Shock Tube Studies of the Reactions of Hydrogen Atoms. I. The Reaction H + NH3 → H2 + NH2

1974 ◽  
Vol 52 (7) ◽  
pp. 1171-1180 ◽  
Author(s):  
John E. Dove ◽  
Wing S. Nip
Keyword(s):  
Shock Tube ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
High Concentration ◽  
Hydrogen Atoms ◽  
Elementary Reactions ◽  
Temperature Range ◽  
Reflected Shock ◽  
Branched Chain ◽  
Chain Explosion

The partial equilibrium state following the branched-chain explosion of shock-heated rich H2/O2/diluent mixtures contains a high concentration of H atoms. The conditions under which this state can be used as a source of H atoms for the study of elementary reactions have been investigated. A small amount of NH3 was added to H2/O2/inert gas mixtures in order to measure the rate of the reaction H + NH3 → H2 + NH2. The pseudo-first order decay of NH3 in an approximately ten-fold excess of H atoms was followed by a time-of-flight mass spectrometer which sampled from the reflected shock region in a shock tube. The rate coefficient for this reaction, determined over the temperature range 1500–2150 °K, is 1013.44±0.10 exp −(17 400 ± 1 300 cal mol−1)/RT cm3 mol−1 s−1.It is pointed out that, under certain stated conditions, the method can also be extended to study the rates of elementary reactions involving O atoms and OH radicals. From our experiments, upper limits on the rate coefficients of the reactions OH + NH3 → H2O + NH2 and O + NH3 → OH + NH2 over the temperature range 1620–1920 °K are 8 × 109T0.08 exp (−1100/RT) and 1 × 1013 exp (−6600/RT), respectively.

Shock-tube study of the decomposition of octamethylcyclotetrasiloxane and hexamethylcyclotrisiloxane

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1395-1426 ◽  
Author(s):  
Paul Sela ◽  
Sebastian Peukert ◽  
Jürgen Herzler ◽  
Christof Schulz ◽  
Mustapha Fikri
Keyword(s):  
Mass Spectrometry ◽  
Shock Tube ◽  
High Repetition Rate ◽  
Rate Coefficients ◽  
Gas Chromatography Mass Spectrometry ◽  
High Concentration ◽  
Gas Phase Chemistry ◽  
Reflected Shock ◽  
Flight Mass Spectrometry ◽  
Phase Chemistry

AbstractShock-tube experiments have been performed to investigate the thermal decomposition of octamethylcyclotetrasiloxane (D4, Si4O4C8H24) and hexamethylcyclotrisiloxane (D3, Si3O3C6H18) behind reflected shock waves by gas chromatography/mass spectrometry (GC/MS) and high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS) in a temperature range of 1160–1600 K and a pressure range of 1.3–2.6 bar. The main observed stable products were methane (CH4), ethylene (C2H4), ethane (C2H6), acetylene (C2H2) and in the case of D4 pyrolysis, also D3 was measured as a product in high concentration. A kinetics sub-mechanism accounting for the D4 and D3 gas-phase chemistry was devised, which consists of 19 reactions and 15 Si-containing species. The D4/D3 submechanism was combined with the AramcoMech 2.0 (Li et al., Proc. Combust. Inst. 2017, 36, 403–411) to describe hydrocarbon chemistry. The unimolecular rate coefficients for D4 and D3 decomposition are represented by the Arrhenius expressions ktotal/D4(T) = 2.87 × 1013 exp(−273.2 kJ mol−1/RT) s−1 and ktotal/D3(T) = 9.19 × 1014 exp(−332.0 kJ mol−1/RT) s−1, respectively.

Multistage auto-ignition of undiluted methane/air mixtures under engine-relevant condition

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Yingjia Zhang ◽  
Wuchuan Sun ◽  
Wenlin Huang ◽  
Xiaokang Qin ◽  
Jinshu Liu ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Shock Tube ◽  
Oh Radicals ◽  
Ignition Process ◽  
Reflected Shock ◽  
Ignition Delay Times ◽  
Auto Ignition ◽  
Kinetic Mechanisms ◽  
Perform Sensitivity Analysis ◽  
The Difference

Gas-phase auto-ignition delay times (IDTs) of methane/“air” (21% O2/79% Ar) mixtures were measured behind reflected shock waves, using a kinetic shock tube. Experiments were performed at fixed pressure of 1.8 MPa and equivalence ratios of 0.5 and 1.0, over the temperature range of 800–1000 K. Overall, the effect of equivalence ratio on IDT is negligible at entire temperatures measured in this study. The difference from traditional ignition regime at high temperatures, the undiluted methane/air mixtures present a four-stage ignition process at lower temperatures, namely deflagration delay, deflagration, deflagration-detonation transition, and detonation. Four popular kinetic mechanisms, UBC Mech 2.1, GRI Mech 3.0, Aramco Mech 2.0, and USC Mech 2.0, were used to simulate the new measurements. Only UBC Mech 2.1 showed satisfactory predictions in the reactivity of the undiluted methane mixtures; it was, thus, adopted to perform sensitivity analysis for identifying dominant reactions in the ignition process. The difference in channels contributing ȮH radicals causes a reduced global activation energy with decreasing temperatures.Keywords: Methane; multistage ignition; shock tube; sensitivity analysis

Kinetics of the reaction H + C2H6 → H2 + C2H5 in the temperature region of 1000 K

1984 ◽  
Vol 62 (1) ◽  
pp. 86-91 ◽  
Author(s):  
J.-R. Cao ◽  
M. H. Back
Keyword(s):  
Equilibrium Constant ◽  
Rate Constant ◽  
Temperature Region ◽  
Recent Measurement ◽  
Hydrogen Atoms ◽  
Elementary Reactions ◽  
Temperature Range ◽  
Hydrogen Molecules ◽  
Kinetics Of ◽  
Rate Controlling Step

