR was conducted by feeding a gas mixture of 1000 ppm NO,1000 ppm n-C4H8,5000 ppm H2,10% O2 and N2 balance with a total flow rate of 200 ml/min to a fixed bed reactor loading desired amount of catalyst. The effect of H2 on n-C4H8-SCR was studied. The results showed that the addition of H2 significantly promoted NOx reduction by n-C4H8 in the low temperature range. With the decrease of GHSV from 48000 h"1 to 9600 h-1, NOx conversion remarkably increased at the reaction temperature ranged from 200℃to 250℃, especially over the Ag/Al2O3 catalysts containing 1.5-2 wt.% of Ag. At GHSV = 9600 h-1, the activity of Ag/Al2O3 influenced by the loading amount of Ag was studied. It indicated that the 2%Ag/Al2O3 is most active in the investigated catalysts, over which, as high as 88% of NOx in the feeding gas was reduced at 250℃. Furthermore, the 2%Ag/Al2O3 gave high NOx reduction selectivity and displayed substantial catalytic stability at the reaction conditions. In the catalytic durability test at 250℃, no deactivation of the catalyst could be found with time on stream. Therefore, the 2%Ag/Al2O3 catalyst can be considered to be suitable for the n-C4H8-H2-SCR at low temperature (250℃).For the 2%Ag/Al2O3 catalyst, the dependence of NOx conversion upon the concentration of n-C4H8 and H2 in the feeding gas was also studied at the reaction temperature of 250℃. The results showed that the NOx conversion markedly increased with the increase of n-C4H8 concentration from 0 to 1000 ppm and the increase of H2 concentration from 0 to 5000 ppm. Nevertheless, when the concentration of H2 further increased from 5000 ppm, less enhanced NOx conversion was observed.更多还原