We have proposed a folding sheet mechanism to form mesoporous crystal from a layered polysilicate, kanemite. This report reviews the structure of layered polysilicates, their intercalation properties, condensation reactions between the polysilicate layers, the mechanism of forming mesoporous materials (FSM) and their applications. SiO₄-tetrahedral sheets and interlayer cations form sodium disilicate (Na₂Si₂O₅) and kanemite (NaHSi₂O₅). An exchange for organic cations gave silicate/organic c omplexes. When we used kanemite as a host material, we observed a condensation reaction between the unit sheets besides the cation exchange. Removing the organic cations by calcination formed mesoporous materials. Cation exchange at pH =12 folded the SiO₄-tetrahedral sheets without the condensation. Following pH adjustment at 8.5 promoted the condensation between adjacent sheets and gave a silicate/organic complex with hexagonal symmetry. Highly ordered crystals with uniform pores were obtained by calcination at 550°C. We call this mechanism and materials folding sheets mechanism and folded sheets mesoporous materials (FSM), respectively. Complexes with layered structure were also made by using a surfactant with cylindrical shape, or by adding an alcohol. The mesoporous crystals (FSM) are expected to be useful as adsorbents, catalysts or host materials for making nano-cluster of metals or semi-conductors.

View full abstract

A recently-developed taste sensor with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information of taste substances into electric signals, which are treated with a computer. The sensor output shows different patterns for chemical substances which have different taste qualities such as saltiness and sourness, while it shows similar patterns for chemicals with similar tastes. The sensor responds to the taste in itself, as can be understood from the fact that the taste interaction such as synergistic and suppression effects can be reproduced well. The sensitivity, reproducibility and durability are superior to those of human taste sense. The human sensory expressions can be quantified using this taste sensor.

View full abstract

Preparation of hollow spheres structured of spherical arrangement of fine particles (component particles) has been reported. The preparation process includes adhesion of component particles onto oil droplets in an aqueous solution and precipitation of binder between the component particles. In this study, quartz hollow spheres with Ni(OH)₂ were prepared using ammoniac alkaline Ni(NO₃)₂ solution as starting solution for binder. The hollow spheres in this system were obtained with much higher efficiency compared to those reported previously by the authors using CaCO₃ binder. Formation mechanism of quartz hollow spheres with N (OH)₂ binder was disc ussed. It was confirmed that adsorbed cationic species (Ni(II) complex, most likely) should play an important role through the whole process. In order to avoid wasteful precipitation of binder in bulk solution, the following conditions would be required for the precipitation behavior: 1) nucleation should occur preferentially on component particles; 2) the supersaturation should decrease sufficiently within the stage 1), so that growth of precipitate on component particles rather than nucleation in bulk solution be enhanced; 3) the low supersaturation of the stage 2) should not be raised until completion of the precipitation.

View full abstract

Stereoselective hydrolysis of the long-chain substrate (p-nitrophenyl ester of N-dodecanoyl-D and L-phenylalanine: C₁₂-D(L)- Phe-PNP) catalyzed by the active tripeptide (N-benzyloxycarbonyl-Lphenylalanyl-L-histidyl-L-leucine: Z-PheHisLeu) in the micellar systems (cationic hexadecyltrimethylammoniumb romide (CTAB); nonionic α -[4 (1, 1, 3, 3-tetramethylbuthyl) phenyl] - ω hydroxydecakis(oxyethylene)(Triton X-100), polyoxyethylene(20) sorbitan monolaurate (Tween 20), a-tetradecyl-co-hydroxyheptakis (oxyethylene)( C₁₄ (EO)₇ ); anionic sodium dodecylsulfate (SDS))was found to be controlled by changing the concentration and structure of surfactants. The noteworthy aspects are as follows: W ith respect to the rate-enhancement, (a)t he apparent rate constant (k_{a, obsd})is markedly enhanced around critical micelle concentration (CMC) and the head group in micellar surfactants takes an important role for the enhancement of rate (cationic CTAB >> nonionic surfactants (C₁₄(EO)₇, Triton X-100, Tween 20) >> anionic SDS). On the other hand, withrespect tothe stereospecificity, (b) kinetic enantioselectivity is exclusively favored for the L-substrate and the enantioselectivity (reflected in k^L_{a, obsd} / k^D_{a, obsd}) is kept constant above CMC in all of micellar systems in this study. The head group in micelles also take an important role to enhance the enantioselectivity (nonionic surfactants (Triton X-100, Tween 20, C₁₄ (EO)₇ ) > anionic SDS > cationic CTAB). In particular, a remarkably high enantioselectivity ( k^L_{a, obsd} / k^D_{a, obsd}= 77) was attained around CMC in the C₁₄(EO)₇ micellar system.

