Mesoporous niobosilicates serving as catalysts for synthesis of fragrances

“…Niobium-based heterogeneous catalysts have been receiving increased attention as epoxidation catalysts [4][5][6][7][8][9][10][11][12][13]. Various Nb-containing catalysts have been shown to exhibit excellent catalytic activities for the epoxidation of cyclic alkenes [5,6,11,[14][15][16][17], oils [10,12] and propylene [18], as well as fine chemical substrates such as limonene, carveol, isopulegol, carvone, and squalene [8,19]. During cyclohexene oxidation with Nb containing MCM-41 and MCM-48 catalysts, similar conversion activities are reported; however, significantly higher epoxide selectivity is reported on Nb-MCM-48 albeit at lower Nb loading [16].…”

Section: Introductionmentioning

confidence: 99%

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

Yan

Ramanathan²,

Patel

et al. 2016

Journal of Catalysis

View full text Add to dashboard Cite

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.

show abstract

“…Recently, the catalysts containing niobium have drawn much attention in the field of the oxidation reactions. Mesoporous Nb-containing silicates obtained by various procedures have been active catalysts for epoxidation of olefins in the presence of hydrogen peroxide as an oxidizing agent (Nowak et al, 2003 ; Kilos et al, 2005 ; Nowak and Ziolek, 2005 ; Feliczak et al, 2009 ; Feliczak-Guzik and Nowak, 2009 ; Selvaraj et al, 2009 ; Nowak, 2012 ; Gallo et al, 2013 ; Tiozzo et al, 2014 , 2015 ; Ivanchikova et al, 2015 ; Thornburg et al, 2015 ; Turco et al, 2015 ).…”

Section: Catalysis On Niobium-containing Mesoporous Silicatesmentioning

confidence: 99%

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

2018

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Mesoporous niobosilicates serving as catalysts for synthesis of fragrances

Cited by 37 publications

References 16 publications

Synthesis and characterization of SBA-16 type mesoporous materials containing amine groups

Synthesis and characterization of SBA-16 type mesoporous materials containing amine groups

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

Contact Info

Product

Resources

About