Evaluation of the Influence of Secondary Processes on the Results of the Measurement of Rate Constants of Gas-Phase Chemical Reactions

Abstract

Using the example of one of the important chemical reactions OH + O → O₂ + H in the mechanism of combustion of a mixture of hydrogen and oxygen, current issues of constructing a model for measuring rate constants are considered, and the role of secondary chemical reactions in this process is analyzed. It is noted that to assess the adequacy of the kinetic model of the measurement process, the intended purpose of the model is important; the difference in requirements for models designed to solve direct and inverse kinetic problems is emphasized. The analysis is focused on one of the components of the uncertainty in the results of measurements of rate constants of chemical reactions, which is due to the systematic effect associated with incomplete consideration of secondary reactions in constructing a kinetic model of the measuring process. In considering this issue, it is proposed to use the principle of necessary and sufficient redundancy, when the relative contributions of reactions are not assessed a priori based on a limited number of leading processes, but are calculated automatically taking into account the entire set of reactions from the basic set. Mathematical modeling was used to numerically analyze the experimental results; the most important secondary processes are identified that can play a significant role in determining the reaction constant. The systematic components of the uncertainty of the measurement results are examined; corrections are proposed to compensate for them, and refined values of the constants at a temperature of T = 295 K are presented.