Tadafumi Adschiri

Hydrolysis of 10 metal salt aqueous solutions of 6 metal oxides was conducted in supercritical water. Continuous and rapid production of metal oxide fine particles was achieved by mixing a metal salt aqueous solution with preheated water fed from another line. The reaction time required was less than 2 min. Particle size, morphology, and crystal structure of the obtained metal (hydrous) oxides were examined. Particle size (20 to 600 nm) was different among the systems but the size range was rela

Supercritical water can provide an excellent reaction environment for hydrothermal crystallization of metal oxide particles. Because of the drastic change of properties of water around the critical point, density, dielectric constant, and ionic product, the phase behavior for the supercritical water−light gas (O2, H2, etc.) system and reaction equilibrium/rate can be varied to synthesize new materials or define particle morphologies. In this work, hydrothermal crystallization experiments were pe

Hydrothermal synthesis of AlOOH particles from an Al(NO 3 ) 3 aqueous solution was examined in subcritical and supercritical water. Continuous and rapid production of AlOOH fine particles was achieved by mixing a metal salt aqueous solution with preheated water fed from another line. The effects of temperature, pressure, and initial concentration of solution on the particle size, morphology, and crystal structure of the metal (hydrous) oxides were examined. These properties are strongly affected

This paper describes the noncatalytic conversion of cellulose in supercritical and subcritical water. First, it was demonstrated that even without any acid catalyst, cellulose was rapidly converted to water soluble species with a relatively high glucose yield in near critical water and glucose yield increased with elevating temperature. Then the rate constants for cellulose decomposition and glucose decomposition were evaluated at a pressure of 25 MPa over a temperature ranging from 473 K to 673

ABSTRACT Supercritical water liquefaction and gasification is reviewed with the introduction of some recent findings by the authors. Supercritical water gasification is suitable for recovery of energy from wet biomass while supercritical water liquefaction opens the door to effective treatment of biomass species in terms of material recovery. Cellulose, one of the main components of biomass, is completely dissolved in supercritical water. Once dissolved, reaction of cellulose can take place swif

We conducted a comparative study of catalytic hydrodesulfurization of dibenzothiophene (DBT) with NiMo/Al2O3 at 673 K and 30 MPa, in various atmospheres (H2−SCW, CO−SCW, CO2−H2−SCW, and HCOOH−SCW), using a tube bomb reactor. Higher conversion of DBT was obtained in CO−SCW, CO2−H2−SCW, and HCOOH−SCW than in H2−SCW. These results clearly indicate that a water−gas shift reaction in supercritical water (SCW) produces species which can hydrogenate DBT more effectively than H2 gas. We also conducted a

Atomic-scale analysis of the cation valence state distribution will help to understand intrinsic features of oxygen vacancies (V_O ) inside metal oxide nanocrystals, which, however, remains a great challenge. In this work, the distribution of cerium valence states across the ultrafine CeO₂ nanocubes (NCs) perpendicular to the {100} exposed facet is investigated layer-by-layer using state-of-the-art scanning transmission electron microscopy-electron energy loss spectroscopy.

Magnetic nanoparticles (MNPs) have many potential biomedical applications. Improvements in their magnetic properties and solubility are necessary for these applications to realize their full potential. In this study, MNPs in the form of raspberry-like magnetite (Fe(3)O(4)) nanoparticle clusters, consisting of tiny Fe(3)O(4) particles with a diameter of approximately 20 nm, were prepared under hydrothermal conditions at 200 °C in the presence of 3,4-dihydroxyhydroxysinnamic acid (DHCA). The prima

Abstract This paper summarizes specific features of supercritical hydrothermal synthesis: Namely, synthesis of nano single crystals and controllable oxidizing and reducing atmosphere. Synthesis of organic–inorganic hybrid nanoparticles is another unique feature of this method. The synthesized hybrid nanoparticles can be dispersed in organic solvents, from which super lattice structure can be formed.