View full abstract

In order to investigate the competitive and exchange adsorption of epoxy resin (EPO) and poly (vinylbutyral) (PVB) onto y-Fe₂O₃ particles, the amounts of adsorbed of these resins in varying organic solvents were measured as a function of concentration of resin at 30° C. The extents of the saturated amounts of adsorption of resins calculated from Langmuir's adsorption equation were order of 2-ethoxyethyl acetate > cyclohexanone > dioxane > 2-butoxyethanol. This order corresponded to the extents of [η ] of each resin in these solvents. The competitive and exchange adsorption of both the resins were carried out in the cyclohexanone or 2-ethoxyethyl acetate systems. In competitive adsorption, the resins, indicating larger interaction force with the particles were adsorbed preferentially at lower concentration. At higher concentration, however, the amount of EPO adsorbed was saturated and that of PVB decreased inversely. On the other hand, the exchange adsorption was carried out by adding the resin into the systems in which the adsorption of another resin was saturated. The saturately adsorbed resins were displaced with the resin added, but at concentration range of 0.5-1.5 g⋅dm^-3 a constant amount of adsorption was observed for both the resins. These behaviors could be explained from the formation of complex between resins, and the difference of interaction force between resins and particles. The formation of the complex was confirmed through viscosity measurement and through IR measurement.

View full abstract

Several kinds of single-phase fluormicas were synthesized by solid reaction method using amorphous silica obtained from serpentinite by acid-treatment, and their expandable properties and the formation mechanism were discussed. Fluormica consisting of Mg, Si, N a, Li, O and F (Mg-mica) was prepared at 725-750° C for 1 hour by treating the mixture with molar ratio of SiO₂: MgO: NaF: LiF = 1.0: 0.5: 0.5: 0.25. By replacing Mg of Mg-mica with Al, Cu, Mn, Ni and Ti, substituted micas were synthesized at 750°C f or 1 hour. End membered mica was obtained only for Ni with the substitution of 75%. Partial replacement of 12.5-25.0% of Mg by the other elements resulted in t he formation of c orresponding single phase mica. Mg-mica and Al, Mn and Ti-substituted micas were found to be expandable by uptak ing mono layered water in the interlayered spaces, while Ni and Cu-substituted ones exhibited no expandable behavior. The crystallization of the amorphous silica into quartz during the formation of the substituted micas caused the restriction of the chemical composition of the products and was not allowed to drop their synthetic temperature.

View full abstract

Brownish and transparent crystals of NiWO₄ were grown from KC1 flux by a slow cooling method. The solubility of NiWO₄ in KCl was also investigated. About 56 mol% NiWO₄ was dissolved in KC1 at 1100° C. The solubility decreased gradually with decreasing temperature. The NiWO₄ KCl system had a eutectic temperature of 725 ± 5° C. The eutectic composition was considered to be approximately 4.5mol% NiWO₄ 95.5 mol% KCl. Flux growth of NiWO₄ crystals was conducted by heating mixtures containing 5 to 60 mol% solute at 1100° C for 10 h, followed by cooling to 500° C at a rate of 5° C h^-1. Needle and bulky crystals of NiWO4 were obtained. The crystal forms were remarkably dependent on the solute concentration. The high-temperature solutions containing 5 and 7.5 mol% solute produced only needle crystals up to 2.1 mm in length and 17 μ m in diameter. The most suitable concentration of solute was 7.5 mol%. The growth direction of needle crystals was ‹ 001 ›. On the other hand, the solutions containing more than 20 mol% gave only bulky crystals up to 15 x 5 mm in size. The most suitable concentration of solute was 50 mol%. The bulky crystals grown were bounded by {100}, {010}, {HO}, {111}, {102} and {231} faces. When the solute concentration was 10 mol%, the bulky crystals coexisted with the needle crystals. The density of needle and bulky crystals, pycnometrically determined, was 7.96 ± 0.02 g cm^-3. It was found that newly chosen KC1 was a suitable flux to grow NiWO₄ crystals. An addition of B₂O₃ to KCl flux resulted in a decrease in length of needle crystals.

View full abstract

Taiheiyo coal has been liquefied at 410, 430, 450 and 470° C with 1-methylnaphthalene (1-MN) or tetralin as vehicle and either with presence or absence of FeS₂ catalyst. The roles of catalyst and solvent in the reaction were investigated by analyzing the liquid and solid products in detail. The liquefaction was considered to involve two types of reaction: very rapid reaction and the successive slow reaction. A recombination of radical intermediates to form tetrahydrofuran-insoluble fraction (THFI) seems to proceed during the former reaction stage and the resulted THFI showed lower reactivity for the secondary cracking. The successive degradations of residual oil and distillable fraction were observed during the latter reaction stage. Tetralin solvent suppressed both the formation of THFI and the secondary cracking of produced oil. The existence of the catalyst resulted in the suppression of recombination to a significant extent.

View full abstract

Copolypeptides with both hydrophilic and hydrophobic side chains, i. e. Poly (Lys, Ala), Poly (Lys, Abu), Poly (Lys, Ser) and Poly (Asp, Ala) were synthesized. Acid-, base-, salt-, and pH-dependent conformational transition of these copolypeptides were compared with those of Poly (Lys) at various buffer solutions by using circular dichroism spectroscopy. Poly (Lys, Ala) was in the helix conformat ion in a citric acid-NaOH at pH 4.53, while random-coil was mainly observed in a KC1 solution at pH 6.25. Poly (Lys, Ala) was also in the helix in the phosphate buffer solution at pH 6.86, but Poly (Lys) was in the coiled form. Since Poly (Lys, Ser) rarely took the helix conformation, intermolecular hydrogen bonding between hydroxyl groups of the Poly (Lys, Ser)may be involved. Confo rmational change of these copolypeptides is dependent on both pH and coexisting ions.

