A Possible Mechanism of Hydrogen Reverse Spillover in Platinum-Zeolite Catalysts

Abstract

Quantum chemical methods (X3LYP and MP2) were applied to investigate the structure and reactivity of anion-radical site in HZSM-5 zeolite. The interaction of hydrogen zeolite with a platinum particle can involve electron transfer to a Brønsted acid site to form an anionradical fragment. A low stability of the latter favors the elimination of atomic hydrogen from the OH-group, an exothermic process with low activation energy. In the metal-zeolite catalysts, the anion-radical fragment formed due to withdrawal of electronic density from the metal particle can be responsible for the reverse spillover of Brønsted hydrogen onto the metal surface.

A mechanistic model for hydrogen activation, spillover, and its chemical reaction in a zeolite-encapsulated Pt catalyst

“…Although there have been several theoretical studies to provide a mechanistic insight into H spillover over the support surface such as zeolites, most of them have mainly focused on the local interaction between the H atom and the support surface or the H transfer step between the support surface and the metal nanoparticle. 15,16,22,23 This can be considered as the 'hydrogenation' (or the reduction) of supports. However, it should be pointed out that the hydrogenation of supports may have little relevance for describing the catalytic usability of H spillover on the This journal is © the Owner Societies 2016 support surfaces.…”

Influence of Brønsted acid sites on the product distribution in the hydrodeoxygenation of methyl laurate over supported Ru catalysts

“…Over the surface of the H-Z5 support with more Brønsted acid sites, the electronic interactions between H + moieties in Si–OH–Al and Ru particles made the surface of Ru particles more electron-deficient. 6,24,33…”

“…Over the surface of the H-Z5 support with more Brønsted acid sites, the electronic interactions between H + moieties in Si-OH-Al and Ru particles made the surface of Ru particles more electrondeficient. 6,24,33 The electronic properties of Ru particles on zeolites, Al 2 O 3 and SiO 2 were further measured by IR spectroscopy using CO as a probe molecule (Fig. 6).…”

Interaction of a Co6 cluster with oxides of different nature: a quantum chemical study

“…A probable mechanism of transfer of the BAS proton to the metal involves withdrawal of the electron density from the cobalt particle to the BAS with the formation of a radical anion center, subsequent cleavage of the О-Н bond, and elimination of the hydrogen atom. 16 (6) Co (2) Co (3) Co (4) Co (1) Co (5) Co (6) Co (2) Co (3) Co (4) Co (1) Co(5) tion of hydrogen atom on the cobalt surface leads to a hydride like structure (Scheme 1). The introduction of the cobalt particle into the acid zeolite ZSM 5 is characterized by a very high adsorption energy (about 80 kcal mol -1 ) and causes suppression of the Brønsted acidity.…”