Sadao Ogasawara

Adsorption of polyethylene glycol from aqueous solution on montmorillonite clays

Adsorption rates and capacities of polyethylene glycol (PEG) were investigated for five montmorillonite clays. The adsorption of PEG for all the montmorillonite clays was rapid, and equilibrium was attained within 30 min. The adsorption isotherms of PEG for all the montmorillonites conformed to the Freundlich equation. The adsorption heats were 7.3 and 11.6 kJ · mol−1(mw.:2000), and 8.7 and 14.2 kJ · mol−1(mw.:20000) for the montmorillonite and the bentonite II-Ca, respectively. Adsorption capacities for all the clay samples approached constants for the molecular weight of PEG over 2000, though they increased with the increase of molecular weight under 2000. The adsorption capacities were slightly influenced by a nearly neutral pH. The montmorillonite clays which had different interlayer cations showed quite different adsorption capacities. The bentonite II-Ca, the acid clay, and the activated clay showed large adsorption capacities that were 30–50 % of that of an activated carbon.

Reaction mechanism for styrene synthesis over polynaphthoquinone

Abstract The styrene synthesis from ethylbenzene over polynaphthoquinone was investigated in the range of temperature 170–270 °C. The formation of styrene on the polynaphthoquinone was observed even at 170 °C. No evolution of hydrogen was found in the dehydrogenation reaction. The dehydrogenation was explained as the hydrogen transfer reaction from ethylbenzene to the quinone monomer. The catalytic activities of the modified polynaphthoquinone in styrene formation were also discussed.

Oxidative coupling of methane over Y2O3CaO catalysts

Abstract Binary oxides of Y 2 O 3 CaO were evaluated as catalysts in the oxidative coupling of methane to C 2+ (sum of C 2 H 6 , C 2 H 4 , C 3 H 8 , and C 3 H 6 ) hydrocarbons. Passing a mixture of CH 4 /O 2 and He gases (at 6, 3 and 31 ml/min respectively) in a fixed-bed flow reactor 13% and 7.5% of C 2+ yields were achieved at 750°C and 650°C, respectively, over 0.5 g of 10 mol-% Y 2 O 3 CaO catalyst prepared by calcining a coprecipitate of their oxalates at 800°C. The C 2+ yields on 10 mol-% Y 2 O 3 CaO, prepared by physical mixing, were lower than those on the coprecipitated catalyst. With increasing Y 2 O 3 content in the coprecipitated catalyst, the C 2+ selectivity at 700°C was significantly enhanced even at ca. 3 mol-%, whereas at 600°C such a change was not observed. A similar dependence on the Y 2 O 3 content was found in the way both surface areas and basicities decreased. Those changes were attributed to the formation of a solid solution accompanying the production of interstitial oxygen ions. Electron-spin resonance (ESR) studies indicated that the ion is a superoxide ion which is responsible for the generation of methyl radical from methane. At low reaction temperatures, 700°C, it was found that a lattice distortion of Y 2 O 3 in the binary oxides also affected the C 2+ selectivity.

Infrared studies of the adsorption and the catalysis of hydrogen chloride on alumina and on silica

Catalytic activity of hydrogen chloride on alumina and silica was studied by infrared technique, and it was found that chemisorption of HCl on dry alumina produced new hydrogen bonded OH groups on the surface. Most of these OH groups exchanged with butenes during the isomerization as fast as the rate proportional to the reaction rate. From these facts and the surface acidity of the HCl-treated alumina, it is concluded that the new OH groups produced by the adsorbed HCl are protonic and participate in the n-butene isomerization as Bronsted acid. On the other hand, HCl scarcely adsorbed on silica. The isomerization of n-butenes on silica did not occur in the presence of gaseous HCl, while OH groups on silica surface exchanged very rapidly with gaseous DCl.

Spectroscopic study on the surface structure and environment of fixed Mo catalysts prepared by use of Mo(π-C3H5)4

The surface structure, the environment and the distribution of the active sites of fixed Mo catalysts were spectroscopically investigated and compared with those of conventional catalysts made by an impregnation method. The fixed catalysts were found to have the tetrahedral dioxostructure of six-valent molybdenum with coordination unsaturation, uniformly and atomically populated at silica or alumina surface, in a different environment from that of the impregnation catalysts. Such properties of molybdenum are thought to be essential factors for catalytic action in the abstraction of a hydrogen atom(hydride) from the C—H bond of a reactant. There are three different types of molybdenum species in the impregnation silica catalysts.

