Studies on solid catalysts with a basic character I

Malinowski, S.; Szczepańska, S.

doi:10.1016/0021-9517(63)90073-3

Cited by 28 publications

(2 citation statements)

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“…Unfortunately the silica surface has been less studied than other surfaces, such as that of alumina, for the preparation of a strong basic solid by the addition of a basic reagent to an inorganic oxide . In the few known studies, after saturation of the surface with an aqueous solution of an alkali-metal hydroxide, acetate, or carbonate, the supported reagents are thermally treated at temperatures between 300 and 650 °C to leave a silica with strong basic surface sites such as alkali-metal silanolates. , It is also known that silica gel can be made more basic simply by treatment with aqueous sodium hydroxide, followed by drying at 120 °C …”

Section: Discussionmentioning

confidence: 99%

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂

et al. 1998

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Reaction of silica-supported α-[Os(CO)3Cl2]2 in the presence of alkali-metal carbonates affords reactive surface osmium(II) species. The nature of the latter depends on the basicity given to the silica surface, with K2CO3 behaving as a stronger base than Na2CO3 when supported on silica. Infrared evidence suggests that with a low basicity (for instance, molar ratio Na2CO3:Os = 2:1), surface species such as [Os(CO)3(OR)2] n (R = H, Si⪪) are initially formed; an increase of the surface basicity (molar ratio (Na2CO3 or K2CO3):Os = (10−20):1) leads to the formation of probably anionic {[Os(CO)3(OR)2] m (OR)}- (R = H, Si⪪; m > 1) entities up to the less reactive species [Os(CO)3(OH)3]-. The high reactivity of these surface species is confirmed by the controlled reduction by CO or H2 of silica-supported [Os(CO)3(OH)2] n in the presence of alkali-metal carbonates, which leads selectively to either neutral ([Os3(CO)12], [H4Os4(CO)12]) or anionic ([H3Os4(CO)12]-, [Os10C(CO)24]2-) clusters, in accord with results obtained with supported α-[Os(CO)3Cl2]2. There is direct and indirect evidence that the aggregation process occurs via silica-anchored [HOs3(CO)10(OSi⪪)] or silica-supported [HOs3(CO)10(OH)] species, followed by further condensation to [H4Os4(CO)12] or [H3Os4(CO)12]- according to the basicity of the surface. The nature and the quantity of added alkali carbonate (Na2CO3 or K2CO3), together with the temperature, influence the formation of either [H3Os4(CO)12]- or [H2Os4(CO)12]2-, which can act as intermediates for further condensation to cluster anions of higher nuclearity. In addition to these reaction parameters, the amount of H2 in the gas phase is also crucial in defining the relative stability and the reactivity of the surface species [H3Os4(CO)12]- and [H2Os4(CO)12]2- and their further condensation to specific carbonyl cluster anions.

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Section: Discussionmentioning

confidence: 99%

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂

et al. 1998

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“…The basic properties were determined by titration with 0.01 M benzoic acid solution in toluene using 0.15 g of vacuum dried solid sample suspended in 2 mL of indicator solution.Indicator solution for the determination of weak basic sites (pKa = 7.1) contained 0.01 g of Bromothymol blue in 100 mL toluene. The amount of strong basic sites (pKa = 9.3) were determined in the presence of an indicator solution containing 0.01 g of Phenolphthalein in 100 mL toluene[31,32].…”

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MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

2017

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A series of Mg3:Fex+Ce1-x LDHs (3:1) were synthesized by co-precipitation method by varying molar ratio of Fe:Ce between 1:0 to 0:1 (LDH-1 to LDH-6). All synthesized LDHs were characterized by XRD, FT-IR, TEM, N2 sorption, benzoic acid titration and XPS in detail and evaluated for selective synthesis of dimethyl carbonate by transesterification of ethylene carbonate with methanol. It was demonstrated that the structural and basic properties of synthesized LDHs were strongly dependent on the Fe:Ce molar ratio (Ce concentration). The correlation between their physicochemical properties and catalytic performance was studied in detail. Among all synthesized LDHs the best result was obtained with LDH-3 (Fe:Ce=0.85:0.15) where LDH structure remained intact, and showed high number of strong basic sites on LDH surface. LDH-3 was recycled 7 times while maintaining high catalyst activity and selectivity towards DMC. The obtained results elucidate the important role of Ce in modifying the basic properties of LDH in enhancing the catalytic activity for DMC synthesis.

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ChemInform Abstract: Solid Acid and Base Catalysts

Tanabe¹

1982

Chemischer Informationsdienst

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Studies on solid catalysts with a basic character I

Cited by 28 publications

References 4 publications

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

ChemInform Abstract: Solid Acid and Base Catalysts

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Studies on solid catalysts with a basic character I

Cited by 28 publications

References 4 publications

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)3Cl2]2

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)3Cl2]2

MgFeCe Ternary Layered Double Hydroxide as Highly Efficient and Recyclable Heterogeneous Base Catalyst for Synthesis of Dimethyl Carbonate by Transesterification

ChemInform Abstract: Solid Acid and Base Catalysts

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Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂

Surface Organometallic Chemistry: Understanding the Multistep Process of Silica-Mediated Synthesis of Various Osmium Carbonyl Clusters from Supported α-[Os(CO)₃Cl₂]₂