Probing the acid sites of zeolites with pyridine: Quantitative AGIR measurements of the molar absorption coefficients

Zholobenko, Vladimir L.; Freitas, Cátia; Jendrlin, Martin; Bazin, Philippe; Travert, Arnaud; Thibault-Starzyk, Frédéric

doi:10.1016/j.jcat.2020.03.003

Cited by 161 publications

(137 citation statements)

References 47 publications

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“…The samples were outgassed at 400 °C for 6 h to desorb water and other contaminants before adsorbing pyridine. Adsorption was carried out at 150 °C for 15 min followed by desorption at 25 °C, as in agreement with well‐established procedures reported in the literature [97] . The relative concentration of either Brønsted or Lewis acid sites was estimated using equations E4 and E5. [74]

true C_{B} = I A ((), B) π \frac{R^{2}}{w ϵ}

true C_{L} = I A ((), L) π \frac{R^{2}}{w ϵ}

…”

Section: Methodsmentioning

confidence: 98%

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

et al. 2021

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The so-called mechanochemical method for the synthesis of zeolites reduces the generation of liquid residues and gaseous pollutants as compared to the conventional solvothermal method. Different types of zeolites have been synthesized at the laboratory scale with this method using mostly pestle and mortar. However, such an approach hinders both the systematic comprehension of the effects of the input variables of the milling process and its further scale-up towards the synthesis of the zeolites and their catalytic application. This work investigates the influence of key factors involved in the ball milling stage of the mechanochemical route for the synthesis of MFI done with the assistance of a commercial MFI seed and in the absence of solvents over the most salient physicochemical properties of this type of materials, i.e. the recovery percentage, production cost, morphology, surface area and porosity, crystallinity, acidity of the protonated MFI and catalytic performance. The synthesis of the materials was planned and executed following a full 2 4 factorial experiment whose input variables were the Na2O/SiO2 and H2O/SiO2 molar ratios and the milling time and speed. The effects of both main and interaction factors over key physicochemical properties, and catalytic behavior of the synthesized materials on the alkylation of phenol with tert-butyl alcohol were established within the explored sampling space. Results showed that the Na2O/SiO2 molar ratio plays a key role for the mechanochemical synthesis of MFI, since this variable may direct the synthesis to the preferential production of MOR instead of MFI. On the other hand, it was found that the milling time and speed and their interactions markedly impact the textural properties of MFI. Furthermore, the triple interaction between the input variables affected the concentration of Lewis acid sites of the produced materials. These effects were rationalized by considering that sodium can act as a structure directing agent during the mechanochemical synthesis of MFI and also can promote the incorporation of aluminum to its structure. On the other hand, the milling time and speed are non-linearly correlated to the milling energy required for forming the aluminosilicate precursor that crystallizes during the hydrothermal stage of the process. Overall, all the zeolites synthesized by the mechanochemical route were less crystalline than both the MFI used as seed and an MFI synthesized by solgel. This was associated to the formation of amorphous agglomerates around the zeolitic crystals. Finally, the catalytic behavior of the mechanochemical MFI zeolites in the studied reaction was found to be linearly and positively correlated with both the concentration of BrØnsted of sites and with the density of acid sites. The catalytic tendencies were consistent with the proposal of a stepwise Langmuir-Hinshelwood mechanism for the alkylation of phenol with tert-butyl alcohol.

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true C_{B} = I A ((), B) π \frac{R^{2}}{w ϵ}

true C_{L} = I A ((), L) π \frac{R^{2}}{w ϵ}

…”

Section: Methodsmentioning

confidence: 98%

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

et al. 2021

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“…The IR spectrum of this sample shows a reversible and instantaneous shift toward the lower wavenumbers (for 3.4 cm -1 ) in the vibration region of v(OH) under visible irradiation in respect to that collected in dark (Figure 9C-D). Such an effect is usually a sign of a temperature increase for few hundreds of degrees 47 .…”

Section: Materials Advances Accepted Manuscriptmentioning

confidence: 99%

Silver quasi-nanoparticles: bridging the gap between molecule-like clusters and plasmonic nanoparticles

et al. 2021

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“…The peak at 1,491 cm −1 is attributed to the overlapping of peaks originated from pyridine interaction with Lewis and Brønsted acid sites. The peak at 1,446 cm −1 is attributed to the interaction of pyridine with the Lewis acid site ( Anunziata et al, 2007 ; Zholobenko et al, 2020 ). In general, HBEA and Pd/HBEA showed similar acidic properties.…”

Section: Resultsmentioning

confidence: 99%

Hydrodeoxygenation of Xylose Isopropylidene Ketal Over Pd/HBEA Catalyst for the Production of Green Fuels

et al. 2021

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1,2:3,5-Di-O-isopropylidene-α-D-xylofuranose (DX) is a major component of a new bio-crude: a viscous oil presenting petroleum-friendly properties produced by the ketalization of sugarcane bagasse. This article studies DX HDO (hydrodeoxygenation) over a Pd/HBEA catalyst in a batch reactor at 250°C. The effects of hydrogen pressure from 10 to 40 bar, catalyst/DX ratio from ½ to 2, and reaction time 0–24 h were investigated. A range of conditions for complete hydrodeoxygenated DX into alkanes with a Pd/HBEA catalyst was found. In these conditions, a low coke yield with water as the principal deoxygenated product was obtained. Further, higher amounts of alkanes containing seven or more carbons (A7+) were favored at 30 bar of hydrogen pressure, Cat/DX ratio = 2, and short reaction time. Products analysis that accompanied the above variations during reaction time led to general insights into reaction pathways. First, in the presence of DX, an effective n-hexane conversion was not observed on experiments of low catalyst/DX ratio (½) or in the initial period of high Cat/DX ratio, suggesting DX is much more successful than n-hexane to compete for active sites. Then, the formation of a pool of oxygenated compounds, such as furans, ketones, and carboxylic acids, along with lighter and heavier alkanes was observed. Hence, the aforementioned oxygenates may undergo reactions, such as aldol condensation with subsequent hydrodeoxygenation reaction, generating heavier alkanes.

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Probing the acid sites of zeolites with pyridine: Quantitative AGIR measurements of the molar absorption coefficients

Cited by 161 publications

References 47 publications

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

Key Factors During the Milling Stage of the Seed‐assisted and Solvent‐free Synthesis of MFI and Catalytic Behavior in the Alkylation of Phenol with Tert‐butyl Alcohol

Silver quasi-nanoparticles: bridging the gap between molecule-like clusters and plasmonic nanoparticles

Hydrodeoxygenation of Xylose Isopropylidene Ketal Over Pd/HBEA Catalyst for the Production of Green Fuels

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