A review on effect of synthesis conditions on the formation of layered double hydroxides

2019 ◽  
Vol 269 ◽  
pp. 494-506 ◽  
Author(s):  
M.V. Bukhtiyarova
Keyword(s):  
Layered Double Hydroxides ◽  
Synthesis Conditions ◽  
Double Hydroxides

scholarly journals Modification of Layered Double Hydroxides Using First-Row Transition Metals for Superior UV-Vis-NIR Absorption and the Influence of the Synthesis Method Used

2020 ◽  
Author(s):  
Bianca Gevers ◽  
Sajid Naseem ◽  
Charles Sheppard ◽  
Andreas Leuteritz ◽  
Johan Labuschagne
Keyword(s):  
Transition Metals ◽  
Absorption Spectra ◽  
Layered Double Hydroxides ◽  
Synthesis Method ◽  
Adequate Explanation ◽  
Standard Methods ◽  
Absorption Intensity ◽  
Synthesis Conditions ◽  
Nir Absorption ◽  
Double Hydroxides

<div>Layered double hydroxides (LDHs) with high and tailorable UV-Vis-NIR absorption were prepared through transition</div><div>metal (TM) modification. The synthesis method used and amount of TM present were found to influence the UV-Vis-</div><div>NIR absorption intensity, -range, and the optical bandgap.</div><div><div>It was found that the incorporation of TMs in MgAl-LDH results in the existence of a "UV-Vis-NIR absorption fingerprint", the intensity of which can be tuned by the amount of TM present. There also exist differences in the UV-Vis-NIR absorption spectra and bandgaps obtained for MgAl-LDH synthesised using different synthesis conditions and methods, but these are not as visible when including transition metals. Further, the materials exhibit very complex spectra for which adequate explanation is lacking in literature. Finally, standard methods to determine the bandgap of materials, did not give conclusive results for all materials, only for some, and indicate that some of the materials might have multiple different transition types.</div></div>

scholarly journals Exploring the Wet Mechanochemical Synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al Layered Double Hydroxides from Oxides, Hydroxides and Basic Carbonates

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 954 ◽  
Author(s):  
Brenda Antoinette Barnard ◽  
Frederick Johannes Willem Jacobus Labuschagné
Keyword(s):  
Mechanochemical Synthesis ◽  
Layered Double Hydroxides ◽  
Raw Materials ◽  
Green Method ◽  
Synthesis Conditions ◽  
Starting Point ◽  
Bead Mill ◽  
One Step ◽  
Synthesis Procedure ◽  
Double Hydroxides

The synthesis of Mg-Al, Ca-Al, Zn-Al and Cu-Al layered double hydroxides (LDHs) was investigated with a one-step wet mechanochemical route. The research aims to expand on the mechanochemical synthesis of LDH using a mill designed for wet grinding application. A 10% slurry of solids was added to a Netzsch LME 1 horizontal bead mill and milled for 1 h at 2000 rpm. Milling conditions were selected according to machine limitations and as an initial exploratory starting point. Precursor materials selected consisted of a mixture of oxides, hydroxides and basic carbonates. Samples obtained were divided such that half was filtered and dried at 60 °C for 12 h. The remaining half of the samples were further subjected to ageing at 80 °C for 24 h as a possible second step to the synthesis procedure. Synthesis conditions, such as selected precursor materials and the MII:MIII ratio, were adapted from existing mechanochemical methods. LDH synthesis prior to ageing was successful with precursor materials observably present within each sample. No Cu-Al LDH was clearly identifiable. Ageing of samples resulted in an increase in the conversion of raw materials to LDH product. The research offers a promising ‘green’ method for LDH synthesis without the production of environmentally harmful salt effluent. The synthesis technique warrants further exploration with potential for future commercial up-scaling.

scholarly journals Controlling the Synthesis Conditions for Tuning the Properties of Hydrotalcite-Like Materials at the Nano Scale

2018 ◽  
Vol 2 (3) ◽  
pp. 31 ◽  
Author(s):  
Raquel Trujillano ◽  
Inés González-García ◽  
Alvaro Morato ◽  
Vicente Rives
Keyword(s):  
Hydrothermal Treatment ◽  
Layered Double Hydroxides ◽  
Room Temperature ◽  
The Other ◽  
Synthesis Conditions ◽  
Nano Scale ◽  
Microwave Hydrothermal ◽  
Double Hydroxides

Three series of layered double hydroxides (LDH) with a hydrotalcite-like structure and composition corresponding to [Mg4Al2(OH)12(CO3)]·3H2O have been prepared from a common batch by applying three different aging procedures, namely, stirring at room temperature, hydrothermal treatment, and microwave-hydrothermal treatment. It has been found that the tested properties of the samples (mainly related to their crystallinity) are considerably improved by using the microwave-hydrothermal treatment. Shorter times are also evinced than in the other two aging treatments; however, if the microwave-hydrothermal treatment is too far extended, incipient destruction of the particles is observed.

Experimental Design for the Optimization of the Synthesis Conditions of Zn-Al-Layered Double Hydroxides Nanoparticles Based on X-ray Diffraction Data

2015 ◽  
Vol 608 (1) ◽  
pp. 177-189 ◽  
Author(s):  
Kamellia Nejati ◽  
Hassan Keypour ◽  
Parvaneh Delir Kheirollahi Nezhad ◽  
Karim Asadpour-zeynali ◽  
Zolfaghar Rezvani
Keyword(s):  
Experimental Design ◽  
Layered Double Hydroxides ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Double Hydroxides

scholarly journals Modification of Layered Double Hydroxides Using First-Row Transition Metals for Superior UV-Vis-NIR Absorption and the Influence of the Synthesis Method Used

2020 ◽  
Author(s):  
Bianca Gevers ◽  
Sajid Naseem ◽  
Charles Sheppard ◽  
Andreas Leuteritz ◽  
Johan Labuschagne
Keyword(s):  
Transition Metals ◽  
Absorption Spectra ◽  
Layered Double Hydroxides ◽  
Synthesis Method ◽  
Adequate Explanation ◽  
Standard Methods ◽  
Absorption Intensity ◽  
Synthesis Conditions ◽  
Nir Absorption ◽  
Double Hydroxides

<div>Layered double hydroxides (LDHs) with high and tailorable UV-Vis-NIR absorption were prepared through transition</div><div>metal (TM) modification. The synthesis method used and amount of TM present were found to influence the UV-Vis-</div><div>NIR absorption intensity, -range, and the optical bandgap.</div><div><div>It was found that the incorporation of TMs in MgAl-LDH results in the existence of a "UV-Vis-NIR absorption fingerprint", the intensity of which can be tuned by the amount of TM present. There also exist differences in the UV-Vis-NIR absorption spectra and bandgaps obtained for MgAl-LDH synthesised using different synthesis conditions and methods, but these are not as visible when including transition metals. Further, the materials exhibit very complex spectra for which adequate explanation is lacking in literature. Finally, standard methods to determine the bandgap of materials, did not give conclusive results for all materials, only for some, and indicate that some of the materials might have multiple different transition types.</div></div>

Cu layered double hydroxides as catalysts for N-methylation of p-anisidine: Influence of synthesis conditions

2019 ◽  
Vol 127 ◽  
pp. 39-44 ◽  
Author(s):  
M.V. Bukhtiyarova ◽  
A.L. Nuzhdin ◽  
A.V. Bukhtiyarov ◽  
T.Y. Kardash ◽  
A.V. Romanenko
Keyword(s):  
Layered Double Hydroxides ◽  
Synthesis Conditions ◽  
Double Hydroxides

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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