The evolution of the constituents of an 8 wt%Ni-5 wt%Fe/MgAl₂O₄ catalyst for dry reforming of methane (DRM) is monitored by in situ quick X-ray absorption spectroscopy (QXAS) and ⁵⁷Fe Mössbauer spectroscopy. In as prepared state, Fe is present as NiFe₂O₄ at the surface and as MgFe³⁺_xAl_2−xO₄ within the support, whereas Ni is mainly present as NiO. During H₂-TPR, NiFe₂O₄ and NiO form an alloy from 500 °C on and MgFe³⁺_xAl_2−xO₄ is partially reduced to MgFe²⁺_xAl_2−xO₄, such that Ni-Fe alloy, MgFe²⁺_xAl_2−xO₄ and MgFe³⁺_xAl_2−xO₄ are the prevalent phases in the reduced catalyst. During DRM, dominantly oxidizing environments (CH₄/CO₂ = 1/2, 1/1.5) lead to formation of FeO_x nanoparticles at the surface of the Ni-Fe alloy, thereby affecting the DRM activity, and possibly to some reincorporation of Fe into the support. For CH₄/CO₂ = 1/1, no significant changes occur in the catalyst’s activated state, as a consequence of reduction by CH₄ dissociation species counteracting oxidation by CO₂. However, Mössbauer analysis detects continued extraction of Fe from the support, sustaining ongoing Ni-Fe alloying.

通过原位快速 X 射线吸收光谱 (QXAS) 和⁵⁷ Fe Mössbauer 光谱监测用于甲烷干重整 (DRM)的 8 wt% Ni-5 wt% Fe/MgAl ₂ O ₄催化剂成分的演变。在制备好的状态下，Fe在表面以NiFe ₂ O ₄形式存在，在载体中以MgFe ³⁺ _x Al _2-x O _{4 形式}存在，而Ni主要以NiO形式存在。在 H ₂ -TPR期间，NiFe ₂ O ₄和 NiO 从 500 °C 开始形成合金，并且 MgFe ³⁺ _x Al _2-x O ₄部分还原为 MgFe²⁺ _x Al _2-x O ₄，例如Ni-Fe合金、MgFe ²⁺ _x Al _2-x O ₄和MgFe ³⁺ _x Al _2-x O ₄是还原催化剂中的主要相。在 DRM 期间，主要氧化环境 (CH ₄ /CO ₂ = 1/2, 1/1.5) 导致在 Ni-Fe 合金表面形成 FeO _x纳米粒子，从而影响 DRM 活性，并可能导致一些铁成支撑。对于 CH ₄ /CO ₂= 1/1，催化剂的活化状态没有发生显着变化，这是由于 CH ₄解离物质的还原抵消了 CO _{2 的}氧化作用。然而，Mössbauer 分析检测到从载体中持续提取 Fe，维持正在进行的 Ni-Fe 合金化。