Reaction of CO2CH4 as a high-level heat transport system

Abstract Heat of reaction can be accumulated as chemical energy, using a reversible reaction. The reaction between carbon dioxide and methane is proposed as a possible high-level heat transport system: CO2 + CH4 = 2CO + 2H2 − 250 kJ mol−1. This process has several advantages over the Eva-Adam Process, which utilizes atomic energy: the heat of reaction available is ≈40 kJmol−1 higher than the Eva-Adam process at almost the same operation conditions; all the components are in the vapour phase, resulting in an easy operation; and side reactions are less. The present study was carried out to discover the most suitable catalyst for the reversible reaction, and a Ni-Al2O3 catalyst was selected.

Surface properties and catalytic activity of a Mo-fixed catalyst. Structure of the active site and mechanism for selective oxidation of ethyl alcohol

The physico-chemical properties of the surface of a Mo-fixed catalyst obtained by a ready reaction between Mo(π-C3H5)4 and surface OH groups of SiO2 were investigated by X-ray photoelectron spectroscopy, photoluminescence technique, u.v. diffuse reflectance spectroscopy, i.r. spectrometry and H2/O2 uptake. The difference between the surface properties of the fixed catalyst and the conventional impregnation catalyst is discussed. The Mo-fixed catalyst showed higher activity and selectivity than the conventional impregnation catalyst in the ethyl alcohol oxidation. Selective oxidation to form acetaldehyde proceeded by a two-stage redox (Mo6+⇌ Mo4+) mechanism. Coordinatively unsaturated dioxomolybdenum of uniform nature in a tetrahedral coordination is the active species in the selective oxidation of ethyl alcohol.

Infrared study of adsorbed state of aniline on alumina and HCl-treated alumina

Infrared spectra of adsorbed aniline on alumina showed bands at 1605, 1575, 1495 and 1470 cm−1 in the region of ring stretching vibration. Among these wave numbers, 1605 and 1575 cm−1 were attributed to the benzene ring stretching (v16a) and NH2 deformation, respectively. The intensity of both bands was decreased in comparison with the band of 1495 cm−1 (v13a) as the adsorption temperature increased. These results could be understood if both benzene ring and amino group had some interaction with the catalyst surface followed by the decrease of resonance effect of the molecule. In the spectra of adsorbed aniline on HCl-treated alumina, the intensity of v13a decreased more than on pure alumina. It was also found that HCl-treated alumina had exclusively Lewis acidity which was revealed in ir measurement. From these results, the adsorbed state of aniline has been discussed.

Olefin metathesis over well-defined active fixed molybdenum catalysts. Structure and oxidation state of the active site and reaction mechanism

Fixed Mo catalysts (supported molecular catalysts), synthesised using the facile reaction between Mo (π-C3H5)4 and the surface acidic OH groups of alumina, silica and silica–alumina, were found to be very active for propene and but-1-ene metathesis in the temperature range 268–308 K. The isolated and coordinatively unsaturated Mo4+ species which are chemically bonded to the support surface are the active species. The nature of the ligands and supports coordinated to the Mo4+ ions produce different catalytic activities and selectivities. The support also works as a reservoir/supplier of reactants. Metathesis on fixed Mo catalysts is explained by a one-site chain mechanism involving carbene intermediates.

Active fixed chromium catalysis for CO oxidation. Preparation and active structure of fixed Cr and Cr2 catalysts

Abstract The catalytic oxidation of CO with O2 (398–509 K) over fixed Cr or Cr2 catalysts, prepared by the fixing reaction of Cr(η3-C3H5)3 or Cr2(η3-C3H5)4 with surface OH groups of SiO2, was studied to determine the structure and environment of active sites in terms of catalytic activities, activation energies, Racah parameters, ESR peak widths, photoluminescence and adsorptions of CO or O2. The monochromate structure fixed on originally acidic OH groups of the SiO2 surface was easily rearranged by three redox treatments to form the surface cluster, with one vacant site on a Cr3+ ion and with a suitable exchange interaction between the Cr3+ ions. This rearranged surface showed a much higher activity than the virgin fixed Cr catalyst with mainly monochromate species, the fixed Cr2 catalyst with mainly dichromate species and a conventional impregnation catalyst.