Cu、Co掺杂Mn基复合金属氧化物的低温NO_x储存还原性能

Cu,Co Doped Manganese Composite Metal Oxides for NO_x Storage and Reduction at Low Temperatures

采用共沉淀法制备了掺杂铜或钴的锰基复合金属氧化物催化剂,考察了其稀燃条件下的NOx储存活性以及"稀燃/富燃"气氛中的NOx储存还原(NSR)性能。结果表明,Mn-O样品在200℃具有较好的NOx储存活性,NO-to-NO2转化率为83.4%,氮氧化物储存量(NSC)为124.2μmol/g;但其在富燃气氛中的NOx还原能力较低。掺杂少量铜或钴元素之后,样品的晶粒尺寸变小,抗烧结能力增强,同时BET比表面积增大,低温下NOx储存和还原活性均有所提高。通过H2-TPR表征发现:掺杂少量铜或钴元素之后,H2还原峰向低温方向偏移,氧物种的活性有所提高,这有助于提高催化剂的氧化还原能力;其中掺杂铜样品的氧化还原能力最强,在富燃条件下表现较高的NSR活性。

Mn-M-O（M = Cu or Co） composite metal oxides were prepared by a co-precipitation method and their abilities concerning the NOxstorage capacity（NSC） in lean-burn atmospheres and NOxstorage reduction（NSR） in the periodically alternative lean-burn/fuel-rich atmospheres were investigated.The results indicated that the Mn-O sample showed good catalytic activity： the NO-to-NO2 conversion was 83.4%,and the NSC was 124.2 μmol/g.However,it had the drawback of the poor reduction activity in the fuel-rich atmospheres.The doping with the Cu or Co element can remarkably decrease the mean crystallite sizes,increase the thermal aging resistance,and consequently enlarge the specific surface areas of the catalysts.This induced the enhancement of the NO storage capacity and the NO reduction ability at low temperatures.The H2-TPR results demonstrate that doping with Cu or Co element can result in theshift of the reduction peak of the H2-TPR profiles toward lower temperature.It indicated an increase in the oxygen activity,which further improved the redox ability of the doped Mn-based oxides.The Mn-CuO sample displayed the best NSR activity due to its good NO reduction activity in the fuel-rich atmospheres.