Sampling of flow systems at atmospheric pressure

Wyatt, J. R.; DeCorpo, J. J.; McDowell, M. V.; Saalfeld, F. E.

doi:10.1016/0020-7381(75)85012-1

Cited by 19 publications

(17 citation statements)

References 8 publications

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“…This approach to setting the photolysis beam diameter (expand and then clip) is intended to reduce radial inhomogeneities at the edges of the beam. A ''funnel-shaped'' pinhole, similar to that used by Wyatt et al, 18 is drilled in the center of the reactor with a 275 mm diameter at the narrowest point. A small portion of the reactor contents are sampled through the pinhole, and the center of the resulting gas expansion is skimmed by a Beam Dynamics skimmer (Model 16.3, 1.0 mm orifice diameter), forming a molecular beam.…”

Section: Methodsmentioning

confidence: 99%

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Buras

Chu

Jamal

et al. 2018

Phys. Chem. Chem. Phys.

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The C9H11 potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C9H11 PES has already been extensively studied both experimentally (under single-collision and thermal conditions) and theoretically, new insights were made in this work by taking a new experimental approach: flash photolysis combined with time-resolved molecular beam mass spectrometry (MBMS) and visible laser absorbance. The C9H11 PES was experimentally accessed by photolytic generation of the phenyl radical and subsequent reaction with excess propene (C6H5 + C3H6). The overall kinetics of C6H5 + C3H6 was measured using laser absorbance with high time-resolution from 300 to 700 K and was found to be in agreement with earlier measurements over a lower temperature range. Five major product channels of C6H5 + C3H6 were observed with MBMS at 600 and 700 K, four of which were expected: hydrogen (H)-abstraction (measured by the stable benzene, C6H6, product), methyl radical (CH3)-loss (styrene detected), H-loss (phenylpropene isomers detected) and radical adduct stabilization. The fifth, unexpected product observed was the benzyl radical, which was rationalized by the inclusion of a previously unreported pathway on the C9H11 PES: aromatic-catalysed 1,2-H-migration and subsequent resonance stabilized radical (RSR, benzyl radical in this case) formation. The current theoretical understanding of the C9H11 PES was supported (including the aromatic-catalyzed pathway) by quantitative comparisons between modelled and experimental MBMS results. At 700 K, the branching to styrene + CH3 was 2-4 times greater than that of any other product channel, while benzyl radical + C2H4 from the aromatic-catalyzed pathway accounted for ∼10% of the branching. Single-collision conditions were also simulated on the updated PES to explain why previous crossed molecular beam experiments did not see evidence of the aromatic-catalyzed pathway. This experimentally validated knowledge of the C9H11 PES was added to the database of the open-source Reaction Mechanism Generator (RMG), which was then used to generalize the findings on the C9H11 PES to a slightly more complicated alkylaromatic system.

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Section: Methodsmentioning

confidence: 99%

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Buras

Chu

Jamal

et al. 2018

Phys. Chem. Chem. Phys.

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“…14,15 The sampling technique had been extensively applied by Gutman, Slagle, and collaborators [16][17][18] in conjunction with the excimer-laser generation of radical reactants. NH 2 radical was produced by photolysis of NH 3 at 193 mm.…”

Section: Methodsmentioning

confidence: 99%

Direct Determination of Product Branching for the NH₂ + NO Reaction at Temperatures between 302 and 1060 K

Park

Lin

1996

J. Phys. Chem.

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The branching ratio of the two product channels of the NH 2 + NO reaction, R and for the formation of N 2 H + OH and N 2 + H 2 O, respectively, have been determined independently at temperatures between 302 and 1060 K by mass spectrometry. For determination, the concentration of H 2 O was measured directly, whereas for R, the yield of OH was monitored by the CO 2 formed by its reaction with added CO. Both [H 2 O] and [CO 2 ] were carefully calibrated with different standard mixtures before each measurement. R was found to increase gradually from 0.11 ( 0.02 at 302 K to 0.30 ( 0.02 at 1060 K, with the concomitant decrease of from 0.89 ( 0.04 to 0.70 ( 0.03. The two independent measurements indicate for the first time that the relationship R + ) 1 holds quantitatively throughout the temperature range studied.

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“…NO titration revealed that on average about 62 -69% of the dissociated acetophenone produced the C 6 H 5 radical. C 6 H 5 COCH 3 carried by an excess amount of He was premixed in corrugated stainless steel tubing with C 4 H 10 before being introduced into the Saalfeld-type quartz reactor [17,18] and the products of the photoinitiated reaction were supersonically sampled and ionized by electron-impact ionization. The mole fractions of C 6 H 5 COCH 3 and 2-methylpropane were typically Ͻ 0.1% and ϳ33%, respectively.…”

Section: B Plp/msmentioning

confidence: 99%

Kinetics of C6H5 radical reactions with 2-methylpropane, 2,3-dimethylbutane and 2,3,4-trimethylpentane

Park

Gheyas

Lin

1999

Int. J. Chem. Kinet.

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The absolute bimolecular rate constants for the reactions of C 6 H 5 with 2-methylpropane, 2,3-dimethylbutane and 2,3,4-trimethylpentane have been measured by cavity ringdown spectrometry at temperatures between 290 and 500 K. For 2-methylpropane, additional measurements were performed with the pulsed laser photolysis/mass spectrometry, extending the temperature range to 972 K. The reactions were found to be dominated by the abstraction of a tertiary C-H bond from the molecular reactant, resulting in the production of a tertiary alkyl radical:

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Sampling of flow systems at atmospheric pressure

Cited by 19 publications

References 8 publications

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Direct Determination of Product Branching for the NH₂ + NO Reaction at Temperatures between 302 and 1060 K

Kinetics of C6H5 radical reactions with 2-methylpropane, 2,3-dimethylbutane and 2,3,4-trimethylpentane

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Sampling of flow systems at atmospheric pressure

Cited by 19 publications

References 8 publications

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

Direct Determination of Product Branching for the NH2 + NO Reaction at Temperatures between 302 and 1060 K

Kinetics of C6H5 radical reactions with 2-methylpropane, 2,3-dimethylbutane and 2,3,4-trimethylpentane

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Direct Determination of Product Branching for the NH₂ + NO Reaction at Temperatures between 302 and 1060 K