Keigo Kamata

Bio: Keigo Kamata is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Catalysis & Hydrogen peroxide. The author has an hindex of 45, co-authored 153 publications receiving 6648 citations. Previous affiliations of Keigo Kamata include University of Tokyo & National Presto Industries.

Efficient Epoxidation of Olefins with ≥99% Selectivity and Use of Hydrogen Peroxide

Abstract: Epoxides are an important class of industrial chemicals that have been used as chemical intermediates. Catalytic epoxidation of olefins affords an interesting production technology. We found a widely usable green route to the production of epoxides: A silicotungstate compound, [gamma-SiW10O34(H2O)2]4-, is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [gamma-SiW10O36]8- and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H2O2) oxidant at 305 kelvin. The effectiveness of this catalyst is evidenced by >/=99% selectivity to epoxide, >/=99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.

Effect of MnO2 Crystal Structure on Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid.

Abstract: Aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) as a bioplastics monomer is efficiently promoted by a simple system based on a nonprecious-metal catalyst of MnO2 and NaHCO3. Kinetic studies indicate that the oxidation of 5-formyl-2-furancarboxylic acid (FFCA) to FDCA is the slowest step for the aerobic oxidation of HMF to FDCA over activated MnO2. We demonstrate through combined computational and experimental studies that HMF oxidation to FDCA is largely dependent on the MnO2 crystal structure. Density functional theory (DFT) calculations reveal that vacancy formation energies at the planar oxygen sites in α- and γ-MnO2 are higher than those at the bent oxygen sites. β- and λ-MnO2 consist of only planar and bent oxygen sites, respectively, with lower vacancy formation energies. Consequently, β- and λ-MnO2 are likely to be good candidates as oxidation catalysts. On the other hand, experimental studies reveal that the reaction rates per surface area for the slowest step (FFCA oxidation to FDCA) decrease in the order of β-MnO2 > λ-MnO2 > γ-MnO2 ≈ α-MnO2 > δ-MnO2 > e-MnO2; the catalytic activity of β-MnO2 exceeds that of the previously reported activated MnO2 by three times. The order is in good agreement not only with the DFT calculation results, but also with the reduction rates per surface area determined by the H2-temperature-programmed reduction measurements for MnO2 catalysts. The successful synthesis of high-surface-area β-MnO2 significantly improves the catalytic activity for the aerobic oxidation of HMF to FDCA.

Aryl-aryl bond formation by transition-metal-catalyzed direct arylation.

Abstract: The biaryl structural motif is a predominant feature in many pharmaceutically relevant and biologically active compounds. As a result, for over a century 1 organic chemists have sought to develop new and more efficient aryl -aryl bond-forming methods. Although there exist a variety of routes for the construction of aryl -aryl bonds, arguably the most common method is through the use of transition-metalmediated reactions. 2-4 While earlier reports focused on the use of stoichiometric quantities of a transition metal to carry out the desired transformation, modern methods of transitionmetal-catalyzed aryl -aryl coupling have focused on the development of high-yielding reactions achieved with excellent selectivity and high functional group tolerance under mild reaction conditions. Typically, these reactions involve either the coupling of an aryl halide or pseudohalide with an organometallic reagent (Scheme 1), or the homocoupling of two aryl halides or two organometallic reagents. Although a number of improvements have developed the former process into an industrially very useful and attractive method for the construction of aryl -aryl bonds, the need still exists for more efficient routes whereby the same outcome is accomplished, but with reduced waste and in fewer steps. In particular, the obligation to use coupling partners that are both activated is wasteful since it necessitates the installation and then subsequent disposal of stoichiometric activating agents. Furthermore, preparation of preactivated aryl substrates often requires several steps, which in itself can be a time-consuming and economically inefficient process.

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

Abstract: 介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Polyoxometalate clusters, nanostructures and materials: From self assembly to designer materials and devices

Abstract: Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures and several structural types and novel physical properties are examined. In this critical review the synthetic and design approaches to the many polyoxometalate cluster types are presented encompassing all the sub-types of polyoxometalates including, isopolyoxometalates, heteropolyoxometalates, and reduced molybdenum blue systems. As well as the fundamental structure and bonding aspects, the final section is devoted to discussing these clusters in the context of contemporary and emerging interdisciplinary interests from areas as diverse as anti-viral agents, biological ion transport models, and materials science.

Polyoxometalates: Building Blocks for Functional Nanoscale Systems

Abstract: Polyoxometalates (POMs) are a subset of metal oxides that represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form dynamic structures that can range in size from the nano- to the micrometer scale Herein we present the very latest developments from synthesis to structure and function of POMs We discuss the possibilities of creating highly sophisticated functional hierarchical systems with multiple, interdependent, functionalities along with a critical analysis that allows the non-specialist to learn the salient features We propose and present a "periodic table of polyoxometalate building blocks" We also highlight some of the current issues and challenges that need to be addressed to work towards the design of functional systems based upon POM building blocks and look ahead to possible emerging application areas

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Abstract: The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...