- Vapour-phase C-C coupling reactions of biomass-derived oxygenates over Pd/CeZrOx catalysts
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Studies of aldol condensation/hydrogenation reactions of 2-hexanone were carried out over Pd/CeZrOx and CeZrOx catalysts at temperatures between 573 and 673 K, and pressures of 5-26 bar. These studies were formulated to address the catalytic upgrading to transportation fuels of the mono-functional oxygenated compounds (consisting primarily of C4-C6 ketones, alcohols, carboxylic acids and heterocyclics) formed by the catalytic conversion of polyols over a Pt-Re/C catalyst. Characterization by XRD, TPR and NH3/CO2-TPD showed that Pd/CeZrOx catalyst consists of a partially reducible solid solution of cerium and zirconium oxides, and possesses both acidic and basic functionalities. Reaction kinetics studies show that in addition to the expected C12 condensation product (7-methyl-5-undecanone), the CeZrOx-based catalysts produce C18 and C9 secondary species, along with light alkanes (≤C7). Low loadings of Pd (e.g., 0.25 wt%) lead to optimal activity and selectivity for the production of C12 species. The high apparent activation energy of the formation of C9 (140 kJ/mol) compared to the formation of C12 and C18 species (15 and 28 kJ/mol, respectively) indicates that these species may be formed as a result of the decomposition of heavier condensation products. The self-coupling of 2-hexanone was found to be positive order in both 2-hexanone and hydrogen. The addition of primary alcohols and carboxylic acids as well as water and CO2 to the feed was found to reversibly inhibit the self-coupling activity of 2-hexanone. This inhibition is strongest in the presence of CO2, and TPSR studies indicate that CO2 is removed from the surface by conversion to CO in the presence of reduced ceria species.
- Kunkes, Edward L.,Guerbuez, Elif I.,Dumesic, James A.
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- Self-coupling of secondary alcohols by Ni/CeO2 catalyst
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Supported nickel catalysts are studied for the liquid phase CC self-coupling of aliphatic secondary alcohols under additive free conditions in N2 atmosphere. Among various Ni catalysts, 1 or 3 wt% Ni/CeO 2 catalysts pre-reduced in H2 shows highest yield (94%) of a dimer product (a higher ketone) for the self-coupling of 1-octanol at 130 C, and the catalyst is reused. The catalysts are also effective for self-coupling of various secondary alcohols, providing the first heterogeneous catalytic system for the self-coupling of secondary alcohols under mild conditions. Effects of support material and oxidation state of Ni on the activity are studied and it is found that both CeO2 and metallic Ni are indispensable for the reaction. A possible reaction mechanism is proposed, in which ketones, formed by dehydrogenation of alcohol, undergone Aldol condensation to give α,β-unsaturated ketone which is finally hydrogenated by in situ formed NiH species.
- Shimura, Katsuya,Kon, Kenichi,Hakim Siddiki,Shimizu, Ken-Ichi
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p. 137 - 142
(2013/07/26)
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- Preparation of imidazolidin-4-ones and their evaluation as hydrolytically cleavable precursors for the slow release of bioactive volatile carbonyl derivatives
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Imidazolidin-4-ones are suitable in practical applications as hydrolytically cleavable precursors for the controlled release of fragrant aldehydes and ketones. The corresponding profragrances were prepared by treating aliphatic carbonyl compounds with commercially available amino acid amines in the presence of a base to yield mixtures of diastereomers. The two diastereomers isolated from the reaction of glycinamide hydrochloride with (-)-menthone were separated by column chromatography. The absolute stereochemistry of the isomers was determined by NMR spectroscopy and confirmed by X-ray single crystal structure analysis. Under acidic conditions and in protic solvents, the two diastereomers slowly isomerized without releasing the ketone. The hydrolysis of the precursors was investigated by solvent extraction from buffered aqueous solutions and a cationic surfactant emulsion, as well as by dynamic headspace analysis after deposition onto a cotton surface. Generally, ketones were shown to be more readily released than aldehydes. Increasing the size of the substituents at C-5 decreased the rate of hydrolysis in solution and on the cotton surface. Glycinamide-based imidazolidin-4-ones were more efficient than the corresponding oxazolidin-4-ones or oxazolidines. Neither the release rates in solution, nor the hydrophobicity of the precursor structure (which influences deposition), nor the combination of these two parameters allowed easily predicting the performance of the delivery systems in application. Copyright
- Trachsel, Alain,Buchs, Barbara,Godin, Guillaume,Crochet, Aurelien,Fromm, Katharina M.,Herrmann, Andreas
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supporting information; experimental part
p. 2837 - 2854
(2012/07/03)
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- Amino-sugar modular ligands - Useful cores for the formation of asymmetric copper 1,4-addition catalysts
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Modular phosphine ligands, synthesised rapidly from commercial N-acetylglucosamine, are very effective in copper(I)-catalysed 1,4-additions of ZnR2 to linear aliphatic enones (87-95% ee). The Royal Society of Chemistry.
