論文 - 大久保　貴広

Adsorption properties of templated mesoporous carbon (CMK-1) for nitrogen and supercritical methane - Experiment and GCMC simulation 査読

Takahiro Ohkubo, Jin Miyawaki, Katsumi Kaneko, Ryong Ryoo, Nigel A. Seaton

Journal of Physical Chemistry B   106 ( 25 )   6523 - 6528   2002年6月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER CHEMICAL SOC  

Nitrogen adsorption isotherms at 77 K and high pressure adsorption of supercritical methane at 303 K were measured on mesoporous carbon (CMK-1) prepared from the templating of MCM-48. These experimental isotherms were simulated with grand canonical Monte Carlo (GCMC) simulation using the rod-aligned slitlike pore (RSP) model. This RSP model gives good agreement with the experimental nitrogen adsorption isotherm in the low-pressure region, while it describes well the observed methane isotherm. The isothermal compressibility of the adsorbed methane at 303 K was calculated from the experimental and simulated isotherms. The isothermal compressibility of the adsorbed methane shows the intermediate state between the supercritical and liquid phase. This indicates that the adsorbed layer of supercritical methane is highly compressed by the strong interaction potential from the pore walls.

DOI： 10.1021/jp0200369

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Oriented structures of alcohol hidden in carbon micropores with ERDF analysis 査読

T Ohkubo, K Kaneko

COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   187   177 - 185   2001年8月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The X-ray diffraction (XRD) of alcohol molecules such as methanol, ethanol, and I-propanol confined in slit-shaped graphitic micropores of activated carbon fibers (ACFs) having different pore widths was measured at 303 K. The effect of the pore width on the molecular assembly structure of alcohol in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The adsorbed density of alcohol in micropores of 1.1 nm in width was close to the solid density, while that in micropores of 0.7 nm in width was smaller than the liquid density. The ERDF of alcohol adsorbed in the 0.7 nm micropores showed a highly ordered structure compared with the 1.1 nm micropores, which is completely different from the adsorbed density results. It was presumed that alcohol molecules are hydrogen-bonded to form a layered structure, which is fit for the slit-shaped micropore. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-7757(01)00627-6

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High-temperature treatment effect of microporous carbon on ordered structure of confined SO2 査読

T Ohkubo, CM Yang, E Raymundo-Pinero, Linares-Solano, K Kaneko

CHEMICAL PHYSICS LETTERS   329 ( 1-2 )   71 - 75   2000年10月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The X-ray diffraction (XRD) of SO2 molecules adsorbed in micropores of activated carbon fiber (ACF) was measured at 303 K. Effect of pore width and high-temperature treatment (HTT) of ACF on the XRD of SO2 in micropores were examined. The HTT gave rise to a more dipole-oriented structure of SO2 molecules in micropores of 1.1 nm width, whereas the opposite effect was observed in micropores of 0.7 nm. The intensified image potential of an SO2 molecule for the heat-treated graphitic pore wall should stabilize the dipole-oriented structure in the case of 1.1 nm micropores, while the heat-treatment provides defective structures in the narrow micropore system. The presence of O-2 stabilized the dipole-oriented structure of SO2 molecules in the micropore. (C) 2000 Elsevier Science B.V.

DOI： 10.1016/S0009-2614(00)00973-8

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In situ X-ray diffraction studies on micropore filling 査読

T. Iiyama, T. Ohkubo, K. Kaneko

Membrane Science and Technology   6 ( C )   35 - 66   2000年

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

The molecular level picture of micropore filling mechanism in carbon micropores was summarized and the necessity of the structural study on molecules confined in carbon micropores with in situ X-ray diffraction is described. The detailed explanation of in situ X-ray diffraction technique for adsorption studies is given. The effectiveness of the in situ X-ray diffraction for elucidation of structures of molecules filled in micropore is shown for CCl4, water, and alcohol molecules. In situ X-ray diffraction studies shows the presence of organized structure inherent to an adsorbate molecule, although only adsorption measurement cannot distinguish the molecular state different from the bulk liquid. © 2000 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0927-5193(00)80004-2

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その他リンク： http://orcid.org/0000-0001-5907-3683

Confined state of alcohol in carbon micropores as revealed by in situ X-ray diffraction 査読

