The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules

Guan, Qı; Urness, Kimberly N.; Ormond, Thomas K.; David, Donald E.; Ellison, G. Barney; Daily, John W.

doi:10.1080/0144235x.2014.967951

Cited by 139 publications

(242 citation statements)

References 28 publications

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“…The present model and simulations explain the observed products distributions from the micro-tubular reactor purely on the basis of gas-phase chemistry without the need for introducing any surface reactions, a conclusion borne out from recent studies on a variety of organic molecules by Barney Ellison and collaborators. 43 and references within The present study also indicates that experiments using these complex micro-tubular reactors, when interpreted with the aid of high-level theoretical calculations and kinetics modeling, can offer insights into the chemistry of elusive intermediates in the high temperature pyrolysis of organic molecules.…”

Section: Kinetic Modelingmentioning

confidence: 86%

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

et al. 2015

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The mechanism for the thermal decomposition of acetaldehyde has been revisited with an analysis of literature kinetics experiments using theoretical kinetics. The present modeling study was motivated by recent observations, with very sensitive diagnostics, of some unexpected products in high temperature microtubular reactor experiments on the thermal decomposition of CH3CHO and its deuterated analogs, CH3CDO, CD3CHO, and CD3CDO. The observations of these products prompted the authors of these studies to suggest that the enol tautomer, CH2CHOH (vinyl alcohol), is a primary intermediate in the thermal decomposition of acetaldehyde. The present modeling efforts on acetaldehyde decomposition incorporate a master equation reanalysis of the CH3CHO potential energy surface (PES). The lowest-energy process on this PES is an isomerization of CH3CHO to CH2CHOH. However, the subsequent product channels for CH2CHOH are substantially higher in energy, and the only unimolecular process that can be thermally accessed is a reisomerization to CH3CHO. The incorporation of these new theoretical kinetics predictions into models for selected literature experiments on CH3CHO thermal decomposition confirms our earlier experiment and theory-based conclusions that the dominant decomposition process in CH3CHO at high temperatures is C-C bond fission with a minor contribution (∼10-20%) from the roaming mechanism to form CH4 and CO. The present modeling efforts also incorporate a master-equation analysis of the H + CH2CHOH potential energy surface. This bimolecular reaction is the primary mechanism for removal of CH2CHOH, which can accumulate to minor amounts at high temperatures, T > 1000 K, in most lab-scale experiments that use large initial concentrations of CH3CHO. Our modeling efforts indicate that the observation of ketene, water, and acetylene in the recent microtubular experiments are primarily due to bimolecular reactions of CH3CHO and CH2CHOH with H-atoms and have no bearing on the unimolecular decomposition mechanism of CH3CHO. The present simulations also indicate that experiments using these microtubular reactors when interpreted with the aid of high-level theoretical calculations and kinetics modeling can offer insights into the chemistry of elusive intermediates in the high-temperature pyrolysis of organic molecules.

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Section: Kinetic Modelingmentioning

confidence: 86%

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

et al. 2015

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“…The SiC reactor is based on the original design pioneered by Chen and co-workers [19], and recently further refined [20]. We have used two distinct schemes for generating molecular beams of C 5 H 4 =O.…”

Section: Methodsmentioning

confidence: 99%

The ionisation energy of cyclopentadienone: a photoelectron–photoion coincidence study

et al. 2015

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Imaging photoelectron photoion coincidence (iPEPICO) spectra of cyclopentadienone (C 5 H 4 =O and C 5 D 4 =O) have been measured at the Swiss Light Source Synchrotron (Paul Scherrer Institute, Villigen, Switzerland) at the Vacuum Ultraviolet (VUV) Beamline. Complementary to the photoelectron spectra, photoionisation efficiency curves were measured with tunable VUV radiation at the Chemical Dynamics Beamline at the Advanced Light ). For both experiments, molecular beams diluted in argon and helium were generated from the vacuum flash pyrolysis of o-phenylene sulphite in a resistively heated microtubular SiC flow reactor. The Franck-Condon profiles and ionisation energies were calculated at the CCSD(T) level of theory, and are in excellent agreement with the observed iPEPICO spectra. The ionisation energies of both cyclopentadienone-d 0 , IE(C 5 H 4 =O), and cyclopentadienoned 4 , IE(C 5 D 4 =O), were observed to be the same: 9.41 ± 0.01 eV. The mass-selected threshold photoelectron spectrum (ms-TPES) of cyclopentadienone reveals that the C=C stretch in the ground state of the cation is excited upon ionisation, supporting computational evidence that the ground state of the cation is X + 2 A 2 , and is in agreement with previous studies. However, the previously reported ionisation potential has been improved considerably in this work. In addition, since o-benzoquinone (o-O=C 6 H 4 =O and o-O=C 6 D 4 =O) is also produced in this process, its ms-TPES has been recorded. From the iPEPICO and photoionisation efficiency spectra, we infer an adiabatic ionisation energy of IE(o-O=C 6 H 4 =O) = 9.3 ± 0.1 eV, but the rather structureless spectrum indicates a strong change in geometry upon ionisation making this value less reliable.

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“…Given the complexity of the phenyl system, it is therefore essential to investigate its products by a structure-sensitive method. It is been shown that high temperature flow (pyrolysis) microreactors 15 provide a suitable environment to investigate combustion processes 16 and can be combined with the tools of gas-phase spectroscopy, which gives the opportunity to test theoretical predictions. The flow dynamics in such a reactor has been analysed in detail.…”

Section: Introductionmentioning

confidence: 99%

“…The flow dynamics in such a reactor has been analysed in detail. 16 Ellison and coworkers studied the thermal decomposition of compounds like furan 17 and anisole. 18 Recently, the work was extended to the decomposition of the benzyl radical.…”

Section: Introductionmentioning

confidence: 99%

Formation of polycyclic aromatic hydrocarbons from bimolecular reactions of phenyl radicals at high temperatures

Constantinidis

Schmitt

Fischer

et al. 2015

Phys. Chem. Chem. Phys.

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The self-reaction of the phenyl radical is one of the key reactions in combustion chemistry. Here we study this reaction in a high-temperature flow reactor by IR/UV ion dip spectroscopy, using free electron laser radiation as mid-infrared source. We identified several major reaction products based on their infrared spectra, among them indene, 1,2-dihydronaphthalene, naphthalene, biphenyl and para-terphenyl. Due to the structural sensitivity of the method, the reaction products were identified isomer-selectively.The work shows that the formation of indene and naphthalene, which was previously considered to be evidence for the HACA (hydrogen abstraction C 2 H 2 addition) mechanism in the formation of polycyclic aromatic hydrocarbons and soot can also be understood in a phenyl addition model.

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The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules

Cited by 139 publications

References 28 publications

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde

The ionisation energy of cyclopentadienone: a photoelectron–photoion coincidence study

Formation of polycyclic aromatic hydrocarbons from bimolecular reactions of phenyl radicals at high temperatures

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