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Ray L. Frost - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and thermal stability of Hydrotalcites based upon gallium
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Laure-marie Grand, Sara J. Palmer, Ray L. FrostAbstract:Hydrotalcites based upon gallium as a replacement for aluminium in Hydrotalcite over a Mg/Al ratio of 2:1 to 4:1 were synthesised. The d(003) spacing varied from 7.83 A for the 2:1 Hydrotalcite to 8.15 A for the 3:1 gallium containing Hydrotalcite. A comparison is made with the Mg/Al Hydrotalcite in which the d(003) spacing for the Mg/Al Hydrotalcite varied from 7.62 A for the 2:1 Mg Hydrotalcite to 7.98 A for the 4:1 Hydrotalcite. The thermal stability of the gallium containing Hydrotalcite was determined using thermogravimetric analysis. Four mass loss steps at 77, 263–280, 485 and 828 °C with mass losses of 10.23, 21.55, 5.20 and 7.58% are attributed to dehydration, dehydroxylation and decarbonation. The thermal stability of the gallium containing Hydrotalcite is slightly less than the aluminium Hydrotalcite.
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Synthesis and thermal stability of Hydrotalcites containing manganese
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Laure-marie Grand, Sara J. Palmer, Ray L. FrostAbstract:Abstract The Hydrotalcite based upon manganese known as charmarite Mn4Al2(OH)12CO3·3H2O has been synthesised with different Mn/Al ratios from 4:1 to 2:1. Impurities of manganese oxide, rhodochrosite and bayerite at low concentrations were also produced during the synthesis. The thermal stability of charmarite was investigated using thermogravimetry. The manganese Hydrotalcite decomposed in stages with mass loss steps at 211, 305 and 793 °C. The product of the thermal decomposition was amorphous material mixed with manganese oxide. A comparison is made with the thermal decomposition of the Mg/Al Hydrotalcite. It is concluded that the synthetic charmarite is slightly less stable than Hydrotalcite.
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determination of the mechanism s for the inclusion of arsenate vanadate or molybdate anions into Hydrotalcites with variable cationic ratio
Journal of Colloid and Interface Science, 2009Co-Authors: Sara J. Palmer, Aurore Soisonard, Ray L. FrostAbstract:Hydrotalcites with cationic ratios of 2:1, 3:1, and 4:1 were synthesised using the co-precipitation method. The mechanism of inclusion of arsenate, vanadate, and molybdate into these structures is investigated using the combination of X-ray diffraction, Raman spectroscopy, and thermal analysis. Results show that Hydrotalcites with cationic ratios of 3:1 are thermally more stable then the 2:1 and 4:1 structures. The increase in thermal stability of the 3:1 Hydrotalcite structures is understood to be due to the intercalation of arsenate, vanadate, or molybdate, by an increase in hydrogen bonds associated with the intercalated anion. The 3:1 vanadate Hydrotalcite is the most thermally stable Hydrotalcite investigated. It is observed that the predominant mechanism for inclusion of the three anionic species is adsorption for 2:1 and 4:1 Hydrotalcites, and intercalation for the 3:1 Hydrotalcite structures. The intercalation of arsenate, vanadate, and molybdate into the Hydrotalcite structure increased the interlayer distance of the Hydrotalcite by 0.14, 0.13, and 0.26 A, respectively.
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Thermal decomposition of Hydrotalcites with variable cationic ratios
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: Sara J. Palmer, Henry J. Spratt, Ray L. FrostAbstract:Abstract Thermal analysis complimented with evolved gas mass spectrometry has been applied to Hydrotalcites containing carbonate prepared by coprecipitation and with varying divalent/trivalent cation ratios. The resulting materials were characterised by XRD, and TG/DTG to determine the stability of the Hydrotalcites synthesised. Hydrotalcites of formula Mg4(Fe,Al)2(OH)12(CO3)·4H2O, Mg6(Fe,Al)2(OH)16(CO3)·5H2O, and Mg8(Fe,Al)2(OH)20(CO3)·8H2O were formed by intercalation with the carbonate anion as a function of the divalent/trivalent cationic ratio. XRD showed slight variations in the d-spacing between the Hydrotalcites. The thermal decomposition of carbonate Hydrotalcites consists of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation of the Hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step is due to the partial dehydroxylation of the lattice, while the second step is due to the...
