Dealuminization for a Modified (Si–OH)_n–Pt Interface: Self-Activation of Pt/NaY Catalysts for Oxidation of Ethylene Glycol in a Base-Free Medium

Abstract

Aqueous oxidation of bio-derived ethylene glycol to glycolic acid represents a sustainable route to polyglycolic acid. However, a strong acidic/basic oxidative medium often causes structural evolution and metal sintering of supported metal catalysts. We reported an unusual self-activation of Pt/NaY catalysts for enhanced oxidation of ethylene glycol in a base-free medium. Owing to a dealuminization-induced shortened Si−OH bond and formulation of a Pt−acid interface caused by glycolic acid, the activity of self-activated Pt/NaY catalysts displays a 2-fold enhancement compared with fresh ones. As the key finding in this work, dealuminization is found to cause an electronic coupling effect through shortened Si−OH bonds and formulating the (Si−OH)−Pt interface. Such a coupling effect leads to electron-rich nature of Pt sites for oxidation reactions, and thus, the self-activated Pt/NaY catalysts display leading performances in terms of activity and durability as seen in literature reports. Various characterization techniques, including transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, provide consistent and supporting evidence for such unique interfacial behaviors. Catalyst characterization further reveals that metallic Pt 0 species is the intrinsically active phase for σ-activation rather than π-activation of ethylene glycol molecules. Isotopic tests and kinetic modeling further confirm the reaction mechanism on the surface of fresh and spent Pt/NaY catalyst samples. The special activity enhancement of spent catalysts can be applied to investigate the plausible mechanism of various other oxidation reactions.

Low‐energy Hemiacetal Dehydrogenation Pathway: Co‐production of Gluconic Acid and Green Hydrogen via Glucose Dehydrogenation

“…This inhibits the adsorption of glucose on the catalyst. In general, electron‐deficient Pt is more conducive to the adsorption of glucose via oxygen atoms than electron‐rich Pt; [36] accounting for the slight deactivation of the catalyst. No matter what alkali metal cation is used, [37] the electronic structure of the catalyst is changed, limiting the industrial viability of glucose dehydrogenation.…”

Design of Bifunctional Nanocatalysts Based on Zeolites for Biomass Processing

“…An unusual phenomenon of self-activation was observed for Pt/NaY catalysts in the base-free oxidation of biomass-derived ethylene glycol to glycolic acid and then to polyglycolic acid, a valuable product [ 195 ]. The thorough physicochemical characterization shows that upon oxidation, zeolite dealumination takes place, which results in the shortening of the Si-OH bond and the special interactions of Pt NPs with gluconic acid, which enhances the catalyst activity by a factor of two.…”

Design of Bifunctional Nanocatalysts for Biomass Processing

“…Unusual phenomenon of self-activation was observed for Pt/NaY catalysts in the base-free oxidation of biomass derived ethylene glycol to glycolic acid to further convert to polyglycolic acid, a valuable product [182]. The thorough physicochemical characterization shows that upon oxidation zeolite dealumination takes place which results in shortening of the Si-OH bond and the special interactions of Pt NPs with gluconic acid which enhances the catalyst activity by a factor of two.…”