scholarly journals Gas-Phase Hydrogenation of Furfural to Furfuryl Alcohol over Cu-ZnO-Al2O3 Catalysts Prepared from Layered Double Hydroxides

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 486
Author(s):  
Guillermo R. Bertolini ◽  
Carmen P. Jiménez-Gómez ◽  
Juan Antonio Cecilia ◽  
Pedro Maireles-Torres
Keyword(s):  
Gas Phase ◽  
Aging Time ◽  
Layered Double Hydroxides ◽  
Furfuryl Alcohol ◽  
Precipitation Method ◽  
Molar Ratio ◽  
X Ray ◽  
General Chemical ◽  
Co Precipitation ◽  
Double Hydroxides

Several layered double hydroxides (LDHs) with general chemical composition (Cu,Zn)1−xAlx(OH)2(CO3)x/2·mH2O have been synthesized by the co-precipitation method, maintaining a (M2+/M3+) molar ratio of 3, and varying the Cu2+/Zn2+ molar ratio between 0.2 and 6.0. After calcination and reduction steps, Cu/ZnO/Al2O3 catalysts were synthesized. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 thermoprogrammed reduction (H2-TPR), N2 adsorption-desorption at −196 °C, N2O titration, X-ray photoelectron miscroscopy (XPS), NH3-thermoprogramed desorption (NH3-TPD) and CO2- thermoprogrammed desorption (CO2-TPD). The characterization data revealed that these catalysts are mainly meso-and macroporous, where Cu, ZnO and Al2O3 are well dispersed. The catalytic results show that these catalysts are active in the gas-phase hydrogenation of furfural, being highly selective to furfuryl alcohol (FOL) and reaching the highest FOL yield for the catalyst with a Cu2+/Zn2+ molar ratio of 1. In an additional study, the influence of the aging time on the synthesis of the LDHs was also evaluated. The catalytic data revealed that the use of shorter aging time in the formation of the LDH has a beneficial effect on the catalytic behavior, since more disordered structures with a higher amount of available Cu sites is obtained, leading to a higher yield towards FOL (71% after 5 h of time-on-stream at 210 °C).

Effect of Doped Iron on Fluoride Sorption by Calcined MgAlFe-CO3 Layered Double Hydroxides

2013 ◽  
Vol 681 ◽  
pp. 21-25
Author(s):  
Yu Bing Pu ◽  
Jia Rui Wang ◽  
Hong Zheng ◽  
Peng Cai ◽  
Si Yuan Wu
Keyword(s):  
Layered Double Hydroxides ◽  
Synthetic Wastewater ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Fluoride Removal ◽  
Maximum Sorption Capacity ◽  
Fluoride Adsorption ◽  
Maximum Sorption ◽  
Co Precipitation ◽  
Double Hydroxides

A series of MgAlFe-CO3 layered double hydroxides (LDHs) were successfully prepared by co-precipitation method. With synthetic wastewater, the effect of doped iron on fluoride sorption by calcined MgAlFe-CO3 layered double hydroxides (CLDH) under different pH and contact time conditions was investigated. The sorption isotherm data were fitted well to Langmuir isotherm at 25 °C. The maximum sorption capacity of fluoride on CLDH increases first and then decreases with the increase of Fe/Al molar ratio and attains maximum of 71.94 mg/g when Fe/Al molar ratio is 1:2, although doped iron is unfavorable to the regeneration of original layered structure for CLDH after fluoride adsorption. No aluminium in the solution after fluoride adsorption was detected when Fe/Al molar ratio is equal to or larger than 1:2. The results indicate that CLDH with proper Fe/Al molar ratio is a promising candidate as an adsorbent material for fluoride removal from aqueous solutions.

scholarly journals Efficient solar heterogeneous photocatalytic degradation of metronidazole using heterojunction semiconductors hybrid nanocomposite, layered double hydroxides

2020 ◽  
Vol 82 (12) ◽  
pp. 2837-2846
Author(s):  
Farid Aoudjit ◽  
Fouzia Touahra ◽  
Lamine Aoudjit ◽  
Ouiza Cherifi ◽  
Djamilla Halliche
Keyword(s):  
Photocatalytic Degradation ◽  
Layered Double Hydroxides ◽  
Environmental Remediation ◽  
Solar Irradiation ◽  
Precipitation Method ◽  
Catalyst Loading ◽  
X Ray ◽  
Constant Ph ◽  
Co Precipitation ◽  
Double Hydroxides

