Heterogeneous Basic Catalysis

Hattori, Hideshi

doi:10.1021/cr00035a005

Cited by 974 publications

(578 citation statements)

References 40 publications

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“…Exposing solid base catalysts to air sometimes causes their severe deactivation. 8 However, such deactivation was not observed for the present reaction system.…”

contrasting

confidence: 53%

Synthesis of N,N′-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO

Fujita¹,

Bhanage²,

Arai³

2004

Chemistry Letters

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“…Exposing solid base catalysts to air sometimes causes their severe deactivation. 8 However, such deactivation was not observed for the present reaction system.…”

contrasting

confidence: 53%

Synthesis of N,N′-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO

Fujita¹,

Bhanage²,

Arai³

2004

Chemistry Letters

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“…11−13 These reactions have conventionally been promoted by homogeneous base catalysts such as NaOH or KOH; however, these catalysts cannot be readily separated from the reaction mixture and are difficult to dispose of. 14,15 We have recently shown that calcined hydrotalcite, HT, is an active and highly selective heterogeneous catalyst for the self-and crosscondensation of biomass-derived C 4 −C 11 methyl ketones to produce cyclic enones, which upon subsequent hydrodeoxygenation produce cyclic alkanes that have properties making them suitable for aviation fuel and lubricants. 6,13,16,17 Hydrotalcite-type layered double hydroxides (LDHs) are inorganic compounds with the chemical composition M 2+ 1−x M 3+ x (OH) 2 (A x/n ) n-·yH 2 O, where M 2+ and M 3+ are divalent and trivalent metal cations, x is the molar ratio of the trivalent cation [M 3+ /(M 2+ + M 3+ )] which can be varied between 17 and 33%, and A n− is an anion with charge n, most often a carbonate ion.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones

Shylesh¹,

Kim²,

Gokhale

et al. 2016

Ind. Eng. Chem. Res.

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The effects of chemical composition and pretreatment on Mg−Al hydrotalcites and alumina-supported MgO were evaluated for the gas-phase, self-condensation reaction of C 3 −C 5 biomass-derived methyl ketones. We show that the selectivity toward the acyclic dimer enone and the cyclic enone trimer can be tuned by controlling the temperature of hydrotalcite calcination. Methyl ketone cyclization is promoted by Lewis acidic sites present on the hydrotalcite catalysts. XRD and thermal decomposition analysis reveal that the formation of periclase MgO starts above 623 K accompanied by complete disappearance of the hydrotalcite structure and is accompanied by an increase in hydroxyl condensation as the formation of well-crystallized periclase. 27 Al MQMAS and 25 Mg MAS NMR show that at progressively higher temperatures, Al 3+ cations diffuses out of the octahedral brucite layers and incorporate into the tetrahedral and octahedral sites of the MgO matrix thereby creating defects to compensate the excess positive charge generated. The oxygen anions adjacent to the Mg 2+ /Al 3+ defects become coordinatively unsaturated, leading to the formation of new basic sites. A kinetic isotope effect, k H /k D = 0.96, is observed at 473 K for the reaction of (CH 3 ) 2 CO versus (CD 3 ) 2 CO, which suggests that carbon−carbon bond formation leading to the dimer aldol product is the ratedetermining step in the condensation reaction of methyl ketones. We also show that acid−base catalysts having similar reactivity and higher hydrothermal stability to that of calcined hydrotalcites can be achieved by creating defects in MgO crystallites supported alumina as a consequence of the diffusion of Al 3+ cations into MgO. The physical properties of these materials are shown to be very similar to those of hydrotalcite calcined at 823 K.

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“…The side-chain alkylation of toluene with methanol over basic materials, can produce styrene and ethylbenzene (1,2). The process has been claimed to be economically attractive (3) offering the advantage of lower raw material cost compared with the traditional process.…”

Section: Introductionmentioning

confidence: 99%

Selective Alkylation of Toluene over Basic Zeolites: Anin SituInfrared Spectroscopic Investigation

Palomares

Eder‐Mirth

Lercher

1997

Journal of Catalysis

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In situ infrared spectroscopy was used to study the sorption and reaction of toluene and methanol over various alkali exchanged X zeolites. The size of the metal cations controls the preference of sorbing methanol or toluene. The smaller the cation, the higher the preference for methanol is. A balanced sorption stoichiometry of the reactants, the intermediate conversion of methanol into formaldehyde and the strong polarization of the methyl group of toluene are critical to catalyze side chain alkylation of toluene. These requirements are best met with very basic zeolites such as the Cs-X and Rb-X.

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Heterogeneous Basic Catalysis

Cited by 974 publications

References 40 publications

Synthesis of N,N′-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO

Synthesis of N,N′-Disubstituted Urea from Ethylene Carbonate and Amine Using CaO

Effects of Composition and Structure of Mg/Al Oxides on Their Activity and Selectivity for the Condensation of Methyl Ketones

Selective Alkylation of Toluene over Basic Zeolites: Anin SituInfrared Spectroscopic Investigation

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