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Thermal decomposition of Hydrotalcite with molybdate and vanadate anions in the interlayer
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: Sara J. Palmer, Ray L. Frost, T. NguyenAbstract:Hydrotalcites containing carbonate, vanadate and molybdate were prepared by coprecipitation. The resulting materials were characterized by XRD, and TG/DTA to determine the stability of the Hydrotalcites synthesized. The thermal decomposition of carbonate Hydrotalcites consist of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation of the Hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step is due to the partial dehydroxylation of the lattice, while the second step is due to the loss of water interacting with the interlayer anions. Dehydroxylation results in the collapse of the Hydrotalcite structure to that of its corresponding metal oxides, including MgO, Al2O3, MgAl2O4, NaMg4(VO4)3 and Na2Mg4(MoO4)5. The presence of oxy-anions proved to be beneficial in the stability of the Hydrotalcite structure, shown by the delay in dehydroxylation of oxy-anion containing Hydrotalcites compared to the carbonate Hydrotalcite. This is due to the substantial amount of hydroxyl groups involved in a network of hydrogen bonds involving the intercalated anions. Therefore, the stability of the Hydrotalcite structure appears to be dependent on the type of anion present in the interlayer. The order of thermal stability for the synthesized Hydrotalcites in this study is Syn-HT-V>Syn-HT-Mo> Syn-HT-CO3-V>Syn-HT-CO3-Mo>Syn-HT-CO3. Carbonate containing Hydrotalcites prove to be less stable than oxy-anion only Hydrotalcites.
Alírio E. Rodrigues - One of the best experts on this subject based on the ideXlab platform.
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co2 sorption on Hydrotalcite and alkali modified k and cs Hydrotalcites at high temperatures
Separation and Purification Technology, 2008Co-Authors: Eduardo L G Oliveira, Carlos A. Grande, Alírio E. RodriguesAbstract:Abstract The concept of in situ removal and capture of CO 2 at high temperature using a sorbent for sorption-enhanced reaction processes (SERP) is an area where improvements of sorptive materials are required. The aim of this work is the development of a suitable adsorbent to be employed at temperatures above 573 K in SERP processes for hydrogen production from methane steam reforming. Sorption of carbon dioxide was studied in three commercial Hydrotalcites with different Mg/Al ratio. To study the effect of impregnation with two alkali metals, the three Hydrotalcites were impregnated with cesium and potassium and a sorbent screening was performed. The novelty of this work was the determination of carbon dioxide sorption equilibrium isotherms at 579, 676 and 783 K on two samples, one modified with potassium carbonate and other with cesium carbonate. The alkali-modified samples showed a maximum loading at 676 K being MG30-K the one with highest capacity (0.76 mol/kg wet basis at 0.40 bar of CO 2 partial pressure). A study of the cyclic stability of this material was performed, showing that there was only small loss of capacity after 75 sorption/desorption cycles.
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CO2 sorption on Hydrotalcite and alkali-modified (K and Cs) Hydrotalcites at high temperatures
Separation and Purification Technology, 2008Co-Authors: Eduardo L G Oliveira, Carlos A. Grande, Alírio E. RodriguesAbstract:The concept of in situ removal and capture of CO2 at high temperature using a sorbent for sorption-enhanced reaction processes (SERP) is an area where improvements of sorptive materials are required. The aim of this work is the development of a suitable adsorbent to be employed at temperatures above 573 K in SERP processes for hydrogen production from methane steam reforming. Sorption of carbon dioxide was studied in three commercial Hydrotalcites with different Mg/Al ratio. To study the effect of impregnation with two alkali metals, the three Hydrotalcites were impregnated with cesium and potassium and a sorbent screening was performed. The novelty of this work was the determination of carbon dioxide sorption equilibrium isotherms at 579, 676 and 783 K on two samples, one modified with potassium carbonate and other with cesium carbonate. The alkali-modified samples showed a maximum loading at 676 K being MG30-K the one with highest capacity (0.76 mol/kg wet basis at 0.40 bar of CO2 partial pressure). A study of the cyclic stability of this material was performed, showing that there was only small loss of capacity after 75 sorption/desorption cycles. © 2008 Elsevier B.V. All rights reserved.
