The Langmuir Research Institute

Lake Saint Louis, MO, United States

The Langmuir Research Institute

Lake Saint Louis, MO, United States

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Yablonsky G.S.,Saint Louis University | Yablonsky G.S.,The Langmuir Research Institute | Constales D.,Ghent University | Marin G.B.,Ghent University
Chemical Engineering Science | Year: 2011

It is shown that equilibrium constants determine the time-dependent behavior of particular ratios of concentrations for any system of reversible first-order reactions. Indeed, some special ratios actually coincide with the equilibrium constant at any moment in time. This is established for batch reactors, and similar relations hold for steady-state plug-flow reactors, replacing astronomic time by residence time. Such relationships can be termed time invariants of chemical kinetics. © 2010 Elsevier Ltd.


Constales D.,Ghent University | Yablonsky G.S.,Saint Louis University | Yablonsky G.S.,The Langmuir Research Institute | Marin G.B.,Ghent University
Chemical Engineering Science | Year: 2012

For dual kinetic experiments, i.e., experiments performed in batch or steady-state plug flow reactors from reciprocal initial conditions, thermodynamic (space-)time invariances for all reversible single reactions of the first and second order have been found explicitly.In all analyzed cases, quotient-like functions of concentrations can be defined which equal the equilibrium constant of the reaction during the whole course of the experiment, and not only at the end, i.e., under equilibrium conditions. The obtained invariances can be used as simple fingerprints for distinguishing the types of reactions.For multistep reactions: (a) a similar invariance was obtained for the two-step catalytic reaction (single route complex reaction) under pseudo-steady-state assumption; (b) for the two-step non-steady-state reaction, an approximation for the thermodynamic invariance was found to be valid in two domains, (1) at the very beginning of the reaction (2) at the end of the reaction, near equilibrium conditions. We hypothesize that such two-domain validity of the thermodynamic invariance is a general feature of dual kinetic experiments performed in complex chemical systems. © 2012 Elsevier Ltd.

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