DTA study of the chlorination of fly ash and bauxite in the presence of carbon

The chlorination processes of fly ash and bauxite in the presence of carbon were studied by means of a gas-flow type DTA, X-ray analysis and SEM observation, and the reactivity of Al-compounds as their constituents was compared. In the case of fly ash, the exothermic peak due to the formation of AlCl₃ (mainly) and FeCl₃ appeared at about 790–920°C. The reactivity of Al estimated from the DTA peak temperature depended on the particle size, carbon content and preparation temperature of fly ash, and was much lower than that of bauxite. Fractional conversion of Al was about 60–70%, when fly ash (?300 mesh) was heated up to 900°C in Cl₂ at 5°C min^?1 of heating rate. In the case of bauxite, two exothermic peaks due to the chlorination of Fe and Al appeared at about 270 and 490°C, respectively. The chlorination of Al was completed at 550°C under the above conditions.     

Radical polymerization of metal-coordinated monomers with ligands of pyrrole-containing schiff bases

The copper complexes and the cobalt complex with the ligand of 3-(2-pyrrolylmethyl-enimino)propene-1 (PIP) or p-(2-pyrrolylmethylenimino)styrene (PIS) were synthesized and homopolymerizations and the copolymerization with styrene, acrylonitrile, methyl methacrylate and acrylic acid studied. In the polymerization of chelate monomers, inhibition of radical polymerization by the central metal ion was observed, but the chelate polymer could be obtained only if the initiator was present in higher concentrations in the feed. It is considered that the strength of inhibition depends on the electronic configuration of d-orbitals of the central metal ion. The initiation mechanism of the cupric chelate monomer may be reduction of the metal ion by the redox reaction with a primary radical via the intramolecular electron transfer through the π-conjugated system of the ligand prior to the propagation step. This mechanism was verified by studying the redox reaction of various copper complexes with DPPH. In the system of the copper complex containing PIS and acylic acid the alternating copolymer could be obtained at any mole fraction of monomer mixture in feed.     

Band gap engineering of CdTe nanocrystals through chemical surface modification

We demonstrate band gap control of CdTe nanocrystals by selective surface modification using alkanethiol molecules. Both absorption and emission wavelengths can be tuned simply by mixing a dispersion of the nanocrystals with alkanethiol at room temperature, resulting in blue shifts in the optical spectra during reaction. The degree of blue shift depends on both the concentration of alkanethiols and the reaction time, thereby providing kinetic control over the emission peak wavelength of the nanocrystals in mild conditions. The observed spectral changes are suggested to be caused by a decrease in the size of the CdTe core through formation of CdTe1-x(SC10)x shells because of specific exchange of Te with alkanethiolates. The results reported herein provide a new band gap engineering scheme for semiconductor nanocrystals and offer opportunities for the design of ligand-stabilized semiconductor nanocrystals with tunable composition and optical properties.     

H2 generation during dry grinding of kaolinite

H2 generation during mechanochemical treatment of kaolinite by dry grinding was examined by X-ray diffraction analysis, Fourier transform infrared spectroscopy, and BET surface area measurement. The H2 concentration in the mill pot, measured by gas chromatography, increased with grinding time up to a maximum concentration of 156 ppm (0.35 micromol) after 600 min. This H2 generation is considered to occur as a result of three processes: (1) structural destruction characterized by the delamination and loss of hydroxyl groups as a result of dry grinding, (2) transformation of liberated hydroxyls into water molecules by mechanochemical effects such as prototropy, and (3) H2 generation through reaction between surface water molecules and mechanoradicals created by the rupture of Si-O or Al-O-Si bonds. Although the surface area plateaued after 240 min grinding, the H2 concentration continued to increase, indicating that surface mechanoradicals are created during this later grinding stage. Thus, H2 generation can be used as an indicator of mechanoradical formation during mechanochemical treatment.     

Oxygen-Binding Profile of the Iron Porphyrin Complex Embedded in Polymerized Liposome: Effect of the Polymerized Liposome on the Stability and the Oxygen-Binding Ability of the Iron Porphyrin Complex

5,10,15,20-Tetra(α,α,α,α, -o-(2′, 2′-dimethyl-20′-(2′ α-trimethylammonioethyl)phosphonatoxyeicosanamido)phenyl)porphinatoiron(II) (lipidheme) complex embedded in polymerized liposome was prepared by polymerizing l-(9-(p-vinylbenzoyl)nonanoyl)-2-O-octadecyl-rac-glycero-3-phosphocholine in the presence of lipid-heme under ultraviolet irradiation. The polymerization proceeded rapidly, and the reduction of the hemin to the heme occurred spontaneously during the polymerization. The lipid-heme complex embedded in the polymerized liposome bound molecular oxygen reversibly under physiological conditions (pH 7, 37°C) and was chemically, physically, and mechanically stable during storage for a long period and even in a high-speed flow system. The oxygen-binding affinity was not affected by the type of medium due to the effect of the rigid polymerized liposome.     