Toyoko Imae - One of the best experts on this subject based on the ideXlab platform.
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Morphological Investigation of Hybrid Langmuir−Blodgett Films of Arachidic Acid with a Hydrotalcite/Dendrimer Nanocomposite
Langmuir, 2004Co-Authors: Alexsandro Santos Costa, Toyoko ImaeAbstract:A Hydrotalcite clay/dendrimer nanocomposite prepared by the ionic exchange process was adsorbed from suspension of the nanocomposite on a Langmuir monolayer of arachidic acid at the air/water interface, followed by compressing and transferring onto an arachidic acid monolayer Langmuir−Blodgett (LB) film on mica. For comparison, the Hydrotalcite-adsorbed hybrid film was also prepared. The morphology of Hydrotalcite and the nanocomposite studied by transmission electron microscopy indicated the layered structures with respectively 1.2 ± 0.3 and 3.2 ± 0.5 nm repeating distances. The hybrid Langmuir films displayed the occupied surface area of 0.24 nm2 for both Hydrotalcite and the nanocomposite. The formation of hybrid Langmuir films was confirmed by Brewster angle microscopy. Atomic force microscopic images of hybrid LB films revealed the formation of plateau domains with the height difference of 6 nm for Hydrotalcite and 12 nm for the nanocomposite and the presence of dendrimers adsorbed on the clay surfac...
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morphological investigation of hybrid langmuir blodgett films of arachidic acid with a Hydrotalcite dendrimer nanocomposite
Langmuir, 2004Co-Authors: Alexsandro Santos Costa, Toyoko ImaeAbstract:A Hydrotalcite clay/dendrimer nanocomposite prepared by the ionic exchange process was adsorbed from suspension of the nanocomposite on a Langmuir monolayer of arachidic acid at the air/water interface, followed by compressing and transferring onto an arachidic acid monolayer Langmuir−Blodgett (LB) film on mica. For comparison, the Hydrotalcite-adsorbed hybrid film was also prepared. The morphology of Hydrotalcite and the nanocomposite studied by transmission electron microscopy indicated the layered structures with respectively 1.2 ± 0.3 and 3.2 ± 0.5 nm repeating distances. The hybrid Langmuir films displayed the occupied surface area of 0.24 nm2 for both Hydrotalcite and the nanocomposite. The formation of hybrid Langmuir films was confirmed by Brewster angle microscopy. Atomic force microscopic images of hybrid LB films revealed the formation of plateau domains with the height difference of 6 nm for Hydrotalcite and 12 nm for the nanocomposite and the presence of dendrimers adsorbed on the clay surfac...
Eduardo L G Oliveira - One of the best experts on this subject based on the ideXlab platform.
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co2 sorption on Hydrotalcite and alkali modified k and cs Hydrotalcites at high temperatures
Separation and Purification Technology, 2008Co-Authors: Eduardo L G Oliveira, Carlos A. Grande, Alírio E. RodriguesAbstract:Abstract The concept of in situ removal and capture of CO 2 at high temperature using a sorbent for sorption-enhanced reaction processes (SERP) is an area where improvements of sorptive materials are required. The aim of this work is the development of a suitable adsorbent to be employed at temperatures above 573 K in SERP processes for hydrogen production from methane steam reforming. Sorption of carbon dioxide was studied in three commercial Hydrotalcites with different Mg/Al ratio. To study the effect of impregnation with two alkali metals, the three Hydrotalcites were impregnated with cesium and potassium and a sorbent screening was performed. The novelty of this work was the determination of carbon dioxide sorption equilibrium isotherms at 579, 676 and 783 K on two samples, one modified with potassium carbonate and other with cesium carbonate. The alkali-modified samples showed a maximum loading at 676 K being MG30-K the one with highest capacity (0.76 mol/kg wet basis at 0.40 bar of CO 2 partial pressure). A study of the cyclic stability of this material was performed, showing that there was only small loss of capacity after 75 sorption/desorption cycles.
