Effect of Tin in the Bulk of Platinum–Tin Alloys for Ethane Dehydrogenation
Effect of Tin in the Bulk of Platinum–Tin Alloys for Ethane Dehydrogenation
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DOI：
10.1007/s11244-020-01297-w
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发表时间：
2020-06
影响因子：
3.6
通讯作者：
J. Nam;Fuat E. Celik
中科院分区：
文献类型：
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作者：
J. Nam;Fuat E. Celik
采用密度泛函理论（DFT）对催化乙烷脱氢过程进行了研究，探讨了锡在PtSn合金体和表面的不同含量对催化剂活性、选择性和稳定性的影响。比较了Pt3Sn/Pt（111）表面合金纯净Pt（111）和Pt3Sn（111）本体合金。锡对两种合金的吸附能均有减弱作用。吸附物的结合几何形状变化不大，结合能的变化主要是由于合金的应变效应和/或带理论的配体效应引起的电子相互作用的变化。特别是配体效应和应变效应的共同作用，使得吸附物的结合能普遍弱于在Pt上的结合能，而强于在表面合金上的结合能。在c2hx的连续脱氢过程中，通过比较乙烯生成的活化能，可以预测其活化度为Pt > Pt3Sn > Pt3Sn/Pt。用两个描述子预测了对乙烯的选择性，其中对Pt3Sn/Pt的选择性最好。体中Sn的存在使得乙烯脱附和进一步脱氢的障碍之间的间隙相当，而Pt3Sn/Pt对乙烯的脱附更有利。在Pt3Sn上，乙基生成乙烯的倾向也减弱了。因此，尽管富锡块状合金的Sn含量较高，但其选择性较表面合金差，其次是Pt。
Catalytic ethane dehydrogenation was studied with density functional theory (DFT) calculations to investigate the differing role of Sn in the bulk and surface of PtSn alloys on the activity, selectivity, and stability of the catalyst. Pristine Pt(111), a surface alloy of Pt3Sn/Pt(111) and a bulk alloy of Pt3Sn(111) were compared. Binding energies of adsorbates were weakened by Sn on both alloys. With few changes for binding geometries of adsorbates, the change in binding energies was mainly attributed to the changes in the electronic interaction due to the strain effect and/or the ligand effect fromd-band theory on the alloys. Especially, the combination of ligand and strain effects on the bulk alloy made the binding energies of adsorbates generally weaker than on Pt but stronger than on the surface alloy. In the successive dehydrogenation of C2Hxspecies, the activity was expected in the order of Pt > Pt3Sn > Pt3Sn/Pt by comparing the activation energies for ethene formation. The selectivity toward ethene was predicted using two descriptors from which the best selectivity was expected on Pt3Sn/Pt. Sn in the bulk made the gap between the barriers for ethene desorption and further dehydrogenation comparable, whereas ethene desorption was much more favorable on Pt3Sn/Pt. The preference for ethene formation from ethyl was also weakened on Pt3Sn. Therefore, despite the higher Sn composition, worse selectivity was predicted for Sn-rich bulk alloy than the surface alloy, followed by Pt.