In situ separation of heterogeneous and homogeneous reaction components in flow experiment

Abstract

A method is suggested for the determination of the character (homogeneous or heterogeneous) of the material transformation in the investigation of gas-phase reactions under tubular flow conditions. The method provides the estimation of the error in the rate constant of a gas-phase reaction due to the possible parallel occurrence of a heterogeneous process. 0 1993

Study of the reactions of OH with HCl, HBr, and HI between 298 K and 460 K

“…They employed a UV absorption at 185 nm to optically control the amount of HCl in the system and thus obtained consistent sets of measurements covering the temperature interval between 200 and 1055 K. Our results obtained between 298 and 460 K by using undiluted HCl in the reactant supply lines are in good agreement with these data thus supporting the recommended 7,8 room temperature value of k HCl (298 K) = 7.8 × 10 −13 cm 3 molecule −1 s −1 and proving our experimental approach. The rate constant k HCl (298 K) = (8.2 ± 0.4) × 10 −13 cm 3 molecule −1 s −1 derived in our earlier study 11 should be slightly corrected by ≈ 3.5% to account for axial diffusion processes and thus coincides with the present result. There is substantial disagreement between data from two studies extended to higher temperature of 1000 K 14,24 .…”

“…In the previous paper, 11 we reported a possibility of heterogeneous reaction between OH and HCl in the low‐pressure flow tube experiments. The experimental technique and data analysis have been suggested to separate the possible heterogeneous reaction channel from the gas phase reaction under study.…”

“…The test experiments using a movable injector were performed at the increased total pressure in the flow reactor of ≈ 1.1 kPa (8 Torr) followed by the data analysis suggested in Ref. 11. The results in the appropriate dimensionless units are presented in Figure 3 along with the net of calculated curves corresponding to various contributions of wall reaction.…”

“…Lines are calculated values of / for various fractions of the total reaction rate due to the potential heterogeneous reaction, W (see Ref. 11). D is a diffusion coefficient, and r is the flow tube radius [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Detailed descriptions of the apparatus and 10experimental methods employed in the present work are given elsewhere 10–12 . Thus, only a brief overview is provided here.…”