THERMAL BEHAVIOR OF HYDROTALCITE-LIKE [Mg 1−x Ga x (OH) 2 ](CO 3 ) x/2 · m H 2 O AS A FUNCTION OF GALLIUM CONTENT

López-Salinas, E.; Torres-Garcı́a, E.; García-Sánchez, Mayela

doi:10.1016/s0022-3697(96)00210-7

Cited by 28 publications

(8 citation statements)

References 20 publications

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“…Calcination temperatures above 673 K yield materials with smaller surface areas. At 673 K GaHTs transform into Ga-substituted MgO-like compound; i.e., the layered structure collapses below 673 K, and above 773 K a spinel type MgGa 2 O 4 compound forms . The decrease in surface area above 673 K may be associated with the formation of MgGa 2 O 4 which has a closed packed structure.…”

Section: Resultsmentioning

confidence: 99%

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O

et al. 1997

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A series of Ga-substituted hydrotalcite-like materials (GaHTs), [Mg 1-x Ga x (OH) 2 ](CO 3 ) x/2 ‚mH 2 O where x ) 0.12-0.36, were prepared in order to examine their textural and basic properties upon different Mg/Ga contents and calcination temperature. Specific surface area increases from 46 to 156 m 2 g -1 (Mg/Ga ) 7.7) when calcining from 523 to 673 K as a consequence of dehydroxylation and decarbonation of the material. The total number of base sites increases upon higher calcination temperatures until reaching a maximum at 873 K and then decreases. CO 2 thermal programmed desorption indicates that different Mg/Ga relative contents have a considerable effect on the amount of base sites. For instance, a GaHT with Mg/Ga ) 7.7 exhibits 2.4 times more total base sites than that of Mg/Ga ) 2.9. Additionally, in the former, the generation of medium and strong base sites is considerably higher than in the latter. By means of CDCl 3 adsorption and FTIR, several types of base sites were identified. The base sites strength (pK a ) -1 to +19) and proton affinity (815-987 kJ mol -1 ) values were estimated considering the ν CD shift of adsorbed CDCl 3 and correlating it with the pK a of bases that form hydrogen-bonded complexes.

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Section: Resultsmentioning

confidence: 99%

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O

et al. 1997

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“…[70,71] Another feature that makes these sol-gel materials distinguishable from and more attractive than the naturally occurring hydrotalcites or those produced from other synthetic methods is their high specific surface area of ca 150 m 2 /g or higher. [26,68,71,72] The specific surface area of the hydrotalcites was 10-25% greater than that achieved by co-precipitation, [17,29,42,68 -90] but with controversial results regarding the basicity and the M II /M III ratios. [26,51,52] …”

Section: Sol-gel Methodsmentioning

confidence: 99%

Synthetic hydrotalcites from different routes and their application as catalysts and gas adsorbents: a review

Othman

Helwani

Martunus

et al. 2009

Applied Organom Chemis

186

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In this paper, widely accepted methods of hydrotalcite preparation such as co-precipitation, urea hydrolysis, hydrothermal, sol-gel, microwave irradiation, steam activation and solvothermal have been selected and reviewed. Our review indicates that the nature of the divalent cations, the synthesis method, the calcination temperature and the nature of the interlayer species are determinant factors in shaping the surface properties of the layered double hydoxides. The basic strength of the surface base site and structural changes produced in the mixed oxides can be adjusted conveniently by varying the Al content during the synthesis. The combination of sol-gel with microwave irradiation during the gelling and crystallization steps has also been found to increase the surface area of the hydrotalcite-like compound.

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“…On the one hand, Mg : Ga molar ratios determined in solution and in solids are similar, ranging from 3 to 4.5, when precipitations are performed at pH ~11-12. [17][18][19] On the other hand, discrepancies are obtained in the case of syntheses performed at pH values above 10. In particular, incomplete incorporation of Mg 21 is reported in some cases, 19 and attributed to the high solubility of Mg(OH) 2 .…”

Section: Investigation Of the Chemical And Structural Properties Of L...mentioning

confidence: 99%

Comparison of the structural and acid–base properties of Ga- and Al-containing layered double hydroxides obtained by microwave irradiation and conventional ageing of synthesis gels

et al. 2002

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THERMAL BEHAVIOR OF HYDROTALCITE-LIKE [Mg 1−x Ga x (OH) 2 ](CO 3 ) x/2 · m H 2 O AS A FUNCTION OF GALLIUM CONTENT

Cited by 28 publications

References 20 publications

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O

Synthetic hydrotalcites from different routes and their application as catalysts and gas adsorbents: a review

Comparison of the structural and acid–base properties of Ga- and Al-containing layered double hydroxides obtained by microwave irradiation and conventional ageing of synthesis gels

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THERMAL BEHAVIOR OF HYDROTALCITE-LIKE [Mg 1−x Ga x (OH) 2 ](CO 3 ) x/2 · m H 2 O AS A FUNCTION OF GALLIUM CONTENT

Cited by 28 publications

References 20 publications

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg1-xGax(OH)2](CO3)x/2·mH2O

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg1-xGax(OH)2](CO3)x/2·mH2O

Synthetic hydrotalcites from different routes and their application as catalysts and gas adsorbents: a review

Comparison of the structural and acid–base properties of Ga- and Al-containing layered double hydroxides obtained by microwave irradiation and conventional ageing of synthesis gels

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Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O

Formation of Base Sites on Calcined Mg−Ga Hydrotalcite-like [Mg₁_-_xGa_x(OH)₂](CO₃)_x_/2·mH₂O