Sorption interactions between ethylene glycol and carbon nanotubes

Russian Journal of Physical Chemistry A - The adsorption of ethylene glycol by carbon nanoparticles is studied. Carbon nanoparticles with the highest affinity to ethylene glycol are identified, and...     

Poly(ethylene glycol)-supported bisoxazolines as ligands for catalytic enantioselective synthesis

Two chiral bisoxazolines (box) supported on a modified poly(ethylene glycol) (PEG) have been prepared by a reaction sequence that involved formation of the properly functionalized box and their attachment to the polymer matrix by means of a spacer and a linker. The solubility properties of PEG allowed use of the supported box as ligands in some catalytic asymmetric transformations carried out under homogeneous conditions and to recover the ligands as if bound to an insoluble support. When the supported box were employed in combination with Cu(II) salts in the Diels-Alder cycloaddition between cyclopentadiene and N-acryloyloxazolidinone, low levels of enantioselectivity were observed (up to 45% ee). Much better results were obtained in the cyclopropanation of styrenes carried out in the presence of CuOTf (up to 93% ee) and in the ene-reaction between alpha-methylstyrene or methylenecyclohexane and ethylglyoxalate (up to 95% ee). One of the ligands, readily recovered by precipitation and filtration, was recycled two times in the ene-reaction with marginal loss in the catalytic activity and very limited erosion of the enantioselectivity.     

Catalytic synthesis of carbon nanotubes from ethylene in the presence of water vapor

Multiwalled carbon nanotubes were synthesized catalytically from ethylene in the presence of water vapor at transition metals of the iron subgroup. The structure of the obtained nanotubes was studied by transmission electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. It was shown that the highest yields of carbon nanotubes with diameters between 20 and 40 nm, lengths of more than 1 μm, and average diameter of 0.92 nm for the innermost tube were obtained at a nickel catalyst with a water vapor concentration of 0.32%. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 4, pp. 227–230, July–August, 2006.     

Fabrication,characterization and photoelectrochemical performance of chromium-sensitized titania nanotubes as efficient photoanodes for solar water splitting

Chromium-sensitized titanium dioxide nanotubes (CTNT) with high photocatalytic activity were prepared by a chemical bath deposition technique. The resulting films were characterized by SEM, EDX, and XRD. Results showed that the fabricated films have the ordered nanotubes with diameter of 90–140 nm, wall thickness of 20–50 nm, and tube lengths in the range of 24 μm. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare titanium dioxide nanotubes (TNT). The photoelectrochemical performance was examined under light irradiation in 1 M NaOH electrolyte. Photoelectrochemical characterization shows that chromium sensitizing efficiently enhances the photocatalytic water splitting performance of CTNT composite. The sample (C3TNT) exhibited better photocatalytic activity than the TNT and CTNT fabricated using other chromium concentrations. This inexpensive photoanodes prepared free of noble metals showed enhanced high photocurrent density with good stability and is a highly promising photoanode for solar hydrogen production.     

Synthesis and characterization of ordered polyurethanes from nonsymmetric diisocyanate and ethylene glycol

An ordered polyurethane with a head‐to‐head (H‐H) or tail‐to‐tail (T‐T) content over 95% was prepared by polyaddition reaction of a nonsymmetric monomer, p‐isocyanatobenzyl isocyanate (1) with a symmetric monomer, ethylene glycol (2). The model reactions were studied in detail to demonstrate the feasibility of polymer formation. The polymerization was conducted in THF in the presence of triethylamine (TEA) at 0 °C by slow addition of a half amount of 2 to 1, followed by removing THF and then adding the rest of 2 in DMF at once at 30 °C in the presence of dibutyltin dilaurate (DBTL). The microstructure of the polymer obtained was investigated by ¹³C NMR spectroscopy, and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2106–2114, 2000     

Catalytic synthesis of carbon nanotubes over ordered mesoporous matrices

Pyrolytic decomposition of acetylene over the surface of nickel-, cobalt- and iron-containing ordered mesoporous MCM-41 silicas has been studied. Catalytically active matrices have been prepared by chemisorption of volatile metal acetylacetonate complexes on the silica surface. Reduction of the supported metal-containing compounds was carried out in hydrogen or acetylene atmosphere. Acetylene is used not only as a source of carbon in synthesis of the nanostructures but also as a reagent capable of reducing metal ions in the surface chemical compounds. Formation of carbon nanotubes and nanofibers is shown to depend on the pyrolysis conditions.     

