Alekseeva Bykova Maria V, Gulyaeva Yuliya K, Bulavchenko Olga A, Saraev Andrey A, Kremneva Anna M, Stepanenko Sergey A, Koskin Anton P, Kaichev Vasily V, Yakovlev Vadim A
Boreskov Institute of Catalysis, Lavrentiev Ave., 5, 630090, Novosibirsk, Russia.
Dalton Trans. 2022 Apr 12;51(15):6068-6085. doi: 10.1039/d2dt00332e.
The dehydrogenation of methylcyclohexane to toluene was investigated over high-loading monometallic Ni-SiO and bimetallic Zn/Ni-SiO catalysts. The catalysts were prepared by the impregnation coupled with the advantageous heterophase sol-gel technique. Their performance was tested in a fixed-bed flow reactor at 250-350 °C, 0.1 MPa pressure, equimolar ratio H/Ar (24 nL h in total), and a methylcyclohexane feed rate of 12 mL h. Information regarding the structure of Ni-Zn catalysts was obtained by N and CO adsorption, temperature-programmed reduction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and X-ray absorption spectroscopy. The results have shown that the addition of zinc leads to the hindrance of Ni reducibility along with weakening the Ni interaction with the silica matrix. This behavior particularly indicated the formation of solid oxide nickel-zinc solutions. The catalytic properties of Zn-modified catalysts in the dehydrogenation of methylcyclohexane appeared significantly superior to their Ni-Cu counterparts. For example, the selectivity of Zn/Ni-SiO catalysts toward toluene formation increased markedly with a decrease in the Ni : Zn mass ratio, achieving 97% at 350 °C over the sample with Ni : Zn = 80 : 20. This is attributed to the promoting geometric and electronic effects arising from the formation of bimetallic Ni-Zn solid solutions. Moreover, a deeper reduction of zinc and a more efficient formation of solid bimetallic solutions are observed after the catalytic tests.
在高负载单金属Ni-SiO和双金属Zn/Ni-SiO催化剂上研究了甲基环己烷脱氢制甲苯的反应。采用浸渍法结合有利的异相溶胶-凝胶技术制备了催化剂。在固定床流动反应器中，于250 - 350℃、0.1 MPa压力、H/Ar等摩尔比（总计24 nL/h）以及甲基环己烷进料速率为12 mL/h的条件下测试了它们的性能。通过N和CO吸附、程序升温还原、高分辨率透射电子显微镜、X射线光电子能谱、X射线衍射和X射线吸收光谱获得了有关Ni-Zn催化剂结构的信息。结果表明，锌的添加导致Ni还原性受阻，同时削弱了Ni与二氧化硅基体的相互作用。这种行为特别表明形成了固态氧化物镍-锌溶液。Zn改性催化剂在甲基环己烷脱氢反应中的催化性能明显优于其Ni-Cu对应物。例如，Zn/Ni-SiO催化剂对甲苯生成的选择性随着Ni : Zn质量比的降低而显著增加，在350℃下，Ni : Zn = 80 : 20的样品上达到了97%。这归因于双金属Ni-Zn固溶体形成所产生的促进几何和电子效应。此外，在催化测试后观察到锌的进一步还原和更有效的双金属固溶体形成。
