- Ceria supported gold-platinum catalysts for the selective oxidation of alkyl ethoxylates
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This work covers the development of a ceria based AuPt catalyst for the selective aerobic oxidation of alkyl ethoxylates to their corresponding carboxylic acids. By optimizing metal loading and the Au to Pt ratio the activity of the catalyst could be increased significantly, while maintaining total selectivity. Although the choice of ceria as a support helped to suppress intermediate metal leaching, the catalyst still showed poor long-term stability in repeated batches. The cause for deactivation could finally be identified by TPR studies as over-oxidation. These suspicions were confirmed by a long-term stability study in continuous-mode. It proved to be possible to deactivate the catalyst on purpose by employing unfavourable oxidising reaction conditions, i.e. low substrate concentrations and excess oxygen. By avoiding such unfavourable conditions either in continuous-flow mode or in repeated batches, the long-term stability of the catalyst increased tremendously. A substrate screening of various ethoxylates showed that the catalyst was very well-suited to selectively oxidize a wide range of alkyl ethoxylates.
- Heidkamp, Katharina,Aytemir, Memet,Vorlop, Klaus-Dieter,Pruesse, Ulf
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p. 2984 - 2992
(2013/11/06)
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- Chromium(VI) oxide oxidation of non-ethoxylated and ethoxylated alcohols for determination by electrospray ionization mass spectrometry
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A new derivatization procedure to increase the sensitivity of electrospray ionization mass spectrometry (ESI-MS) to non-ethoxylated and ethoxylated alcohols was investigated. The analytes were oxidized with chromium(VI) oxide and the resulting carboxylic and ethoxy-carboxylic acids were isolated by extraction with ethyl acetate; the extracts were alkalinized and infused into the ESI-MS system working in the negative-ion mode. The yields of the combined oxidation-extraction were ca. 100% for non-ethoxylated fatty alcohols dissolved in acetone and they decreased moderately in samples containing increasing amounts of water (e.g., a 75% yield was obtained with 50% water). Ethoxylated alcohols with more than two ethylene oxide units resulted in yields of ca. 60%. Low limits of detection (LODs) were obtained when the procedure was applied to the analysis of body- care products and cosmetics containing fatty alcohols, e.g., in a varicose-vein cream, the LODs were 25 μ cetyl alcohol and 7.5 μ stearyl alcohol (detected as palmitic acid and stearic acid, respectively) per gram of sample. High molecular mass alcohols were also detected in seawater after pre- concentration by solid-phase extraction. Thus, the proposed method is particularly valuable for use in industrial samples having complex matrices and in environmental samples and it is competitive with other methods for the analysis of trace amounts of fatty alcohols.
- Beneito-Cambra, Miriam,Bernabe-Zafon, Virginia,Simo-Alfonso, Ernesto F.,Ramis-Ramos, Guillermo
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experimental part
p. 2093 - 2100
(2011/11/06)
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- Trifluorothymidine derivatives, process for producing the same and anti-cancer agent containing the same
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Novel trifluorothymidine derivatives having anti-cancer activities are disclosed. The trifluorothymidine derivatives of the present invention are represented by the formula [I]: (wherein R1 represents hydrogen atom or C1 - C4 alkyl group; R2 represents hydrogen atom, C1 - C30 saturated or unsaturated alkyl-substituted carbonyl group, alkyl-substituted benzoyl group, C1 - C4 alkyloxycarbonyl group; dimethylaminoethyloxycarbonyl group, C1 - C4 alkyloxymethyl group, butoxyethoxyacetyl group, benzyl group, C1 - C20 alkyl-substituted silyl group, silyl group substituted with C1 - C10 alkyl group and/or phenyl group, C1 - C30 cyclic or chain alkyl-substituted carbamoyl group, diethylaminopropylcarbamoyl group, N-alkylpiperazinylacetyl group, N-alkylprolyl group, valyl group, trityl group, alkyl-substituted phosphoryl group or propargyl group; R3 represents hydrogen atom, C1 - C4alkyl group, benzyl group, benzoyl group, C1 - C4 alkyloxy-substituted benzoyl group, furoyl group, C1 - C4 alkyloxymethyl group or C1 - C4 alkyl-substituted carbonyl group).
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