Effect of Synthesis Method on Properties of Layered Double Hydroxides Containing Ni(III (original) (raw)
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Journal of Solid State Chemistry, 2009
The Ni-Al layered double hydroxides (LDHs) with Ni/Al molar ratio of 2, 3, and 4 were prepared by coprecipitation and treated under hydrothermal conditions at 180 1C for times up to 20 h. Thermal decomposition of the prepared samples was studied using thermal analysis and high-temperature X-ray diffraction. Hydrothermal treatment increased significantly the crystallite size of coprecipitated samples. The characteristic LDH diffraction lines disappeared completely at ca. 350 1C and a gradual crystallization of NiO-like mixed oxide was observed at higher temperatures. Hydrothermal treatment improved thermal stability of the Ni2Al and Ni3Al LDHs but only a slight effect of hydrothermal treatment was observed with the Ni4Al sample. The Rietveld refinement of powder XRD patterns of calcination products obtained at 450 1C showed a formation of Al-containing NiO-like oxide and a presence of a considerable amount of Al-rich amorphous component. Hydrothermal aging of the LDHs resulted in decreasing content of the amorphous component and enhanced substitution of Al cations into NiO-like structure. The hydrothermally treated samples also exhibited a worse reducibility of Ni 2+ components. The NiAl 2 O 4 spinel and NiO still containing a marked part of Al in the cationic sublattice were detected in the samples calcined at 900 1C. The Ni2Al LDHs hydrothermally treated for various times and related mixed oxides obtained at 450 1C showed an increase in pore size with increasing time of hydrothermal aging. The hydrothermal treatment of LDH precursor considerably improved the catalytic activity of Ni2Al mixed oxides in N 2 O decomposition, which can be explained by suppressing internal diffusion effect in catalysts grains.
Structural, vibrational and morphological properties of layered double hydroxides containing Ni
Layered double hydroxides are anionic clays with formula [M II 1-x M III x (OH) 2 ] q+ [A n-.] q/n. mH 2 O, finding possible uses as catalyst support, adsorbents and so on. In this paper, we address the phase formation of layered double hydroxides containing Ni 2+ , Zn 2+ , Al 3+ and Zr 4+ cations, namely, NiZn-Al, NiZn-AlZr and NiZn-Zr compositions obtained by the coprecipitation method. Such systems were characterized by X-ray diffraction, confirming the phase formation for NiZn-Al and NiZn-AlZr samples. Infrared/Raman spectroscopies elucidated the anion and water molecules occurrence in the interlayer. Nitrogen physisorption (BET method) determined the presence of pores and specific surface area. The isotherm shapes were Type IV, according to the IUPAC, and represent a mesoporous structure. A morphological study was performed by means of scanning and transmission electron microscopies, and particle size values of 120, 131 and 235 nm for NiZn-Al, NiZn-AlZr and NiZn-Zr, respectively, were determined. Thermogravimetric analysis of the decomposition of the systems revealed that their complete disintegration occurred at ~ 550°C and resulted in mixed oxides.
Journal of Physics and Chemistry of Solids, 2008
Two main reactions occur in polyol media: reduction and hydrolysis. In the case of systems with two easily reducible elements Ni and Fe for instance, previous works have shown that bimetallic particles or the oxide spinel particles can be obtained. This paper shows that polyols can also be used to elaborate Layered Double Hydroxides LDH-Ni-Fe. In this case, the hydrolysis ratio must be adjusted to avoid both reduction and oxolation reactions in favor of hydroxylation. The compound can be obtained either in powder or gel forms. The gel enables elaboration of film by spin-coating process. The compound is poor-crystallised and exhibits a turbostractic character. Its interlamellar distance (12.89Å) is slightly higher than that of similar compound elaborated in aqueous solution via titration method (12.02Å). 57 Fe Mössbauer spectrometry allows to conclude to the presence of HS Fe 3+ cations which occupy two different octahedral sites. XRD and Mössbauer studies reveal interesting preferential orientation features of the film with an anisotropy of the crystalline grains having their c axis perpendicular to the film.
Open Chemistry, 2011
Three layered double hydroxides (LDH) [Mg1−xAlx(OH)2]x+(Am−)x/m]·nH2O and [MII 1−xMIII x (OH)2]x+(Am−)x/m]·nH2O (MII — Mg, Co, Ni; MIII — Al; A — CO3 2−) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of...