- De Roma, Antonella,Ruffo, Francesco,Woodward, Simon
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supporting information; experimental part
p. 5384 - 5386
(2009/03/11)
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- Effect of residual Na on Cu-ZnO catalyst in dehydrogenation of 2-butanol
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A series of residual Na on Cu-ZnO catalysts were prepared by co-precipitation method. The effect of residual Na on catalysts was examined in dehydrogenation of 2-butanol. The catalysts were characterized by BET, ICP, XRD, TPR and XPS techniques. The TPR result showed that residual Na made CuO exists in different phases, the higher the content of Na the harder the reduction of CuO. For reduced or used catalyst with a high content of Na, the XPS result indicated that Na diffused to the catalyst surface and inhibited the interaction between Cu and ZnO. The sharp decrease in catalytic activity by Na incorporation could be interpreted mainly in terms of the copper particle size increasing during reaction. Interaction between Cu and ZnO could have stabilized the copper species. The Na free catalyst shows high and stable activity in dehydrogenation of 2-butanol.
- Wang,Wang,Zhu,Yang,Ma,Liu,Qu,Yu
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p. 861 - 868
(2007/10/03)
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- Direct Synthesis of Sulfines by Oxidation of Enethiolizable Thioketones
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Reaction of enethiolizable thioketones 2 with one equivalent of meta-chloroperoxybenzoic acid affords quantitatively the corresponding E sulfines 1.In contrast to literature expectations, direct synthesis of aliphatic sulfines by oxidation of thiocarbonyl compounds is thus possible; no divinyl disulfide 4 has been formed.
- Nocher, Anne Marie Le,Metzner, Patrick
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p. 747 - 750
(2007/10/02)
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- Synthesis of Alkyl-Substituted 1,3-Diketones via the 1,4-Addition of the Grignard Reagents to α,β-Unsaturated Imidates
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4-Propyl-3,5-nonanedione was selectively formed by the reaction of methyl N-phenylacrylimidate with ethylmagnesium bromide in 80percent yield.Similar diketones were obtained from methyl N-phenylcrotonimidate and N-phenylcinnamimidate with the Grignard reagents.The coupling of N-magnesio α-methoxy enamine and ketenimine, both of which are formed through the initial 1,4-addition of the Grignard reagent to α,β-unsaturated imidate, is the most plausible pathway for the formation of the diketones.
- Inoue, Seiichi,Suzuki, Osamu,Sato, Kikumasa
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p. 1601 - 1605
(2007/10/02)
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- Reaction of α,β-Unsaturated Imidates with Grignard Reagents Leading to 2-Alkyl 1,3-Diimines
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Methyl N-phenylacrylimidate (1a) reacted with alkyl- and aryl-magnesium bromides in ether at O deg C to give 2-alkyl 1,3-diketones (3a) in a good yield after aqueous work-up; methyl N-phenylcrotonimidate (1b) and N-phenylcinnamimidate (1c) with alkylmagnesium bromides furnished analogous 1,3-diketones (3) as the major products after hydrolysis of the corresponding stable diimines (2).
- Inoue, Seiichi,Suzuki, Osamu,Sato, Kikumasa
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p. 1773 - 1774
(2007/10/02)
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