Selective steam reforming of n‐dodecane over stable subnanometric NiPt clusters encapsulated in Silicalite‐1 zeolite

Abstract

Multimetallic nanocatalysts have attracted increasing attention for steam reforming owing to highly exposed active sites, but often suffering from severe sintering. Herein, we design subnanometric Ni‐Pt bimetal clusters (ca. 1.7 nm) encapsulated in Silicalite‐1 zeolite (2Ni0.5Pt@S‐1) through ligand‐stabilized method to prevent sintering by fixing the metal into microporous channels. In the steam reforming of n‐dodecane test, 2Ni0.5Pt@S‐1 gave an excellent activity and stability with a decrease of conversion only 4% at 600°C for 4 hr, which was about a quarter that of 2Ni0.5Pt/S‐1 synthesized by co‐impregnation method, ascribing to superior sinter‐resistance of encapsulation structure. Moreover, 2Ni0.5Pt@S‐1 exhibited a higher H2 selectivity up to 69.9% than that of 2Ni0.5Pt/S‐1 (64.4%), owing to suppressed methanation reaction based on subnanometric clusters. Shape‐selective steam reforming of n‐dodecane and ofm‐xylene was also observed, because of m‐xylene could hardly diffuse into the zeolite channels due to its bulky molecular size, further preventing potential deactivation by tars in reforming process.

PtZn intermetallic nanoalloy encapsulated in silicalite‐1 for propane dehydrogenation

“…In the TEM tomographic images of PtZn@S‐1 and K‐PtZn@S‐1 (Figure 2A,J), PtZn nanoparticles could be observed. It provides the direct evidence that metal nanoparticles were encapsulated in the silicalite‐1 crystals as the “raisin in bread model” 45 . The average size of PtZn nanoparticles in PtZn@S‐1 is 2.4 ± 0.3 nm, whereas the average particle size in PtZn/S‐1 is 5.5 ± 1.8 nm with a bimodal distribution.…”

“…And the Mears and Weisz–Prater criteria evidenced the eliminate of external and internal mass transfer limitation (Table S4). 45 In summary, due to the beneficial spatial and lattice confinement, PtZn@S‐1 exhibited excellent stability and propylene selectivity together with a high activity.…”

“…The encapsulation strategy is an efficient method to protect metal nanoparticles from agglomeration and sintering through spatial confinement 37–41 . Zeolites with ordered microporous structures and excellent thermal stability have been proved as ideal supports for fixing small metal nanoparticles 42–46 . Corma and co‐workers prepared PtSn clusters encapsulated in the sinusoidal channels of MFI zeolite via a ligand‐assisted method, which showed high stability and selectivity for propane dehydrogenation 6 .…”

Incorporation of Active Metal Species in Crystalline Porous Materials for Highly Efficient Synergetic Catalysis

“…Constructing these subnanometric metal clusters into zeolite crystals is undoubtedly a very practical and promising strategy to address this issue. [35,[154][155][156][157][158][159][160][161][162][163][164][165][166][167][168][169][170] For instance, Iglesia et al successfully encaged Pt, Pd, Ir, Rh, and Ag clusters into the micropores of Linda A zeolite via a ligand-stabilized method. [166] As a consequence of confinement effect, the resulting samples exhibited high thermal sintering and remarkable resistance against sulfur poisoning in hydrogenation and oxidative dehydrogenation reactions.…”

“…In addition, the zeolite fixed subnanometric bimetallic clusters has also attracted increasing attention due to the synergistic effect of metal species and considerably improved catalytic performance. [156,160,161,163,165] For example, Yu and coworkers reported a facile and one-pot hydrothermal synthesis strategy for the encapsulation of subnanometric hybrid bimetallic palladium-transition metal hydroxide clusters Pd-M(OH) 2 (M = Ni, Co) within nano-sized S-1 zeolite. [163] The as-synthesized catalyst exhibited excellent catalytic activity and superior thermal stability in the complete decomposition of FA.…”