The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy

Rodríguez-González, L.; Hermes, Florian; Bertmer, Marko; Rodríguez‐Castellón, Enrique; Jiménez‐López, Antonio; Simon, Ulrich

doi:10.1016/j.apcata.2007.06.003

Cited by 325 publications

(183 citation statements)

References 32 publications

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“…8. Two notable peaks, at 250°C representing the weak acid sites and 450°C representing the strong acid ones [30,31]. According to the areas of the NH 3 -TPD profiles, the relative acid densities can be calculated and estimated, indicating that the total acid densities of ZSM-5 zeolites were slightly increased after alkali-and acid-treatment.…”

Section: Acidity Of Zeolitesmentioning

confidence: 99%

A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

Yuan

Tang

et al. 2014

J Porous Mater

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Desilicication and dealuminzation with weak alkaline solution and acid liquor is an effective way to construct hierarchically mesoporous without damaging its crystallinity and preserving its acidity in ZSM-5 zeolites. We investigated the influence of the concentration of NaAlO 2 , treatment time, temperature and the concentration of HCl on the crystallinity of ZSM-5 and characterized the products with XRD, SEM, XRF, BET, NH 3 -TPD, etc. The results showed that the appropriate concentration of NaAlO 2 solutions extract selectively silicon from the framework of the zeolites while a small portion of aluminum would patch some parts of vacancies produced by the removal of silicon, then the HCl would dealuminize to maintain the SiO 2 /Al 2 O 3 ratios, which preserved the crystallinity of ZSM-5 perfectly. Furthermore, the micro-reaction activity tests displayed that the obtained products had higher catalytic than the parent zeolites because of their optimized hierarchical micro-mesoporous.

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Section: Acidity Of Zeolitesmentioning

confidence: 99%

A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

Yuan

Tang

et al. 2014

J Porous Mater

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“…Microcalorimetry, [14][15][16] temperature-programmed desorption (TPD), 17,18 infrared (IR) [19][20][21][22][23][24][25][26][27] and nuclear magnetic resonance (NMR) spectroscopy 17,28 are among other experimental techniques some of the most frequently used ones. A fundamental challenge of zeolite acidity characterisation is that different experimental techniques provide different aspects of the zeolite acidity, which includes type, number, location and strength of acid sites.…”

mentioning

confidence: 99%

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

Bräuer

Situmorang

et al. 2017

RSC Adv.

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In this work, we have systematically investigated the effect of the Al content on the number and location of bridging hydroxyls (Brønsted acid sites) and terminal hydroxyls (terminal silanol sites) in ZSM-5 zeolites with varying silica-alumina ratio (SAR ¼ SiO 2 /Al 2 O 3 ) using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) without molar extinction coefficients. Two base probe molecules with different kinetic diameters, pyridine (5.7Å) and collidine (7.4Å), were used. The total content of Brønsted acid sites is obtained by elemental analysis of the proton form and sodium exchanged form of ZSM-5. To quantify the number of internal and external Brønsted acid sites the change in area of the Brønsted acid site peak in the O-H stretching region is then used; thus, the need for molar extinction coefficients to quantify Brønsted acid sites is thereby eliminated. The results reported here show that for ZSM-5 the number of external Brønsted sites, in absolute terms, increases with increasing total Al content, as evidenced by collidine adsorption. The number of terminal silanol acid sites was found to be proportional to the external surface area probed by argon sorption experiments. In summary, this work shows that the use of DRIFTS in conjunction with elemental analysis is a valid alternative to qualitatively and quantitatively probe the number and location of hydroxyl acid sites without the use of molar extinction coefficients and gives a comprehensive picture of the effect of Al content on number and location of hydroxyl acid species in ZSM-5 zeolites with varying SAR. The work contributes to advancing the range of characterisation protocols for solid acid catalysts.

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“…Fig.3. In Fig.3 curve a, the reduction peak at 197 °C can be attributed to the reduction of ruthenium oxide [24] . When the addition amount of lanthanum was 3%, the reduction temperature of ruthenium oxide increased from 197 °C [25] for the monometallic Ru catalyst to 261 °C for 4%Ru-3%La/γ-Al 2 O 3 (I) and the reduction peak intensity of ruthenium oxide became weak( Fig.3 curve b).…”

Section: Characterization Of Catalystsmentioning

confidence: 95%

“…Because of the weak polarity and intrinsic steric hindrance of carboxylic group [7] , the hydrogenation of carboxylic acids and esters is very difficult. For instance, the hydrogenation of esters over copper-based catalysts, which are widely used in industry [8] , is carried out at a high temperature of 200-300 °C and a high hydrogen pressure of [20][21][22][23][24][25][26][27][28][29][30] MPa. Therefore, to develop an active catalyst system for the hydrogenation of esters to the corresponding alcohols under a mild condition is of great importance in research as well as in industry.…”

Section: Introductionmentioning

confidence: 99%

Effect of lanthanum on catalytic performance of Ru/Al2O3 catalyst for hydrogenation of esters to corresponding alcohols

Zhang

Zheng

2015

Chem. Res. Chin. Univ.

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Ru-La/γ-Al 2 O 3 catalyst was prepared by impregnation method and characterized by temperature programmed reduction(TPR), transmission electron microscopy(TEM), X-ray photoelectron spectra(XPS), BrunauerEmmett-Teller(BET), X-ray diffraction(XRD), and NH 3 -temperature programmed desorption(NH 3 -TPD). NH 3 -TPD revealed that the strong acidic centers in γ-Al 2 O 3 are not the major factor to cause the hydrolysis of esters to acids in the hydrogenation of esters. The results of TPR and TEM indicate that the appropriately added lanthanum results in the good dispersion of ruthenium and the easy reduction of ruthenium oxide on Ru-La/γ-Al 2 O 3 , which could promote the catalytic activity of Ru-La/γ-Al 2 O 3 for the hydrogenation of methyl propionate to propanol. When the amount of lanthanum added in the catalyst was up to 9%(mass fraction), 4%Ru-9%La/γ-Al 2 O 3 catalyst gave a conversion of methyl propionate of 98.1% and a selectivity of 94.8% to propanol at a reaction temperature of 180 °C and a hydrogen pressure of 5.0 MPa.

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The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy

Cited by 325 publications

References 32 publications

A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

Effect of lanthanum on catalytic performance of Ru/Al2O3 catalyst for hydrogenation of esters to corresponding alcohols

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