Pan Hua, Jian Yan-Fei, Chen Ning-Na, Liu Hong-Xia, He Chi, He Ya-Fei
Department of Environmental Science and Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Qiyuan(Xi'an) Dae Young Environmental Protection Technology Co., Ltd., Xi'an 710018, China.
Huan Jing Ke Xue. 2017 Jul 8;38(7):3085-3094. doi: 10.13227/j.hjkx.201610195.
Catalytic behavior of Co-based/zeolites catalysts was investigated in NO reduction by CH. Optimization of promoter and support was investigated by catalytic tests, and the relationship between catalytic activity and catalyst structure was illustrated by catalyst characterization. Co-Fe/SAPO-34 exhibited the highest activity among various Co-base/zeolites catalysts. The maximum conversion of NO with 52.7% was obtained on Co-Fe/SAPO-34 at 450℃. The inhibition of activity of Fe/zeolites became severe in the presence of SO, CO, and HO. CO exerted virtually no effect on the SCR activity of Co-Fe/zeolites. The inhibition of NO conversion by HO was reversible for Co-Fe/zeolites catalysts. Cobalt species were mainly present in CoO and Co(OH) states in Co-Fe/SAPO-34. CoOand Co(OH) were the main cobalt species of Co-Fe/ZSM-5, while CoO, CoAlO and CoO might be present in Co-Fe/Beta. The ratio of Fe/Fe in the surface layer of Co-Fe/zeolites decreased in the order of Co-Fe/ZSM-5(3.98) > Co-Fe/SAPO-34(0.52) > Co-Fe/Beta(0.43). The active states of cobalt species and suitable ratio of Fe/Fe were important for the activity of Co-Fe/zeolites in CH-SCR. CH-SCR over Co-Fe/zeolite catalysts started with the adsorption of NO and CH on Brønsted acid sites of the zeolite to produce NOand carbon-containing species(-C=O and -COO) in the presence of oxygen, respectively. Subsequently, the important intermediates of nitrate species were generated from NO at the active sites. Finally, nitrate species reacted with carbon-containing species to form N and CO.
研究了钴基/沸石催化剂在CH还原NO反应中的催化行为。通过催化试验研究了助剂和载体的优化，并通过催化剂表征阐述了催化活性与催化剂结构之间的关系。在各种钴基/沸石催化剂中，Co-Fe/SAPO-34表现出最高的活性。在450℃下，Co-Fe/SAPO-34上NO的最大转化率达到52.7%。在SO、CO和HO存在的情况下，Fe/沸石的活性抑制变得严重。CO对Co-Fe/沸石的SCR活性几乎没有影响。HO对Co-Fe/沸石催化剂的NO转化抑制是可逆的。在Co-Fe/SAPO-34中，钴物种主要以CoO和Co(OH)的形式存在。CoO和Co(OH)是Co-Fe/ZSM-5的主要钴物种，而Co-Fe/Beta中可能存在CoO、CoAlO和CoO。Co-Fe/沸石表层中Fe/Fe的比例按Co-Fe/ZSM-5(3.98)>Co-Fe/SAPO-34(0.52)>Co-Fe/Beta(0.43)的顺序降低。钴物种的活性状态和合适的Fe/Fe比例对Co-Fe/沸石在CH-SCR中的活性很重要。Co-Fe/沸石催化剂上的CH-SCR首先是NO和CH分别在沸石的布朗斯台德酸位上吸附，在氧气存在下分别生成NO和含碳物种(-C=O和-COO)。随后，在活性位点上由NO生成重要的硝酸盐物种中间体。最后，硝酸盐物种与含碳物种反应生成N和CO。
