富氧条件下氮氧化物的选择性催化还原Ⅱ．Ag／Al2O3催化剂上含氧有机物选择性还原NOx的性能

Selective Catalytic Reduction of NO_x in the Presence of Excess OxygenⅡ. SCR of NO_x with Oxo-Organic Compounds over Ag/Al_2O_3

在富氧条件下分别以含氧有机物甲醇、乙醇、乙醛和乙酸等为还原剂，考察了Ag／Al2O3对NOx选择性催化还原的活性．结果表明，当银负载量为4％时，催化剂具有最高的催化活性．在整个实验温度范围内，乙醇较丙烯具有更高的还原NOx的活性，且操作温度范围更宽(300～610℃)，NOx脱除率可高达90％，更加适合柴油机尾气中NOx的净化．添加10％的水可提高乙醇还原NOx的低温活性．随着乙醇浓度的增加，NOx转化率显著提高．在相同的浓度下，甲醇和乙酸还原脱除NOx的效率较低；而乙醛还原脱除NOx的效率与乙醇相当．原位红外光谱研究结果表明，反应过程中生成大量吸附态的烯醇式物种(CH2：CHO^-)是乙醇和乙醛呈现较高还原活性的主要原因．

The selective catalytic reduction (SCR) of NO x with oxo-organic compounds (CH 3OH, C 2H 5OH, CH 3CHO, CH 3COOH, etc) over Ag/Al 2O 3 in excess oxygen was studied. When using C 2H 5OH as a reductant, the 4%Ag/Al 2O 3 gave the highest NO x conversion (the maximal value was up to 99% and the average value was ca 90%) in a wide temperature range (300～610 ℃). C 2H 5OH was more efficient for SCR of NO x than C 3H 6, CH 3OH, or CH 3COOH, while extremely similar NO x conversion was obtained when using CH 3CHO as a reductant. In-situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) showed that the formation of enolic species over Ag/Al 2O 3 resulted in high efficiency of C 2H 5OH and CH 3CHO for SCR of NO x. The presence of H 2O enhanced the NO x reduction by C 2H 5OH at low temperature, while the influence of H 2O on the NO x reduction was little at high temperature.