Single pulse shock tube

Comparison of results of single-pulse shock-tube experiments with those from an earlier study suggest that the existing rate expression for HF elimination from 1,1,1-trifluoroethane may need to be re-evaluated. ... 

Lifshitz, A. Tamburu, C. Suslensky, A. Dubnikova, F. Decomposition of Anthranil. Single Pulse Shock-Tube Experiments, Potential Energy Surfaces and Multiwell Transition-State Calculations. The Role of Intersystem Crossing. Phys. Chem. A 2006, no, 8248-8258. 

This new technique incorporates a catalyzed short contact time (SCT) substrate into a shock tube. Fig. 13. These SCT reactors are currently used in industry for a variety of applications, including fuel cell reformers and chemical synthesis.The combination of a single pulse shock tube with the short contact time reactor enables the study of complex heterogeneous reactions over a catalyst for very well defined regimes in the absence of transport effects. These conditions initiate reaction in a real environment then abruptly terminate or freeze the reaction sequence. This enables detection of intermediate chemical species that give insight into the reaction mechanism occurring in the presence of the chosen catalyst. There is no limitation in terms of the catalyst formulations the technique can study. 

McHale et al, Determination of the Decomposition Kinetics of Hydrazine Using a Single-Pulse Shock Tube , Ibid, 341-51 28) A.I. 

The above conclusions were substantiated by the work of Bauer, Hou, and Resler.20 They shock-heated C2F4-02 mixtures diluted in 99% Ar to temperatures of 1200-2400°K in a single-pulse shock tube. The oxidation products were analyzed after each run and found to be principally CF20 and CO with slightly smaller amounts of CF4. The minor products included C2F6 and trace amounts of C3F6 and C02. At the lower temperatures CF20 was the most important product, but as the temperature was... 

Tetrahydrofuran (THF, 52) is a very stable five-membered ring ether. The thermal decomposition of THF was studied in a heated bulb over the temperature range 530-670°C (46JA506 51JA175) and behind reflected shocks in a single-pulse shock tube over the temperature range 1070-1530 K... 

Dehydrofluorination is used to obtain fluorinated acetylenes. Thermolysis of a dilute mixture of 1,1-difluoroethene (11) in argon has been studied in a single-pulse shock tube over the temperature range 1017-1427 C at low conversions, below 1107 C, the principal reaction is unimolccular elimination of hydrogen fluoride to yield fluoroacetylene (H).52 5- Elimination of hydrogen fluoride from 1,1-difluoroethene (11) by r-butyllithium also provides fluoroacetylene (12), in 90% yield.54... 

The rate of fluorine displacement from fluorotoluenes by H-atoms has been measured in single-pulse shock tubes at 988-114 K.158 The addition of CF3 to CgFsCl has been studied.159 The intermediate adduct radical (CF3C6F5C1) was shown to react with an additional CF3 to give CF3CI and C6F5CF3. A range of fluorinated biphenyls can be produced by the reaction of pentafluorobenzene radicals with both electron-rich and -poor aromatics. The isomeric ratios of biphenyls produced indicated an efficient homolytic chain process.160... 

Single-pulse shock-tube thermal decomposition of furonitrile (1135-1380 K) affords primarily but-2-yne 1-nitrile via a radical intermediate.250 Radicals are also implicated in the thermolysis of furan-2,3-dione analogues.251 Explosive-driven shock waves of up... 

The gas-phase unimolecular pyrolysis of 2,4-dimethylpentane-2,4-diol has been found to occur by eliminative formation of acetone, isobutene, and H20 via a concerted six-membered cyclic transition state (Scheme 10).69 Single-pulse shock tube studies of the eliminative decomposition of ethoxy compounds have also been reported.70... 

W. Tsang, D. Robaugh, W.G. Mallard, Single-Pulse Shock-Tube Studies on C-NO2 Bond Cleavage During Decompositbn of Some Nitroaromatic Compounds, . Phys. Chem., 90 (1986) 5968-5973. 

A comparison of two single-pulse shock-tube-technique experiments applied to the HC1 elimination of ethyl chloride and -propyl chloride in the temperature range of 960-1100 K was made by Evans and coworkers48. The observed rate coefficients were compared with those of previous works. In this investigation it was believed that the activation energy Ea of 242.6 kJ mol-1 for CH3CH2C1 - CH2=CH2 + HC1 is more appropriate than the most commonly reported E values of 234.2-236.8 kJ mol-1. 