T Ohkubo, T Iiyama, T Suzuki, K Kaneko

CHARACTERIZATION OF POROUS SOLIDS V   128   411 - 419   2000年

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The X-ray diffraction (XRD) of ethanol and methanol molecules confined in carbon micropores was measured at 303 K. The effect of the pore width in the range of 0.7-1.1 nm on the molecular assembly structure of ethanol and methanol in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The density of alcohol molecular assemblies in micropores was determined by using ethanol or methanol adsorption at 303 K and nitrogen adsorption at 77 K. The density of alcohol molecular assemblies in pores of 1.1 nm was close to the solid density of alcohol, whereas that in micropores of 0.7 nm was almost equal tr, the bulk liquid density. However the amplitudes of the ERDFs of alcohol in both micropores were much greater than that of bulk liquid, indicating that the serious confinement in micropores gives rise to their solid-like ordering even at 303 K.

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その他リンク： http://orcid.org/0000-0001-5907-3683

Cluster mediated filling of water and alcohol on microporous carbon alloys 査読

K Kaneko, CM Yang, T Ohkubo, T Kimura, T Iiyama, H Touhara

ADSORPTION SCIENCE AND TECHNOLOGY   1 - 5   2000年

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD  

Adsorption isotherms of water and ethanol on fluorinated, nitrogen-alloyed, and pristine pitch-based activated carbon fiber(ACF)s were measured in order to elucidate water adsorption mechanism in hydrophobic micropores. States of alloyed fluorine and nitrogen atoms were examined by XPS. Fluorine atoms are bound by covalent bonding, while the presence of the pyridinic nitrogen was observed. Fluorination of ACF lowered the adsorptivity for water and ethanol. On the contrary, the nitrogen alloying enhanced the adsorptivity for ethanol. The adsorption states of water and ethanol in micropores of ACF were examined by use of in situ X-ray diffraction. The electron radial distribution function (ERDF)s from X-ray diffraction patterns showed that water and ethanol molecules form highly ordered structures in micropores at the saturated filling. The in situ small angle X-ray scattering (SAXS) of water-adsorbed ACF indicated the presence of different physical processes upon adsorption and desorption, which can be associated with the adsorption hysteresis. These integrated information on water and ethanol adsorption on F or N-alloyed and pristine ACFs were summarized to understand the cluster-mediated filling of water in hydrophobic micropores.

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Organized structures of methanol in carbon nanospaces at 303 K studies with in situ X-ray diffraction 査読

T Ohkubo, T Iiyama, K Kaneko

CHEMICAL PHYSICS LETTERS   312 ( 2-4 )   191 - 195   1999年10月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The X-ray diffraction of methanol molecules confined in carbon micropores having different pore widths (micropore widths, 0.7 and 1.1 nm) was measured at 303 K and the structural results were compared with those of ethanol, The methanol molecules confined in micropores of 0.7 nm have a more solid-like ordered structure than in 1.1 nm. The nearest-neighbor Peak of the electron radial distribution function of confined methanol did not shift from that of bulk methanol, but the amplitude was much greater than that of bulk methanol. These results were different from those of confined ethanol. Methanol molecules confined in carbon micropores have a rigid organized structure even at 303 K. However, no remarkable orientation effect, as in confined ethanol, was observed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0009-2614(99)01001-5

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Pore-width-dependent ordering of C2H5OH molecules confined in graphitic slit nanospaces 査読

T Ohkubo, T Iiyama, K Nishikawa, T Suzuki, K Kaneko

JOURNAL OF PHYSICAL CHEMISTRY B   103 ( 11 )   1859 - 1863   1999年3月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER CHEMICAL SOC  

The X-ray diffraction (XRD) of C2H5OH molecules confined in slit-shaped graphitic micropores of activated carbon fibers having different pore widths was measured at 303 K. The effect of the pore width in the range 0.7-1.1 nm on the molecular assembly structure of C2H5OH in the micropores was examined. The XRD patterns were analyzed by use of the electron radial distribution function (ERDF) analysis. The densities of C2H5OH molecular assemblies in micropores were determined by C2H5OH adsorption at 303 K and N-2 adsorption at 77 K. The density of C2H5OH molecular assemblies in the 0.9 and 1.1 nm pores was close to the solid density of C2H5OH. The ERDFs showed that the first and second nearest-neighbor peaks shift to a shorter distance with a decrease of the pore width while their peak heights increase. These changes of the ERDFs coincided very well with the adsorbed density of C2H5OH, indicating that the serious confinement by the micropores gives rise to the solidlike ordering even at 303 K.

DOI： 10.1021/jp984261v

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