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Aleksandrov, Yu. I.; Korchagina, E. N.; Чуновкина, А. Г.

doi:10.1023/a:1015981904187

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…As in the case of CO 2 , all determinations used in the TN were recalculated and/or rechecked from the original data. The determinations included in the Core TN were extracted from Roth and Banse (−213.33 ± 0.50 kcal/mol at 20 °C = −892.6 ± 2.1 kJ/mol), Rossini ,, and Prosen and Rossini (−889.849 ± 0.350 kJ/mol at 30 °C), and Pittam and Pilcher (−890.699 ± 0.430 kJ/mol at 25 °C), as well as the newer determinations by Dale et al (−890.61 ± 0.21 kJ/mol at 25 °C) and by Alexandrov et al , (−890.43 ± 0.35 kJ/mol at 25 °C).…”

Section: Core (Argonne) Thermochemical Networkmentioning

confidence: 99%

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

et al. 2004

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The concept behind active thermochemical tables (ATcT) is presented. As opposed to traditional sequential thermochemistry, ATcT provides reliable, accurate, and internally consistent thermochemistry by utilizing the thermochemical network (TN) approach. This involves, inter alia, a statistical analysis of thermochemically relevant determinations that define the TN, made possible by redundancies in the TN, such as competing measurements and alternate network pathways that interrelate the various chemical species. The statistical analysis produces a self-consistent TN, from which the optimal thermochemical values are obtained by simultaneous solution in error-weighted space, thus allowing optimal use of all of the knowledge present in the TN. ATcT offers a number of additional features that are not present nor possible in the traditional approach. With ATcT, new knowledge can be painlessly propagated through all affected thermochemical values. ATcT also allows hypothesis testing and evaluation, as well as discovery of weak links in the TN. The latter provides pointers to new experimental or theoretical determinations that will most efficiently improve the underlying thermochemical body of knowledge. The ATcT approach is illustrated by providing improved thermochemistry for several key thermochemical species.

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Section: Core (Argonne) Thermochemical Networkmentioning

confidence: 99%

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

et al. 2004

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“…Suffice it to say here that the determinations influencing the ATcT result for the bond dissociation enthalpy of toluene into benzyl and H ͓reaction ͑18a͔͒ are those listed in the recent IUPAC recommendation for the thermochemistry of benzyl. 94 The manifold of C͑A͒TN interdependencies determining the bond dissociation enthalpy of toluene into phenyl and methyl ͓reaction ͑18b͔͒ is substantially more complex, but the ATcT sensitivity analysis indicates that the current result is heavily dominated by the negative-ion-cycle determination of the bond dissociation energy of benzene, 21,22 the positive-ion-cycle determinations of the bond dissociation energy of methane, [121][122][123][124] and the calorimetric determinations of the combustion enthalpies of methane, [125][126][127][128][129][130][131][132] and liquid benzene [133][134][135] and toluene, 133,135,136 coupled to the determinations of the vaporization enthalpies of benzene [137][138][139][140] and toluene. [137][138][139][140][141] The entropy changes of reactions ͑18a͒ and ͑18b͒, needed to relate reaction enthalpies to corresponding free energies, and the temperature dependences of the enthalpy and free energy of both reactions are based on the partition functions ͑and their various derivatives͒ for toluene, benzyl, phenyl, methyl, and hydrogen atom, contained in ATcT.…”

