Mechanism and types of explosive behavior in hydrogen–fluorine systems

Abstract

0 -+ HF + 2F (2). The asterisks indicate a vibrationally excited molecule. Rate coefficients derived for these reactions depend slightly on the computational model. For a model that is adiabatic and in which HF(O) is not absorbed on the wall, 6 X 10 4 < k [ < 2 X 10 5 and 5 X 10 6 < k, < 7 X 10 6 cm 3 /mol-s when all vibrationally excited molecules of HF and H, are included in HF* and H, *. For a model that includes flow of heat out of the reacting gas and also diffusion of HF(O) to the wall, the coefficients are 6X10 4 < k[ < lX10 5 and 2X10 6 < k, < 5X10 6 cm 3 /mol-s. The computations show that quenched reactions take place during the time of experimental manipulation, so that the stability of H,-F,-O, and H,-F,-O,-M mixtures can be due in large measure to the HF produced during mixing. Double explosions and oscillatory reactions can also occur.The data in Ref. 3 are sufficiently extensive and precise to warrant analysis using a chemical mechanism containing all the elementary reactions that occur and for which rate coefficients are known or can be estimated within bounds. Very recent work l3 -ao on the rates of vibrational relaxation of HF 13 -17 and Ha 18-ao allows us to use measured rate coefficients for these important reactions. Also, recent work a1 -a4 on the quenching reaction H+ Oa+ M-HOa+ M provides rate coefficients for a number of inert gases M.

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

“…According to Sullivan and co-workers [18] reaction (2) would be dominant in the present reaction system. The authors report a rate constant of 2 X lo6 < hb2 < 5 X lo6 cm3/mol sec a t 350 K, with a slight temperature dependence for this reaction.…”

“…Atoms and radicals are supplied by the propagation steps. Thus, it is not surprising that two recent reaction schemes for the Hz/F2 reaction [18,19], designed to model flames and explosion limits, are unable to explain the observed yield of the HF product. Obviously there is some faster initiation reaction than included in the models.…”

“…ko was now determined as a function of temperature by matching the result of the numerical integration, which was done in the way described above, to the experimental HF mole fraction. In these calculations we did not use the above simplified scheme but the more elaborate schemes of [18] and [19] with the additional initiation and termination reactions. The rate constants h3 and k 4 were estimated from @ID, where 6 is the sticking probability, C the mean thermal velocity and D the tube diameter.…”

Experimental and Numerical Investigation of the Subatmospheric H2-F2Reaction

“…Basov et al (1969) considered that the reaction between H 2 and F 2 involves a branched chain mechanism. According to Sullivan et al (1975), the H 2 -F 2 reaction is a chain type in which free radicals help in propagation of reaction steps. The rate of this reaction is very fast.…”

Stability and nonexplosive hydrogen fluoride production in atmospheric- pressure hydrogen--oxygen--fluorine mixtures

“…10 ' 11 Additional chemical kinetic information concerning this system has been obtained from analysis of behavior near or at the second explosion limit 12 and from more traditional studies of the pertinent elementary reactions. 13 Under concentrated, ambient temperature conditions, the chemical mechanism by which reactants are converted to products must include at least the following elementary steps.…”