Preparation and characterization of platinum nanoparticles immobilized in dihydrocinchonidine-modified montmorillonite and hectorite

摘要: Abstract A novel synthetic method is reported for the preparation of highly dispersed platinum nanoparticles immobilized in swelling clay minerals Na-montmorillonite and Optigel (synthetic Na-hectorite), modified by cation exchange with dihydrocinchonidine hydrochloride (DHCd·HCl). For both smectites, X-ray diffraction (XRD) data confirmed intercalation chiral modifier between mineral layers. After ion exchange, ability montmorillonite to undergo organic solvents was found be superior that Optigel. The surface-modified smectites were impregnated H 2 PtCl 6 precursor subsequently reduced NaBH 4 . Transmission electron microscopy (TEM) images Pt-montmorillonite (Pt-M) Pt-Optigel (Pt-O) revealed formation ultrafine, monodispersed Pt nanoparticles, mean crystallite sizes 0.8 1.2 nm Pt-M Pt-O, respectively. Both samples proved mildly enantioselective catalysts asymmetric hydrogenation ethyl pyruvate, leading predominant ( R )-ethyl lactate. finding efficiency affected dispersion medium through disaggregation suggested access reactant active centres rather limited. On other hand, improved enantiodifferentiation lack a solvent effect Pt-O indicated easier pyruvate molecules located mainly on external surface sites lamellae. above reaction, occurrence such considered responsible catalytic performance, whereas role particle size regarded as less significant.