Competitive Adsorption of Nitrite and Hydrogen on Palladium during Nitrite Hydrogenation,ChemCatChem

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Competitive Adsorption of Nitrite and Hydrogen on Palladium during Nitrite Hydrogenation
ChemCatChem ( IF 3.8 ) Pub Date : 2018-07-05 , DOI: 10.1002/cctc.201800523
Rolf Sybren Postma ₁ , Roger Brunet Espinosa _{1,

2} , Leon Lefferts ₁

Affiliation

Nitrite hydrogenation is studied in steady‐state as well as transient operation using a Pd catalyst in a tubular membrane contactor reactor. A negative reaction order in hydrogen in steady state operation proofs that hydrogen and nitrite adsorb competitively. In transient operation, feeding nitrite to the Pd surface fully covered with hydrogen results initially in very low conversion of nitrite, speeding up once hydrogen is removed from part of the Pd surface. Additional proof for competitive adsorption between hydrogen and nitrite is provided by the observation that exposure of a nitrite‐covered catalyst to hydrogen induces desorption of nitrite. Formation of ammonia in these experiments proceeds via two pathways, first via a fast reaction followed by extremely slow hydrogenation of adsorbed N atoms, which is kinetically not relevant. This information is relevant for designing effective and selective catalysts when operating at very low nitrite concentration.

中文翻译：

亚硝酸盐加氢过程中亚硝酸盐和氢气在钯上的竞争吸附

在管式膜接触器反应器中使用 Pd 催化剂研究稳态和瞬态操作下的亚硝酸盐加氢。稳态操作中氢气的负反应级证明氢气和亚硝酸盐竞争性吸附。在瞬态操作中，将亚硝酸盐供给到完全被氢气覆盖的钯表面，最初会导致亚硝酸盐的转化率非常低，一旦从部分钯表面去除氢气，亚硝酸盐的转化率就会加快。通过观察将亚硝酸盐覆盖的催化剂暴露于氢气会诱导亚硝酸盐解吸，为氢气和亚硝酸盐之间的竞争吸附提供了额外的证据。在这些实验中氨的形成通过两种途径进行，首先是通过快速反应，然后是吸附的氮原子的极其缓慢的氢化，这在动力学上是不相关的。该信息对于在非常低的亚硝酸盐浓度下操作时设计有效和选择性的催化剂相关。

更新日期：2018-07-05

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