Microporous and Mesoporous Materials, 2012
Supported nickel catalysts were obtained by exchange of Mg/Al Layered Double Hydroxides (LDHs) compensated with NO À 3 ions with negatively charged Ni complexes, followed by thermal reduction. With this aim, suspensions of Ni complexes were prepared by controlled hydroxylation of Ni 2+ cations in the presence of citrate (obtaining ½NiðC 6 H 5 O 7 ÞðOHÞ 2yÀ y species) or chloride (obtaining [NiCl 4 ] 2À species) complexing ions. For comparative purposes, other two supported Ni catalysts were prepared starting from Mg/Al LDHs compensated with Cl À ions and thereafter exchanged with ½NiðC 6 H 5 O 7 ÞðOHÞ 2yÀ y species (nominal degree of exchange: 100% and 20%).
Glycine-Assisted Hydrothermal Synthesis of NiAl-Layered Double Hydroxide Nanostructures
Crystal Growth & Design, 2009
Flower-like NiAl-layered double hydroxides (LDH) were successfully synthesized by a straightforward one-pot hydrothermal method using Ni(II) glycinate complex as a chemical precursor under extremely high basic conditions and soft hydrothermal conditions. Systematic screening of synthesis parameters such as reaction time and hydrothermal process temperature was carried out. The materials have been thoroughly characterized via a set of techniques including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, chemical analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TG). The results demonstrate that a too long reaction time value disrupts the flower-like microspheres and a too high temperature value is deleterious for the LDH structure. Transition mixed oxides with the same flowerlike morphology were readily obtained by thermal treatment at a moderate temperature of the above LDH precursors.
Materials Characterization, 2017
Layered double hydroxides are anionic clays with formula [M II 1-x M III x (OH) 2 ] q+ [A n-.] q/n. mH 2 O, finding possible uses as catalyst support, adsorbents and so on. In this paper, we address the phase formation of layered double hydroxides containing Ni 2+ , Zn 2+ , Al 3+ and Zr 4+ cations, namely, NiZn-Al, NiZn-AlZr and NiZn-Zr compositions obtained by the coprecipitation method. Such systems were characterized by X-ray diffraction, confirming the phase formation for NiZn-Al and NiZn-AlZr samples. Infrared/Raman spectroscopies elucidated the anion and water molecules occurrence in the interlayer. Nitrogen physisorption (BET method) determined the presence of pores and specific surface area. The isotherm shapes were Type IV, according to the IUPAC, and represent a mesoporous structure. A morphological study was performed by means of scanning and transmission electron microscopies, and particle size values of 120, 131 and 235 nm for NiZn-Al, NiZn-AlZr and NiZn-Zr, respectively, were determined. Thermogravimetric analysis of the decomposition of the systems revealed that their complete disintegration occurred at ~ 550°C and resulted in mixed oxides.
Preparation of layered nickel aluminium double hydroxide from waste solution of nickel
Minerals Engineering, 2014
The separation of nickel has been carried out from a waste solution containing 3.18 g/L Ni with other impurities such as Fe, Zn, Cu and As. Iron was removed by precipitation and Cu and Zn were removed by solvent extraction using LIX 622N and NaTOPS-99, respectively. After removal of all these impurities nickel was extracted by 1.5 M NaTOPS-99 in two counter-current stages at A:O ratio of 3:1 and the loaded organic was stripped with 30 g/L H 2 SO 4 at phase ratio of unity. The strip solution of nickel was treated with Al 2 (NO) 3 Á 9H 2 O for co-precipitation by increasing the pH of solution with 1 M NaOH up to 10. The Ni-Al layered double hydroxide was confirmed through XRD characterization.
Dalton Transactions, 2013
Terephthalate-intercalated nickel-aluminum layered double hydroxides (LDHs) were prepared by a coprecipitation method, with nominal x values in the general formula Ni (1−x) Al x (OH) 2 (C 8 H 4 O 4) x/2 in the range 0.3-0.8. The materials were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, CHN analysis, thermogravimetric analysis, FTIR spectroscopy, EXAFS at the Ni edge and 27 Al NMR spectroscopy. A combination of XRD, XRF and CHN analysis indicated that crystalline LDHs with true x values up to 0.5 were obtained, along with increasing segregation of an aluminum hydroxide phase with increasing aluminum content. The EXAFS analysis indicated an upper limit of ca. 0.6 for the atomic fraction of aluminum at the second nickel coordination sphere. The 27 Al NMR analysis suggested that a phase containing octahedrally coordinated Al 3+ is segregated for nominal x values from 0.6 upwards.