Suppression of Spinel Formation to Induce Reversible Thermal Behavior in the Layered Double Hydroxides (LDHs) of Co with Al, Fe, Ga, and In

2007 ◽  
Vol 111 (13) ◽  
pp. 3384-3390 ◽  
Author(s):  
Radha ◽  
Grace S. Thomas ◽  
P. Vishnu Kamath ◽  
C. Shivakumara
Keyword(s):  
Thermal Behavior ◽  
Layered Double Hydroxides ◽  
Spinel Formation ◽  
Double Hydroxides

Thermal Behavior of Oxometalate (Mo, W)-Intercalated Layered Double Hydroxides: Study of the Grafting Phenomenon

2002 ◽  
Vol 167 (1) ◽  
pp. 59-72 ◽  
Author(s):  
C. Vaysse ◽  
L. Guerlou-Demourgues ◽  
A. Demourgues ◽  
C. Delmas
Keyword(s):  
Thermal Behavior ◽  
Layered Double Hydroxides ◽  
Double Hydroxides

Observation of a Collapsing Layer Structure in Mg/Al Layered Double Hydroxides with Interlayer Hydrogen Phosphate by High Temperature In Situ X-Ray Diffraction with Synchrotoron Radiation

2011 ◽  
Vol 700 ◽  
pp. 67-70
Author(s):  
Akihiro Shimamura ◽  
Linus Perander ◽  
Eiji Kanezaki ◽  
Mark Ian Jones ◽  
James B. Metson
Keyword(s):  
High Temperature ◽  
Thermal Behavior ◽  
Layered Double Hydroxides ◽  
Layer Structure ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Hydrogen Phosphate ◽  
X Ray ◽  
Double Hydroxides

The collapsing layer structure of hydrogen phosphate intercalated Mg/Al-layered double hydroxides (LDH-HPO4) was investigated by high temperature in-situ X-ray diffraction with synchrotron radiation (in-situ XRD). The thermal behavior of the layer structure of LDH-HPO4 showed the same behavior in both in-situ and ex-situ XRD up until 109 °C as previously reported. The basal spacing of LDH-HPO4 continuously decreases above this temperature and finally the layer structure of LDH-HPO4 collapses. Another diffraction peak, d110, which gives a lattice constant a0, decreases at 62 °C, keeps constant to 120°C, increases up to 176°C and again keeps constant until the layer collapse. In this study, the different thermal behavior is observed between two reflections by in-situ XRD measurement, which explains the mechanism of the collapse of the layer structure in LDH-HPO4.

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>

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