摘要 :
The energies of combustion of single-walled and multi-walled carbon nanotubes were measured by using an isoperibolic micro-combustion calorimeter. The values of the massic energy of combustion in oxygen at T = 298.15 K and pAA = 0...
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The energies of combustion of single-walled and multi-walled carbon nanotubes were measured by using an isoperibolic micro-combustion calorimeter. The values of the massic energy of combustion in oxygen at T = 298.15 K and pAA = 0.1 MPa of the compounds under study were obtained as: (- 27,635.0 +/- 9.5) and (- 32,347.3 +/- 15.3) J g(-1), respectively. The corresponding standard molar enthalpies of formation were derived as: (4.7 +/- 1.3) and (0.8 +/- 0.9) kJ mol(-1), respectively. The used calorimeter to test the compounds was calibrated previously with benzoic acid NIST 39j, salicylic acid and 1,2,4-triazole.
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To obtain reliable standard energies of combustion with small amounts of C, H, O compounds, a new microcombustion calorimetry system has been set up. The design, construction, calibration and measurement experiments are described....
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To obtain reliable standard energies of combustion with small amounts of C, H, O compounds, a new microcombustion calorimetry system has been set up. The design, construction, calibration and measurement experiments are described. The system includes a commercial combustion bomb with an internal volume of 22 cm{sup}3. Samples of around 80 mg are suitable if one wants to retain the same levels of accuracy and reproducibility as those in macrocombustion experiments. Calibration of the calorimeter was performed using benzoic acid. ε(calorimeter)=2083.74 ± 0.48 J K{sup}(-1) was obtained. Combustion measurements using m-methoxybenzoic acid were made in order to verify the chemistry of the combustion process involved in the corresponding analysis of results and the accuracy of the measurement of combustion energy. The uncertainty of the results shows that the instrument described and the experimental procedure used for the determination of enthalpies of formation of compounds containing C, H and O provide a high reliability.
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An isoperibolic combustion calorimeter developed to measure the enthalpy of combustion of organic compounds containing carbon, hydrogen, oxygen, and nitrogen atoms has been assembled, calibrated, and tested. The calorimeter was ca...
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An isoperibolic combustion calorimeter developed to measure the enthalpy of combustion of organic compounds containing carbon, hydrogen, oxygen, and nitrogen atoms has been assembled, calibrated, and tested. The calorimeter was calibrated with benzoic acid NIST 39j, and the resulting energy equivalent was epsilon(calor) = (10116.8 +/- 0.5) J K-1. Salicylic acid, 1,2,4-triazole, and acetanilide were used as test compounds. The main result is that all obtained values of the standard molar enthalpy of formation for the test compound are in agreement with the results available in the literature.
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Optimal conditions for investigations of thermodynamic properties have been determined experimentally by the method of combustion calorimetry for compounds of the o-benzoquinone series. In the present work, the energies of combust...
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Optimal conditions for investigations of thermodynamic properties have been determined experimentally by the method of combustion calorimetry for compounds of the o-benzoquinone series. In the present work, the energies of combustion in oxygen were measured at T = 298.15 K by static bomb combustion calorimetry for 3,5-di-tert-butyl-o-benzoquinone and 3,6-di-tert-butyl-o-benzoquinone. The experimental values have been used to calculate the standard (p degrees = 0.1 MPa) molar enthalpy of combustion Delta H-c(m)degrees and formation Delta H-f(m)degrees for the examined compounds in the crystalline phase. (C) 2015 Elsevier Ltd. All rights reserved.
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An isoperibolic micro-combustion calorimeter was designed, built and set up in our laboratory, taking as base a 1107 Parr combustion bomb of 22 cm(3) of volume. Taken into account the geometrical form of the bomb, it was designed ...
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An isoperibolic micro-combustion calorimeter was designed, built and set up in our laboratory, taking as base a 1107 Parr combustion bomb of 22 cm(3) of volume. Taken into account the geometrical form of the bomb, it was designed and constructed a vessel and a submarine chamber in brass. All of the pieces of the calorimeter were chromium-plated to reduce heat loss by radiation. The calorimeter was calibrated by using pellets of standard benzoic acid (mass approximate of 40 mg) leading to the energy equivalent of epsilon(calor) = (1283.8 +/- 0.6) J center dot K-1. In order to test the calorimeter, combustion experiments of salicylic acid were performed leading to a value of combustion energy of Delta(c)u degrees = -(21,888.8 +/- 10.9) J center dot g(-1) which agrees with the reported literature values. The combustion of piperonylic acid was carried out as a further test leading to a value of combustion energy of Delta(c)u degrees = -(20,215.9 +/- 10.4) J center dot g(-1) in accordance with the reported literature value. The uncertainty of the calibration and the combustion of salicylic acid and piperonylic acid was 0.05%. (c) 2006 Elsevier Ltd. All rights reserved.
