S 8. The kinetics of the thermal decomposition of magnesium hydroxide

Gregg, S. J.; Razouk, R. I.

doi:10.1039/jr9490000s36

Cited by 54 publications

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“…The average reaction order was 0.67. This value is consistent with the results obtained by Gregg and Razouk [19]. A was 1.51 Â 10 8 as calculated from Equation (8).…”

Section: Lower Limit Of the Dehydration Temperaturesupporting

confidence: 90%

Dehydration/hydration of MgO/H2O chemical thermal storage system

Pan

Zhao

2015

Energy

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“…The average reaction order was 0.67. This value is consistent with the results obtained by Gregg and Razouk [19]. A was 1.51 Â 10 8 as calculated from Equation (8).…”

Section: Lower Limit Of the Dehydration Temperaturesupporting

confidence: 90%

Dehydration/hydration of MgO/H2O chemical thermal storage system

Pan

Zhao

2015

Energy

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“…Table 1 shows that the activation energy for all the electrolysed samples is decreased by an average of 6.2 kcal/mole, comparable with the decrease observed in electrolysed kaolinite [1]. Although comparisons of activation energies obtained under differing experimental conditions are not very meaningful, the present activation energies are of the order of those obtained by Gordon and Kingery for polycrystalline brucite [5] and by Turner et al for powder samples [8] but are at variance with other reported values [6,7]. The pre-exponential factors (Table 1) are virtually unaffected by the field, there being a large error in the graphical determination of this parameter.…”

Section: Resultssupporting

confidence: 73%

Thermal reactions of inorganic hydroxy-compounds under applied electric fields, II

MacKenzie

1973

Journal of Thermal Analysis

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The effect of electric fields on the thermal dehydroxylation of Mg(OH)2 (brucite) and AI(OH)3 (gibbsite) have been studied by thermogravimetry in a controlled inert atmosphere. Electric fields exert no beneficial effect on the reaction of gibbsite; in some cases the reaction is slightly retarded. By contrast, a small but significant beneficial effect is observed in brucite, in which the initiation temperature and activation energy is lowered at field strengths of about 10 5 V/m. The difference in behaviour of the two hydroxides is attributed to differences in the mobility of anionic defects and oxygen-containing "proton-transfer complexes". The transport of the various protonbearing species in an electric field is discussed.

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“…Thus, Gregg and Razouk [2] found that the rate of dehydroxylation was of two-thirds order. The activation energies for two brucite samples of 10-80 mesh and 100-200 mesh were 21.0 and 27.6 kcal/mole, respectively.…”

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confidence: 97%

Thermal analysis of magnesium hydroxide

Chen

Fong

1977

Journal of Thermal Analysis

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Natural brucite and two precipitated Mg(OH)2 samples were analysed in a simultaneous TG-DTG-DSC analyser. The initial dehydroxylafion temperature of natural brucite is lower than those of the precipitated samples, but the maximum and final temperatures of the former are higher than those of the latter. The maximum temperatures of individual samples obtained from DTG and DSC curves are almost the same: Heats of reaction derived from peak areas for the three samples are not exactly the same, as they are influenced by the specific surface area of the individual sample. Activation energies deduced by Freeman and Carroll's method are very different from one another. This is attributed to the difference in pressure when the sample is crimped. A linear relationship is observed between the deduced activation energy and the specific height of the DSC peak.In a series of papers [1 ], Freeman and Carroll's treatment was applied to investigate the kinetic parameters of some reactions in solution. Activation energies and orders of reaction derived therefrom agree very well with the accepted values.The thermal dehydroxylation of Mg(OH)2 has been investigated by many authors, but agreeing conclusions were not obtained. Thus, Gregg and Razouk [2] found that the rate of dehydroxylation was of two-thirds order. The activation energies for two brucite samples of 10-80 mesh and 100-200 mesh were 21.0 and 27.6 kcal/mole, respectively. The activation energies of several precipitated Mg(OH)2 samples varied from 12.4 to 27.4 kcal/mole. Kenya [3] claimed that the initial stage of dehydration of Mg(OH)2 was a first-order reaction, and an activation energy of 23 kcal/mole was observed. Turner, Hoffman and Chen [4] investigated several preparations of Mg(OH)2 with a thermobalance. Assuming a two-thirds order reaction and taking the first two terms of Schlomich's expansion as the approximation of the integral, they obtained 51.4 and 57.0 kcal/mole for the activation energies of the precipitated Mg(OH)2 and natural brucite, respectively. Their values are much higher than the previous ones. A review has recently been published by Sharp [5]. Activation energies varying from 16 to 95 kcal/mole, and reaction orders varying from 0 to 1.8 have been reported by various authors for the dehydroxylation of different types of Mg(OH)2 samples, using different methods of data treatment. It is desirable, therefore, to apply Freeman and Carroll's method to analyse thermogravimetric data for the dehydroxylation of Mg(OH)2.

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S 8. The kinetics of the thermal decomposition of magnesium hydroxide

Cited by 54 publications

References 0 publications

Dehydration/hydration of MgO/H2O chemical thermal storage system

Dehydration/hydration of MgO/H2O chemical thermal storage system

Thermal reactions of inorganic hydroxy-compounds under applied electric fields, II

Thermal analysis of magnesium hydroxide

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