A system for the measurement of rate constants for elementary reactions of hydrogen atoms in the temperature region of 1000 K is described. The concentration of hydrogen atoms is controlled by the equilibrium constant for dissociation of hydrogen molecules. The kinetics of the rate of conversion of ethane to ethylene in this system has been studied over the temperature range 876–1016 K. The results show that the rate-controlling step is[Formula: see text]and the value obtained for the rate constant is[Formula: see text](R = 1.987 cal mol−1 deg−1). This value is compared with values obtained from other methods over the temperature range 300–1400 K. Combination with a recent measurement of the rate constant for the reverse reaction yields an experimental value for the equilibrium constant for the reaction.

scholarly journals A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals

2017 ◽  
Vol 19 (10) ◽  
pp. 7147-7157 ◽  
Author(s):  
Fethi Khaled ◽  
Binod Raj Giri ◽  
Milán Szőri ◽  
Tam V.-T. Mai ◽  
Lam K. Huynh ◽  
...  
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
Kinetic Study ◽  
Reaction Kinetics ◽  
Dimethyl Carbonate ◽  
Oh Radicals ◽  
Temperature Range ◽  
Reflected Shock ◽  
Kinetics Of

The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872–1295 K and at pressures near 1.5 atm.

The Shock Tube Autoignition of Biodiesels and Biodiesel Components

2013 ◽  
Author(s):  
Weijing Wang ◽  
Matthew A. Oehlschlaeger
Keyword(s):  
High Temperature ◽  
Methyl Ester ◽  
Shock Tube ◽  
Ignition Delay ◽  
Methyl Esters ◽  
Acid Methyl Ester ◽  
Oh Radicals ◽  
Reflected Shock ◽  
Ignition Delay Times ◽  
Delay Times

The autoignition of fatty-acid methyl ester biodiesels and methyl ester biodiesel components was studied in gas-phase shock tube experiments. Ignition delay times for two reference methyl ester biodiesel fuels, derived from methanol-based transesterification of soybean oil and animal fats, and four primary constituents of all methyl ester biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate, were measured behind reflected shock waves for fuel/air mixtures at temperatures ranging from 900 to 1350 K and at pressures around 10 and 20 atm. Ignition delay times were determined by monitoring pressure and chemiluminescence from electronically-excited OH radicals around 310 nm. The results show similarity in ignition delay times for all methyl ester fuels considered, irrespective of the variations in organic structure, at the high-temperature conditions studied and also similarity in high-temperature ignition delay times for methyl esters and n-alkanes.

Experimental and theoretical study on thermal decomposition of methyl butanoate behind reflected shock waves

RSC Advances ◽  
2015 ◽  
Vol 5 (105) ◽  
pp. 86536-86550 ◽  
Author(s):  
A. Parandaman ◽  
M. Balaganesh ◽  
B. Rajakumar
Keyword(s):  
Thermal Decomposition ◽  
Shock Waves ◽  
Theoretical Study ◽  
Rate Coefficients ◽  
Temperature Range ◽  
Reflected Shock ◽  
Methyl Butanoate

The rate coefficients for total decomposition of MB in the temperature range of 1229–1427 K, were reported.

scholarly journals Arrhenius parameters for the OH-initiated degradation of methyl crotonate, methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate over the temperature range of 288–314 K

RSC Advances ◽  
2016 ◽  
Vol 6 (59) ◽  
pp. 53723-53729 ◽  
Author(s):  
Juan P. Colomer ◽  
María B. Blanco ◽  
Alicia B. Peñéñory ◽  
Ian Barnes ◽  
Peter Wiesen ◽  
...  
Keyword(s):  
Relative Rate ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Arrhenius Parameters ◽  
Temperature Range

The relative-rate technique has been employed to obtain rate coefficients for the reactions of OH radicals with methyl crotonate, methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate between 288 and 314 K in 760 Torr of air.

scholarly journals Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad Akbar Ali ◽  
M. Balaganesh ◽  
Faisal A. Al-Odail ◽  
K. C. Lin
Keyword(s):  
Water Molecule ◽  
Energy Surface ◽  
Rate Coefficient ◽  
Water Concentration ◽  
State Theory ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Experimental And Theoretical Studies ◽  
Effective Reaction ◽  
Effective Reaction Rate

AbstractThe rate coefficients for OH + CH3OH and OH + CH3OH (+ X) (X = NH3, H2O) reactions were calculated using microcanonical, and canonical variational transition state theory (CVT) between 200 and 400 K based on potential energy surface constructed using CCSD(T)//M06-2X/6-311++G(3df,3pd). The results show that OH + CH3OH is dominated by the hydrogen atoms abstraction from CH3 position in both free and ammonia/water catalyzed ones. This result is in consistent with previous experimental and theoretical studies. The calculated rate coefficient for the OH + CH3OH (8.8 × 10−13 cm3 molecule−1 s−1), for OH + CH3OH (+ NH3) [1.9 × 10−21 cm3 molecule−1 s−1] and for OH + CH3OH (+ H2O) [8.1 × 10−16 cm3 molecule−1 s−1] at 300 K. The rate coefficient is at least 8 order magnitude [for OH + CH3OH(+ NH3) reaction] and 3 orders magnitude [OH + CH3OH (+ H2O)] are smaller than free OH + CH3OH reaction. Our calculations predict that the catalytic effect of single ammonia and water molecule on OH + CH3OH reaction has no effect under tropospheric conditions because the dominated ammonia and water-assisted reaction depends on ammonia and water concentration, respectively. As a result, the total effective reaction rate coefficients are smaller. The current study provides a comprehensive example of how basic and neutral catalysts effect the most important atmospheric prototype alcohol reactions.

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