scholarly journals Influence of Dry Milling on Phase Transformation of Sepiolite upon Alkali Activation: Implications for Textural, Catalytic and Sorptive Properties

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3936
Author(s):  
Anna Walczyk ◽  
Robert Karcz ◽  
Joanna Kryściak-Czerwenka ◽  
Bogna D. Napruszewska ◽  
Dorota Duraczyńska ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Magnesium Silicate ◽  
Magic Angle Spinning ◽  
Planetary Mill ◽  
Alkali Activation ◽  
Magic Angle ◽  
Surface Basicity ◽  
Angle Spinning ◽  
Adsorption Desorption ◽  
Synthesized Materials

Activation of natural sepiolite by means of grinding in a planetary mill followed by wet NaOH activation was studied for the purpose of endowing the product with enhanced basicity for potential catalytic/sorptive applications. Synthesized solids were characterized with X-ray powder diffraction (XRD), N2 adsorption/desorption, scanning electron microscopy (SEM), energy dispersive (EDX), atomic absorption (AAS), Fourier-transform infrared (FTIR) and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies. Surface basicity was determined by titration with benzoic acid. Grinding changed the pathway of sepiolite phase transformation upon NaOH treatment. The as-received sepiolite evolved to Na-sepiolite (loughlinite) with a micropore system blocked by nanocrystalline Mg(OH)2, while ground samples yielded magnesium silicate hydrate phase (MSH), with well-developed microporous texture. In unmilled sepiolite desilication involved preferential leaching of Si from the center of the structural ribbons, while in ground samples additional loss of Si from ribbon-ribbon corner linkages was observed. In all cases treatment with NaOH led to enhancement of surface basicity. Synthesized materials were tested as catalysts in a base-catalyzed aldol self-condensation of acetone and oxidation of cyclohexanone to ε-caprolactone, as well as CO2 sorbents. Catalytic trends depended not only on samples’ basicity, but also on texture and phase composition of the catalysts. Grinding combined with alkali activation proved a simple and effective method for boosting CO2-sorption capacity of sepiolite to the level comparable to amine-functionalized, acid-activated sepiolite sorbents.

Synthesis and Characterization of Hierarchical ZSM-48 Zeolite

2012 ◽  
Vol 503-504 ◽  
pp. 756-759 ◽  
Author(s):  
Xiao Ling Liu ◽  
Xu Jin Wang ◽  
Yan Wang ◽  
Yan Jun Gong ◽  
Tao Dou
Keyword(s):  
Electron Microscope ◽  
Textural Properties ◽  
Total Surface Area ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
Secondary Porosity ◽  
Transmission Electron ◽  
Angle Spinning ◽  
Adsorption Desorption

A series of hierarchical ZSM-48 zeolites was prepared by seed silanization. The structural and textural properties of the hierarchical ZSM-48 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), and Fourier transform infrared spectroscopy adsorbed by pyridine (Py-IR). It was found that the crystal size of ZSM-48 was significantly reduced by seed silanization. Due to the secondary porosity in the mesopore region generated in hierarchical ZSM-48, both the total surface area and the pore volume of the material have a considerable increase. The enhancement of the textural properties could be controlled by changing the amount of silanizaiton agent.

Aerosol-generated mesoporous silicon oxycarbide particles

2009 ◽  
Vol 81 (8) ◽  
pp. 1449-1457 ◽  
Author(s):  
Alberto Pauletti ◽  
Guillaume Moskowitz ◽  
Thomas Millan ◽  
Cristina Fernández-Martín ◽  
Cédric Boissière ◽  
...  
Keyword(s):  
Inert Atmosphere ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Silicon Oxycarbide ◽  
Magic Angle ◽  
Mesoporous Silicon ◽  
Mesoporous Organosilica ◽  
Transmission Electron ◽  
Angle Spinning ◽  
Adsorption Desorption

Aerosol-generated mesoporous organosilica submicronic spheres have been converted into porous silicon oxycarbide (SiCO) glasses by pyrolysis at 1000 °C in an inert atmosphere. Spherical mesoporous particles obtained from acidic solutions of 1,2-bis(triethoxysilyl)ethane and Pluronic® F127 structuring agent were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption, and multinuclear solid-state magic-angle spinning (MAS) NMR. These particles were then pyrolyzed at 1000 °C and transformed into a SiCO phase as evidenced by 29Si MAS NMR, while TEM shows preserved mesoporosity, unfortunately difficult to access owing to the presence of an outer layer of dense silica.

