Activation and Spillover of Hydrogen on Sub‐1 nm Palladium Nanoclusters Confined within Sodalite Zeolite for the Semi‐Hydrogenation of Alkynes

Abstract

The search for efficient nontoxic catalysts able to perform industrial hydrogenations is a topic of interest, with relevance to many catalytic processes. Herein, we describe a mechanistic phenomenon for the activation and spillover of hydrogen for remarkable selectivity in the semi‐hydrogenation of acetylene over sub‐1 nm Pd nanoclusters confined within sodalite (SOD) zeolite (Pd@SOD). Specifically, hydrogen is dissociated on the Pd nanoclusters to form hydrogen species (i.e., hydrogen atoms and hydroxyl groups) that spill over the SOD surfaces. The design and utilization of the small‐pore zeolite SOD (six‐membered rings with 0.28×0.28 nm channels) is crucial as it only allows H2 diffusion into the channels to reach the encapsulated Pd nanoclusters and thus avoids over‐hydrogenation to form ethane. Pd@SOD exhibits an ethylene selectivity of over 94.5 %, while that of conventional Pd/SOD is approximately 21.5 %.

Recent advances in the synthesis, characterization, and catalytic consequence of metal species confined within zeolite for hydrogen-related reactions

“…28,29 Kurbanova et al 30 obtained Fe@MFI (Alfree MFI zeolite encapsulated Fe metal) by the reduction of Fe-MFI (Fe atom sitting in MFI zeolite framework) in a flow of H 2 / N 2 mixture at 900 °C for 10 h. Second, metal species without capability of incorporating into the zeolite framework (e.g. Pt, Pd or Ni) are introduced within zeolite micropores and then calcinated or reduced to encapsulated metal or metal oxides, such as Ni@NaX, 31 Pd@SOD, 32 Pt@S-1, 33 and Fe 3 O 4 @ZSM-5. 34 These metal clusters with 1-2 nm are encapsulated within zeolite micropores or channels and restricted by small zeolite aperture (<0.7 nm) and show excellent thermal stability and resistance to large poisoning reactants.…”

Promoting Catalytic Performance Involving Hydrogen Spillover by Ion Exchange of Pt@A Catalysts to Regulate Reactant Adsorption

“…14,15 Nevertheless, activated H 2 molecules adsorbed on metal sites yield dissociated H atoms, which can migrate by a hydrogen spillover process to the zeolite surface where the adsorbed reactants can be hydrogenated without reaching metal sites inside micropores directly. 16 Provided that the substrate molecule has a larger size than zeolite micropores, the metal@zeolite structure can guarantee that all conversions of substrates are attributed to the spillover hydrogenation on the surface of zeolites without direct contact with hydrogendissociated metal sites encapsulated in zeolite micropores. In this case, the interaction of substrates with the zeolite surface possesses a significant impact on catalytic activity and selectivity.…”

Robust NixSn/ZSM-12 Catalysts with Zeolite as the Support and Sn as the Promoter for Acetylene Semi-hydrogenation

“…Previous theoretical and experimental studies have intensively investigated the selective hydrogenation of acetylene to remove the acetylene impurities in ethylene. , It is reported that Pd, Pt, Rh, Co, Cu, Ni, , Au, and Fe , are active components of the catalysts, following the order: Pd > Pt > Ni–Rh > Co > Fe > Cu–Au . The traditional supports, such as alumina, silica, titania, ceria, g-C 3 N 4 , carbon, MOFs, and zeolites − could be employed for acetylene hydrogenation.…”