Showing papers by "Takehiko Sasaki published in 2019"

Amine-Functionalized Graphene Oxide-Stabilized Pd Nanoparticles (Pd@APGO): A Novel and Efficient Catalyst for the Suzuki and Carbonylative Suzuki–Miyaura Coupling Reactions

Abstract: Palladium nanoparticles (NPs) are decorated on the surface of an amine-functionalized graphene oxide (Pd@APGO) and characterized by using various analytical techniques. In this methodology, the surface of graphene oxide is modified using the amine functional groups which help stabilization and distribution of Pd NPs very well and increases the surface electron density of NPs by electron donating from amine groups. This developed catalyst shows a high catalytic activity toward the Suzuki coupling and carbonylative Suzuki-Miyaura coupling reactions at mild reaction conditions. The amine on the graphene oxide plays a very crucial role to stabilize and increase the electron density of Pd NPs and prevents the leaching of Pd metals. The Pd@APGO catalyst showed excellent catalytic activity (>90%) with a large range of substrates for both of the reactions and provides five recycle runs without the loss of its activity.

Fabrication of Au Nanoparticles Supported on One-Dimensional La2O3 Nanorods for Selective Esterification of Methacrolein to Methyl Methacrylate with Molecular Oxygen

Abstract: Here we demonstrate a simple and cost effective synthetic route for selective esterification of aldehydes with high productivity in the presence of molecular oxygen (O2) on a gold supported lanthan...

Development of Highly Efficient and Durable Three-DimensionalOctahedron NiCo 2 O 4 Spinel Nanoparticles towardthe Selective Oxidation of Styrene

Abstract: Herewith, we have prepared poly(vinylpyrrolidone)-assisted water-based synthesis of the nanocrystalline spinel NiCo2O4 nanocatalyst by a one-pot hydrothermal route. The formation of the synthesized spinel NiCo2O4 nanoparticle has been confirmed by X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectrometry, transmission electron microscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure (EXAFS) analyses. The SEM results confirmed the formation of the three-dimensional octahedron structure with an average size of 20–30 nm. The EXAFS results further confirmed that the spinel NiCo2O4 nanoparticles exist in a pure phase. The catalytic activity of the synthesized spinel NiCo2O4 octahedron nanoparticles was evaluated for the conversion of styrene to styrene oxide by the oxidation reaction. It was found that the conversion of styrene was 78% with 67% of styrene oxide selectivity in the presence of hydrogen peroxide as an oxidant. The catalyst has also pro...

Metal Nanoparticles Syntheses on Ionic Liquids Functionalized Mesoporous Silica SBA‐15

Abstract: Supported metal nanoparticles hold great promise in heterogeneous catalysis as active and reusable catalysts for various organic transformations. Preparation methods of metal nanoparticles with excellent control over size, shape, and morphology on supports has significantly advanced to improve the performances of the resulting catalysts. Here, we aim to discuss the development of supported metal nanoparticles on mesoporous silica SBA-15 in the presence of immobilized ionic liquids mostly based on examples from the previously reported results. This review highlights the preparation methods for size-controlled syntheses and the immobilization of metal nanoparticles on solid supports, especially SBA-15 by various techniques.

Understanding Competition of Polyalcohol Dehydration Reactions in Hot Water

Abstract: Dehydration of biomass-derived polyalcohols has recently drawn attention in green chemistry as a prototype of selective reactions controllable in hot water or hot carbonated water, without any use ...

NH3 -Driven Benzene C-H Activation with O2 that Opens a New Way for Selective Phenol Synthesis.

Abstract: Catalytic benzene C-H activation toward selective phenol synthesis with O2 remains a stimulating challenge to be tackled. Phenol is currently produced industrially by the three-steps cumene process in liquid phase, which is energy-intensive and not environmentally friendly. Hence, there is a strong demand for an alternative gas-phase single-path reaction process. This account documents the pivotal confined single metal ion site platform with a sufficiently large coordination sphere in β zeolite pores, which promotes the unprecedented catalysis for the selective benzene hydroxylation with O2 under coexisting NH3 by the new inter-ligand concerted mechanism. Among alkali and alkaline-earth metal ions and transition and precious metal ions, single Cs+ and Rb+ sites with ion diameters >0.300 nm in the β pores exhibited good performances for the direct phenol synthesis in a gas-phase single-path reaction process. The single Cs+ and Rb+ sites that possess neither significant Lewis acidic-basic property nor redox property, cannot activate benzene, O2 , and NH3 , respectively, whereas when they coadsorbed together, the reaction of the inter-coadsorbates on the single alkali-metal ion site proceeds concertedly (the inter-ligand concerted mechanism), bringing about the benzene C-H activation toward phenol synthesis. The NH3 -driven benzene C-H activation with O2 was compared to the switchover of the reaction pathways from the deep oxidation to selective oxidation of benzene by coexisting NH3 on Pt6 metallic cluster/β and Ni4 O4 oxide cluster/β. The NH3 -driven selective oxidation mechanism observed with the Cs+ /β and Rb+ /β differs from the traditional redox catalysis (Mars-van Krevelen) mechanism, simple Langmuir-Hinshelwood mechanism, and acid-base catalysis mechanism involving clearly defined interaction modes. The present catalysis concept opens a new way for catalytic selective oxidation processes involving direct phenol synthesis.