Ion Tunneling in Polymeric Solid Electrolytes for Batery and Electrochromic Display in the Dry State

Polymeric solid electrolytes which show bi-or single-ionic tunneling were prepared, and their unique ion conduction was applied for the design of some devices. Poly [(oligooxyethylene) methacrylatel] /MX hybrids and poly [(oligooxyethylene) methacrylate-co-methacrylic acid alkali metal salts] were prepared as typical models of those tunneling systems. These showed ionic conductivities above 10^?5 and 10^?7 S/cm at room temperature, respectively. An all-solid-state electrochromic display and a dry battery were prepared with these polymeric solid electrolytes. The all-solid-state electrochromic display showed excellent coloring and bleaching response by 1–3 V. The all-solid-state battery showed V _oc = 3.1 V stability for over 2 weeks. Their characteristics as well as their mechanism are also reported.     

Synthesis and Systematic Structural Analysis of Cationic Half-Sandwich Ruthenium Chalcogenocarbonyl Complexes

Although the chemistry of transition-metal complexes with carbonyl (CO) and thiocarbonyl (CS) ligands has been well developed, their heavier analogues, namely selenocarbonyl (CSe) and tellurocarbonyl (CTe) complexes remain scarce. The limited availability of such CSe and CTe complexes has so far hampered our understanding of the differences between such chalcogenocarbonyl (CE: E=O, S, Se, Te) ligands. Herein, we report the synthesis and properties of a series of cationic half-sandwich ruthenium CE complexes of the type [CpRu(CE)(H₂IMes)(CNCH₂Ts)][BAr^F₄] (Cp=η⁵-C₅H₅⁻; H₂IMes=1,3-dimesitylimidazolin-2-ylidene; Ar^F=3,5-(CF₃)₂C₆H₃). A combination of X-ray diffraction analyses, NMR spectroscopic analyses, and DFT calculations revealed an increasing π-accepting ability of the CE ligands in the order O<S<Se<Te. A variable-temperature NMR analysis of the thus obtained chiral-at-metal CE complexes indicated high stereochemical stability.     

Heat-Resistant Polymer-Grafted Carbon Black: Grafting of Poly(Organophosphazenes) onto Carbon Black Surface

Abstract

The grafting of poly(organophosphazenes) onto carbon black surface by the reaction of poly(dichlorophosphazene) (PDCP) with carbon black having sodium phenoxide groups was investigated. PDCP was prepared by the ring-opening polymerization of hexachlorocyclotriphos-phazene in solution using sulfamic acid as a catalyst. The introduction of sodium phenoxide groups onto carbon black was achieved by treatment of phenolic hydroxyl groups on the surface with sodium hydroxide in methanol. Poly(diphenoxyphosphazene) (PDPP) was successfully grafted onto carbon black by the reaction of PDCP with sodium phenoxide groups introduced onto the surface followed by the replacement of chlorine atoms in PDCP with phenoxy groups. The percentage of grafting onto carbon black increased to 206% at 30°C after 12 h. It was found that only 1.4% of sodium phenoxide groups on carbon black surface was used for the grafting of PDCP because of the blocking of the surface by grafted polymer chains. Poly(diaminophenylphosphazene) and poly-(diethoxyphosphazene) were also grafted onto carbon black surface by the treatment of PDCP-grafted carbon black with aniline and sodium ethoxide, respectively. Poly(organophosphazenes)-grafted carbon blacks produced stable colloidal dispersions in good solvents for grafted polymers. Furthermore, thermogravimetric analysis indicated that poly-(organophosphazenes)-grafted carbon blacks were stable in air about 300°C.     

Approaches to Artificial Macromolecular Oxygen Carriers

Construction of artificial oxygen carriers by use of iron or cobalt complexes bound to synthetic polymers was attempted. Radical copolymerization of porphyrin vinyl monomers with styrene gave the metalloporphyrins covalently bonded to a polymer chain at low concentration. For these metalloporphyrin polymers, irreversible oxidation via dimerization was prevented in aprotic solvents and reversible oxygenation was observed. The chemical environment around the oxygen-binding site was presumed to play an important role on the stability of oxygenated complex as in the case of the tetraamide groups on the porphyrin plane. When ethylenebis(salicylideniminato)cobalt chelate coordinated to a polymer-ligand, it formed a stable oxygenated complex at room temperature. Rotational motion of the chelate was decreased markedly by the polymer chain to enhance the coordinate bond between the metal ion and the bound oxygen molecule. Furthermore, the iron porphyrin with bulky substituents was oxygenated even in homogeneous aqueous solutions by combining it with the rigid, hydrophobic domain of a water-soluble block copolymer.     

Synthesis,Redox Behavior,Sensitizer Activity,and Oxygen Transfer of Covalently Bound Polymeric Porphyrins

Metal complexes of covalently bound porphyrins are used as sensitive probes for several investigations. Substituted derivatives of tetraphenyl-porphin, phthalocyanine, and naphthalocyanine are synthesized at positively and negatively charged as well as uncharged polymers. The photo-redox activities were studied under irradiation with visible light in the presence of a donor and an acceptor. The triplet life times of covalently bound porphyrin moieties are strongly enhanced compared with the analogous monomeric porphyrins. In addition, the polymer binding results in higher photocatalytic activity. The electron-transfer reactions of Mn(III)-containing porphyrins using the reducing agent dithionite are strongly influenced by the polymer environment. In contrast to monomeric Mn(III)-porphyrins, the porphyrins containing polymers exhibit a two-step reduction which may be due to the change of the conformation of the polymer coil. The catalytic epoxidation of 2,5-dihydrofuran with hypochlorite with formation of 3,4-epoxytetrahydrofuran occurs with water-soluble porphyrins in water. No influence of the polymer environment exists. The different reactions require reaction times from milliseconds up to hours.