Section: B Pyrolysis Of Aromatic Fuelsmentioning

confidence: 99%

Unimolecular thermal fragmentation ofortho-benzyne

Zhang

Maccarone

Nimlos

et al. 2007

The Journal of Chemical Physics

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The ortho-benzyne diradical, o-C(6)H(4) has been produced with a supersonic nozzle and its subsequent thermal decomposition has been studied. As the temperature of the nozzle is increased, the benzyne molecule fragments: o-C(6)H(4)+Delta--> products. The thermal dissociation products were identified by three experimental methods: (i) time-of-flight photoionization mass spectrometry, (ii) matrix-isolation Fourier transform infrared absorption spectroscopy, and (iii) chemical ionization mass spectrometry. At the threshold dissociation temperature, o-benzyne cleanly decomposes into acetylene and diacetylene via an apparent retro-Diels-Alder process: o-C(6)H(4)+Delta-->HC triple bond CH+HC triple bond C-C triple bond CH. The experimental Delta(rxn)H(298)(o-C(6)H(4)-->HC triple bond CH+HC triple bond C-C triple bond CH) is found to be 57+/-3 kcal mol(-1). Further experiments with the substituted benzyne, 3,6-(CH(3))(2)-o-C(6)H(2), are consistent with a retro-Diels-Alder fragmentation. But at higher nozzle temperatures, the cracking pattern becomes more complicated. To interpret these experiments, the retro-Diels-Alder fragmentation of o-benzyne has been investigated by rigorous ab initio electronic structure computations. These calculations used basis sets as large as [C(7s6p5d4f3g2h1i)H(6s5p4d3f2g1h)] (cc-pV6Z) and electron correlation treatments as extensive as full coupled cluster through triple excitations (CCSDT), in cases with a perturbative term for connected quadruples [CCSDT(Q)]. Focal point extrapolations of the computational data yield a 0 K barrier for the concerted, C(2v)-symmetric decomposition of o-benzyne, E(b)(o-C(6)H(4)-->HC triple bond CH+HC triple bond C-C triple bond CH)=88.0+/-0.5 kcal mol(-1). A barrier of this magnitude is consistent with the experimental results. A careful assessment of the thermochemistry for the high temperature fragmentation of benzene is presented: C(6)H(6)-->H+[C(6)H(5)]-->H+[o-C(6)H(4)]-->HC triple bond CH+HC triple bond C-C triple bond CH. Benzyne may be an important intermediate in the thermal decomposition of many alkylbenzenes (arenes). High engine temperatures above 1500 K may crack these alkylbenzenes to a mixture of alkyl radicals and phenyl radicals. The phenyl radicals will then dissociate first to benzyne and then to acetylene and diacetylene.

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“…Another indicator to evaluate the economy of IIAR is the methane efficiency ratio (MER), which is determined by the mole of CH 4 gas produced to the mole of CH 4 gas consumed for in situ heating considering the combustion heat of methane is 890 kJ/mol. 50 It was denoted that the values of MER were ∼2.6 for IIAR with CO 2 /N 2 through four different heating modes at 275.15 K and ∼13.00 MPa. However, the actual end of 2 h, 7.5 mins-12 h-6 times was at third IIAR instead of sixth IIAR.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Methane Production Efficiency with In Situ Intermittent Heating Assisted CO₂ Replacement of Hydrates

et al. 2020

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Natural gas hydrates attract worldwide attention for extensive reserve. Current exploitation methods of thermal stimulation, depressurization, and inhibitor injection consume much energy, inducing formation instability or marine biological problems. In this work, a novel in situ intermittent heating-assisted CO 2 replacement (IIAR) method was proposed to enhance methane production efficiency of hydrates. Experiments investigated recovery performance with an electrical rod simulating the in situ heating, tested at 275.15−279.15 K and 4.00−13.06 MPa. The results indicated that the presence of N 2 and liquid CO 2 was conducive to CH 4 hydrate exploitation. Rising temperature and decreasing pressure assisted IIAR dissociate partial hydrates and promote further CH 4 −CO 2 /N 2 replacement. The maximum CH 4 recovery percentage was 52.42% obtained at 279.15 K and 8.01 MPa in 48 h. The exploitation time could be shortened by 40−60% using IIAR compared with pure CO 2 and CO 2 /N 2 replacement. The improved recovery performance indicated that IIAR was more competitive than pure CO 2 and CO 2 /N 2 replacement and CO 2 replacement combined with thermal stimulation. Further reduction of exploitation time and improvement of methane production efficiency demonstrated that intensive heating modes of IIAR increased exploitation economy and reduced methane consumption.

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Untitled

Cited by 4 publications

References 1 publication

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

Unimolecular thermal fragmentation ofortho-benzyne

Enhanced Methane Production Efficiency with In Situ Intermittent Heating Assisted CO₂ Replacement of Hydrates

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Untitled

Cited by 4 publications

References 1 publication

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

Introduction to Active Thermochemical Tables: Several “Key” Enthalpies of Formation Revisited

Unimolecular thermal fragmentation ofortho-benzyne

Enhanced Methane Production Efficiency with In Situ Intermittent Heating Assisted CO2 Replacement of Hydrates

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Enhanced Methane Production Efficiency with In Situ Intermittent Heating Assisted CO₂ Replacement of Hydrates