Cheng Kang, van der Wal Lars I, Yoshida Hideto, Oenema Jogchum, Harmel Justine, Zhang Zhaorong, Sunley Glenn, Zečević Jovana, de Jong Krijn P
Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584 CG, Utrecht, The Netherlands.
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
Angew Chem Int Ed Engl. 2020 Feb 24;59(9):3592-3600. doi: 10.1002/anie.201915080. Epub 2020 Jan 22.
Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the "intimacy criterion" for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.
通过在纳米尺度上控制功能位点的空间组织来提高产物选择性是双功能催化中的一项关键挑战。我们展示了一系列由一维沸石（ZSM - 22和丝光沸石）和γ - 氧化铝粘结剂组成的复合双功能催化剂，其中铂颗粒可控地沉积在氧化铝粘结剂上或沸石晶体内部。正庚烷的加氢异构化表明，铂颗粒位于粘结剂上的催化剂，在纳米尺度上分离了铂和酸性位点，比铂颗粒位于沸石晶体内部的催化剂能产生更高产率的所需异构体。沸石晶体内的铂颗粒对反应中间体施加了明显的扩散限制，这导致了二次裂解反应，特别是对于具有窄微孔或大沸石晶体的催化剂。这些发现扩展了对用于低分子量反应物转化的双功能催化剂合理设计的“亲密准则”的理解。
