A new synthesis route for the preparation of highly efficient and stable porous Ni-based alumina catalysts for CO₂ methanation is presented. It is based on the use of MIL-53(Al), an Al-containing metal-organic framework (MOF) with high surface area, as sacrificial support. A series of Ni-Al₂O₃ powder samples with Ni loadings ranging from 5 to 20 wt% was thus obtained. Their properties were thoroughly characterized by a set of complementary techniques including N₂-sorption, X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), CO₂ adsorption, temperature programmed reduction (H₂-TPR) and transmission electron microscopy (TEM). After nickel impregnation and thermal assisted organic ligands elimination, the resulting Ni-Al₂O₃ materials appear as interwoven alumina nanosheets in which Ni cations are intimately mixed forming NiAl₂O₄ spinel nanophases dispersed within amorphous alumina. This nanosheet morphology is preserved after the reduction of the Ni cations that leads to Ni⁰-Al₂O₃ catalysts composed of homogeneously and highly dispersed Ni⁰ nanoparticles, even at the highest 20 wt% Ni content. As a result, the activity in CO₂ methanation, evaluated between 250–450 °C under atmospheric pressure, using a constant gas hourly space velocity of 68,900 h⁻¹ and a molar reactant ratio H₂/CO₂ of 4, increased proportionally with respect to the Ni loading. On the most active catalyst, the selectivity to CH₄ was always excellent (between 96 % and 100 %) and the obtained CH₄ yield (∼70 % at 300 °C) was about two times higher than on a commercial Ni-based Al₂O₃ catalyst containing 25 wt% of Ni. The catalytic performances were also better than those of the already reported porous catalysts Ni/USY, Ni/SBA-15 as well as a Ni-Al₂O₃ synthesized by a EISA one-pot procedure, tested under the same reaction conditions for comparison. In this work the utilization of MIL-53(Al) as starting material for the synthesis of Ni-Al₂O₃ catalysts was responsible for a peculiar improvement of the metallic dispersion due to the high surface area of this MOF and of the metal-support interaction likely due to the existence of remaining NiAl₂O₄ at the metal-support interface after reduction. Sintering and agglomeration (the main cause of deactivation) were therefore limited, thus boosting the catalytic performance (activity, selectivity and stability).

提出了一种制备高效稳定的用于CO ₂甲烷化的多孔镍基氧化铝催化剂的新合成路线。它基于使用 MIL-53(Al)，一种具有高表面积的含铝金属有机框架 (MOF)，作为牺牲支撑。由此获得一系列Ni-Al ₂ O ₃粉末样品，其Ni负载量为5至20wt%。它们的性质通过一组补充技术得到彻底表征，包括 N ₂吸附、X 射线衍射 (XRD)、热重分析 (TGA)、CO ₂吸附、程序升温还原 (H ₂-TPR) 和透射电子显微镜 (TEM)。在镍浸渍和热辅助有机配体消除后，所得 Ni-Al ₂ O ₃材料表现为交织的氧化铝纳米片，其中 Ni 阳离子紧密混合，形成分散在无定形氧化铝中的NiAl ₂ O ₄尖晶石纳米相。这种纳米片形态在 Ni 阳离子还原后得以保留，这导致 Ni ⁰ -Al ₂ O ₃催化剂由均匀且高度分散的 Ni ⁰纳米粒子组成，即使在最高 20 wt% 的 Ni 含量下也是如此。因此，CO _{2 中}的活性甲烷化，在大气压下在 250–450 °C 之间进行评估，使用 68,900 h ^-1的恒定气时空速和 4 的反应物摩尔比 H ₂ /CO ₂与 Ni 负载成比例地增加。在最活跃的催化剂上，对 CH ₄的选择性总是非常好（在 96 % 和 100 % 之间）并且获得的 CH ₄产率（在 300 °C 下约为 70 %）比商业镍基铝高约两倍含有25wt％Ni的₂ O ₃催化剂。催化性能也优于已经报道的多孔催化剂 Ni/USY、Ni/SBA-15 以及 Ni-Al ₂ O ₃通过 EISA 一锅法合成，在相同反应条件下进行测试以进行比较。在这项工作中，利用 MIL-53(Al) 作为合成 Ni-Al ₂ O ₃催化剂的起始材料，由于该 MOF 的高表面积和金属-载体相互作用可能是由于还原后金属-载体界面处残留的 NiAl ₂ O ₄的存在。因此，烧结和团聚（失活的主要原因）受到限制，从而提高了催化性能（活性、选择性和稳定性）。