scholarly journals Synthesis and Characterization of Novel Pyridine Periodic Mesoporous Organosilicas and Its Catalytic Activity in the Knoevenagel Condensation Reaction

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1097 ◽  
Author(s):  
Fatemeh Rajabi ◽  
Arezoo Zare Ebrahimi ◽  
Ahmad Rabiee ◽  
Antonio Pineda ◽  
Rafael Luque
Keyword(s):  
Catalytic Activity ◽  
Knoevenagel Condensation ◽  
Condensation Reaction ◽  
Nitrogen Adsorption ◽  
Magic Angle Spinning ◽  
Catalyst Stability ◽  
Magic Angle ◽  
Mesoporous Organosilica ◽  
Angle Spinning ◽  
Mesoporous Organosilicas

The preparation of novel organic-inorganic hybrid mesoporous organosilica containing pyridinedicarboxamide functional groups uniformly distributed inside the nanostructured pore walls has been addressed. The mesoporosity and uniformity of the synthesized nanomaterials were characterized by different techniques such as nitrogen adsorption/desorption measurements and powder X-ray diffraction (PXRD). Additionally, the presence of the pyridinedicarboxamide in the pore walls of the nanomaterials was assessed by Fourier-transform infrared spectroscopy (FT-IR), as well as 29Si and 13C solid-state cross-polarization and magic angle spinning nuclear magnetic resonance (CP/MAS-NMR). The Knoevenagel condensation of aldehydes with active methylene compounds was carried out over the pyridinedicarboxamide functionalized mesoporous organosilica, which has been proven to be an efficient heterogeneous basic catalyst in the presence of ethanol as solvent. The catalytic activity of the investigated materials was investigated in the Knoevenagel condensation between malononitrile and several benzaldehyde derivatives exhibiting a high conversion (>90%) and excellent selectivity toward the final condensation products under very mild reaction conditions. Furthermore, the catalyst stability is noteworthy as it could be recycled and reused at least twelve times without any significant change in the performance.

Rattle-Type Diamine-Functionalized Mesoporous Silica Sphere for Carbon Dioxide Adsorption

2018 ◽  
Vol 53 ◽  
pp. 13-21 ◽  
Author(s):  
Ning Yuan ◽  
Zhi Wei Liu ◽  
Li Yan Wang ◽  
Bao Hang Han
Keyword(s):  
Carbon Dioxide ◽  
Mesoporous Silica ◽  
Nitrogen Adsorption ◽  
Magic Angle Spinning ◽  
Silica Sphere ◽  
Magic Angle ◽  
Templating Method ◽  
Functionalized Mesoporous Silica ◽  
Angle Spinning ◽  
Mesoporous Silica Sphere

A rattle-type diamine-functionalized mesoporous silica sphere (DA-RMSS) was fabricated stepwise using a self-templating method through cationic surfactant assisted selective etching strategy. The rattle-type morphology of the obtained DA-RMSS material was disclosed by transmission electron microscopy, while its chemical composition was characterized by CHN elemental analysis, Fourier transform infrared spectroscopy, and solid-state 29Si cross-polarization/magic-angle-spinning nuclear magnetic resonance spectroscopic measurement, which corroborates the successful formation of siloxane network and the incorporation of organic component. Moreover, nitrogen adsorption–desorption isotherm measurement was conducted to reveal that DA-RMSS possesses large Brunauer–Emmett–Teller (BET) specific surface area of 814 m2g–1, pore volume of 0.78 cm3g–1, and narrow pore size distribution centered at 3.0 nm. Furthermore, its uptake property on carbon dioxide was also investigated in this contribution.

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

Wideline 2H -NMR Spectroscopy and Imaging of Solids

1994 ◽  
Vol 49 (1-2) ◽  
pp. 19-26 ◽  
Author(s):  
B. Blümich
Keyword(s):  
Nmr Spectroscopy ◽  
Excitation Power ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
2H Nmr ◽  
Stochastic Excitation ◽  
2H Nmr Spectroscopy ◽  
Spatially Inhomogeneous ◽  
Recent Developments ◽  
Angle Spinning

Abstract Recent developments, focussing on reduction of the rf excitation power by stochastic excitation, on improvements in sensitivity and excitation bandwidth by magic angle spinning, and on combining wideline spectroscopy with spatial resolution for investigations o f spatially inhomogeneous objects are reviewed.

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