scholarly journals Introduction of Al into the HPM-1 Framework by In Situ Generated Seeds as an Alternative Methodology

2018 ◽  
Vol 8 (9) ◽  
pp. 1634 ◽  
Author(s):  
Paloma Vinaches ◽  
Alex Rojas ◽  
Ana de Alencar ◽  
Enrique Rodríguez-Castellón ◽  
Tiago Braga ◽  
...  
Keyword(s):  
Textural Properties ◽  
Magic Angle Spinning ◽  
Ethanol Conversion ◽  
Magic Angle ◽  
Pure Silica ◽  
Acidic Sites ◽  
Alternative Methodology ◽  
Angle Spinning ◽  
Zeolitic Framework

An alternative method for the introduction of aluminum into the STW zeolitic framework is presented. HPM-1, a chiral STW zeolite with helical pores, was synthesized in the pure silica form, and an aluminum source was added by in situ generated seeds. Displacements of the peak positions in the Al samples were found in the X-ray diffractograms, indicating the possible incorporation of the heteroatom into the framework. Using an analysis of the 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra, we concluded that the aluminum was effectively introduced into the framework. The (AlTETRAHEDRAL/AlOCTAHEDRAL) ratio and its textural properties were studied to explain the catalytic ethanol conversion results at medium temperatures. The sample with the lowest Si/Al ratio showed the best results due to its higher surface area and pore volume, in comparison to those observed for the sample with the highest Si/Al ratio, and due to its higher bulk tetrahedral aluminum content, in comparison to the intermediate Si/Al ratio sample. All catalysts were selective to ethylene and diethyl ether, confirming the presence of acidic sites.

Continuous Flow Hyper-Polarized 129Xe-Mas Nmr Studies of Microporous Materials.

2003 ◽  
Vol 775 ◽  
Author(s):  
Andrei Nossov ◽  
Flavien Guenneau ◽  
Marie-Anne Springuel-Huet ◽  
Valérie Montouillout ◽  
Jean-Pierre Cognec ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Nmr Spectra ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Original Design ◽  
Nmr Studies ◽  
Powder Samples ◽  
Angle Spinning

Summary:A Magic Angle Spinning (MAS) NMR probe has been designed allowing the in-situ measurements of NMR spectra of working catalyst. The probe was built following the original design of M. Hunger [Hunger, 1995 #2]. It allows the magic angle spinning of powder samples up to 3.5 kHz, under gas flowing conditions, and at temperatures up to 573K.

Lithium-7 NMR Studies of Li1−xCoO2 Battery Cathodes

1994 ◽  
Vol 369 ◽  
Author(s):  
B. Ouyang ◽  
X. Cao ◽  
H.W. Lin ◽  
S. Slane ◽  
S. Kostov ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Parent Compound ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
Relaxation Measurements ◽  
Angle Spinning

AbstractLithium-deficient cathode materials Li1-xCoO2 where x = 0.1, 0.4 and 0.6 were prepared electrochemically from the stoichiometric parent compound (x = 0.0).The materials were observed to be air-stable, and x-ray diffraction characterization yielded good agreement with the in situ studies of Dahn and co-workers, regarding changes in lattice parameters. In addition to both static and magic angle spinning (MAS) 7Li NMR, measurements, the samples were investigated by EPR and cobalt K-edge NEXAFS. The removal of Li is accompanied by compensating electrons from the Co d-orbitals, asevidenced by both shifts in the NEXAFS peak and the observation of EPR signals due to spins localized on the Co ions. These spins, in turn, result in dramatic 7Li chemical shifts (89 ppm for x = 0.6) and line broadening. Whereas MAS analysis of Li0.9CoO2 indicates two magnetically inequivalent Li sites, the spectra becometoo broad to resolve different sites for higher values of x. Finally NMR linewidth and spinlattice relaxation measurements as a function of temperature suggest a modest increase in Li+ ion mobility for Li-deficient samples as compared to the parent compound.

scholarly journals An NMR Investigation of Phase Structure and Chain Dynamics in the Polyethylene/Montmorillonite Nanocomposites

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Wei Li ◽  
Linxi Hou ◽  
Zhongren Chen
Keyword(s):  
Phase Structure ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Chain Dynamics ◽  
Chain Mobility ◽  
The Difference ◽  
Angle Spinning ◽  
Cp Mas Nmr

Novel exfoliated and interacted polyethylene (PE)/montmorillonite (MMT) nanocomposites prepared byin situpolymerization were characterized by solid-state nuclear magnetic resonance (NMR). The phase structure and molecular mobility were investigated by proton and carbon NMR under static and magic-angle spinning (MAS) conditions. The results showed that incorporation of MMT layer enhanced the polyethylene crystallinity behavior. The chain mobility of crystalline phase, interphase and amorphous phase was hindered in the nanocomposites. The phase structure and chain dynamics were also investigated upon changing the temperature. The orthorhombic and monoclinic phases were detected according to the13CP/MAS NMR. Quantitative characterization of the phase structure was also conducted by13C DP/MAS upon changing the temperature. Finally, the difference in the phase structure and chain dynamics in each phase of PE/nanocomposites was compared based on the NMR results when fiber filler was introduced.

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