The single-pulse shock tube method in the thermal decomposition of l,l,l-trifluoro-2-chloroethane gave parallel eliminations135. The major reaction involved HC1 elimination which was believed to be formed by an a,a-elimination (equation 45) with a concerted transfer of a fluorine atom, while to a lesser extent a slower a,/Felimination of HF also took place (equation 46). 

The nature of the products evidently suggests a Wagner-Merweein rearrangement. Moreover, preliminary examination in a single-pulse shock tube was reported to confirm the molecular nature of the reaction and the rearrangement of neopentyl bromide to 2-methyl-1-butene and 2-methyl-2-butene. When this bromide was thermally decomposed in the absence of the chain inhibitor cyclochexene, the reaction proceeded in a radical process. 

To illustrate the concepts of determining, non-determining and negligible processes, the mechanism of the pyrolysis of neopentane will be discussed briefly here. Neopentane pyrolysis has been chosen because it has been studied by various techniques batch reactor [105— 108], continuous flow stirred tank reactor [74, 109], tubular reactor [110], very low pressure pyrolysis [111], wall-less reactor [112, 113], non-quasi-stationary state pyrolysis [114, 115], single pulse shock tube [93, 116] amongst others, and over a large range of temperature, from... 

The thermal reactions of dihydrobenzo[c]furan 258 were studied behind reflected shock waves in a single pulse shock tube over the temperature range 1050-1300 K to lead to products from a unimolecular cleavage of 258 <2001PCA3148>. Intriguingly, carbon monoxide and toluene were among the products of the highest concentration, while benzo[f]furan, benzene, ethylbenzene, styrene, ethylene, methane, and acetylene were the other products. Trace amounts of allene and propyne were also detected. 

Single pulse, shock tube decomposition of acetic acid in argon inv olves the same pair of homogeneous, molecular first-order reactions as thermolysis (19). Platinum on grapliite catalyzes the decomposition at 500—800 K at low pressures (20). Ketene, methane, carbon oxides, and a variety of minor products are obtained. Photochemical decomposition yields methane and carbon dioxide and a number of free radicals, wliich have complicated pathways (21). Electron impact and gamma rays appear to generate these same products (22). Electron cyclotron resonance plasma made from acetic acid deposits a diamond [7782-40-3] film on suitable surfaces (23). The film, having a polycrystalline stmcture, is a useful electrical insulator (24) and widespread industrial exploitation of diamond films appears to be on the horizon (25). 

An alternative detailed interpretation is that of Lin and Bauer [439], who investigated the reaction between CO and N2O in a single pulse shock tube at temperatures between 1320 and 2280 K. At the lower end of the temperature range the direct bimolecular reaction between CO and N2O was important, but above 1600 K the dominant reaction path was the dissociation of N2O followed by reactions of O atoms. In the analysis of their results, Lin and Bauer used the rate coefficient from Olschewski et al. [324] for the primary N2O dissociation step, and they obtained an apparent negative activation energy of — 23.4 kcal. mole" for reaction (Ivii)... 

Brabbs and Belles studied the recombination of O + CO in the expansion wave of a single-pulse shock tube at 2800-3600 °K and at pressures from 8.8 to 22.6 atm. They also found that the intensity of chemiluminescence, /, was directly proportional to [0][CO]. They concluded that the recombination rate coefficient assuming a third-order reaction, had an average lower limit of2x 10 P.mole . ... 

In a single-pulse shock-tube study of the isotope exchange reaction of N2, Bar-Nun and Lifshitz have obtained data which can not be interpreted in terms of a radical chain. It is suggested that vibrational excitation of nitrogen molecules to a certain critical level is the rate-determining step for the overall reaction... 

Single pulse shock tube study with 1 % reactant in argon analysis by glc. 

The trans - cis isomerization of this molecule under purely homogeneous conditions has been studied in a single-pulse shock tube. The first order rate coefficient measured" over the temperature range 570-615 °K had the value of 10 exp ( — 32, 200/RT) sec . The low activation energy has been interpreted in terms of an adiabatic process implying a linear transition state. 

Reaction (lA) is the other major primary initiation process, particularly above 1000 K. Kinetic data have been available for a number of years, partly because /cia is relatively easy to measure because secondary initiation is effectively absent. Nevertheless, the systems used are invariably complex and care is necessary in abstracting /cia- Tsang [47,48] has used a single-pulse shock-tube with considerable success by use of an approach whereby relative rate constants are obtained with one known accurately as a reference. Baldwin, Walker and Drewery [34] have shown that Eia can... 

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