Platinum-Containing Hyper-Cross-Linked Polystyrene as a Modifier-Free Selective Catalyst for l-Sorbose Oxidation

Abstract

Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses.

D-glucose catalytic oxidation over palladium nanoparticles introduced in the hypercrosslinked polystyrene matrix

“…This indicates that reduction occurs inside the pores, without a mass transfer between them, while the size decrease is consistent with the density increase from Pd(CH 3 COO) 2 to Pd metal. A similar phenomenon was observed for fully microporous HPS, where mass transfer between pores was slow due to their small size [ 19 ]. The HPS sample used in this work consists of micropores, small and large mesopores as indicated earlier [ 35 ], but apparently the presence of large mesopores does not jeopardize the control over Pd NP formation.…”

Influence of the Mesoporous Polymer Matrix Nature on the Formation of Catalytically Active Ruthenium Nanoparticles

“…This material can act as a nanostructured matrix which governs the metal particle growth. As we demonstrated earlier, HPS perfectly controls the formation of Co- [34], Pt- [35,36], Pd- [37] and Ru-NPs [38]. These NPs showed excellent activity and selectivity in the reaction of fine organic synthesis.…”

Palladium nanoparticles stabilized in block-copolymer micelles for highly selective 2-butyne-1,4-diol partial hydrogenation

“…After impregnation of g-Al 2 O 3 (153 m 2 /g) and drying, the specific surface area increased up to 204 m 2 /g due to the presence of polymeric chains, which are known to possess high surface areas [37]. A slight decrease of the average pore diameter (from 35.9 to 30.2 Å ) was observed suggesting that pore blocking does not take place.…”