View full abstract

Transport of Cu (II)1 from leucine-containing tripeptides, L-leucylglycylglycine, glycyl-L-leucylglycine and glycylglycyl-L-leucine, to cysteine was examined by a stopped-flow spectrophotometric method. The reaction was observed by changes in the intensity of S→ Cu (II) charge transfer bands observed on coordinating Cu (II) with cysteine. Initially formed was an intermediary complex, which was the mixed-ligand complex consisting from Cu (II), the tripeptide and cysteine. The transient subsequently reacted with another cysteine undergoing prompt ligand-exchange to yield Cu (II)biscysteinate. Both the transient and the binary complexs showed the charge transfer bands; the former at 330-335 nm and the latter at 335 nm and 385 nm. The isobutyl side chain in the second position from the amino terminal and that at the carboxylate-end reduced the rate of formation of the transient complex. On the contrary, the side chain at the amino terminal reduced the rate of formation of the binary complex, while the chain in the second position accelerated the reaction.

View full abstract

N-(4-Substituted phenyl) azoles possessing electron attracting substituents were studied from the viewpoints of substituent effect on absorption maxima (λ _max) and nonlinear optical properties. The substitution effect on λ _max as studied from the viewpoint of contribution ratio of resonance effect and inductive effect. A substituent constant, which has much more resonance contribution than σ _p or σ _p^-, is necessary to describe good relationship. The substituent constant is symbolized by ‹σ› in this paper, which has shown good correlation with 1/λ _max in negative mode. On the other hand, molecular hyperpolarizabilities (β) have shown good correlation with σ _p^-. From the viewpoint of nonlinear optical material, 1 (4-acetylphenyl) -1H-1, 2, 4-triazole (13), which is superior in blue-light transparency to nitro derivatives, were found as expected one. From oriented gas model using crystal structure and β _ijvalues calculated, nonlinear optical constants (d_ij's) of 13 are obtained to be 16.2 pm/V (d₂₂) and 21.5pm/V (d₂₃).

View full abstract

Under the conditions of the oxidation decomposition reaction using sodium hypochlorite of liquid waste containing cyanide, methyl ketones and certain other compounds with bromide often afforded the reaction products, such as trichloromethane, bromodichloromethane, dibromochloromethane and tribromomethane (referred to as “ trihalomethanes” ). Trihalomethanes are regulated as environmental pollutants. In order to control the formation of trihalomethanes, threfore, the formation conditions were examined. Using acetone, one of the trihalomethane precursors, the experimental results indicated that most of trihalomethanes were given by the first step reaction of the cyanide decomposition, and that large amounts of tribromomethane were produced on approximately pH 12. However, some of the formation conditions for trihalomethanes were different from those for the cyanide decomposition. It might mean that the formation reaction could be suppressed by the accurate control of the cyanide decomposition.

View full abstract

The total dissolution in sulfuric acid of spent hydrodesulfurization catalyst yields an acidic solution containing molybdenum, vanadium, cobalt, nickel, aluminum and iron. For the purpose of recovering the rare metals from the solution, the fundamental extraction characteristics of these metals involved with a novel type of commercial extractant PIA-8, and the synergistic extraction behaviors of cobalt, nickel and aluminum with a mixture consisting of PIA-8 and LIX 63 were investigated in the present work. Based on the results obtained, an elemental process for recovery of molybdenum, vanadium, cobalt and nickel from the actual solution of the total dissolution mentioned above was proposed. This process includes mainly the following steps:
1). The selective extraction of molyb denum, vanadium and iron from the solution in the presence of cobalt, nickel and aluminum at pH around 1.5 with PIA-8 in EXXSOL D80.
2). The scrub of vanadium from the loaded organic phase with H2SO4s olution and the second extraction of vanadium from the scrub solution at pH 1.5 with PIA-8 in EXXSOL D80.
3). The strip of molybdenum and vanadium from the loaded organic phase by aqueous ammonia.
4). The recovery of cobalt and nickel from the raffinate containing an appreciable amoun t of aluminum. This can be achieved by two special approaches. One is to separate aluminum first from cobalt and nickel by precipitating aluminum as hydroxides with aqueous ammonia at pH 6.2, then to extract cobalt selectively from the filtrate at equilibrium pH ca.5.2 with PIA-8 and to recover nickel from the raffinate. Another is to extract cobalt and nickel directly in the presence of aluminum by contacting with a maixture of PIA-8 in combination with LIX 63 at pH approx.2.4 and then to further separate cobalt from nickel by stripping the two metals from the loaded organic phase selectively with solutions of different H₂SO₄ concentrations.

View full abstract