Grigoriy Yablonsky

Grigoriy Yablonsky (or Yablonskii) (Григорий Семенович Яблонский) is an expert in the area of chemical kinetics and chemical engineering, particularly in catalytic technology of complete and selective oxidation, which is one of the main driving forces of sustainable development.

His theory of complex steady-state and non-steady-state catalytic reactions is widely used by research teams in many countries of the world (the USA, UK, Belgium, Germany, France, Norway, and Thailand).

Yablonsky serves as an associate research professor of chemistry at Saint Louis University's Parks College of Engineering, Aviation and Technology and college of arts and sciences.

The authors have started with the catalytic trigger (1976 ), the simplest catalytic reaction without autocatalysis that allows multiplicity of steady states.

Then they have supplemented this classical adsorption mechanism of catalytic oxidation by a "buffer" step

Here, A2, B, and AB are gases (for example, O2, CO, and CO2), Z is the "adsorption place" on the surface of the solid catalyst (for example, Pt), AZ and BZ are the intermediates on the surface (adatoms, adsorbed molecules, or radicals), and (BZ) is an intermediate that does not participate in the main reaction.

Let the concentration of the gaseous components be constant.

Then the law of mass action gives for this reaction mechanism a system of three ordinary differential equations that describe kinetics on the surface.

where

z = 1 − (x + y + s)

is the concentration of the free places of adsorption on the surface ("per one adsorption center"), x and y are the concentrations of AZ and BZ, correspondingly (also normalized "per one adsorption center").

and s is the concentration of the buffer component (BZ).

This three-dimensional system includes seven parameters.

The detailed analysis shows that there are 23 different phase portraits for this system, including oscillations, multiplicity of steady states, and various types of bifurcations.

Let the reaction mechanism consist of reactions.

where A_i are symbols of components, r is the number of the elementary reaction and are the stoichiometric coefficients (usually they are integer numbers).

(The components that are present in excess and the components with almost constant concentrations are not included.)

The Eley–Rideal mechanism of CO oxidation on PT provides a simple example of such a reaction mechanism without interaction of different components on the surface:

Let the reaction mechanism have the conservation law

and let the reaction rate satisfy the mass action law:

where c_i is the concentration of A_i.

Then the dynamic of the kinetic system is very simple: the steady states are stable and all solutions with the same value of the conservation law monotonically converge in the weighted l_1 norm: the distance between such solutions ,

monotonically decreases in time.

This quasithermodynamic property of the systems without interaction of different components is important for the analysis of the dynamics of catalytic reactions: nonlinear steps with two (or more) different intermediate reagents are responsible for nontrivial dynamical effects like multiplicity of steady states, oscillations, or bifurcations.

Without interaction between different components, the kinetic curves converge into a simple norm, even for open systems.

The detailed mechanism of many real physico-chemical complex systems includes both reversible

and irreversible reactions.

Such mechanisms are typical in homogeneous combustion,

heterogeneous catalytic oxidation, and complex enzyme reactions.

The classical

thermodynamics of perfect systems is defined for reversible kinetics and has no limit for

irreversible reactions.

On the contrary, the mass action law gives the possibility to write the chemical kinetic equations for any

combination of reversible and irreversible reactions.

A simple scheme for the nonlinear kinetic oscillations in heterogeneous catalytic reactions has been proposed by Bykov, Yablonsky, and Kim in 1978.

Since 2006, Yablonsky has been an editor of the Russian-American Middle West.

Yablonsky, together with Lazman, developed the general form of steady-state kinetic description (the kinetic polynomial’), which is a non-linear generalization of many theoretical expressions proposed previously (the Langmuir –Hinshelwood and Hougen–Watson equations).

Yablonsky also created a theory of precise catalyst characterization for the advanced worldwide experimental technique (temporal analysis of products) developed by John T. Gleaves at Washington University in St. Louis.

In 2008–2011, Yablonsky, together with Constales and Marin (Ghent University, Belgium), and Alexander Gorban (University of Leicester, UK), obtained new results on coincidences and intersections in kinetic dependences and found a new type of symmetry relation between the observable and initial kinetic data.

Together with Alexander Gorban, Yablonsky developed the theory of chemical thermodynamics and detailed balance in the limit of irreversible reactions.