Abstract This study focuses on the synthesis of various nanocomposites with heterojunction structures, MgAl-LDH (LDH = layered double hydroxides) hybrid with semiconductor such as MoO3 and CuO. These solids were synthesized by co-precipitation method at constant pH and have been characterized extensively using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and transmission electron microscopy-energy dispersive X-ray (TEM-EDX) methods. The catalytic activity of nanocomposites was tested in the photocatalytic degradation under solar irradiation of emerging pollutants as the pharmaceutical metronidazole (MNZ). The experimental parameters, including initial MNZ concentration, the nature of oxide incorporate in the photocatalyst, catalyst loading were explored. All the synthesized samples showed high photocatalytic performances; the highest photocatalysis efficiency was achieved with the photocatalyst dose 1.5 g/L and initial MNZ concentration of 10 mg/L at neutral pH. The photocatalytic experimental results were fitted very well to the Langmuir-Hinshelwood model. From the obtained results the calcined LDH/semiconductors could be efficient for the photocatalytic process under solar irradiation of pharmaceuticals and may contribute in environmental remediation.

scholarly journals Mixed Oxide Layered Double Hydroxide Materials: Synthesis, Characterization and Efficient Application for Mn2+ Removal from Synthetic Wastewater

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4089
Author(s):  
Cristina Modrogan ◽  
Simona Cǎprǎrescu ◽  
Annette Madelene Dǎncilǎ ◽  
Oanamari Daniela Orbuleț ◽  
Eugeniu Vasile ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Layered Double Hydroxides ◽  
Synthetic Wastewater ◽  
Precipitation Method ◽  
Metallic Ions ◽  
Materials Synthesis ◽  
Experimental Conditions ◽  
Edx Analysis ◽  
Co Precipitation ◽  
Double Hydroxides

Magnesium–aluminum (Mg-Al) and magnesium–aluminum–nickel (Mg-Al-Ni) layered double hydroxides (LDHs) were synthesized by the co-precipitation method. The adsorption process of Mn2+ from synthetic wastewater was investigated. Formation of the layered double hydroxides and adsorption of Mn2+ on both Mg-Al and Mg-Ni-Al LDHs were observed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDX) analysis. XRD patterns for prepared LDHs presented sharp and symmetrical peaks. SEM studies revealed that Mg-Al LDH and Mg-Al-Ni LDH exhibit a non-porous structure. EDX analysis showed that the prepared LDHs present uniformly spread elements. The adsorption equilibrium on these LDHs was investigated at different experimental conditions such as: Shaking time, initial Mn2+ concentration, and temperatures (10 and 20 °C). The parameters were controlled and optimized to remove the Mn2+ from synthetic wastewater. Adsorption isotherms of Mn2+ were fitted by Langmuir and Freundlich models. The obtained results indicated that the isotherm data fitted better into the Freundlich model than the Langmuir model. Adsorption capacity of Mn2+ gradually increased with temperature. The Langmuir constant (KL) value of Mg-Al LDH (0.9529 ± 0.007 L/mg) was higher than Mg-Al-Ni LDH (0.1819 ± 0.004 L/mg), at 20 °C. The final adsorption capacity was higher for Mg-Al LDH (91.85 ± 0.087%) in comparison with Mg-Al-Ni LDH (35.97 ± 0.093%), at 20 °C. It was found that the adsorption kinetics is best described by the pseudo-second-order model. The results indicated that LDHs can be considered as a potential material for adsorption of other metallic ions from wastewater.

scholarly journals Potential Sustainable Slow-Release Fertilizers Obtained by Mechanochemical Activation of MgAl and MgFe Layered Double Hydroxides and K2HPO4

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 183 ◽  
Author(s):  
Roger Borges ◽  
Fernando Wypych ◽  
Elodie Petit ◽  
Claude Forano ◽  
Vanessa Prevot
Keyword(s):  
Layered Double Hydroxides ◽  
Slow Release ◽  
Mechanochemical Activation ◽  
Molar Ratio ◽  
X Ray ◽  
Dipotassium Hydrogen Phosphate ◽  
Before And After ◽  
Noticeable Improvement ◽  
Slow Release Fertilizers ◽  
Double Hydroxides

This study describes the behavior of potential slow-release fertilizers (SRF), prepared by the mechanochemical activation of calcined Mg2Al-CO3 or Mg2Fe-CO3 layered double hydroxides (LDH) mixed with dipotassium hydrogen phosphate (K2HPO4). The effects of LDH thermal treatment on P/K release behavior were investigated. Characterizations of the inorganic composites before and after release experiments combined X-Ray diffraction (XRD), Fourier-transform infra-red spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The best release profile (<75% in 28 days and at least 75% release) was obtained for MgAl/K2HPO4 (9 h milling, 2:1 molar ratio, MR). Compared to readily used K2HPO4, milling orthophosphate into LDH matrices decreases its solubility and slows down its release, with 60% and 5.4% release after 168 h for MgAl/K2HPO4 and MgFe/K2HPO4 composites, respectively. Mechanochemical addition of carboxymethylcellulose to the LDH/K2HPO4 composites leads to a noticeable improvement of P release properties.

