Abstract
Recently, a method based on non-equilibrium continuum thermodynamics which derives thermodynamically consistent reaction rate models together with thermodynamic constraints on their parameters was analyzed using a triangular reaction scheme. The scheme was kinetically of the first order. Here, the analysis is further developed for several first and second order schemes to gain a deeper insight into the thermodynamic consistency of rate equations and relationships between chemical thermodynamic and kinetics. It is shown that the thermodynamic constraints on the so-called proper rate coefficient are usually simple sign restrictions consistent with the supposed reaction directions. Constraints on the so-called coupling rate coefficients are more complex and weaker. This means more freedom in kinetic coupling between reaction steps in a scheme, i.e., in the kinetic effects of other reactions on the rate of some reaction in a reacting system. When compared with traditional mass-action rate equations, the method allows a reduction in the number of traditional rate constants to be evaluated from data, i.e., a reduction in the dimensionality of the parameter estimation problem. This is due to identifying relationships between mass-action rate constants (relationships which also include thermodynamic equilibrium constants) which have so far been unknown.
Highlights
Investigating impacts of thermodynamics on kinetics of chemical reactions is an area of unflagging interest and continuous research
The transformed thermodynamic polynomial corresponding to the function J(T, A, B) is: J
We select k110 = k101 = k011 = 0.Using the same procedure as previously (Pekar, 2016), we find the same relationships between first order rate constants and first degree polynomial coefficients
Summary
Investigating impacts of thermodynamics on kinetics of chemical reactions is an area of unflagging interest and continuous research. The third system is just the mixture of three isomers (A, B, and C) analyzed in the previous work, but, here, modeled with the second degree thermodynamic polynomial: J = k100(cA − K1−1cB) + k001(cC − K2cB) + k020(cB2 − K12cA2 ) The traditional mass-action kinetics expressed in the form of the first-degree version of (3), including the sign of the rate constant, is fully consistent with non-equilibrium thermodynamics— with entropic inequality (the second law).
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