A study of the reactions of fluorine with hydrogen and methane in the initiation phase using a miniature tubular reactor

Abstract

A small tubular reactor having an inner diameter of 1-2 mm and used as the source in a molecular beam apparatus is described in detail. This arrangement allows the study of fast reactions with reaction times smaller than 1 msec. The preexplosive reaction phase between Fz and Hz and CHI, respectively, is investigated to find out the initiation reactions. In the Fz/H2 reaction, initiation is brought about by heterogeneous generation of F atoms or some other surface reaction. Evidence is also obtained for chain branching reactions. In the F&H4 case the dominant initiation reaction is the homogeneous reaction CHI + F2 -CH:J

Chain Reaction Mechanism in Hydrogen/Fluorine Combustion

“…Therefore, the reaction is not responsible for the chain-branching step in the H 2 /F 2 /O 2 /N 2 flame, and the upper bound of its rate constant was determined to be ∼10 –13 cm 3 s –1 . This upper bound is smaller by a factor of ∼10 2 than the value of the rate constant employed by Warnatz et al , in their kinetic modeling studies of the H 2 /F 2 /Ar flame; however, the value is consistent with those obtained in the studies of Sullivan et al and Seeger et al, who suggested the values of k 1 = (3–12) × 10 –18 cm 3 s –1 at 350 K and k 1 < 1.7 × 10 –13 cm 3 s –1 at ∼400 K, respectively.…”

“…The mixtures of H 2 and F 2 are known to explode spontaneously, and their explosion limits have been studied in the 1960–70s. − The kinetic behavior of H 2 /F 2 mixtures has also been examined in flow reactors. − These studies indicated rapid reactions of H 2 /F 2 mixtures even at room temperature due to the chain reaction mechanism outlined below. They also suggested inhibition of the reactions and explosions upon addition of a small amount of O 2 .…”

Fluorine Plasma Treatments of Polypropylene Films, 1 – Surface Characterization

“…Hydrogen abstraction by F is also fast and efficient. An informative comparison of the rates of hydrogen abstraction from n ‐butane for various active species is given in Table 3 29–32. A more detailed analysis of hydrogen abstraction is included in Part 2 of this paper 11…”

Review of Rate Constants and Exploration of Correlations of the Halogen Transfer Reaction of Trisubstituted Carbon-Centered Radicals with Molecular Halogens

“…The database of rate constants for fluorine transfer is even more sparse than that for iodine transfer and tends to rely on more specialized methods. It is summarized in Table . ,,,− …”

“…For methyl, pulsed laser photolysis of F 2 in the presence of methane and time-resolved detection of the IR emission from vibrationally excited HF allowed the extraction of both the rate constants for hydrogen and fluorine transfer ( 1a″′ ) . Study of the pre-explosive phase of CH 4 –F 2 mixtures at 300–400 K in a small tubular reactor functioning as the source in a molecular beam apparatus with mass spectroscopic detection gave the composite quantities A o A F and E o + E F , where reaction “o” is the proposed initiation step: CH 4 + F 2 → CH 3 • + HF + F • . These were deconvoluted by a computer fit of the data to give the quite similar value 1b″′ .…”