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Toyonaka, Japan

Kuwahara Y.,Osaka University | Tsuji K.,BEL Japan Inc. | Ohmichi T.,Osaka University | Kamegawa T.,Osaka University | And 2 more authors.
ChemSusChem | Year: 2012

Blast furnace slag (BFS), a high-volume byproduct resulting from iron-making processes, can be considered as a low-cost and abundant precursor for preparing layered double hydroxide (LDH) compounds. Here we demonstrate that a Ca-based LDH compound (hydrocalumite) synthesized from waste BFS through facile two-step procedures and its derivatives work as useful heterogeneous base catalysts for multiple chemical reactions including the Knoevenagel condensation, oxidation of alkylaromatics with O 2, transesterification, and cycloaddition reaction of epoxides with atmospheric CO 2. Structures were verified by using XRD and thermogravimetric analysis. The surface basicity and coordination geometry of the active metal species that substantially affect the catalytic activity were investigated by CO 2-temperature programmed desorption (TPD) and X-ray absorption fine structure (XAFS) measurements, respectively. These characterization results revealed that the slag-derived impurity elements, such as Fe, Ti, and Mn, effectively act either as active sites or as catalyst promoters in particular reactions and that the kind of guest counter anion (Cl - or NO 3 -) also plays a key role for achieving high catalytic efficiencies. In any reaction, the catalyst was easily separated by filtration and recyclable in multiple catalytic runs with retention of its activity and fine selectivity, irrespective of its considerable impurity level. It is believed that the slag-made hydrocalumite can replace existing LDH catalysts as a low-cost alternative and potentially contribute to sustainable chemical processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Miyahara M.T.,Kyoto University | Numaguchi R.,Kyoto University | Hiratsuka T.,Kyoto University | Nakai K.,BEL Japan Inc. | Tanaka H.,Kyoto University
Adsorption | Year: 2014

We have analyzed various phenomena that occur in nanopores, focusing on elucidating their key mechanisms, to advance the effective engineering use of nanoporous materials. As ideal experimental systems, molecular simulations can effectively provide information at the molecular level that leads to mechanistic insight. In this short review, several of our recent results are presented. The first topic is the critical point depression of Lennard-Jones fluid in silica slit pores due to finite size effects, studied by our original Monte Carlo (MC) technique. We demonstrate that the first layers of adsorbed molecules in contact with the pore walls act as a "fluid wall" and impose extra finite size effects on the fluid confined in the central portion of the pore. We next present a new kernel for pore size distribution (PSD) analysis, based entirely on molecular simulation, which consists of local isotherms for nitrogen adsorption in carbon slit pores at 77 K. The kernel is obtained by combining grand canonical Monte Carlo (GCMC) method and open pore cell MC method that was developed in the previous study. We show that overall trends of the PSDs of activated carbons calculated with our new kernel and with conventional kernel from non-local density functional theory are nearly the same; however, apparent difference can be seen between them. As the third topic, we apply a free energy analysis method with the aid of GCMC simulations to investigate the gating behavior observed in a porous coordination polymer, and propose a mechanism for the adsorption-induced structural transition based on both the theory of equilibrium and kinetics. Finally, we construct an atomistic silica pore model that mimics MCM-41, which has atomic-level surface roughness, and perform molecular simulations to understand the mechanism of capillary condensation with hysteresis. We calculate the work required for the gas-liquid transition from the simulation data, and show that the adsorption branch with hysteresis for MCM-41 arise from spontaneous capillary condensation from a metastable state. © 2013 Springer Science+Business Media New York. Source

Abdul Razak M.,University of Queensland | Do D.D.,University of Queensland | Horikawa T.,Tokushima University | Tsuji K.,BEL Japan Inc. | Nicholson D.,University of Queensland
Adsorption | Year: 2013

Different potential models for methane and ethylene are tested for their suitability for the description of bulk phase behavior, including coexistence, and adsorption on a graphite surface under sub- and super-critical conditions using GCMC simulation. Under sub-critical conditions, those intermolecular potential models that describe correctly the vapor-liquid equilibria were found to be adequate for the description of surface adsorption. These potential models can also give a good account of adsorption under supercritical conditions or near-critical conditions, provided the experimental data (in terms of excess) are correctly obtained with the reliably determined void volume as illustrated in this paper with methane adsorption. © 2012 Springer Science+Business Media New York. Source

Asai M.,Chiba University | Asai M.,Shinshu University | Ohba T.,Chiba University | Iwanaga T.,Chiba University | And 7 more authors.
Journal of the American Chemical Society | Year: 2011

Graphene and graphitic nanoribbons possess different types of carbon hybridizations exhibiting different chemical activity. In particular, the basal plane of the honeycomb lattice of nanoribbons consisting of sp 2-hybridized carbon atoms is chemically inert. Interestingly, their bare edges could be more reactive as a result of the presence of extra unpaired electrons, and for multilayer graphene nanoribbons, the presence of terraces and ripples could introduce additional chemical activity. In this study, a remarkable irreversibility in adsorption of CO 2 and H 2O on graphitic nanoribbons was observed at ambient temperature, which is distinctly different from the behavior of nanoporous carbon and carbon blacks. We also noted that N 2 molecules strongly interact with the basal planes at 77 K in comparison with edges. The irreversible adsorptions of both CO 2 and H 2O are due to the large number of sp 3-hybridized carbon atoms located at the edges. The observed irreversible adsorptivity of the edge surfaces of graphitic nanoribbons for CO 2 and H 2O indicates a high potential in the fabrication of novel types of catalysts and highly selective gas sensors. © 2011 American Chemical Society. Source

Information used for creating an adsorption isostere of a substance to be measured in a measuring system (container) is obtained by repeating alternately a first control step of changing temperature or pressure of the measuring system by a fixed amount by adjusting a gas amount supplied to/discharged from the measuring system, and a second control step of changing pressure or temperature of the measuring system by adjusting the gas amount supplied to/discharged from the measuring system until a gas adsorption amount of the substance to be measured becomes the same as before execution of the first control step.

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