Controlled synthesis of mesoporous NbMSU-X: influence of the preparation route

Feliczak, Agnieszka; Nowak, Izabela

doi:10.1016/s0167-2991(07)80886-x

Cited by 3 publications

(2 citation statements)

References 12 publications

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“…Diffuse reflectance UV-Vis spectra of Nb-TUD-1 samples reveal a well-defined absorption peak around 212-229 nm with a tail extending from 270 nm ( Figure 4). The absorption peak is attributed to isolated, well dispersed NbO 4 tetrahedral units whereas the tailing around 270 nm is due to oligomeric NbO 4 units [7,13,26,33,34]. The absorption in the range of ca.…”

Section: Resultsmentioning

confidence: 98%

Mechanistic insights for enhancing activity and stability of Nb-incorporated silicates for selective ethylene epoxidation

Yan

Ramanathan²,

Patel

et al. 2016

Journal of Catalysis

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Significant ethylene epoxidation activity was observed over niobium (Nb) incorporated mesoporous silicate materials Nb-KIT-5, Nb-MCM-48, and Nb-TUD-1, with hydrogen peroxide (H 2 O 2) as oxidant and methanol (MeOH) as solvent under mild operating conditions (35 °C and 50 bars). No CO 2 as byproduct was detected at these conditions. The measured ethylene oxide (EO) productivity over Nb-TUD-1 materials (342-2539 g EO h-1 kg-1 Nb) spans a greater range than those observed with Nb-KIT-6 (234-794 g EO h-1 kg-1 Nb), Nb-KIT-5 (273-867 g EO h-1 kg-1 Nb) and Nb-MCM-48 (71-219 g EO h-1 kg-1 Nb) materials at similar operating conditions. However, significant H 2 O 2 decomposition and Nb leaching were observed in all cases. Computational studies employing minimal models of the catalytically active sites, suggest how the Brønsted acidity may lead to these detrimental pathways. Indeed, lowering the metal loading to significantly reduce the Brønsted acidity results in a dramatic increase in H 2 O 2 utilization towards EO formation (4304 g EO h-1 kg-1 Nb). The increased EO productivity either matches or surpasses that observed on the conventional Ag-based heterogeneous catalyst (with O 2 as oxidant) as well as a Re-based homogeneous catalyst (with H 2 O 2 as oxidant). These results are paving the way for further computational and experimental investigations aimed at the rational design of improved epoxidation catalysts that reduce H 2 O 2 decomposition and metal leaching to practically viable levels.

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Section: Resultsmentioning

confidence: 98%

Mechanistic insights for enhancing activity and stability of Nb-incorporated silicates for selective ethylene epoxidation

Yan

Ramanathan²,

Patel

et al. 2016

Journal of Catalysis

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“…Nowak et al described the selective oxidation of terpenes and terpenoids, such as geraniol, limonene, α-terpineol using H 2 O 2 as an oxidant over NbMSU-X-catalysts (Feliczak-Guzik et al, 2009 ), which are characterized by a 3D interconnecting network of “worm-like” pores (Feliczak and Nowak, 2007 ). The oxidation of terpenes/terpenoids was performed in glass batch reactor upon dynamic stirring at 313 K for 23 h. Products of reaction were evaluated by GC and GC-MS.…”

Section: Catalysis On Niobium-containing Mesoporous Silicatesmentioning

confidence: 99%

Toward Exploiting the Behavior of Niobium-Containing Mesoporous Silicates vs. Polyoxometalates in Catalysis

2018

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Classification of polyoxometalates (POMs) is based on their chemical composition, basically represented by two general formulae: a) [MmOy]p− b) [XxMmOy]q−, where M is the main transition metal, O is the oxygen atom and X can be a non-metal atom such as Si. Additionally, in the most cases, the structure of the polyoxometalates is derived from a combination of octahedral units MO6 with a central metal atom M and the oxygen atoms placed at their corners. In such octahedra, oxygen atoms allow the condensation between two octahedral units, while one oxygen atom (or max. two atoms) makes double bond with the central metal atom and is not shared with other metal atoms within the complex (terminal oxygens). On the other hand, niobium-containing mesoporous silicates contain mainly MO4 tetrahedra and reveal superior activity in heterogeneous catalysis. Thus, the proper coordination of niobium is crucial for the catalytic activity and will be deeply discussed. The similarity in the catalytic behavior of niobium-polyoxometalates and heterogeneous niobium single-site catalysts in selective oxidations will be demonstrated.

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Mesoporous niobosilicates serving as catalysts for synthesis of fragrances

Feliczak-Guzik

Nowak

2009

Catalysis Today

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Controlled synthesis of mesoporous NbMSU-X: influence of the preparation route

Cited by 3 publications

References 12 publications

Mechanistic insights for enhancing activity and stability of Nb-incorporated silicates for selective ethylene epoxidation

Mechanistic insights for enhancing activity and stability of Nb-incorporated silicates for selective ethylene epoxidation

Toward Exploiting the Behavior of Niobium-Containing Mesoporous Silicates vs. Polyoxometalates in Catalysis

Mesoporous niobosilicates serving as catalysts for synthesis of fragrances

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