Trivalent Cation Substitution Effect into Layered Double Hydroxides Co2Fey Al1−y(OH)6Cl·nH2O: Study of the Local Order

2002 ◽  
Vol 167 (2) ◽  
pp. 508-516 ◽  
Author(s):  
Mourad Intissar ◽  
Rachid Segni ◽  
Christophe Payen ◽  
Jean-Pierre Besse ◽  
Fabrice Leroux
Keyword(s):  
Layered Double Hydroxides ◽  
Substitution Effect ◽  
Local Order ◽  
Trivalent Cation ◽  
Cation Substitution ◽  
Double Hydroxides ◽  
Cation Substitution Effect

scholarly journals Cation Substitution Effect on a Molecular Analogue of Perovskite Manganites

2017 ◽  
Vol 121 (20) ◽  
pp. 10893-10898 ◽  
Author(s):  
Yun-Peng Wang ◽  
Xiang-Guo Li ◽  
X.-G. Zhang ◽  
George Christou ◽  
Hai-Ping Cheng
Keyword(s):  
Substitution Effect ◽  
Perovskite Manganites ◽  
Cation Substitution ◽  
Cation Substitution Effect

Substitution Effect in the Ion Conductor Li3InBr6, Studied by Nuclear Magnetic Resonance

2002 ◽  
Vol 57 (6-7) ◽  
pp. 447-450 ◽  
Author(s):  
Yasumasa Tomita ◽  
Hiroshi Yonekura ◽  
Yasuo Yamauchi ◽  
Koji Yamada ◽  
Kenkichiro Kobayashi
Keyword(s):  
Nmr Spectra ◽  
Substitution Effect ◽  
The Other ◽  
Temperature Phase ◽  
Cation Substitution ◽  
Ion Conductor ◽  
X Ray ◽  
Lattice Constants ◽  
Low Temperature Phase ◽  
Cation Substitution Effect

Li3-2x Mg InBr6 (x= 0.02 - 0.4) was synthesized, and the cation substitution effect on the conductivity was investigated by means of 7Li and 115In NMR, and X-ray diffraction.With increasing x the lattice constants a and c increased, but b and β did not show significant changes. The conductivity of the low temperature phase increased with x, associated with a narrowing of the 7Li NMR spectra. In the high temperature superionic phase, on the other hand, the conductivity decreased with x accompanied by a broadening of the 115In NMR spectra

scholarly journals Investigation of layered double hydroxides type ZnMgAl-carbonate and derivates.

2014 ◽  
Vol 70 (a1) ◽  
pp. C1100-C1100
Author(s):  
Weberton do Carmo ◽  
Gustavo de Carvalho ◽  
Juliana da Silva ◽  
Luciano Chagas ◽  
Alexandre Leitão ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Mixed Oxides ◽  
Inorganic Materials ◽  
Precipitation Method ◽  
Trivalent Cation ◽  
Catalyst Precursor ◽  
Step Size ◽  
Co Precipitation ◽  
Double Hydroxides ◽  
Urea Method

Layered double hydroxides (LDHs) or hydrotalite-like compounds belong to a class of synthetic two-dimensional inorganic materials with lamellar structures, where the hydroxyl-hydrated compounds are formed by chemical substitution of divalent ion of the brucite-like octahedral layers by trivalent ions [1]. The LDH are represented by the general formula, Figure a , where M2+, M3+ are divalent and trivalent cation and Am- is interlayer anion responsible by charge balancing, the range of divalent and trivalent ions (x) varies normally between 0.17 a 0.33. According Montanari and co-works [2] compounds type ZnAl-hydrotalcites (ZnAl-HT) have relevant industrial interest; however the scientific literature concerning this material as catalysts or catalyst precursor is scarce. Based on this fact, in the present communication we will present a studied on how the variation in percentage of Zinc in a ZnMgAl-HT catalyst precursor can influence the formation of mixed oxides after calcination. The ZnMgAl-HTs, Figure b , y=5, 10,15,20,25,50,75 and 100% were prepared by co-precipitation and urea method. Mg-Zn/Al mixed oxides were prepared from calcinations of hydrotalcites precursors at 5000C for 4 hours. The material synthesized were characterized by X-ray powder diffraction, the measurements were carried out in Bruker D8 DaVinci diffractometer, equipped with CuKα radiation , LynxEye linear Position Sensitive Detector, Ni-filter. Data was collect between 8 and 800in 2θ with step size of 0.020and the count time of 0.05 per step. Soller slit 2.50of divergence and 0.2 mm primary slit were used. For the ZnMgAl-HT samples the measurements were performed at different temperatures, range 25-12000C, heating rate 50C/min. It was observed differences among XRD patterns for y greater than 25% of Zn in urea method at 5000C, and for co-precipitation method just for the substitution at 50 and 75% of Zn. These results suggested that the increase in Zn percentage change the structure of calcinated samples.

Acceptorless amine dehydrogenation and transamination using Pd-doped layered double hydroxides

2018 ◽  
Author(s):  
Diana Ainembabazi ◽  
Nan An ◽  
Jinesh Manayil ◽  
Kare Wilson ◽  
Adam Lee ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Oxidation States ◽  
Secondary Amines ◽  
Primary Amines ◽  
Acid Dissolution ◽  
Oxidative Amination ◽  
Strong Function ◽  
Excellent Activity ◽  
High Yields ◽  
Double Hydroxides

<div> <p>The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity. Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation.</p> </div> <br>

Antibiotic-anionic Clay Matrix Used for Drug Controlled Release

2018 ◽  
Vol 69 (2) ◽  
pp. 321-323
Author(s):  
Georgeta Zegan ◽  
Elena Mihaela Carausu ◽  
Loredana Golovcencu ◽  
Alina Sodor Botezatu ◽  
Eduard Radu Cernei ◽  
...  
Keyword(s):  
Controlled Release ◽  
Layered Double Hydroxides ◽  
Bioactive Molecules ◽  
Drug Controlled Release ◽  
Anionic Clays ◽  
Anionic Clay ◽  
Toxicological Studies ◽  
High Efficient ◽  
Clay Matrix ◽  
Double Hydroxides

Anionic clay matrix acting as drug controlled release system have shown in last years a great potential for delivery of bioactive molecules and chemical therapeutics. This organic-inorganic nanohybrid system is high efficient offering an excellent protection of intercalated compounds from degradation. Compared to other nanoparticles used in medical area, anionic clays type layered double hydroxides have found to be biocompatible according to toxicological studies. Ampicillin containing MgAlLDHs and ZnAlLDH samples have been prepared following two routes: anion-exchange procedure and reconstruction from calcined layered double hydroxides. Solid samples have been characterized by FTIR and SEM-EDX highlighting the alteration of pristine LDHs structure when the antibiotic is introduced in the interlayer gallery.

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