Properties of the sol–gel TiO2–SiO2 oxidation catalysts prepared using ethyl silicate 40 as a silica precursor

Mrowiec-Białoń, Julita; Jarzębski, Andrzej B.; Kholdeeva, Oxana A.; Trukhan, Natalia; Zaikovski, Vladimir; Kriventsov, V. V.; Olejniczak, Zbigniew

doi:10.1016/j.apcata.2004.06.040

Cited by 27 publications

(17 citation statements)

References 20 publications

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“…The oxidation of alkylphenols with H 2 O 2 over Ti,Siand Ti-POM-catalysts has been studied using 2,3,6-trimethylphenol (TMP) as model substrate [73][74][75][76][77]135,136]. For both types of catalysts we found the same products, 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E precursor) and 2,2´,3,3´,5,5´-hexamethyl-4,4´-biphenol (BP) (scheme 5).…”

Section: Oxidation Of Alkylphenolsmentioning

confidence: 99%

“…To overcome the steric limitation of TS-1, a considerable amount of research was focused on the preparation of titanium-containing materials with lager pores [29][30][31][32][33][34][35][36][37][38][39][40][41]63]. In the late 1990s, we also started our activity in the development of mesoporous Ti,Si-catalysts for selective oxidation of bulky organic substrates with H 2 O 2 [71][72][73][74][75][76][77][78][79]. For successful designing new catalysts and processes, we needed a basic knowledge about the mechanism of the formation of active titanium species and the mechanisms of their interaction with organic substrates.…”

Section: Introductionmentioning

confidence: 99%

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Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

Kholdeeva

2006

Top Catal

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Section: Oxidation Of Alkylphenolsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

Kholdeeva

2006

Top Catal

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“…It should be noted that there have been substantial synthetic efforts to minimize V leaching from various silicate-based catalysts via V-tethering [13], grafting [11], incorporation [5,11,16], and immobilization [11,15,17]. However, the loss of active V species during the reactions was unavoidable due possibly to insufficient chemical stability between silicate and V species under the reaction conditions employed (Table S1) [20,[35][36][37]. Carbon is a promising support material because it can provide several advantages such as high surface area [38][39][40], high dispersion of active V species [25,41], high resistance to thermochemical oxidation [42][43][44], and compatibility with a wide range of active V phases [25,45].…”

Section: Introductionmentioning

confidence: 99%

Catalytic activity and stability of carbon supported V oxides and carbides synthesized via pyrolysis of MIL-47 (V)

Kim

McNamara

Hicks

2016

Applied Catalysis A: General

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Substantial leaching of active V species often limits the reusability of V-based soild catalysts in liquidphase oxidation reactions and therefore requires the development of more stable, novel materials. This paper first reports the synthesis of active vanadium (V) oxide and carbide species dispersed on a carbon support via the pyrolysis of MIL-47 (V), a V-based metal-organic framework (MOF) template. The phase transition of V species present in this MOF template was achieved by varying the pyrolysis temperatures ranging from 600 to 1100 °C to synthesize a series of carbon catalysts with different surface and bulk phases of V. Notably, the pyrolysis of MIL-47 (V) provided carbon supports with high surface areas (~ 350 m 2 g-1), high mesoporosities (V MESO /V PORE~ 0.88), high V quantities (35-70 wt. %), and small (~ 18 nm) V crystallites dispersed on the surface. These desired properties were not observed when V was supported on activated carbon (V/AC) via conventional impregnation. The V/AC catalyst showed lower mesoporosity (~0.63), lower V quantity (~25 wt. %), and larger V crystallites (~ 27 nm) compared to the catalyst produced from MIL-47 (V) pyrolysis under identical conditions. Of additional note, the pyrolysis of MIL-47 (V) could yield an isolated bulk phase of V carbide at low pyrolysis temperatures (i.e., >900 °C). This phase was not attainable when V/AC was synthesized via pyrolysis even at higher temperatures (i.e., 1100 °C). The catalytic performance of the resulting V on carbon catalysts was evaluated in a liquidphase oxidation reaction of dibenzothiophene. The V carbide catalysts exhibited good activities and enhanced stabilities, as evidenced by lower amounts of V species leached (< 20%) during recycle runs compared to the conventional V/AC catalyst (V leaching ~56%). This study marks a signifcant improvement in the synthesis of supported V catalysts with reduced leaching in liquid-phase oxidation reactions compared to materials synthesized via conventional impregnation techniques.

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“…Catalytic properties were initially ascribed to the presence of isolated, tetrahedrally coordinated Ti(IV) sites. Then, highly dispersed dimeric forms of Ti were also found to provide good catalytic properties (Kholdeeva et al, 2002;Mrowiec-Białoń et al, 2004). Thus, an excellent dispersion of titanium in the silica skeleton is indispensable for the good catalytic properties of titania-silica mixed oxides, irrespective of their pore structure.…”

Section: Monolithic Microchannel Reactors Functionalized With Transition Metalsmentioning

confidence: 99%

“…The MMRs with titania-silica monolithic cores (3.5 × 40 mm) were prepared by two methods: 1. direct synthesis of titania-silica monoliths with a nominal titanium content of 1, 2, and 5 wt% (D1, D2, and D5 samples) and 2. post-synthesis incorporation of titanium into silica monoliths using the grafting method (I1, I2, and I5 samples) (Mrowiec-Białoń et al, 2004). The preparation method appeared to be critical for macro-and mesopore structures of the monoliths, as well as for the dispersion of Ti species in the silica matrix.…”

Section: Monolithic Microchannel Reactors Functionalized With Transition Metalsmentioning

confidence: 99%

Catalytic Functionalized Structured Monolithic Micro-/Mesoreactors: Engineering, Properties, and Performance in Flow Synthesis: An Overview and Guidelines

et al. 2021

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In this review article, we first discussed the development of silica monoliths with hierarchical macro-/mesopore structure and their potential figures of merit as continuous-flow micro-/mesoreactors of up to 30 ml working volume. Making use of the flow hindrance of different pore structures seen from the Darcy law perspective, we discriminated four structures of the monoliths (M1–M4). We then summarized the most important results, mainly from our studies of continuous-flow structured monolithic reactors and rotating bed reactors (RBRs) filled with structured pellets, activated with various catalytic entities and enzymes. The results show that an increase in the flow rate and thus velocity in reactors activated with more conventional catalytic sites has no or a minor positive effect on the apparent reaction rate. On the contrary, in those with the most open structure (M1) and functionalized with enzymes, it could increase by more than two orders of magnitude even at low overpressures. The production systems worked stably for at least 200 h. To conclude, the synthetic system made of the hierarchically structured monoliths, or RBRs filled with structured catalytic pellets, lay the foundation for a new platform for the high-yield production of a wide variety of specialty chemicals, even on a multikilogram scale, in a safe and sustained manner.

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Properties of the sol–gel TiO2–SiO2 oxidation catalysts prepared using ethyl silicate 40 as a silica precursor

Cited by 27 publications

References 20 publications

Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

Catalytic activity and stability of carbon supported V oxides and carbides synthesized via pyrolysis of MIL-47 (V)

Catalytic Functionalized Structured Monolithic Micro-/Mesoreactors: Engineering, Properties, and Performance in Flow Synthesis: An Overview and Guidelines

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