Effect of the support on the basic and catalytic properties of KF

Clacens, Jean‐Marc; Genuit, Daisy; Delmotte, Luc; Garcı́a-Ruiz, A.; Bergeret, G.; Montiel, Ramón; López, Joaquín; Figuéras, F.

doi:10.1016/j.jcat.2003.09.009

Cited by 53 publications

(40 citation statements)

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“…The observed chemical shift, À134 ppm, is close to the values À132 and À133 ppm, previously reported shifts of KF. 47,48 Neither by recording 192 19 F NMR scans of as-prepared DD3R with an interscan delay of 600 s during 32 hours, nor by accumulating 1024 scans with an interscan delay of 30 s, any 19 F NMR signal was detected. No signal from, e.g., residual KF at À134 ppm, nor from F À anions within the cages around À180 ppm 49 have been observed.…”

Section: Advances In the Fluoride Routementioning

confidence: 99%

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

et al. 2011

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Small pore size and hydrophobic nature of DD3R make this material a unique zeolite with high potential in industrial separation applications. However, the reproducible rapid synthesis of this zeolite is still a problem. In this work, a thorough assessment of different synthetic methods revealed that synthesis reproducibility relies on two main pillars: the use of properly cleaned autoclave liners and the synthesis composition. High quality DD3R crystals are obtained when KOH is used as a cleaning agent, eliminating memory effects, and when KF is used in the synthesis as a mineralizing agent. H NMR reveals that template molecules accommodated within the cages are sticking to these 8-ring windows through their amine group. High quality DD3R crystals are applied in the adsorptive separation of buta-1,3-diene and but-2-ene isomers, one of the most energy intensive separations in chemical industry. Mixture separation experiments revealed that the 8-ring apertures of the DD3R cages are only accessible to trans-but-2-ene and buta-1,3-diene, while excluding but-1-ene and cis-but-2-ene molecules, resulting in shape-selective separation in the presence of C4 mixtures.

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Section: Advances In the Fluoride Routementioning

confidence: 99%

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

et al. 2011

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“…The inhibition by the products was earlier proposed to explain the lower reaction rate on KF/a-alumina in the absence of solvent. [13] From a synthetic point of view it is, however, interesting to work in concentrated media, and the catalytic properties reported here for Mg-La are probably underestimated. The low activity of supported quaternary amines, [25] can also be a result of a high concentration.…”

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confidence: 81%

“…ing KF/ a-Al 2 O 3 as catalyst, [13] nitromethane was found to be only two times less reactive than nitroethane. Therefore the activity of the mixed oxide is of the same magnitude as that of the superbase for this type of reaction, in DMF as solvent.…”

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confidence: 96%

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Magnesium‐Lanthanum Mixed Metal Oxide: a Strong Solid Base for the Michael Addition Reaction

2005

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Michael additions were achieved quantitatively at room temperature with a broad spectrum of acceptors and donors, using a magnesium-lanthanum mixed oxide, a strong solid base. The best solvent for the reaction is dimethylformamide, but good yields were also obtained using toluene as solvent. The results obtained with magnesium-lanthanum are comparable to those reported for super bases. The catalyst can be separated from the reaction mixture and recycled five times without loss of activity with no other treatment.Keywords: basic catalysis; magnesium-lanthanum mixed oxide; Michael additions; recyclability; solvent effectsThe Michael addition is a reaction for C À C bond formation, involving the nucleophilic addition of a carbanion to a,b-unsaturated carbonyl compounds and is therefore base-catalysed. This reaction has found multiple industrial applications for the production of monomers, [1,2] corrosion inhibitors, [3] coatings, [4] and pharmaceuticals.[5] This reaction is industrially catalysed by liquid bases such as alkoxides, tertiary amines, non-ionic bases, [6,7] and superbases such as proazaphosphatranes. [8 -10] A variety of solid bases has also been described including barium hydroxide, [11] KF supported on g-Al 2 O 3 , [12] a-Al 2 O 3 , [13] phosphates, [14,15] on hydrotalcites, [16,17] amines anchored at surfaces, [18] and organic resins.[19]Most of these solids are weak bases which are effective only with a restricted class of electrophilic olefins such as a,b-unsaturated esters or conjugated enones. Recycling of the catalyst has seldom been demonstrated except for KF/natural phosphate which can be recycled after calcination at 973 K, which represents a severe limitation to its practical use. We report here the properties of Mg-La mixed oxides for different Michael additions. This catalyst has been recently used for the transesterification of diethyl carbonate by alcohols.[20] A comparison of substrates with different pK a allows us to estimate the possibilities of the catalyst and also gives an evaluation of the basic strength at the surface.[21] We used here donors with pK a values, measured in DMSO, [22] varying from 8 for thiocresol to 16.4 for diethyl malonate and 17.2 for nitromethane.The Mg-La mixed oxide was obtained by co-precipitation of Mg and La nitrates (0.386 and 0.129 mol, in water 0.5 L, for an atomic ratio Mg/La ¼ 3) at a constant pH ¼ 10 using a mixture of KOH (1 mol) and K 2 CO 3 (0.26 mol) in 0.52 L of distilled water. The samples (about 0.15 g) were activated at 923 K in an air flow, using a temperature ramp of 10 K/min. Just before use, they were reactivated at 773 K in air and not rehydrated.The chemical analyses of the solid catalyst give the composition: La: 39.8%; K: 5.4%; H 2 O: 37%. The Mg/ La ratio in the solid is then 4.26, compared to 3 in the solution, therefore the precipitation of La is not complete at pH 10. The powder XRD pattern of the uncalcined Mg-La mixed oxide contains diffraction lines of a hydrated lanthanum carbonate as well as magnesium and lanth...

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“…[4b-d, 6] For many years, we have been investigating the use of unconventional reaction media that could replace harmful organic solvents while maintaining the highest chemical efficiency. In particular, we have been focusing our attention on the use of water [7] or SolFC, [8] proving that, by using these alternatives to organic solvents, significant improvements of both chemical efficiency and sustainability of a process can be obtained.…”

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confidence: 99%

Polystyryl‐BEMP as an Efficient Recyclable Catalyst for the Nucleophilic Addition of Nitroalkanes to α,β‐Unsaturated Carbonyl Compounds under Solvent‐Free Conditions

et al. 2008

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2-tert-Butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine supported on polystyrene (PS-BEMP) is an efficient catalyst for the addition of nitroalkanes (1-1.5 equiv.) to a,b-unsaturated carbonyl compounds (1.0 equiv.) in the absence of a reaction medium (solvent-free conditions). The corresponding g-nitro carbonyl compounds have been isolated in excellent yields but the catalyst can be satisfactorily recovered and used for only 3 times due to the magnetic stirring which caused crunching of the catalyst beads thus hampering its complete recovery. To optimize the catalysts reuse and improve the environmental efficacy of solvent-free conditions, the first solvent-free cyclic continuous-flow reactor has been set up. This reactor has allowed the product to be isolated in an almost quantitative yield by using a very small amount of organic solvent, making the recovery and reuse of the catalyst efficient and reproducible.

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Effect of the support on the basic and catalytic properties of KF

Cited by 53 publications

References 10 publications

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Facile synthesis of the DD3R zeolite: performance in the adsorptive separation of buta-1,3-diene and but-2-ene isomers

Magnesium‐Lanthanum Mixed Metal Oxide: a Strong Solid Base for the Michael Addition Reaction

Polystyryl‐BEMP as an Efficient Recyclable Catalyst for the Nucleophilic Addition of Nitroalkanes to α,β‐Unsaturated Carbonyl Compounds under Solvent‐Free Conditions

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