Ni–M–O (M = Sn, Ti, W) Catalysts Prepared by a Dry Mixing Method for Oxidative Dehydrogenation of Ethane

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• 作者：Haibo Zhu ; Devon C. Rosenfeld ; Moussab Harb ; Dalaver H. Anjum ; Mohamed Nejib Hedhili ; Samy Ould-Chikh ; Jean-Marie Basset
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：May 6, 2016
• 年：2016
• 卷：6
• 期：5
• 页码：2852-2866
• 全文大小：966K
• 年卷期：0
• ISSN：2155-5435

文摘

A new generation of Ni–Sn–O, Ni–Ti–O, and Ni–W–O catalysts has been prepared by a solid-state grinding method. In each case the doping metal varied from 2.5% to 20%. These catalysts exhibited higher activity and selectivity for ethane oxidative dehydrogenation (ODH) than conventionally prepared mixed oxides. Detailed characterization was achieved using XRD, N₂ adsorption, H₂-TPR, SEM, TEM, and HAADF-STEM in order to study the detailed atomic structure and textural properties of the synthesized catalysts. Two kinds of typical structures are found in these mixed oxides, which are (major) “Ni_xM_yO” (M = Sn, Ti, W) solid solution phases (NiO crystalline structure with doping atom incorporated in the lattice) and (minor) secondary phases (SnO₂, TiO₂, or WO₃). The secondary phase exists as a thin layer around small “Ni_xM_yO” particles, lowering the aggregation of nanoparticles during the synthesis. DFT calculations on the formation energies of M-doped NiO structures (M = Sn, Ti, W) clearly confirm the thermodynamic feasibility of incorporating these doping metals into the NiO struture. The incorporation of doping metals into the NiO lattice decreases the number of holes (h⁺) localized on lattice oxygen (O^2– + h⁺ → O^•–) , which is the main reason for the improved catalytic performance (O^•– is known to favor complete ethane oxidation to CO₂). The high efficiency of ethylene production achieved in these particularly prepared mixed oxide catalysts indicates that the solid grinding method could serve as a general and practical approach for the preparation of doped NiO-based catalysts.