Grigoriy Yablonsky (or Yablonskii) () is an expert in the area of
chemical kinetics
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a ...
and
chemical engineering
Chemical engineering is an engineering field which deals with the study of the operation and design of chemical plants as well as methods of improving production. Chemical engineers develop economical commercial processes to convert raw materials ...
, 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
In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p'' ...
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.
Since 2006, Yablonsky has been an editor of the Russian-American ''Middle West''.
Scientific contributions
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
Ghent University (, abbreviated as UGent) is a Public university, public research university located in Ghent, in the East Flanders province of Belgium.
Located in Flanders, Ghent University is the second largest Belgian university, consisting o ...
, 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
Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics. Chemical thermodynamics involves not only laboratory measure ...
and
detailed balance
The principle of detailed balance can be used in Kinetics (physics), kinetic systems which are decomposed into elementary processes (collisions, or steps, or elementary reactions). It states that at Thermodynamic equilibrium, equilibrium, each elem ...
in the limit of irreversible reactions.
[A. N. Gorban and G. S. Yablonsky]
"Extended detailed balance for systems with irreversible reactions"
''Chemical Engineering Science'', 66:5388–5399, 2011; , [A.N. Gorban, E.M. Mirkes, G.S. Yablonsky]
"Thermodynamics in the limit of irreversible reactions"
''Physica A'' 392 (2013) 1318–1335; ,
Catalytic trigger and catalytic oscillator
A simple scheme for the nonlinear kinetic oscillations in heterogeneous catalytic reactions has been proposed by Bykov, Yablonsky, and Kim in 1978. The authors have started with the
catalytic trigger (1976), the simplest catalytic reaction without
autocatalysis
In chemistry, a chemical reaction is said to be autocatalytic if one of the reaction products is also a catalyst for the same reaction. Many forms of autocatalysis are recognized.Steinfeld J.I., Francisco J.S. and Hase W.L. ''Chemical Kinetics and ...
that allows multiplicity of steady states.
Then they have supplemented this classical
adsorption mechanism of catalytic oxidation by a "buffer" step
Here, A
2, B, and AB are gases (for example, O
2, CO, and CO
2), 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 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 portrait
In mathematics, a phase portrait is a geometric representation of the orbits of a dynamical system in the phase plane. Each set of initial conditions is represented by a different point or curve.
Phase portraits are an invaluable tool in st ...
s for this system, including oscillations, multiplicity of steady states, and various types of
bifurcations.
Reactions without the interaction of different components
Let the reaction mechanism consist of reactions.
:
where
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:
:
2Pt(+O2) <=> 2Pt; \;\; + CO <=> + CO2\!\uparrow.
Let the reaction mechanism have the conservation law
:
and let the
reaction rate
The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per u ...
satisfy the
mass action law:
:
where
is the concentration of
.
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
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 extended principle of detailed balance
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. Without additional restrictions,
this class of equations is extremely wide and can approximate any
dynamical system
In mathematics, a dynamical system is a system in which a Function (mathematics), function describes the time dependence of a Point (geometry), point in an ambient space, such as in a parametric curve. Examples include the mathematical models ...
with preservation of positivity of concentrations and the linear conservation laws. (This
general approximation theorem was proved in 1986.) The model
of real systems should satisfy some restrictions. Under the standard
microscopic reversibility The principle of microscopic reversibility in physics and chemistry is twofold:
* First, it states that the microscopic detailed dynamics of particles and fields is time-reversible because the microscopic equations of motion are symmetric with respe ...
requirement, these restrictions should be formulated as follows: A
system with some irreversible reactions should be at the limit of the systems with all reversible reactions and the detailed balance conditions.
Such systems have been completely described in 2011.
The ''extended principle of detailed balance'' is the
characteristic property of all systems that obey the generalized mass action law and is
the limit of systems with detailed balance when some of the reaction rate constants
tend to zero (the
Gorban-Yablonsky theorem).
The extended principle of detailed balance consists of two parts:
* The ''algebraic condition'': The principle of detailed balance is valid for the reversible part. This means that for the set of all reversible reactions, there exists a positive equilibrium where all the elementary reactions are equilibrated by their reverse reactions.
