ALUMINA SUPPORTED MANGANESE OXIDES FOR THE LOW-TEMPERATURE SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE WITH AMMONIA
ALUMINA SUPPORTED MANGANESE OXIDES FOR THE LOW-TEMPERATURE SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE WITH AMMONIA
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DOI：
10.1016/0926-3373(92)80055-5
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发表时间：
1992-12-15
影响因子：
22.1
通讯作者：
MOULIJN, J
中科院分区：
文献类型：
--
作者：
SINGOREDJO, L;KORVER, R;MOULIJN, J
氧化铝负载的锰氧化物在385 ~ 575 K范围内对氨催化还原一氧化氮表现出较高的选择性活性。在22000 - 116000 h-1空速和500 ppm NO， 550 ppm NH3和2% O2的标准条件下，研究了锰含量为3- 15wt .-%的样品。与硝酸锰作为前驱体相比，醋酸锰能更好地分散氧化锰在载体上，具有更高的催化活性，并能检测到其晶体结构。程序升温还原表明，在γ -氧化铝载体上，乙酸酯生成Mn2O3和硝酸盐，主要生成MnO2。每量锰的一氧化氮转化率与由每种前驱体制备的催化剂的负载无关。（NH3）-N-15的使用表明它与一氧化氮以1:1的摩尔比反应(NN)-N-15和/或(NNO)-N-15。SCR活性（对氮）强烈依赖于氧分压，而水具有可逆抑制作用。催化剂的点阵氧在无氧条件下不能维持SCR反应。氧化亚氮的形成与氧分压无关，但随着锰负荷的增加和温度的升高而增加，导致氮形成的选择性降低。氮和氧化亚氮的形成可能发生在不同的位置。在525 K以上，(NH3)-N-15发生氧化，根据温度的不同，主要生成(N2O)-N-15和(NO)-N-15。在这种类型的催化剂上，一氧化二氮不会被氨进一步还原。在催化剂中加入钨大大提高了对氮的选择性。除乙酸酯催化剂稳定性好，至少在600 h内活性保持不变。TPR表明，由于与氧化铝载体的强相互作用，催化剂对二氧化硫的敏感性最低，而精确催化剂对二氧化硫的敏感性最低。
Alumina supported manganese oxides exhibit a high and selective activity for the catalytic reduction of nitric oxide with ammonia (SCR) between 385 and 575 K. Samples with 3-15 wt.-% manganese were studied at space velocities between 22 000-116 000 h-1 and at standard conditions of 500 ppm NO, 550 ppm NH3 and 2% O2. Manganese acetate results in a better dispersion of the manganese oxide on the support and a higher specific catalyst activity than manganese nitrate as precursor, for which crystalline structures could be detected. Temperature-programmed reduction revealed that acetate yields Mn2O3 and nitrate mainly MnO2 on the gamma-alumina support. The nitric oxide conversion per amount of manganese is fairly independent of the loading for the catalysts prepared from each precursor. The use of (NH3)-N-15 reveals that it reacts in a 1:1 molar ratio with nitric oxide towards (NN)-N-15 and/or (NNO)-N-15. The SCR activity (to nitrogen) is strongly dependent on the oxygen partial pressure, whereas water inhibits reversibly. Lattice oxygen of the catalyst is not able to maintain the SCR reaction in the absence of oxygen. The nitrous oxide formation is independent of the oxygen partial pressure, but increases with increasing manganese loading and with temperature, resulting in lower selectivities for nitrogen formation. The nitrogen and nitrous oxide formation probably occur at different sites. Above 525 K (NH3)-N-15 oxidation occurs, yielding mainly (N2O)-N-15 and (NO)-N-15, depending on the temperature. The nitrous oxide is not further reduced by ammonia over this type of catalyst. The addition of tungsten to the catalyst increases the selectivity for nitrogen considerably. The stability of the ex-acetate catalyst is good, for at least 600 h the activity remained constant. The catalysts are sensitive towards sulphur dioxide, the exacetate catalysts the least, due to the strong interaction with the alumina support, as is revealed by TPR.