Ethylene glycol aluminum as a novel catalyst for the synthesis of poly(ethylene terephthalate)

Ethylene glycol aluminum was prepared efficiently and characterized by FT-IR and NMR.It exhibited higher catalytic activity and had profitable effect than titanium glycolate and ethylene glycol antimony for the synthesis of poly(ethylene terephthalate) (PET).It was only used as polycondensation catalyst because it was sensitive to water.For this catalyst,the degree of esterification of the theoretical amount of water was produced up to 95%at 260℃,while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PET polyester,polymerized at 280℃,70 Pa for 39 min,was 0.87 dL/g and 23.0μmol/g,respectively. Ethylene glycol aluminum was a promising catalyst for the synthesis of PET polyester.     

Precipitation temperature of poly(ethylene glycol) in some electrolyte solutions

The effect of sodium fluoride, sodium bromide, tetramethyl ammonium chloride, tetramethyl ammonium bromide and sodium formate on both precipitation and θ-temperatures of poly(ethylene glycol) (M_w = 4000) in aqueous solution have been determined. Curves have been drawn to represent the effect of such ions on both the θ and the precipitation temperatures of the polymer. The effectiveness increases in the order (CH₃)₄ NBr, NaBr, (CH₃)₄NCl, NaF and HCOONa. The M_w-temperatures obtained at infinite dilution are 445 K for NaBr, NaF, (CH₃)₄ NBr and (CH₃)₄NCl and 415 K for HCOONa.     

Controlled synthesis of polymethylene-b-poly(ethylene glycol) as well as its crystallization and self-assembly behavior

Polymethylene-b-poly(ethylene glycol) (PM-b-PEG) with different block length ratio was synthesized by a combination of polyhomologation and coupling reaction. The effect of hydrophilic and hydrophobic block length on the crystallization process and self-assembly behavior of PM-b-PEG was self-assembled were investigated. The results showed that with the increase of methylene units, the crystallization temperature of PM block raised from 54.59?°C to 70.93?°C gradually, while that of the PEG block reduced from 17.54?°C to 15.23?°C. In addition, the amphiphilic PM-b-PEG was self-assembled into star-like micelles in water, and its diameter extended from 98.2?nm to 151.9?nm as the block length of hydrophobic PM increased from 30 to 70. And the micelles also exhibit super stability when the concentration of copolymer precursor is 0.50?～?0.90?mg/ml and the storage temperature lies in the range of 25?～?60?°C.     

A highly ordered titania nanotube array as a supercapacitor electrode

We report the synthesis of self-organized titania nanotubes and nanocrystalline titania powders employing an alternative and novel approach. Integrating these nanostructures in a binder-free working electrode improved the capacitance up to 911 μF cm(-2), which is around one to two orders of magnitude higher than the conventional electric double layer capacitors.     

Electrochemical synthesis of free-standing CdS nanoparticles in ethylene glycol

A novel one-step electrochemical method for the preparation of capping-free cadmium sulfide nanoparticles is described. With gold as the working electrode, capping-free CdS nanoparticles are synthesized very conveniently at 70°C in the ethylene glycol (EG) solution of elementary sulfur, cadmium salt, and supporting electrolyte at −0.1 V. By carefully selecting the reductive potential, elementary sulfur is reduced while the reduction of Cd²⁺ is blocked by the formation of a sulfur monolayer on the gold electrode surface. The produced S²⁻ reacts with cadmium cations in the solution to produce CdS. In this method, magnetic stirring can effectively prevent the deposition of CdS on the electrode surface. XRD analysis indicates that the product is pure cubic-phase CdS. The size and morphology of the particles are studied by TEM. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 9, pp. 1060–1064. The text was submitted by the authors in English.     

