Progresses of coal liquefaction catalysts in Japan

Research and development of catalysts and their performances for coal liquefaction are reviewed, enphasizing the contribution of recent 20 years from Japan. A variety of iron based catalysts were extensively examined to define the pyrrhotite as the active species produced in the liquefaction process. Synthetic pyrite, synthesized hydroxy ferric oxide, finely ground pyrite and limonite have been applied in the process development of coal liquefaction. Iron impregnation onto coal particles using waste water was examined also in a continuous-flow reactor. Finer particles were found to reduce significantly the amount of the catalyst to obtain the same oil yield. Usefulness of such catalysts is proved in the continuous operation of a large scale pilot plant. Iron, iron–nickel, and iron–molybdenum sulfides were found to be active catalysts when they are supported on nano-particles of carbon. Catalysts for recovery and repeated use and for selective aromatic ring opening are under current research.     

Long-lasting afterglow in Tb-doped SiO2-Ga2O3-CaO-Na2O glasses and its sensitization by Yb

Long-lasting afterglow due to Tb³⁺ ions has been observed in a Tb³⁺-doped SiO₂-Ga₂O₃-CaO-Na₂O glass, where a 4s empty orbital of Ga³⁺ probably works as an electron-trapping center. The sensitization effect of Yb³⁺ on the afterglow has been noticed.     

Estimation of rate constants for hydrogen atom abstraction by OH radicals using the C?H bond dissociation enthalpies: Haloalkanes and haloethers

We propose a semiempirical procedure for the estimation of the rate constants for hydrogen atom abstraction reactions of OH radicals with haloalkanes and haloethers. Our procedure is derived from the collision theory based kinetic equation, which was originally proposed by Heicklen (Int. J. Chem. Kinet. 1981, 13 , 651). This equation provides the estimates for the rate constants of hydrogen abstraction from the C? H bond dissociation enthalpy for each potential hydrogen atom abstraction site. We reparameterized the equation and then applied this procedure to a series of haloalkane and haloether molecules. The results obtained from the new equations are found to be quite satisfactory. In addition, we also report highly reliable calculated values of the C? H bond dissociation enthalpies for six environmentally important haloether molecules (CH₂FOCH₂F, CHF₂CF₂OCH₂CF₃, CF₃CH₂OCH₂CF₃, CF₃CF₂CH₂OCHF₂, CHF₂OCF₂CHFCl, and CHF₂OCHClCF₃). © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 130–138, 2003     

Tetrasila-1,3-butadiene and its transformation to disilenyl anions

The reaction of dilithiosilane, ( ^t Bu₂MeSi)₂SiLi₂ (2), with 1,1,2,2-tetrachloro-1,2-dimesityldisilane produced the tetrasila-1,3-butadiene derivative, ( ^t Bu₂MeSi)₂Si=Si(Mes)–(Mes)Si=Si(SiMe ^t Bu₂)₂ (3, Mes = 2,4,6-trimethyl-phenyl), which was isolated as reddish-purple crystals. The structure of 3 was determined by both spectroscopic and crystallographic methods; the Si=Si double bond lengths are 2.2003(12) and 2.1983(12) Å, and the length of the central Si?Si single bond is 2.3376(11) Å. The tetrasilabutadiene moiety is highly twisted, the torsional angle of Si1=Si2?Si3=Si4 being 72^°. The reaction of 3 with ^t BuLi or KC₈ in THF gave the disilenyllithium 4 and disilenylpotassium 5, which contain an sp ²-type silyl anion, by the reductive cleavage of the central Si–Si bond in 3.     

Structure of the jet-cooled 1-naphthol dimer studied by IR dip spectroscopy: cooperation between the pi-pi interaction and the hydrogen bonding

The structure of a jet-cooled 1-naphthol (1-NpOH) dimer was investigated by using resonant-enhanced two-photon ionization (R2PI) and ion-detected infrared (IR) dip spectroscopy. A geometrical optimization and a frequency calculation in (1-NpOH)2 were also performed at the MP2/cc-pVDZ level. Stable isomers in the MP2/cc-pVDZ calculation were classified into a structure dominated only by the pi-pi interaction and structures formed by cooperation between the pi-pi interaction and hydrogen bonding. On the basis of a comparison between the observed and calculated IR spectra, the geometry of (1-NpOH)2 was concluded to be a pi-pi stacking structure supported by hydrogen bonding.     

Anion-exchange chromatographic study of the chlorine isotope effect accompanying hydration

The single-stage separation factor for chlorine isotopes ((35)Cl and (37)Cl) was determined to be 1.00034 by anion exchange chromatography on a 4.5-m column operated in reverse breakthrough manner at 25 degrees C. This value is in good agreement with those obtained in our previous works. It was confirmed that the lighter isotope ((35)Cl) was preferentially fractionated into the resin phase, whereas the heavier isotope ((37)Cl) partitioned into the aqueous phase. This observation, however, contradicts the experimental results for Cl isotope fractionation during NaCl precipitation and the recent theoretical results on Cl isotope fractionation: the (37)Cl isotope selectively enriched into the solid phase and not into the aqueous phase. This discrepancy is discussed based on the theory of isotope distribution between two phases. It is suggested that the chromatographic results reflect an isotope effect accompanying hydration rather than an isotope effect due to a phase change, whereas the reverse is the case for the results in the NaCl precipitation study.