Laboratory of Industrial Chemistry, Ruhr-University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany.
Phys Chem Chem Phys. 2011 Mar 7;13(9):3701-10. doi: 10.1039/c0cp01875a. Epub 2010 Dec 17.
The adsorption of carbon monoxide on an either unpromoted or potassium-promoted bulk iron catalyst was investigated at 303 K and 613 K by means of pulse chemisorption, adsorption calorimetry, temperature-programmed desorption and temperature-programmed surface reaction in hydrogen. CO was found to adsorb mainly molecularly in the absence of H(2) at 303 K, whereas the presence of H(2) induced CO dissociation at higher temperatures leading to the formation of CH(4) and H(2)O. The hydrogenation of atomic oxygen chemisorbed on metallic iron was found to occur faster than the hydrogenation of atomically adsorbed carbon. At 613 K CO adsorption occurred only dissociatively followed by recombinative CO(2) formation according to C(ads) + 2O(ads)→ CO(2(g)). The presence of the potassium promoter on the catalyst surface led to an increasing strength of the Fe-C bond both at 303 K and 613 K: the initial differential heat of molecular CO adsorption on the pure iron catalyst at 303 K amounted to 102 kJ mol(-1), whereas it increased to 110 kJ mol(-1) on the potassium-promoted sample, and the initial differential heat of dissociative CO adsorption on the unpromoted iron catalyst at 613 K amounted to 165 kJ mol(-1), which increased to 225 kJ mol(-1) in the presence of potassium. The calorimetric CO adsorption experiments also reveal a change of the energetic distribution of the CO adsorption sites present on the catalyst surface induced by the potassium promoter, which was found to block a fraction of the CO adsorption sites.
一氧化碳在未经促进或钾促进的块状铁催化剂上的吸附在 303 K 和 613 K 下通过脉冲化学吸附、吸附量热法、程序升温脱附和程序升温表面反应在氢气中进行了研究。在 303 K 下，在没有 H(2)的情况下，CO 主要以分子形式吸附，而在较高温度下 H(2)的存在导致 CO 离解，形成 CH(4)和 H(2)O。化学吸附在金属铁上的原子氧的氢化被发现比原子吸附的碳的氢化更快。在 613 K 下，CO 吸附仅发生离解，随后根据 C(ads) + 2O(ads)→ CO(2(g))发生重组 CO(2)形成。在催化剂表面上存在钾促进剂会导致 Fe-C 键在 303 K 和 613 K 下的强度增加：在 303 K 下，纯铁催化剂上分子 CO 吸附的初始微分热为 102 kJ mol(-1)，而在钾促进的样品中增加到 110 kJ mol(-1)，在未促进的铁催化剂上的离解 CO 吸附的初始微分热在 613 K 下为 165 kJ mol(-1)，在钾存在下增加到 225 kJ mol(-1)。量热 CO 吸附实验还揭示了钾促进剂诱导的催化剂表面上存在的 CO 吸附位的能量分布的变化，发现它会阻止一部分 CO 吸附位。