碘催化合成环己酮乙二醇缩酮

环缩酮类香料性能优良,在日用香精和食品香精中用途广泛。合成缩酮的传统催化剂为硫酸,反应时间长,副反应多,对反应设备腐蚀严重,废液排放量大,后处理工艺复杂,人们一直在寻求更优良的催化剂。本文利用单质碘催化剂合成了环己酮缩乙二醇。     

Effect of water and fluoride content on morphology and barrier layer properties of TiO2 nanotubes grown in ethylene glycol-based electrolytes

This paper studies the effect of H₂O and NH₄F content on morphology and barrier layer properties of TiO₂ nanotubes grown by potentiostatic anodization in ethylene glycol-based electrolytes. The increase in these two variables leads to an increase in the chemical attack of the formed oxide. However, each of these variables plays a different role in the formation of TiO₂ nanotubes. On the one hand, a higher percentage of H₂O in the electrolyte leads to a transition from a nanoporous to a nanotubular structure, as well as to a greater diameter of the tubes and a decrease in their length and barrier layer thickness. In contrast, a higher NH₄F concentration decreases nanotube diameter and increases their length modifying barrier layer properties due to insertion of F^? ions into the lattice. This diminishes the barrier layer resistance, but increases both the adsorption and the diffusion coefficient of F^? ions. The different roles of H₂O and NH₄F in film formation are also associated with the presence of sub-oxides detected by XPS.     

Crystal structures of ethylene glycol and ethylene glycol monohydrate

We have carried out a neutron powder diffraction study of deuterated ethylene glycol (1,2-ethanediol), and deuterated ethylene glycol monohydrate with the D2B high-resolution diffractometer at the Institut Laue-Langevin. Using these data, we have refined the complete structure, including all hydrogen atoms, of the anhydrous phase at 220 K. In addition, we have determined the structure of ethylene glycol monohydrate at 210 K using direct space methods. Anhydrous ethylene glycol crystallizes in space-group P2(1)2(1)2(1) with four formula units in a unit-cell of dimensions a = 5.0553(1) ?, b = 6.9627(1) ?, c = 9.2709(2) ?, and V = 326.319(8) ?(3) [ρ(calc)(deuterated) = 1386.26(3) kg m(-3)] at 220 K. Ethylene glycol monohydrate crystallizes in space-group P2(1)/c with four formula units in a unit-cell of dimensions a = 7.6858(3) ?, b = 7.2201(3) ?, c = 7.7356(4) ?, β = 92.868(3)°, and V = 428.73(2) ?(3) [ρ(calc)(deuterated) = 1365.40(7) kg m(-3)] at 210 K. Both the structures are characterized by the gauche conformation of the ethylene glycol molecule; however, the anhydrous phase contains the tGg' rotamer (or its mirror, g'Gt), whereas the monohydrate contains the gGg' rotamer. In the monohydrate, each water molecule is tetrahedrally coordinated, donating two hydrogen bonds to, and accepting two hydrogen bonds from the hydroxyl groups of neighboring ethylene glycol molecules. There are substantial differences in the degree of weak C-D···O hydrogen bonding between the two crystals, which calls into question the role of these interactions in determining the conformation of the ethylene glycol molecule.     

Ytterbium stabilized ordered mesoporous titania for near-infrared photocatalysis

An effective synthetic strategy is demonstrated for preparing highly ordered crystallized mesoporous TiO(2) by introducing rare earth in the synthesis process; the obtained product exhibits near-infrared photocatalytic activity.     

1-Alkylbenzimidazoles as unique promoters for a homogeneous ruthenium catalyst for direct ethylene glycol formation from synthesis gas

1-Alkylbenzimidazoles such as 1-methylbenzimidazole and 1,5,6-trimethylbenzimidazole have been found to be excellent promoters for direct ethylene glycol formation from hydrogen and carbon monoxide in the presence of a homogeneous ruthenium catalyst. High pressure IR analyses revealed that three Ru species, [HRu₃(CO)₁₁]⁻ (I), Ru(CO)₅ (II) and Ru(CO)₄(1-alkylbenzimidazole) (III) had formed. An analysis of the relationship between activity and identity of Ru species showed that ruthenium species III plays an important role in ethylene glycol formation, and that the high coordination ability of benzimidazoles is essential to the promoting effect on ethylene glycol formation.     

Theoretical study of ethylene glycol synthesis in a reaction-rectification column

Principles of construction of a mathematical model of a reaction-rectification column for ethylene glycol synthesis are considered. Some specific features of the operation of the reaction-rectification column are analyzed. The correctness of the assumptions and limitations of the model is substantiated and the adequacy of the model is assessed.