High-Entropy Intermetallics Serve Ultrastable Single-Atom Pt for Propane Dehydrogenation

Abstract

Propane dehydrogenation has been a promising propylene production process that can compensate for the increasing global demand for propylene. However, Pt-based catalysts with high stability at ≥600 °C have barely been reported because the catalysts typically result in short catalyst life owing to side reactions and coke formation. Herein, we report a new class of heterogeneous catalysts using high-entropy intermetallics (HEIs). Pt−Pt ensembles, which cause side reactions, are entirely diluted by the component inert metals in PtGe-type HEIs. The resultant HEI (PtCoCu) (GeGaSn)/Ca−SiO 2 exhibited an outstandingly high catalytic stability, even at 600 °C (k d −1 = τ = 4146 h = 173 d), and almost no deactivation of the catalyst was observed for 2 months for the first time. Detailed experimental studies and theoretical calculations demonstrated that the combination of the site-isolation and entropy effects upon multimetallization of PtGe drastically enhanced the desorption of propylene and the thermal stability, eventually suppressing the side reactions even at high reaction temperatures.

Bimetallic Sites for Catalysis: From Binuclear Metal Sites to Bimetallic Nanoclusters and Nanoparticles

“…The introduction of a third metal (such as Pb) into the bimetallic PtGa nanoparticles leads to further improvement in the catalyst’s lifetime because the Pb atoms can bond with the Pt atoms surface of PtGa alloy particles and then transform the Pt ensembles into isolated Pt sites, which are highly active and selective for transforming propane into propylene but not active for cleavage of the C–H bonds in propylene, thus suppressing the coke deposition . The catalyst’s lifetime can be further extended by employing high-entropy PtCoCuGeGaSn alloy nanoparticles supported on SiO 2 as the catalysts, in which the Pt sites are claimed separated by the transition and main-group metals . As shown in Figure , the catalyst’s lifetime increases with the degree of Pt isolation represented by the loading of Pt in the high-entropy alloy particles.…”

“…(h) C 3 H 6 -TPD for Pt-based catalysts (adsorption temperature: −35 °C). Reproduced with permission from ref . Copyright 2022 American Chemical Society,.…”

The synthesis of single-atom catalysts for heterogeneous catalysis

“…The catalytic performance of PtGa–Pb/SiO 2 hardly changed after 96 h reaction. The group of Furukawa 106 further substituted separately the Pt and Ge sites of intermetallic PtGe with Co/Cu and Ga/Sn to form the nanoparticulate (PtCoCu)(GeGaSn) high-entropy intermetallics on the Ca–SiO 2 support. The sufficient isolation of Pt was obtained when the Pt fraction in the Pt site [Pt/(Pt + Co + Cu) ratio] was tuned to 0.25.…”

Isolated Pt Species Anchored by Hierarchical-like Heteroatomic Fe-Silicalite-1 Catalyze Propane Dehydrogenation near the Thermodynamic Limit

“…based high entropy intermetallic compounds (HEIs). 14 In another study, Chen et al constructed stable single-site [PtZn 4 ] catalysts by assembling atomically ordered intermetallic alloy (IMA), achieving the highest propylene productivity of 83.2 mol C3H6 g Pt −1 h −1 . 15 Furthermore, inert metals are essentially alloyed with Pt to dilute the Pt−Pt ensemble effect and thereby enhance catalyst stability and propylene selectivity against intermetallic compounds accompanied by a trade-off in initial intrinsic activity.…”

“…For example, PtSn (Pt1Sn1) nanoparticles have been reported to operate as PDH catalysts at thermodynamically limited conversion levels with great stability and propylene selectivity . In addition, the specific contribution of the second metal in the PtZn and PtSn-based cluster catalysts for the PDH reaction has been demonstrated. − Besides, Nakaya et al proposed two construction strategies to achieve enhanced thermal stability of the single-atom Pt; the first included the introduction of Ca and Pb to simultaneously modulate the electronic and geometrical properties of Pt sites and the second illustrated Pt stabilization by synthesizing Pt-based high entropy intermetallic compounds (HEIs) . In another study, Chen et al constructed stable single-site [PtZn 4 ] catalysts by assembling atomically ordered intermetallic alloy (IMA), achieving the highest propylene productivity of 83.2 mol C3H6 g Pt –1 h –1 .…”