Enhanced catalytic phenol hydroxylation by CuZnFeAl layered double hydroxides: synergistic effects of Cu+ and oxygen vacancies

2021 ◽  
Vol 45 (1) ◽  
pp. 179-188
Author(s):  
Yong Jiang ◽  
Wenlong Xu ◽  
Jinhua Liang ◽  
Jiecan Shen ◽  
Xiaomin Fu ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Oxygen Vacancies ◽  
Synergistic Effects ◽  
Phenol Oxidation ◽  
Precipitation Method ◽  
Phenol Hydroxylation ◽  
Co Precipitation ◽  
Double Hydroxides

In this work, a series of CuZnFeAl-LDH catalysts for phenol oxidation to dihydroxybenzene have been prepared through a co-precipitation method.

Nanoparticles of Cu–Co alloy derived from layered double hydroxides and their catalytic performance for higher alcohol synthesis from syngas

RSC Advances ◽  
2015 ◽  
Vol 5 (72) ◽  
pp. 58804-58812 ◽  
Author(s):  
Ang Cao ◽  
Guilong Liu ◽  
Yizhi Yue ◽  
Lihong Zhang ◽  
Yuan Liu
Keyword(s):  
Layered Double Hydroxides ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Higher Alcohol Synthesis ◽  
Higher Alcohol ◽  
Alcohol Synthesis ◽  
Co Precipitation ◽  
Double Hydroxides

A series of layered double hydroxides (LDHs) with different Cu/Co ratios were prepared according to the co-precipitation method and used as catalyst precursors for higher alcohol synthesis.

scholarly journals Synthesis of hybrid materials based on layered double hydroxides

2019 ◽  
pp. 4-10
Author(s):  
Olga Nestroinaia ◽  
Oksana Ponomarenko
Keyword(s):  
Hybrid Materials ◽  
Layered Double Hydroxides ◽  
Microwave Method ◽  
Hydrothermal Conditions ◽  
Promising Direction ◽  
X Ray ◽  
Constant Ph ◽  
Co Precipitation ◽  
Double Hydroxides ◽  
Scanning Electron

The use of pesticides adversely affects not only the environment, but also human health. A promising direction in solving this problem is to obtain hybrid materials capable of controlled release of pesticides. Layered double hydroxides (LDHs) can act as a matrix. Layered double hydroxides with intercalated glyphosate anions (MgAl-Gly-LDH) were synthesized by different methods: coprecipitation at constant pH (MgAl-Gly-LDH-c), synthesis under hydrothermal conditions (MgAl-Gly-LDH-ht), microwave method (MgAl-Gly-LDH-mw) and rehydration method (MgAl-Gly-LDH-re). All the synthesized samples were analyzed by X-ray phase analysis (XRD), energy dispersive X-ray spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. It is shown that the methods of co-precipitation and synthesis under hydrothermal conditions are most suitable for the synthesis of hybrid materials. Samples of MgAl-Gly-LDH-ht and MgAl-Gly-LDH-c have a well-crystallized structure, unlike the sample of MgAl-Gly-LDH-re, in which the LDH phase is practically absent.

scholarly journals Kinetic Adsorption of Direct Yellow Onto Zn/Al and Zn/Fe Layered Double Hydroxides

2019 ◽  
Vol 4 (4) ◽  
pp. 101
Author(s):  
Neza Rahayu Palapa ◽  
Bakri Rio Rahayu ◽  
Tarmizi Taher ◽  
Aldes Lesbani ◽  
Risfidian Mohadi
Keyword(s):  
Layered Double Hydroxides ◽  
Kinetic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
Bet Method ◽  
Pseudo Second Order ◽  
Time Variations ◽  
Co Precipitation ◽  
Double Hydroxides

Zn/Al and Zn/Fe layered double hydroxides has successfully synthesized by co-precipitation methods with molar ration 3:1. The samples were characterized using X-Ray Diffraction, Fourier Transform Infrared Spectroscopy and Surface Area using BET method. In this study, Zn/Al and Zn/Fe layered double hydroxides were used to remove direct yellow dye in aqueous solution. The experiments were carried out time variations with the aim of observing the kinetic studies. The results showed that the adsorption of direct yellow onto Zn/Al and Zn/Fe layered double hydroxides based on co-efficient correlation kinetic models more fit using pseudo-second-order than pseudo-first-order.

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