Search results for "methanol"

A Covalently Cross-linked Polyetheretherketone Proton Exchange Membrane for DMFC

2009

The proton exchange membrane was prepared by covalent cross-linking sulfonated-sulfinated polyetheretherketone. The cross-linked membrane showed high proton conductivity (0.04 S/cm) with suitable water uptake, low methanol permeability (2.21 × 10-7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application.

Herstellung molekulareinheitlicher, aus methylenverbrückter 4-Hydroxybenzoesäre bestehender Mehrkernverbindungen sowie einiger einfacher und gemischt…

1971

Mit einer besonderen Methode, bei der halogensubstituierte Ausgangsverbindungen storende Nebenreaktionen verhindern, wurden molekulareinheitliche aus methylenverbruckter 4-Hydroxybenzoesaure bestehende Zwei- und Dreikernverbindungen hergestellt. Die Veresterung aller Carboxylgruppen in den Mehrkernverbindungen mit Athanol und bei einigen Verbindungen mit Methanol gab kristallisierte Ester. Alle phenolischen Hydroxylgruppen dieser Ester konnten auserdem acetyliert werden; auch diese gemischten Derivate waren kristallisiert. Hiernach sind fruhere Angaben zu der Zweikernverbindung 2.2′-Dihydroxy-5.5′-dicarboxydiphenylmethan und ihren Derivaten zu berichtigen. A special method which inhibits un…

Electroactivation of Transition Metal Redox Couples for the Carbonylation of Alcohols to Dialkylcarbonates

1998

Electrochemical systems which promote the carbonylation of methanol to dimethylcarbonate, based on the anodic activation of transition metal redox couples, or the Br−/Br2 couple, are poorly active for the carbonylation of ethanol to diethylcarbonate at room temperature and atmospheric pressure. Positive results have been obtained by combined addiction of PdBr2 and Bu4NBr to the system. In this way yields up to 50% in diethylcarbonate were obtained, with very good conductivities in long range electrolyses.

Electrochemical Syntheses Involving Carbon Dioxide

1990

The recent developments of electrosynthetic processes involving carbon dioxide are reviewed. Both processes involving carbon dioxide alone and electrocarboxylations are taken under consideration. The first of these two fields, mainly projected towards the production of basic chemicals such as methanol or carbon monoxide, is at present at a stage of fundamental research. Some interesting developments have recently appeared in the literature, concerning the use of electrode materials, or of transition metal complexes with particular catalytic activity. Electrocarboxylations are at a stage of more applicative development: some processes have reached the stage of pilot plant, and other have int…

Methacrylate ester-based monolithic columns for nano-LC separation of tocopherols in vegetable oils

2010

The separation and determination of tocopherols (Ts) in vegetable oils by nano-LC chromatography with UV-vis detection using lauryl methacrylate ester-based monolithic columns has been developed. The separation of Ts was optimized in terms of mobile phase composition on the basis of the best compromise among efficiency, resolution and analysis time. Using a mobile phase composed of ACN/methanol/water, an excellent resolution between Ts was achieved within 18 min. The LODs were lower than 0.26 μg/mL, being repeatability values of retention time and peak area below 0.15 and 3.1%, respectively. The method was applied to the quantification of Ts and tocotrienols present in several vegetable oil…

ChemInform Abstract: COMPLEXES OF ORGANOMETALLIC COMPOUNDS PART 42, SPECTROSCOPIC STUDIES OF N,N′-ETHYLENEBIS(ACETYLACETONEIMINE) AND N,N′-ETHYLENEBI…

1975

Abstract The nature of the 1 1 adducts formed from the ligands N,N′-ethylenebis(acetylacetonemine) and N,N′-ethylenebis(salicylideneimine) with Ph2PbCl2 and PhTlCl2 was investigated in the solid state and in methanol solution by IR, electronic and PMR spectroscopy, and by osmometry and conductivity. The adducts exist only in the solid state and dissociate fully into the parent compounds in solution. Polymeric structures are proposed for the solids, in which bis-monodentate ligands bridge the organometallic moieties.

Competing Ring-Photoisomerization Pathways in the 1,2,4-Oxadiazole Series. An Unprecedented Ring-Degenerate Photoisomerization

2002

The irradiation of some 5-alkyl-3-amino-1,2,4-oxadiazoles at lambda = 254 nm in methanol in the presence of triethylamine (TEA) gave ring-photoisomerization both into 2-alkyl-5-amino-1,3,4-oxadiazoles and, unprecedently, into the ring-degenerate 3-alkyl-5-amino-1,2,4-oxadiazoles. The competing ring contraction-ring expansion route and the internal cyclization-isomerization mechanism explain the results.

1990

Intrinsic viscosities, [η], second virial coefficients, A2, and interaction potentials, g12, for the ternary systems alcohol (1)/3-heptanone (2)/poly(1-vinyl-2-pyrrolidone) (3), with the unbranched alcohols methanol, ethanol and 1-propanol, were determined at 25°C. Taking into account the dependence of the viscometric interaction parameter, B, with the molecular weight of the polymer, the unperturbed dimensions parameter, KΘ, of the polymer was unambiguously obtained. Relationships between ΔKΘ (defined as ΔKΘ = ΔK − KΘ) and excess Gibbs energies, GE, and between excess viscosity, Δ[η], and GE allow to obtain equations relating A2 to ΔKΘ or to Δ[η]. Therefore, A2 can be evaluated from experi…

Photoinduced functionalization of the C-20 methyl group of the nor-diterpene atractyligenin

2001

Abstract Irradiation of the nor-diterpene atractyligenin at λ =254 nm in methanol gave, on one hand, the decarboxylation product, and provided, on the other hand, the transformation of the C-20 angular methyl into a methylene-carbomethoxy group. A photochemical pathway involving formation of C-19/C-20 bond is suggested.

SOFT AND HARD ACIDITY IN ZEOLITES AND ZEOTYPES: EVALUATION AND CATALYTIC IMPLICATIONS

1993

It has been found by Molecular Orbital calculations, that the energy of the LUMO of a zeolite cluster can be used to measure the softness–hardness acidity. It has been found that the higher the framework Si/AI ratio the softer is the acidity. When applied to the alkylation of aromatics, it has been calculated that the higher the framework Si/AI ratio of the zeolite, the more “orbital controlled” will be the reaction, and therefore a higher para to ortho ratio is expected. This has been confirmed experimentally during the alkylation of toluene and m–xylene by methanol on HY zeolites with different framework Si/AI ratio.