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CO2 sorption on Hydrotalcite and alkali-modified (K and Cs) Hydrotalcites at high temperatures
Separation and Purification Technology, 2008Co-Authors: Eduardo L G Oliveira, Carlos A. Grande, Alírio E. RodriguesAbstract:The concept of in situ removal and capture of CO2 at high temperature using a sorbent for sorption-enhanced reaction processes (SERP) is an area where improvements of sorptive materials are required. The aim of this work is the development of a suitable adsorbent to be employed at temperatures above 573 K in SERP processes for hydrogen production from methane steam reforming. Sorption of carbon dioxide was studied in three commercial Hydrotalcites with different Mg/Al ratio. To study the effect of impregnation with two alkali metals, the three Hydrotalcites were impregnated with cesium and potassium and a sorbent screening was performed. The novelty of this work was the determination of carbon dioxide sorption equilibrium isotherms at 579, 676 and 783 K on two samples, one modified with potassium carbonate and other with cesium carbonate. The alkali-modified samples showed a maximum loading at 676 K being MG30-K the one with highest capacity (0.76 mol/kg wet basis at 0.40 bar of CO2 partial pressure). A study of the cyclic stability of this material was performed, showing that there was only small loss of capacity after 75 sorption/desorption cycles. © 2008 Elsevier B.V. All rights reserved.
Sara J. Palmer - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and thermal stability of Hydrotalcites based upon gallium
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Laure-marie Grand, Sara J. Palmer, Ray L. FrostAbstract:Hydrotalcites based upon gallium as a replacement for aluminium in Hydrotalcite over a Mg/Al ratio of 2:1 to 4:1 were synthesised. The d(003) spacing varied from 7.83 A for the 2:1 Hydrotalcite to 8.15 A for the 3:1 gallium containing Hydrotalcite. A comparison is made with the Mg/Al Hydrotalcite in which the d(003) spacing for the Mg/Al Hydrotalcite varied from 7.62 A for the 2:1 Mg Hydrotalcite to 7.98 A for the 4:1 Hydrotalcite. The thermal stability of the gallium containing Hydrotalcite was determined using thermogravimetric analysis. Four mass loss steps at 77, 263–280, 485 and 828 °C with mass losses of 10.23, 21.55, 5.20 and 7.58% are attributed to dehydration, dehydroxylation and decarbonation. The thermal stability of the gallium containing Hydrotalcite is slightly less than the aluminium Hydrotalcite.
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Synthesis and thermal stability of Hydrotalcites containing manganese
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Laure-marie Grand, Sara J. Palmer, Ray L. FrostAbstract:Abstract The Hydrotalcite based upon manganese known as charmarite Mn4Al2(OH)12CO3·3H2O has been synthesised with different Mn/Al ratios from 4:1 to 2:1. Impurities of manganese oxide, rhodochrosite and bayerite at low concentrations were also produced during the synthesis. The thermal stability of charmarite was investigated using thermogravimetry. The manganese Hydrotalcite decomposed in stages with mass loss steps at 211, 305 and 793 °C. The product of the thermal decomposition was amorphous material mixed with manganese oxide. A comparison is made with the thermal decomposition of the Mg/Al Hydrotalcite. It is concluded that the synthetic charmarite is slightly less stable than Hydrotalcite.
