Temperature sensitivity of the gas phase

From Eq. (3.78), it can be seen that the temperature sensitivity depends on two par-ameters,[iil O and W O is the so-called temperature sensitivity of the gas phase , which is determined by the parameters of the gas phase, and W is the so-called temperature sensitivity of the condensed phase , which is determined by the parameters of the condensed phase. 

Fig. 7.22 Temperature sensitivities of the gas phase and the condensed phase of AP-HTPB composite propellants.

Substituting the and data into Eqs. (3.75) and (3.76), the temperature sensitivity of the gas phase, O, as defined in Eq. (3.79), and of the solid phase, as defined in Eq. (3.80), are determined as 0.0028 and 0.0110 respectively W is approximately four times greater than O. The computed Op represented by the sum of O and W is therefore 0.014 which is approximately equal to the Op derived from burning rate experiments. The heat of reaction at the burning surface is the dominant factor on the temperature sensitivity of the burning rate of the BAMO copolymer. 

The relationship between temperature sensitivity and burning rate is shown in Fig. 7.21 as a function of AP particle size and burning rate catalyst (BEFP).li31 The temperature sensitivity decreases when the burning rate is increased, either by the addition of fine AP particles or by the addition of BEFP. The results of the temperature sensitivity analysis shown in Fig. 7.22 indicate that the temperature sensitivity of the condensed phase, W, defined in Eq. (3.80), is higher than that of the gas phase, 5), defined in Eq. (3.79). In addition, 4> becomes very small when the propel-... 

The temperature sensitivity of gas phase 4> defined in Eq. (3.79) and the temperature sensitivity of the condensed phase V defined in Eq. (3.80) are obtained from the data of the burning surface temperature Ts, the temperature in the fizz zone Tg, the activation energy in the fizz zone Eg, the heat of reaction at the burning surface Qj, the temperature gradient in the fizz zone (f>, and the burning rate r. Figure 7-43 shows the temperature sensitivity of the burning rate of HMX-CMDB propellants as... 

As discussed above, the level of sensitivity of most gas-phase oxidation catalysts is high with regard to the reaction temperature. Therefore, any Stage II-screening tool should operate under isothermal conditions for all active materials, and it is a given prerequisite that thermal equilibrium of the reactor and a homogeneous temperature distribution are essential. 

There are also two factors that have already been noted in the numerical analysis of the kinetic model of CO oxidation (1) fluctuations in the surface composition of the gas phase and temperature can lead to the fact that the "actual multiplicity of steady states will degenerate into an unique steady state with high parametric sensitivity [170] and (2) due to the limitations on the observation time (which in real experiments always exists) we can observe a "false hysteresis in the case when the steady state is unique. Apparently, "false hysteresis will take place in the region in which the relaxation processes are slow. 

E. R. Bell et al., Ind. Eng. Chem., 41, 2597 (1949), were able to prepare large yields of <-butyl hydroperoxide by using HBr to sensitize the oxidation of isobutane. In this case, at the lower temperatures the HBr acted as an H donor to the t-Bu02 radical. See E. R. Bell et al., Discussions Faraday Soc.j 10, 242 (1951), for a detailed discussion of the gas-phase behavior of peroxy and alkoxy radicals. 

There is no evidence in any of the gas phase systems for initial multiple bond rupture (i.e., fragmentation reactions). Because of the low reaction temperatures, the alkoxy radical intermediates of the bond fission reactions (or radicals resulting from alkoxy radicals) are mainly involved in radical-radical termination processes ( 0) rather than participating in hydrogen abstraction from the parent peroxide E oi 6-8). Thus it has been commonly believed that the peroxide decompositions were classic examples of free radical non-chain processes. Identification of the rate coefficients and the overall decomposition Arrhenius parameters with the initial peroxide bond fission kinetics were therefore made. However, recent studies indicate that free radical sensitized decompositions of some peroxides do occur, and that the low Arrhenius parameters obtained in many of the early studies (rates measured by simple manometric techniques) were undoubtedly a result of competitive chain processes. The possible importance of free radical reactions in peroxide decompositions is illustrated below with specific regard to the dimethyl peroxide decomposition. 

Contributions in this section are important because they provide structural information (geometries, dipole moments, and rotational constants) of individual tautomers in the gas phase. The molecular structure and tautomer equilibrium of 1,2,3-triazole (20) has been determined by MW spectroscopy [88ACSA(A)500].This case is paradigmatic since it illustrates one of the limitations of this technique the sensitivity depends on the dipole moment and compounds without a permanent dipole are invisible for MW. In the case of 1,2,3-triazole, the dipole moments are 4.38 and 0.218 D for 20b and 20a, respectively. Hence the signals for 20a are very weak. Nevertheless, the relative abundance of the tautomers, estimated from intensity measurements, is 20b/20a 1 1000 at room temperature. The structural refinement of 20a was carried out based upon the electron diffraction data (Section V,D,4). 

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