Development in Process of Direct Decomposition of Nitrogen Monoxide over Copper Ion-exchanged Zeolite Catalysts

提出了在铜离子交换沸石催化剂上直接分解和选择性还原一氧化氮作为脱除一氧化氮的新方法。铜离子交换ZSM-5沸石（Cu-Z）是分解NO最活跃的催化剂。Cu-Z分子筛的活性随交换水平的增加而增加。ZSM-5沸石在高GHSV区和氧气条件下，通过在醋酸铜水溶液中或在硝酸铜水溶液中加入氨水进行重复离子交换，可以制备出铜离子交换水平达到100%或更高的沸石。通过IR、ESR、磷光、TPD和CO吸附等测试，明确了Cu- z(1)交换到沸石中的Cu^<2+ b>离子在高温下通过抽吸被还原为Cu^+和/或Cu^+-Cu^+；(2)在773 K下暴露于氧气后再抽吸，zeo中约有40%的铜离子以Cu^+的形式存在；(3)NO在Cu^+上吸附形成的NO^-是NO分解的中间体。(4)沸石中Cu^+<@2<@>D2 <@D1>@>D1Cu<@ d12 +@>D1的氧化还原循环可能是实现分解反应的关键步骤。作者首次发现在氧存在下碳氢化合物选择性还原NO， Cu-Z在低至473-573 K的温度下对NO的去除效果显著。选择性还原NO+C<@D23@>D2H<@D26@>D2+O<@D22@>D2的活性不受SO<@D22@>D2的影响。在没有SO<@D22@>D2的情况下，N<@D22@>D2的转化率为100%，而在有SO<@D22@>D2的情况下，N<@D22@>D2的转化率为85% (773 K)，这与添加相同量的SO<@D22@>D2时，NO直接分解的催化活性完全丧失形成了对比。此外，在525 K时Cu-Z的还原率高于h -沸石和氧化铝催化剂在673和773 K时的还原率，这两种催化剂在673和773 K时都有活性。少

Direct decomposition and selective reduction of nitrogen monoxide over copper ion-exchanged zeolite catalysts are proposed as new methods for removal of NO. The copper ion-exchanged ZSM-5 zeolite (Cu-Z) was the most active catalyst for decomposition of NO. The activity of Cu-Z zeolites increased with increase in the exchange level. The zeolites with copper ion-exchange levels of 100% or more, which could be prepared by repeating ion exchange of the ZSM-5 zeolite using aqueous copper (II) acetate solution or addition of ammonia into the aqueous copper (II) nitrate solution, showed significantly high activity even in the presence of oxygen and at high GHSV region. It was clarified concerning Cu-Z, by using IR, ESR, phosphorescence, TPD, and CO adsorption measurements that (1) the Cu^<2+> ions exchanged into zeolite were reduced to Cu^+ and/or Cu^+-Cu^+ through evacuation at elevated temperature, (2) after exposure to oxygen at 773 K and subsequent evacuation, about 40% copper ions in zeo … More lite existed as Cu^+ ions, (3) the NO^- species formed by adsorption of NO on Cu^+ would be an intermediate in the NO decomposition, and (4) redox cycle of Cu^+<@2<@>D2 <@D1>@>D1Cu<@D12+@>D1 in the zeolite is probably a key step to achieve the decomposition reaction. Selective reduction of NO by hydrocarbon in the presence of oxygen was first found by the authors and Cu-Z was remarkably effective for NO removal at temperatures as low as 473-573 K. The activity for this selective reduction in NO+C<@D23@>D2H<@D26@>D2+O<@D22@>D2 system was not poisoned very much by addition of SO<@D22@>D2. The conversion into N<@D22@>D2 was changed to 85% (773 K) in the presence of SO<@D22@>D2, from 100% in the absence of SO<@D22@>D2, which is in contrast with the fact that the catalytic activity for direct decomposition of NO was completely lost on adding the same amount of SO<@D22@>D2. Furthermore, the reduction rate over Cu-Z at 525 K was higher than those over H-zeolite and alumina catalysts at 673 and 773 K, respectively, which have been reported to be active, after findings by the authors. Less