Mechanism and types of explosive behavior in hydrogen–fluorine systems

Abstract

The experimental data of Kapralova et al. [Kinet. Catal. (USSR) 10, 23 (1969)] have been modeled on a computer to show that two chain−branching reactions occur, H2* + F2 → HF + H + F (1), HF* + F2 → 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(0) is not absorbed on the wall, 6×104 < k1 < 2×105 and 5×106 < k2 < 7×106 cm3/mol−s when all vibrationally excited molecules of HF and H2 are included in HF* and H2*. For a model that includes flow of heat out of the reacting gas and also diffusion of HF(0) to the wall, the coefficients are 6×104 < k1 < 1×105 and 2×106 < k2 < 5×106 cm3/mol−s. The computations show that quenched reactions take place during the time of experimental manipulation, so that the stability of H2−F2−O2 and H2−F2−O2−M mixtures can be due in large measure to the HF produced during mixing. Double explosions and oscillatory reactions can also occur.