Design of composite micro/mesoporous molecular sieve catalysts

2004 ◽  
Vol 76 (9) ◽  
pp. 1647-1657 ◽  
Author(s):  
I. I. Ivanova ◽  
A. S. Kuznetsov ◽  
V. V. Yuschenko ◽  
E. E. Knyazeva
Keyword(s):  
Mesoporous Materials ◽  
Active Sites ◽  
Nitrogen Adsorption ◽  
Mesoporous Molecular Sieve ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
Temperature Programmed ◽  
Angle Spinning ◽  
Adsorption Desorption

Two series of composite micro/mesoporous materials with different contributions of micro- and mesoporosity were prepared by dealumination and recrystallization of mordenite zeolite. The materials were characterized by X-ray diffraction, infrared spectroscopy, 27Al magic angle spinning (MAS) NMR, nitrogen adsorption–desorption, and temperature-programmed desorption of ammonia (TPD NH3). Catalytic properties were studied in transalkylation of biphenyl with diisopropylbenzene. Both types of composite materials showed remarkably high activity, stability, and selectivity toward formation of di-isopropylbiphenyls with respect to both pure microporous and mesoporous materials. The effect is due to high zeolitic acidity combined with improved accessibility of active sites and transport of bulky molecules provided by mesopores.

Chemical Evolution of the Volcanic Tuff from the Santa Mónica Church in Guadalajara, Mexico

2012 ◽  
Vol 1374 ◽  
pp. 195-203
Author(s):  
Nora A. Pérez ◽  
Enrique Lima
Keyword(s):  
Thermo Gravimetric Analysis ◽  
Nitrogen Adsorption ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Gravimetric Analysis ◽  
Structural Level ◽  
Volcanic Tuff ◽  
Santa Monica ◽  
Angle Spinning ◽  
Adsorption Desorption

ABSTRACTThe Santa Mónica Church is one of the most representative buildings in Guadalajara, Mexico as it is the finest Solomonic Baroque temple in the city. The church was built in the XVIII century with different types of volcanic tuffs, which have been studied from the macroscopic level to the structural level with the aim to determine the deterioration degree of the church’s tuffs.Textural, morphological and structural properties of Tuff were characterized using X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR ATR) and 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR), nitrogen adsorption-desorption techniques, scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), compressive strength tests were also performed.Characterization data has provided a comprehensive view of the alterations on the volcanic tuff of Santa Mónica Church. Then the study focused on proposing the best strategy for the understanding and conservation of Churches and other buildings in Guadalajara which have been built with the same stone. Currently, siliceous materials doped with aluminum are being tested as consolidate.

Pulse Shaped Dynamic Nuclear Polarization Under Magic Angle Spinning

2019 ◽  
Author(s):  
ASIF EQUBAL ◽  
Kan Tagami ◽  
Songi Han
Keyword(s):  
Electron Spin ◽  
Lattice Relaxation ◽  
Magic Angle Spinning ◽  
Spin Lattice Relaxation ◽  
Magic Angle ◽  
Total Electron ◽  
Spin Lattice ◽  
Maximum Benefit ◽  
Selective Saturation ◽  
Angle Spinning

In this paper, we report on an entirely novel way of improving the MAS-DNP efficiency by shaped μw pulse train irradiation for fast and broad-banded (FAB) saturation of the electron spin resonance. FAB-DNP achieved with Arbitrary Wave Generated shaped μw pulse trains facilitates effective and selective saturation of a defined fraction of the total electron spins, and provides superior control over the DNP efficiency under MAS. Experimental and quantum-mechanics based numerically simulated results together demonstrate that FAB-DNP significantly outperforms CW-DNP when the EPR-line of PAs is broadened by conformational distribution and exchange coupling. We demonstrate that the maximum benefit of FAB DNP is achieved when the electron spin-lattice relaxation is fast relative to the MAS frequency, i.e. at higher temperatures and/or when employing metals as PAs. Calculations predict that under short T<sub>1e </sub>conditions AWG-DNP can achieve as much as ~4-fold greater enhancement compared to CW-DNP.

High Resolution Magic Angle Spinning NMR in Combinatorial Chemistry

2001 ◽  
Vol 4 (4) ◽  
pp. 333-351 ◽  
Author(s):  
G. Lippens ◽  
R. Warrass ◽  
J. Wieruszeski ◽  
P. Rousselot-Pailley ◽  
G. Chessari
Keyword(s):  
High Resolution ◽  
Combinatorial Chemistry ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Angle Spinning
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