Au/Al_2O_3/Mn_2O_3催化剂的低温NO_x储存还原性能

Performance of NO_x Storage and Reduction over Au/Al_2O_3/Mn_2O_3 Catalyst at Low Temperatures

采用球磨法制取了Au/Al_2O_3/Mn_2O_3催化剂,并对其进行了NO_x储存还原(NSR)性能研究。实验结果表明,Au担载量对该催化剂的低温NSR催化活性有很大的影响,随着Au担载量的增加,其NSR催化活性呈上升趋势:当Au担载量不高于1.0%(质量分数,下同)时,分散度高,与载体Al_2O_3、Mn_2O_3之间存在强的相互作用力,导致在150℃条件下Au的氧化物难以被还原成活性组分Au^0,所以没有活性;当Au担载量大于1.0%时,颗粒尺寸变大,与载体Al_2O_3、Mn_2O_3之间相互作用力变弱,使得Au的氧化物在150℃条件下较容易被还原成Au^0,所以活性得到显著提升。当Au担载量为2.0%时,NO_x转化率和N_2选择性分别能够达到49.6%和71.9%。

A series of the Au/Al_2O_3/Mn_2O_3 catalysts with different Au loadings were prepared by the mechanical mixing method,and their catalytic activities on the NO_xstorage-reduction(NSR) were studied.Results showed that the Au loading had the significant influence on the NSR activity. The catalyst showed very poor NSR activity when the Au loading was less than 1. 0%. The reason might be that the low Au loading with a high gold dispersion would lead to a strong metal-support interaction over the Au/Al_2O_3/Mn_2O_3 catalyst. As a result,the gold oxides were difficultly reduced to Au^0 at 150 ℃. Contrarily,the catalyst showed the much better NSR activity when the Au loading was above 1. 0%. It is because the size of the Au particles increased with the increase of Au loading,which consequently induced the weaker metal-support interaction as compared with the low Au loading catalysts. Thus,the gold oxides could be readily reduced to Au^0 at 150 ℃. Herein,the Au/Al_2O_3/Mn_2O_3 catalyst with the 2. 0% Au loading presented the best NSR performance: the NO_xconversion and the N_2 selectivity could reach 49. 6% and71. 9%,respectively.