Epoxidation of cyclohexene on Nb-containing meso- and macroporous materials

Nowak, Izabela; Kilos, Beata A.; Ziółek, Maria; Lewandowska, Anna E.

doi:10.1016/s0920-5861(02)00332-2

Cited by 84 publications

(55 citation statements)

References 16 publications

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“…Thus, the optimum solvents for amorphous (acetonitrile) and crystalline (methanol) mesoporous Nb 2 O 5 catalysts can be interpreted in terms of hydrophilicity and pydrophobicity. [25]. This is due to the isolated Nb active sites embedded in silica matrix similarly to Ti active sites.…”

Section: Surface Properties Of Mesoporous Nb 2 O 5 Catalystsmentioning

confidence: 98%

Changes in Surface Property and Catalysis of Mesoporous Nb2O5 from Amorphous to Crystalline Pore Walls

et al. 2010

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The amorphous inorganic phase of an ordered amorphous mesoporous Nb 2 O 5 with two dimensional hexagonal (2D-hex) structure was crystallized with maintaining the original well arranged porous structure. The difference in surface property between amorphous and crystalline Nb 2 O 5 with similar ordered mesoporous structure was compared. It was found from water adsorptiondesorption isotherms and observation by infrared (IR) spectroscopy that the amorphous sample was hydrophilic and that the surface OH groups were acidic. On the other hand, the OH groups on crystalline mesoporous Nb 2 O 5 were non-acidic and inside the pores was less hydrophilic. The surface property was also compared by a catalytic reaction, oxidation of cyclohexe by an aqueous solution of H 2 O 2 . The high (95%) selectivity for 1,2-epoxycyclohexane was obtained at 40°C for 2 h in methanol solvent over crystalline mesoporous Nb 2 O 5 at 12% conversion, while amorphous mesoporous Nb 2 O 5 showed high (68%) selectivity for 1,2-cyclohexanediol in acetonitrile solvent at 60°C for 2 h at 22% conversion. The differences in selectivity and the optimal solvent between amorphous and crystalline samples were interpreted in terms of the acidic feature of surface OH groups and hydrophilicity. While similar selectivity was observed over non-porous crystalline Nb 2 O 5 , much higher conversion over crystalline mesoporous Nb 2 O 5 was attained at the same surface area. Thus, an advantage of mesoporous structure is attributed to the higher contact time of molecules inside the pores to the catalyst surface than those outside the particles.

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Section: Surface Properties Of Mesoporous Nb 2 O 5 Catalystsmentioning

confidence: 98%

Changes in Surface Property and Catalysis of Mesoporous Nb2O5 from Amorphous to Crystalline Pore Walls

et al. 2010

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“…The catalytic systems based on niobium oxide are reasonably selective in oxidative processes [58], such as the selective epoxidation of allylic alcohols [59], the opening of epoxy rings [60], the selective oxidation of geraniol [61], the cyclohexene epoxidation [62], the selective oxidation of terpenes [63,64] and the oxidation of unsaturated fatty acid derivatives [49,65].…”

Section: Introductionmentioning

confidence: 99%

New Insights on the Oxidation of Unsaturated Fatty Acid Methyl Esters Catalyzed by Niobium(V) Oxide. A Study of the Catalyst Surface Reactivity

et al. 2018

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Abstract:The catalytic properties of niobium(V) oxide (Nb 2 O 5 -CBMN) of different grades: amorphous, optical and ultra-pure, untreated or heat-treated at 400, 500, 700 and 900 • C were studied, before and after interaction with H 2 O 2 , by in situ Raman, FTIR-ATR and diffuse reflectance UV-Visible spectroscopy. The presence of different reaction sites for NbO 7 and NbO 8 type systems, which are directly related to surface defects present in different states of crystallization, were fully characterized. The reactivity of different catalysts obtained from niobium(V) oxide was investigated, using the oxidation of methyl linoleate in the presence of hydrogen peroxide as probe reaction. The reaction was followed by GC-MS, as well as by 1 H and 13 C NMR spectrometry and the dominant product was 9-oxo-nonanoic acid methyl ester. A reaction mechanism related to an auto-oxidation process must be occurring, leading initially to the formation of hydroperoxides, which decompose rapidly via Hock-type rearrangement, leading to the formation of aldehydes.

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“…Meanwhile, Gallo et al [23] have reported that the oxidation activity of niobiumcontaining MCM-41 (Nb-MCM-41) in the epoxidation of alkene at higher temperature. Nb-MCM-41 also was applied in the oxidation of butyl sulfide and cyclohexene using H 2 O 2 at low temperature [41][42][43][44]. In that case, niobium species is located in the framework of molecularsieves.…”

Section: Performance Of Catalystsmentioning

confidence: 99%

Characterization and Catalytic Performance of Niobic Acid Dispersed over Titanium Silicalite

Prasetyoko

Ramli

Endud

et al. 2008

Advances in Materials Science and Engineering

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Niobic acid, Nb 2 O 5 ·nH 2 O, has been supported on the titanium silicalite by impregnation method. The obtained materials were characterized by X-ray diffraction, infrared, and ultra-violet-visible diffuse reflectance spectroscopy, temperature programmed reduction, pyridine adsorption, and field emission scanning electron microscopy techniques. It was demonstrated that the tetrahedral titanium species still retained after impregnation of niobic acid. The results revealed that niobium species interacted with hydroxyl groups on the surface of TS-1. The niobium species in the catalysts are predominantly polymerized niobium oxides species or bulk niobium oxide with the octahedral structure. All catalysts showed both Brønsted and Lewis acid sites. The catalysts have been tested for epoxidation of 1-octene with aqueous hydrogen peroxide. It was found that the presence of niobic acid in the catalysts enhanced the rate of the formation of epoxide at the initial reaction time. Diol as a side product was also observed due to the acidic properties of the catalysts.

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Epoxidation of cyclohexene on Nb-containing meso- and macroporous materials

Cited by 84 publications

References 16 publications

Changes in Surface Property and Catalysis of Mesoporous Nb2O5 from Amorphous to Crystalline Pore Walls

Changes in Surface Property and Catalysis of Mesoporous Nb2O5 from Amorphous to Crystalline Pore Walls

New Insights on the Oxidation of Unsaturated Fatty Acid Methyl Esters Catalyzed by Niobium(V) Oxide. A Study of the Catalyst Surface Reactivity

Characterization and Catalytic Performance of Niobic Acid Dispersed over Titanium Silicalite

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