On the structure and composition of the phosphosulfide overlayer on Ni2P at hydrotreating conditions
On the structure and composition of the phosphosulfide overlayer on Ni2P at hydrotreating conditions
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DOI：
10.1016/j.jcat.2006.04.023
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发表时间：
2006-07
影响因子：
7.3
通讯作者：
A. Nelson;Mingyong Sun;A. Junaid
中科院分区：
文献类型：
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作者：
A. Nelson;Mingyong Sun;A. Junaid
Ni2P作为加氢处理催化剂显示出非常有前途的催化活性，但实际活性相的确切结构尚不清楚。本工作系统地研究了Ni2P（001）表面可能的表面组成的结构和能量学（即，Ni3P2平面）。通过比较吸附的H2S，SH和原子硫的表面的能量和磷被硫取代的表面作为（001）表面上的浓度和原子位置的函数，我们已经确定了一个稳定的硫化磷表面与Ni3PS的表面化学计量一致。在加氢处理条件下，这种表面组合物比本体Ni 2P或Ni 3S2在能量上更稳定。为了提供额外的确认建议的表面结构，我们计算了CO的吸收频率在Ni3P2和Ni3PS表面作为表面CO覆盖的函数，并发现它们与先前发表的实验红外光谱数据非常吻合。这些计算与文献实验观察相结合，表明在典型加氢处理条件下，具有50%磷被硫取代和一些原子硫沉积在三重中空位点上的表面是Ni2P的实际活性相或所谓的“磷硫化物”表面的准确表示。
Ni2P has shown very promising catalytic activity as a hydrotreating catalyst, but the exact structure of the actual active phase is not understood. The present work has systematically studied the structures and energetics of possible surface compositions of the (001) surface of Ni2P (i.e., the Ni3P2plane) at hydrotreating conditions using density functional theory calculations. By comparing the energetics of surfaces with adsorbed H2S, SH, and atomic sulfur and the surfaces with phosphorous replaced by sulfur as a function of concentration and atomic location on the (001) surface, we have identified a stable phosphosulfide surface consistent with a surface stoichiometry of Ni3PS. This surface composition is energetically more stable than bulk Ni2P or Ni3S2at hydrotreating conditions. To provide additional confirmation of the proposed surface structure, we calculated CO absorbance frequencies on the Ni3P2and Ni3PS surfaces as a function of surface CO coverage, and found that they are in excellent agreement with previously published experimental infrared spectroscopy data. These calculations, combined with literature experimental observations, indicate that the surface with 50% phosphorus replaced by sulfur and some atomic sulfur deposited on the three-fold hollow sites is an accurate representation for the actual active phase, or the so-called “phosphosulfide” surface, of Ni2P at typical hydrotreating conditions.