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determination of the mechanism s for the inclusion of arsenate vanadate or molybdate anions into Hydrotalcites with variable cationic ratio
Journal of Colloid and Interface Science, 2009Co-Authors: Sara J. Palmer, Aurore Soisonard, Ray L. FrostAbstract:Hydrotalcites with cationic ratios of 2:1, 3:1, and 4:1 were synthesised using the co-precipitation method. The mechanism of inclusion of arsenate, vanadate, and molybdate into these structures is investigated using the combination of X-ray diffraction, Raman spectroscopy, and thermal analysis. Results show that Hydrotalcites with cationic ratios of 3:1 are thermally more stable then the 2:1 and 4:1 structures. The increase in thermal stability of the 3:1 Hydrotalcite structures is understood to be due to the intercalation of arsenate, vanadate, or molybdate, by an increase in hydrogen bonds associated with the intercalated anion. The 3:1 vanadate Hydrotalcite is the most thermally stable Hydrotalcite investigated. It is observed that the predominant mechanism for inclusion of the three anionic species is adsorption for 2:1 and 4:1 Hydrotalcites, and intercalation for the 3:1 Hydrotalcite structures. The intercalation of arsenate, vanadate, and molybdate into the Hydrotalcite structure increased the interlayer distance of the Hydrotalcite by 0.14, 0.13, and 0.26 A, respectively.
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Thermal decomposition of Hydrotalcites with variable cationic ratios
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: Sara J. Palmer, Henry J. Spratt, Ray L. FrostAbstract:Abstract Thermal analysis complimented with evolved gas mass spectrometry has been applied to Hydrotalcites containing carbonate prepared by coprecipitation and with varying divalent/trivalent cation ratios. The resulting materials were characterised by XRD, and TG/DTG to determine the stability of the Hydrotalcites synthesised. Hydrotalcites of formula Mg4(Fe,Al)2(OH)12(CO3)·4H2O, Mg6(Fe,Al)2(OH)16(CO3)·5H2O, and Mg8(Fe,Al)2(OH)20(CO3)·8H2O were formed by intercalation with the carbonate anion as a function of the divalent/trivalent cationic ratio. XRD showed slight variations in the d-spacing between the Hydrotalcites. The thermal decomposition of carbonate Hydrotalcites consists of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation of the Hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step is due to the partial dehydroxylation of the lattice, while the second step is due to the...
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Thermal decomposition of Hydrotalcite with molybdate and vanadate anions in the interlayer
Journal of Thermal Analysis and Calorimetry, 2008Co-Authors: Sara J. Palmer, Ray L. Frost, T. NguyenAbstract:Hydrotalcites containing carbonate, vanadate and molybdate were prepared by coprecipitation. The resulting materials were characterized by XRD, and TG/DTA to determine the stability of the Hydrotalcites synthesized. The thermal decomposition of carbonate Hydrotalcites consist of two decomposition steps between 300 and 400°C, attributed to the simultaneous dehydroxylation and decarbonation of the Hydrotalcite lattice. Water loss ascribed to dehydroxylation occurs in two decomposition steps, where the first step is due to the partial dehydroxylation of the lattice, while the second step is due to the loss of water interacting with the interlayer anions. Dehydroxylation results in the collapse of the Hydrotalcite structure to that of its corresponding metal oxides, including MgO, Al2O3, MgAl2O4, NaMg4(VO4)3 and Na2Mg4(MoO4)5. The presence of oxy-anions proved to be beneficial in the stability of the Hydrotalcite structure, shown by the delay in dehydroxylation of oxy-anion containing Hydrotalcites compared to the carbonate Hydrotalcite. This is due to the substantial amount of hydroxyl groups involved in a network of hydrogen bonds involving the intercalated anions. Therefore, the stability of the Hydrotalcite structure appears to be dependent on the type of anion present in the interlayer. The order of thermal stability for the synthesized Hydrotalcites in this study is Syn-HT-V>Syn-HT-Mo> Syn-HT-CO3-V>Syn-HT-CO3-Mo>Syn-HT-CO3. Carbonate containing Hydrotalcites prove to be less stable than oxy-anion only Hydrotalcites.
