Spectroscopic studies of the stability of zeolitic deNOx catalysts
Spectroscopic studies of the stability of zeolitic deNOx catalysts
复制标题
DOI：
10.1016/s0920-5861(96)00144-7
复制
发表时间：
1997-03
期刊：
影响因子：
5.3
通讯作者：
M. Rokosz;A. Kucherov;H. Jen;M. Shelef
中科院分区：
文献类型：
--
作者：
M. Rokosz;A. Kucherov;H. Jen;M. Shelef
Cu-ZSM-5被认为是用于选择性催化还原（SCR）的NOx流与ca。10%H2O，导致脱铝和活性损失。多价的Co ~（2+）、Ni ~（2+）、Pd ~（2+）、Cu ~（2+）、Ga ~（3+）、Al ~（3+）、Fe ~（3+）、La ~（3+）和Ce ~（3+）离子被用作稳定剂。四面体27 Al的MAS-NMR是脱铝的标尺。还从~ 1H、~（23）Na和~（29）Si的NMR中获得了信息。一些离子La 3+和Ce 3+抑制脱铝，但含有活性Cu 2+和La 3+的样品不如单一改性的材料稳定，并且在SCR中不比未改性的Cu-ZSM-5更有活性。通过ESR在流通条件下原位监测Cu 2+。在650°C下的蒸汽处理或在850°C下的煅烧不可逆地改变了所有正方形平面Cu 2+的配位。通过合并CA。5wt%的La或Ce，一部分铜（20-30%）甚至在850°C下0.5小时后仍保持活性方形平面Cu 2+配位。这反映在较高的乙烷氧化活性中。
Cu-ZSM-5 is considered for selective catalytic reduction (SCR) of NOxin streams with ca. 10% H2O which causes dealumination and activity loss. Multivalent Co2+, Ni2+, Pd2+, Cu2+, Ga3+, A13+, Fe3+, La3+and Ce3+ions were tried as stabilizers. MAS-NMR of tetrahedral27Al was the dealumination yardstick. Information was also obtained from NMR of1H,23Na and29Si. Some ions, La3+and Ce3+, suppress the dealumination but samples containing the active Cu2+and the La3+are not as stable as singly modified materials and not more active in SCR than non-modified Cu-ZSM-5. The Cu2+was monitored in-situ by ESR under flow-through conditions. Steaming at 650°C or calcination at 850°C irreversibly changes the co-ordination of all square-planar Cu2+. By incorporating ca. 5 wt% of La or Ce, a part of the copper (20–30%) preserves the active square-planar Cu2+co-ordination even after 0.5 h at 850°C. This is reflected in a higher ethane oxidation activity.