Formaldehyde Oligomerization on Silicalite: An FTIR and NMR Study

Xamena, Françesc X. Llabrés i; Areán, C. Otero; Spera, Silvia; Merlo, Edoardo; Zecchina, A.

doi:10.1023/b:catl.0000023721.90964.e2

Cited by 16 publications

(4 citation statements)

References 16 publications

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“…Interestingly we observed a 1 H signal at δ = 5.05 ppm with no observable 13 C–H splitting pattern that correlated to a 13 C shift at δ = 92 ppm. Based on reference patterns , and our own studies of authentic samples, we tentatively assign this feature to either hydroxymethyl hydroperoxide or trioxane, both of which are possible in our system and give key mechanistic information about the radical processes involved. We favor the product as hydroxymethyl hydroperoxide since there is no splitting of the 13 C signal as would result from 13 C labeled trioxane.…”

Section: Results and Discussionmentioning

confidence: 72%

Partial Oxidation of Ethane to Oxygenates Using Fe- and Cu-Containing ZSM-5

et al. 2013

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Iron and copper containing ZSM-5 catalysts are effective for the partial oxidation of ethane with hydrogen peroxide giving combined oxygenate selectivities and productivities of up to 95.2% and 65 mol kgcat(-1) h(-1), respectively. High conversion of ethane (ca. 56%) to acetic acid (ca. 70% selectivity) can be observed. Detailed studies of this catalytic system reveal a complex reaction network in which the oxidation of ethane gives a range of C2 oxygenates, with sequential C-C bond cleavage generating C1 products. We demonstrate that ethene is also formed and can be subsequently oxidized. Ethanol can be directly produced from ethane, and does not originate from the decomposition of its corresponding alkylperoxy species, ethyl hydroperoxide. In contrast to our previously proposed mechanism for methane oxidation over similar zeolite catalysts, the mechanism of ethane oxidation involves carbon-based radicals, which lead to the high conversions we observe.

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Section: Results and Discussionmentioning

confidence: 72%

Partial Oxidation of Ethane to Oxygenates Using Fe- and Cu-Containing ZSM-5

et al. 2013

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“…[27,32] Remarkably, a broad band at 3460 cm À1 appeared, which relates to silanol nests. [32,39] Previous work on ZSM-5 showed that, upon alkaline treatment, this band decreases or disappears, which was attributed to either the preferential attack of OH À , or the deposition of Si or Al species. [27,32] An additional HCl treatment (sample AT-Al-0.003W) was performed to remove the deposited aluminum from the solid.…”

mentioning

confidence: 99%

“…No distinct adsorption was detected near 3630 cm À1 in AT-Al-0.003 or AT-Al-0.003W, which suggests the absence of Brønsted acidity related to (bulk) framework aluminum. [39] The acidity of selected samples was studied by infrared spectroscopy of pyridine adsorbed. From the bands at 1450 and 1545 cm…”

mentioning

confidence: 99%

Desilication Mechanism Revisited: Highly Mesoporous All‐Silica Zeolites Enabled Through Pore‐Directing Agents

Verboekend

Pérez‐Ramírez

2011

Chemistry A European J

250

246

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The role of pore-directing agents (PDAs) in the introduction of hierarchical porosity in silicalite-1 in alkaline medium was investigated. By incorporation of various PDAs in aqueous NaOH, homogenously distributed mesopores were introduced in 2.5 μm silicalite-1 crystals. It was proven for the first time that framework aluminum is not a prerequisite for the introduction of intracrystalline mesoporosity by desilication. The pore-directing role is not directly exerted by framework trivalent cations metals, but by species on the external surface of the zeolite. The inclusion of metal complexes (Al(OH)(4)(-), Ga(OH)(4)(-)) and tetraalkyl ammonium cations (tetramethyl ammonium (TMA(+)), tetrapropyl ammonium (TPA(+))) in the alkaline solution led to distinct mesopore surface areas (up to 286 m(2) g(-1)) and pore sizes centered in the range of 5-20 nm. In the case alkaline treatment was performed in the presence of Al(OH)(4)(-), all aluminum partially integrated in the zeolite giving rise to both Lewis and Brønsted acidity. Apart from the concentration and location, the affinity of the PDA to the zeolite surface plays a crucial role in the pore formation process. If the PDA is attracted too strongly (e.g., TMA(+)), the dissolution is reduced dramatically. When the pore-directing agent is not attracted to the zeolite's external surface, excessive dissolution occurs (standard alkaline treatment). TPA(+) proved to be the most effective PDA as its presence led to high mesopore surface areas (>200 m(2) g(-1)) over a broad range of PDA concentrations (0.003-0.1 M). Importantly, our results enable to extend the suitability of desilication for controlled mesopore formation to all-silica zeolites.

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“…The observed shoulder at 1 631.11 cm -1 in Fig. 1(A , appearing on both spectra, indicates a long carbon chain with a high degree of regularity for the linear backbone structure (Xamena et. al., 2004).…”

Section: Ftir Characterisationmentioning

confidence: 93%

A new spectrophotometric method for determination of residual polydiallyldimethylammonium chloride flocculant in treated water based on a diazotization-coupled ion pair

Mwangi¹,

Ngila²,

Ndungu³

2012

WSA

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Polydiallyldimethylammonium chloride (polyDADMAC) is a water-soluble cationic polyelectrolyte used for water treatment. Its residues in treated water are contaminants as they react with chlorine to produce a carcinogenic compound. Commonly-used techniques for quantification of the polycation, such as colloidal and potentiometric titration as well as 1 H NMR, have poor sensitivity and detection limits. This paper describes a more sensitive UV spectrophotometric method for quantitative determination of residual polyDADMAC in treated water, through formation of an ion pair with (4-hydroxy-1-napthylazo) benzene-sulphonic acid (dye). The ion pair, which is a colloidal solid material, was characterised by FTIR, 13 C NMR and 1 H NMR techniques. The colloid materials formed with different concentrations of polyDADMAC were dissolved in either N,N-dimethylformamide or 1,4-dioxane, followed by determination with UV spectrophotometry. The wavelength of maximum absorption (λ max ) was found to be dependent on the solvent used, with 1,4-dioxane showing a better linear range of 0.1-1.8 mg•ℓ -1 polyDADMAC. Varying the pH of the solutions had no significant effect on λ max .

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Formaldehyde Oligomerization on Silicalite: An FTIR and NMR Study

Cited by 16 publications

References 16 publications

Partial Oxidation of Ethane to Oxygenates Using Fe- and Cu-Containing ZSM-5

Partial Oxidation of Ethane to Oxygenates Using Fe- and Cu-Containing ZSM-5

Desilication Mechanism Revisited: Highly Mesoporous All‐Silica Zeolites Enabled Through Pore‐Directing Agents

A new spectrophotometric method for determination of residual polydiallyldimethylammonium chloride flocculant in treated water based on a diazotization-coupled ion pair

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