Salimi Saeideh, F Farnia S Morteza, Akhbari Kamran, Tavasoli Ahmad
School of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6455 Tehran, Iran.
Inorg Chem. 2023 Oct 30;62(43):17588-17601. doi: 10.1021/acs.inorgchem.3c01094. Epub 2023 Oct 19.
Today, the importance of decreasing and converting CO gases from the atmosphere into value-added chemicals by catalytic hydrogenation reactions has become one crucial challenge. In the current work, to facilitate the hydrogenation of CO, several mesoporous alumina catalysts with high efficiency and stability were synthesized using the MIL-68(Al) platform, a nanoporous MOF with a high surface area as a precatalyst, encapsulating nickel or nickel-iron nanoparticles (NPs). After removing the organic linker of MIL-68(Al) by calcination in air, two types of catalysts, promoted and unpromoted, were obtained with various loads of nickel and iron. A set of analyses (PXRD, BET-N, TEM, FE-SEM, ICP-OES, EDX-map, CO-TPD, H-TPR, and H-TPD) were performed to evaluate the physicochemical properties of catalysts. Based on the analysis results, the promoted catalyst had smaller particles and pores due to the effective and uniform distribution of nickel NPs. Also, H-TPR and CO-TPD results in samples containing Fe promoter demonstrated the facilitation of the reduction process and the adsorption and activation of CO, respectively. The results of CO methanation indicated an improved catalytic performance for promoted samples, especially at low temperatures (200-300 °C), compared to unpromoted catalysts. 5Fe·15Ni@AlO catalyst displayed the best performance compared to other catalysts, with a conversion of 92.4% and selectivity of 99.6% at 350 °C and GHSV = 2500 h. Moreover, the 5Fe·15Ni@AlO catalyst facilitated the CO methanation reaction by reducing the activation energy to 42.5 kJ mol compared with other reported catalysts. Both types of catalysts performed 100% hydrogenation of CO to CH with full selectivity at 250 °C and exhibited high stability for at least 100 h at 300 °C. Notably, such high significant catalytic performance is only achieved by the usage of the "MOFs templating strategy" due to the high surface area for the effective distribution of NPs, the strong metal-support interaction, and the formation of nickel aluminate species, preventing the sintering of NPs.
如今，通过催化加氢反应将大气中的一氧化碳气体减少并转化为增值化学品的重要性已成为一项关键挑战。在当前工作中，为促进一氧化碳的加氢反应，使用具有高表面积的纳米多孔金属有机框架（MOF）MIL-68(Al)作为前催化剂，封装镍或镍铁纳米颗粒（NPs），合成了几种具有高效率和稳定性的介孔氧化铝催化剂。在空气中煅烧去除MIL-68(Al)的有机连接体后，获得了负载不同镍和铁含量的两类催化剂，即促进型和未促进型。进行了一系列分析（粉末X射线衍射、BET比表面积分析、透射电子显微镜、场发射扫描电子显微镜、电感耦合等离子体发射光谱、能谱图、一氧化碳程序升温脱附、氢气程序升温还原和氢气程序升温脱附）以评估催化剂的物理化学性质。基于分析结果，促进型催化剂由于镍纳米颗粒有效且均匀的分布而具有更小的颗粒和孔隙。此外，含铁促进剂样品的氢气程序升温还原和一氧化碳程序升温脱附结果分别表明还原过程的促进以及一氧化碳的吸附和活化。一氧化碳甲烷化结果表明，与未促进型催化剂相比，促进型样品的催化性能有所改善，尤其是在低温（200 - 300℃）下。与其他催化剂相比，5Fe·15Ni@AlO催化剂表现出最佳性能，在350℃和空速为2500 h时转化率为92.4%，选择性为99.6%。此外，与其他报道的催化剂相比，5Fe·15Ni@AlO催化剂通过将活化能降低至42.5 kJ/mol促进了一氧化碳甲烷化反应。两类催化剂在250℃时均能将一氧化碳100%加氢转化为甲烷且具有完全选择性，并且在300℃下至少100小时表现出高稳定性。值得注意的是，由于纳米颗粒有效分布的高表面积、强金属 - 载体相互作用以及镍铝酸盐物种形成防止了纳米颗粒的烧结，只有通过使用“MOF模板策略”才能实现如此高的显著催化性能。
