单中心阳离子镍催化剂实现高效稳定的甲烷干重整,Journal of the American Chemical Society

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单中心阳离子镍催化剂实现高效稳定的甲烷干重整
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-11-10 , DOI: 10.1021/jacs.3c04581
Qingpeng Cheng _{1,

2} , Xueli Yao ₂ , Lifeng Ou ₃ , Zhenpeng Hu ₃ , Lirong Zheng ₄ , Guanxing Li ₁ , Natalia Morlanes ₂ , Jose Luis Cerrillo ₂ , Pedro Castaño ₂ , Xingang Li ₅ , Jorge Gascon ₂ , Yu Han _{1,

2,

6,

7}

Affiliation

沸石负载的镍 (Ni) 催化剂已被广泛研究用于甲烷干重整 (DRM)。一般认为，在反应之前或反应过程中，Ni被还原成金属态以充当催化位点。在这里，我们采用配体保护的合成方法来实现 Ni 高度结合到 MFI 沸石的骨架中。在 600 °C 下进行的 DRM 反应过程中，掺入的 Ni 物质保留了其阳离子性质，与相同负载量的负载金属 Ni 颗粒相比，表现出更高的表观催化活性和显着更高的催化稳定性。根据理论和实验证据，我们得出结论，将 Ni 纳入沸石骨架中会形成金属-氧 (Ni ^δ+ –O ^(2−xi)– ) 对，这些对作为催化活性位点，促进解离。 CH ₄中的C-H键通过与金属Ni不同的机制形成。阳离子Ni单位点CH ₄的转化遵循CH _x氧化途径，其特点是部分裂解中间体CH _x^*快速转化，有效抑制焦炭形成。通过鉴定反应中间体，实验验证了CH _x氧化途径的存在。这些新的机理见解阐明了所开发的 Ni-MFI 催化剂的卓越性能，并为设计更高效、更稳定的镍基 DRM 催化剂提供了指导。

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Highly Efficient and Stable Methane Dry Reforming Enabled by a Single-Site Cationic Ni Catalyst

Zeolite-supported nickel (Ni) catalysts have been extensively studied for the dry reforming of methane (DRM). It is generally believed that prior to or during the reaction, Ni is reduced to a metallic state to act as the catalytic site. Here, we employed a ligand-protected synthesis method to achieve a high degree of Ni incorporation into the framework of the MFI zeolite. The incorporated Ni species retained their cationic nature during the DRM reaction carried out at 600 °C, exhibiting higher apparent catalytic activity and significantly greater catalytic stability in comparison to supported metallic Ni particles at the same loading. From theoretical and experimental evidence, we conclude that the incorporation of Ni into the zeolite framework leads to the formation of metal–oxygen (Ni^δ+–O^(2−ξ)–) pairs, which serve as catalytic active sites, promoting the dissociation of C–H bonds in CH₄ through a mechanism distinct from that of metallic Ni. The conversion of CH₄ on cationic Ni single sites follows the CH_x oxidation pathway, which is characterized by the rapid transformation of partial cracking intermediates CH_x^*, effectively inhibiting coke formation. The presence of the CH_x oxidation pathway was experimentally validated by identifying the reaction intermediates. These new mechanistic insights elucidate the exceptional performance of the developed Ni-MFI catalyst and offer guidance for designing more efficient and stable Ni-based DRM catalysts.

更新日期：2023-11-10

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