Atomic-scale insight into the origin of pyridine inhibition of MoS2-based hydrotreating catalysts
Atomic-scale insight into the origin of pyridine inhibition of MoS2-based hydrotreating catalysts
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DOI：
10.1016/j.jcat.2010.02.007
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发表时间：
2010-05-04
影响因子：
7.3
通讯作者：
Besenbacher, Flemming
中科院分区：
文献类型：
--
作者：
Temel, Burcin;Tuxen, Anders K.;Besenbacher, Flemming
众所周知，碱性含氮化合物如吡啶是MoS_2基催化剂加氢脱硫(HDS)反应的抑制剂。通过扫描隧道显微镜(STM)实验和密度泛函理论(DFT)计算的相互作用，获得了吡啶在MoS_2表面吸附的原子尺度的观察结果。与以前的红外光谱和密度泛函研究结果一致，STM结果表明，吡啶分子本身与MoS_2纳米团簇的相互作用很弱，甚至根本不相互作用。然而，在MoS_2边缘存在氢的情况下，STM也在边缘发现了吸附物种。计算的DFT能量和模拟的STM图像允许我们得出结论，这些物种是位于催化活性的边缘位置的吡啶离子。此外，吸附的吡啶物种的振动模式的密度泛函理论计算结果与先前在高表面氧化铝负载的MoS_2催化剂上观察到的结果一致。吸附位置似乎与加氢反应中涉及的边缘位置非常相似。因此，STM和DFT的结合结果为碱性N-化合物在HDS中的缓蚀作用提供了新的原子尺度的见解，并首次直接观察到碱性N-化合物在催化活性MoS_2边缘上的吸附模式。我们的结果进一步支持了先前报道的含氮化合物的抑制强度和质子亲和力之间的相关性。(C)2010 Elsevier Inc.保留所有权利。
Basic nitrogen-containing compounds such as pyridine are well known to be inhibitors of the hydrodesulfurization (HDS) reaction for the MoS2-based catalysts. From an interplay of scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, atomic-scale insight into pyridine adsorption on MoS2 is obtained. In agreement with previous IR-spectroscopy and DFT studies, the STM results show that the pyridine molecule itself interacts weakly or not at all with the MoS2 nanoclusters. However, in the presence of hydrogen at the MoS2 edges, adsorbed species are revealed by STM also at the edges. The calculated DFT energies and simulated STM images allowed us to conclude that these species are pyridinium ions located at the catalytically active brim sites. Furthermore, the DFT results for the vibrational modes of the adsorbed pyridinium species agree well with those observed in earlier IR experiments on high surface alumina-supported MoS2 catalyst. The adsorption sites appear to be very similar to the brim sites involved in hydrogenation reactions in HDS. Thus, the combined STM and DFT results provide new atomic-scale insight into the inhibition effect of basic N-compounds in HDS and the first direct observation of the adsorption mode of basic N-compounds on the catalytically active MoS2 edges. Our results lend further support to previously reported correlations between inhibiting strength and proton affinity for the N-containing compounds. (C) 2010 Elsevier Inc. All rights reserved.