CuO/γ-Al_2O_3上NO吸附及其歧化反应的低温红外光谱研究

A Low Temperature Infrared Spectroscopic Study of NO Adsorption and Disproportionation Reaction on CuO/γ Al_2O_3

应用原位低温红外光谱技术，研究了ＮＯ在氧化态和还原态ＣｕＯ／γ－Ａｌ２Ｏ３催化剂上，从－１５０℃到室温的吸附及其在表面上发生的反应．重点研究了歧化反应与温度的关系和歧化产物之一Ｎ２Ｏ在表面的吸附．观察到在－１４５℃的低温下，ＮＯ在催化剂表面即已发生歧化反应；约在－１３０℃时Ｎ２Ｏ在表面吸附峰最强，更高温度时吸附峰减弱．随温度的变化，表面上吸附物种发生了变化．应用双探针分子ＣＯ和ＮＯ的交替吸附的红外光谱研究发现，预吸附ＣＯ阻碍了ＮＯ的氧化，却有利于ＮＯ歧化反应的进行．

The adsorption of NO and its reaction on the surface of oxidized and reduced CuO/γ Al_2O_3 at temperature from -150℃ to room temperature were studied by in situ low temperature IR spectroscopy. It is found that surface adsorption species of NO on CuO/γ Al_2O_3 vary with the temperature. The NO disproportionation to N_2O and NO_2 can take place on the surface of both the oxidized and reduced samples at a temperature as low as -145℃. The adsorption band of N_2O at 2225 cm -1 on the surface is the strongest at -130℃, and becomes weaker as temperature rises. NO_2, another product of the disproportionation reaction, forms a large amount of nitrate species on the surface of the oxidized samples, while on the surface of the reduced samples forms much less nitrate species than the former and exists mainly in the gas phase. The alternative adsorption of multiple probe molecules CO and NO on the catalyst, was also studied. It shows that the preadsorption of CO hinders the oxidation of NO, but enhances the disproportionation of NO.