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In order to obtain reliable data of the standard enthalpy of combustion of compounds containing carbon, hydrogen, oxygen, and nitrogen atoms, an isoperibolic micro-combustion calorimeter has been developed from a 22 cm ~3 1109A Pa...
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In order to obtain reliable data of the standard enthalpy of combustion of compounds containing carbon, hydrogen, oxygen, and nitrogen atoms, an isoperibolic micro-combustion calorimeter has been developed from a 22 cm ~3 1109A Parr semi-micro oxygen bomb. The calorimeter was calibrated with standard benzoic acid and the resulting energy equivalent was ε(calor) = (1497.39 ± 0.37) J · K~(-1), which means an uncertainty of 0.027%. Combustion measurements using salicylic acid and 1,2,4-triazole were made in order to verify the accuracy of the device. The values of -Δ_cu° at T = 298.15 K for the compounds were (21877.2 ± 4.6) J · g~(-1), and (19217.7 ± 1.9) J · g~(-1), respectively, in agreement with the literature values.
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The present work is part of a research program on the energetics of the linear 4-n-alkoxybenzoic acids, aiming the study of the enthalpic effect of the introduction of an alkoxy chain in the position 4- of the benzoic acid ring. I...
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The present work is part of a research program on the energetics of the linear 4-n-alkoxybenzoic acids, aiming the study of the enthalpic effect of the introduction of an alkoxy chain in the position 4- of the benzoic acid ring. In this work, we present the results of the thermochemical research on 4-n-alkoxybenzoic acids with the alkoxy chain length n = 2, 4, and 8. The standard (p{ring operator} = 0.1 MPa) molar enthalpy of formation of crystalline 4-ethoxybenzoic acid, 4-butoxybenzoic acid, and 4-(octyloxy)benzoic acid was measured, at T = 298.15 K, by static-bomb calorimetry. These values, combined with the values of standard molar enthalpies of sublimation, were used to derive the standard molar enthalpies of formation in the gaseous phase.{A table is presented}. From those experimental values, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, are interpreted in terms of structural contributions to the energetics of the substituted benzoic acids and compared with the same parameters estimated from the Benson's Group Method.
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The enthalpy of formation can be determined indirectly with different calorimetric techniques; one of the most used is combustion calorimetry. During a combustion process, there are multiple energy variables that can significantly...
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The enthalpy of formation can be determined indirectly with different calorimetric techniques; one of the most used is combustion calorimetry. During a combustion process, there are multiple energy variables that can significantly influence the overall result of the measurement. One of these variables is the energy exchange that exists between the calorimeter and the surroundings. To reduce this energy contribution and obtain more precise measurements of combustion energies of compounds containing the elements C, H, O and N, a combustion calorimeter in isoperibolic operation was designed, constructed and calibrated. The measurements made with this instrument show good precision; the results obtained for internal energy and the combustion enthalpy of succinic acid (solid sample) and for glycidol, glycidyl isopropyl ether, glycidyl butyrate and glycidyl methacrylate (liquid samples) are presented. The error percentage for the epsilon(calor) of the calorimetric system proposed was compared with a commercial calorimeter and published results in the literature.
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The standard molar enthalpies of combustion for three methyl and dimethyl nitrooxazol - idine derivatives in the liquid and crystalline states were determined using a high-precision static bomb combustion calorimeter. The resultin...
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The standard molar enthalpies of combustion for three methyl and dimethyl nitrooxazol - idine derivatives in the liquid and crystalline states were determined using a high-precision static bomb combustion calorimeter. The resulting values were used to derive the standard molar enthalpies of formation of the azidomethyl-N-nitrooxazolidines. The standard molar enthalpies of vaporization for these compounds were measured using a Calvet microcalorimeter. The enthalpies of formation of some nitrooxazolidine-derived radicals and biradicals were calculated.
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The standard (p~({ring operator}) = 0.1 MPa) molar enthalpies of formation, in the crystalline state, of 1,5-diaminonaphthalene and 1,8-diaminonaphthalene were derived from the standard molar energies of combustion, in oxygen, at ...
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The standard (p~({ring operator}) = 0.1 MPa) molar enthalpies of formation, in the crystalline state, of 1,5-diaminonaphthalene and 1,8-diaminonaphthalene were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static-bomb combustion calorimetry. The Knudsen mass-loss effusion technique was used to measure the dependence of the vapour pressure of the solid isomers of diaminonaphthalene with the temperature, from which the standard molar enthalpies of sublimation were derived using the Clausius-Clapeyron equation. {A table is presented}. Combining these two experimental values, the gas-phase standard molar enthalpies of formation, at T = 298.15 K, were derived and compared with those estimated using two different empirical methods of Δ_f H_m~({ring operator}) (g) estimation: the Cox scheme and the Benson's Group Method. Moreover, the standard (p~({ring operator}) = 0.1 MPa) molar entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived for the two diaminonaphthalene isomers.
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