K. Fukuda

Highly selective synthesis of light olefins from methanol on a novel Fe-silicate

Methanol to hydrocarbon conversion on a number of metallosilicates having the pentasil pore-opening structure were investigated to develop a highly selective catalyst for the olefin synthesis from methanol. The metallosilicates were prepared by replacing the Al ingredient with various metal salts at the stage of gel formation in a modified preparation method (the rapid crystallization method) of ZSM-5. The catalysts were active for the methanol to hydrocarbon conversion, and the selectivity to lower olefins, gasoline, or aromatics changed greatly with the kind of metal incorporated. As for the conversion to lower olefins, silicates of Fe, Co, and Pt exhibited the best selectivity. Among them, the Fe-silicate was least active for the formation of aromatics—undesirable products caused by a consecutive reaction of olefins. Further investigations were then made for the preparation, characterization, and methanol to hydrocarbon conversion on Fe-silicates. It was found that various amounts of Fe up to 10 wt% as Fe2O3 are incorporated in the crystal having pentasil pore-opening structure by the rapid crystallization method. The incorporated Fe was highly dispersed in the crystal and a considerable part of Fe was suggested to be in its framework. The incorporated Fe produced both strong and weak acid sites, and their amounts were controlled by changing Fe content in the catalyst. It was also suggested that a part of the Fe ingredient plays a role as nuclei of crystal growth of the high-silica crystal. The selectivity to C2C4 olefins was greatly increased by the incorporation of Fe in the crystal. The total selectivity to C2-C4 olefins was achieved as high as 97.6 C-mol%, and the space-time yield attained 11.9 C-mol/liter · h at 295 °C.

Control of pore structures of γ-alumina by the calcination of boehmite prepared from gibbsite under specific conditions

Abstract Hydrothermal treatment of gibbsite to boehmite and subsequent calcination to form alumina have been investigated. The aqueous solution of 0.5 – 1.0 M concentration alkali metal salts, such as NaNO3, KNO3 and LiNO3,accelerated boehmite formation and the gibbsite conversion to boehmite could be controlled with good reproducibility. The resulting boehmite had a good thermal resistance and γ-alumina with a BET surface area of ~100 m2 g−1 could be obtained by calcination, even at moderate temperatures of 500 – 700°C.

New Aspects in Catalytic Performance of Novel Metallosilicates Having the Pentasil Pore-Opening Structure

A series of novel metallosilicates having the pentasil pore-opening structure were synthesized by replacing the Al ingredient with various metal salts at the stage of gel formation in the rapid crystallization method of ZSM-5, and their catalytic performances were examined for the conversions of methanol to hydrocarbon, light olefins to gasoline, and light paraffins to aromatics. The catalytic performance changed greatly with the kind of metal incorporated in the silicate crystal. In the methanol to hydrocarbon conversion, for example, silicates of Ga, Cr, and V were more selective than ZSM-5 for the formation of gasoline and aromatics, while those of Fe, Co, and Pt exhibited the best selectivity to the formation of lower olefins. Improvements in the preparation condition of the Fe-silicate led to a highly selective Fe-silicate catalyst for conversions of methanol to C 2 -C 4 olefins and of light olefins to a high octane-number gasoline. The Gasilicate was more effective than the Ga ion exchanged H-ZSM-5 in the aromatization of light paraffins, and Pt ion exchange of the Ga-silicate significantly increased the activity.

Optical properties of impurity atoms in pressurized superfluid helium

We report on the optical properties of alkali atoms (Cs and Rb) in the pressurized superfluid helium. We observed excitation and emission spectra at various pressures from the saturated vapor pressure to about 25 atm. The theoretical calculations on the basis of the atomic bubble model have also been worked out. The qualitative agreement between the theoretical and experimental results with respect to the peak shift, the linewidth, and their pressure dependence is achieved in the framework of the spherical atomic bubble model. TheD2 excitation spectra with the double peaks are interpreted qualitatively in terms of the Jahn-Teller effect, indicating the existence of the nontotally symmetrical density distribution of the surrounding helium atoms.

RISING beamline (BL28XU) for rechargeable battery analysis

The BL28XU beamline, dedicated to rechargeable battery analysis, is described.

Sublevel spectroscopy of alkali atoms in superfluid helium

We report the results of optical pumping and optical detection of magnetic resonance of alkali atoms (Cs and Rb) in superfluid helium. The magnetic resonances between the ground-state Zeeman sublevels and hyperfine levels are observed through monitoring theD1 fluorescence by means of the optical-rf double resonance technique. Although the ground stateg values in superfluid helium are the same as in vacuum within the experimental error, the hyperfine constant of the ground state of the Cs atom in superfluid helium is found to be slightly larger than in vacuum. Coherent transient spectroscopy is also performed.

Revisit to diffraction anomalous fine structure

The diffraction anomalous fine structure method has been revisited by applying this measurement technique to polycrystalline samples and using an analytical method with the logarithmic dispersion relation.

Laser spectroscopy and optical pumping of alkali atoms in superfluid helium

In this paper, our recent works on the alkali atoms in superfluid helim (HeII) are reported. At first we mentions the laser-sputtering method for implantation, which is simple but is very efficient to produce various kinds of neutral atoms and molecules in HeII. Secondly, we report on the laser spectroscopy of alkali atoms in HeII. Optical excitation and emission spectra are found to be roughly explained by a spherical atomic bubble model, but the spectra corresponding to the D2 lines indicate the quadrupole oscillation of the bubble shape. Optical pumping by a circularly polarized laser beam is found to produce perfect polarization, for both electron and nuclear spins. Using the rf-optical double resonance techniques, the magnetic and hyperfine resonances are observed. It is discussed also about the phenomena which have observed in the experiments done so far but have not been fully explained.

Dynamics of electronically excited alkali atoms in superfluid helium

By spectroscopic method, the excited-state dynamics of alkalis implanted in liquid4He were found to depend on the kind of atoms. A new model based on a quasi-molecule, “alkali-HeN” is presented, where He atoms are localized in a particular anisotropic configuration and the number ofN and locations depend on the fine-structure intervals. With this model, the mechanisms for various optical responses are discussed.

Liquid helium line broadening and shifts of alkaline earth and alkali metal atoms

With newly developed laser sputtering method we implanted various kinds of atoms in superfluid helium. An atomic bubble model could rather quantitatively explain the results of laser and rf spectroscopy of these atoms.