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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Effect of water and ammonia on surface species formed during NO_x storage-reduction cycles over Pt-K/Al2O3 and Pt-Ba/Al2O3 catalysts
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Effect of water and ammonia on surface species formed during NO_x storage-reduction cycles over Pt-K/Al2O3 and Pt-Ba/Al2O3 catalysts

机译：水和氨对Pt-K / Al2O3和Pt-Ba / Al2O3催化剂在NO_x储存-还原循环中形成的表面物种的影响

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摘要

The effect of water, in the temperature range 25-350 °C, and ammonia at RT on two different surface species formed on Pt-K/Al2O3 and Pt-Ba/Al2O3 NSR catalysts during NO_x storage-reduction cycles was investigated. The surface species involved are nitrates, formed during the NO_x storage step, and isocyanates, which are found to be intermediates in N2 production during reduction by CO. FT-IR experiments demonstrate that the dissociative chemisorption of water and ammonia causes the transformation of the bidentate nitrates and linearly bonded NCO~- species into more symmetric species that we call ionic species. In the case of water, the effect on nitrates is observable at all the temperatures studied; however, the extent of the transformation decreases upon increasing temperature, consistent with the decreased extent of dissociatively adsorbed water. It was possible to hypothesize that the dissociative chemisorption of water and ammonia takes place in a competitive way on surface sites able to give bidentate nitrates and linearly bonded NCO~- that are dislocated, remaining on the surface as ionic species.
机译：研究了温度在25-350°C的水和室温下的氨对在NO_x储存-还原循环中Pt-K / Al2O3和Pt-Ba / Al2O3 NSR催化剂上形成的两种不同表面物质的影响。涉及的表面物质是在NO_x储存步骤中形成的硝酸盐和异氰酸酯，它们被发现是在CO还原过程中产生N2的中间产物。硝酸盐和线性键合的NCO〜-物质成为更对称的物质，我们称为离子物质。在水的情况下，在所有研究温度下都可以观察到对硝酸盐的影响。然而，转变的程度随着温度的升高而降低，这与分解吸附的水的减少程度一致。可以假设，水和氨的解离性化学吸附以竞争的方式发生在能够产生双齿硝酸盐和线性键合的NCO〜-的位错上，并以离子形式保留在表面上。

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