* The ''structural condition'' is that the
convex hull
In geometry, the convex hull, convex envelope or convex closure of a shape is the smallest convex set that contains it. The convex hull may be defined either as the intersection of all convex sets containing a given subset of a Euclidean space, ...
of the stoichiometric vectors of the irreversible reactions has an empty intersection with the
linear span
In mathematics, the linear span (also called the linear hull or just span) of a set S of elements of a vector space V is the smallest linear subspace of V that contains S. It is the set of all finite linear combinations of the elements of , and ...
of the stoichiometric vectors of the reversible reactions. (Physically, this means that the irreversible reactions cannot be included in oriented cyclic pathways.)
The stoichiometric vector of the reaction
is the ''gain minus loss'' vector with coordinates
.
(It may be useful to recall the formal convention: the linear span of an empty set is 0;
the convex hull of an empty set is empty.)
The extended principle of detailed balance gives an ultimate and complete answer to the following problem: ''how to throw away some reverse reactions without violating thermodynamics and microscopic reversibility?'' The answer is that the
convex hull
In geometry, the convex hull, convex envelope or convex closure of a shape is the smallest convex set that contains it. The convex hull may be defined either as the intersection of all convex sets containing a given subset of a Euclidean space, ...
of the stoichiometric vectors of the irreversible reactions should not intersect with the
linear span
In mathematics, the linear span (also called the linear hull or just span) of a set S of elements of a vector space V is the smallest linear subspace of V that contains S. It is the set of all finite linear combinations of the elements of , and ...
of the stoichiometric vectors of the reversible reactions, and the reaction rate constants of the remaining reversible reactions should satisfy the
Wegscheider identities.
Career

From 1997 to 2007, Yablonsky was a research associate professor in the department of energy, environmental, and chemical engineering at
Washington University in St. Louis. Since 2007, Yablonsky has been an associate professor at Saint Louis University's Parks College of Engineering, Aviation, and Technology as well as in the department of chemistry.
During his career, Yablonsky has organized many conferences and workshops at national and international levels. Yablonsky frequently participates in interdisciplinary dialogues involving mathematicians, chemists, physicists, and chemical engineers.
Yablonsky was selected in 2013 for the
James B. Eads Award, which recognizes a distinguished individual for outstanding achievement in engineering or technology.
Honors and awards
* Lifetime Achievement Award, in recognition of outstanding contributions to the research field of chemical kinetics, Mathematics in Chemical Kinetics and Engineering, MaCKiE, 2013
* James B. Eads Award, Academy of Science of St. Louis Outstanding Scientist Award (2013).
* Honorary Doctor Degree from the University of Ghent, Belgium (2010)
* Chevron Chair Professorship at the Indian Institute of Technology (IIT), Madras (2011)
* Honorary Fellow of the Australian Institute of High Energetic Materials, Gladstone, Australia (2011)
Professional memberships and associations
Yablonsky has numerous international designations as an honorary professor, fellow, doctor, and member of prestigious science academies and universities in Belgium, India, China, Russia, and Ukraine.
* 1996–present:
American Institute of Chemical Engineers
The American Institute of Chemical Engineers (AIChE) is a professional organization for chemical engineers. AIChE was established in 1908 to distinguish chemical engineers as professionals independent of chemists and mechanical engineers.
Curr ...
* 2011–present:
American Chemical Society
The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all ...
* 2011–present: Member of the Scientific Council on Catalysis at the
Russian Academy of Sciences
The Russian Academy of Sciences (RAS; ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across the Russian Federation; and additional scientific and social units such ...
* 2013–present: Fellow,
Academy of Science of St. Louis
Notable publications
Yablonsky is the author of seven books, most recently ''Kinetics of Chemical Reactions: Decoding Complexity'' Wiley-VCH (2011) (together with Guy B. Marin), and more than 200 papers.
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See also
*
Chemical reaction network theory
References
External links
Yablonsky's faculty profile at Parks College of Engineering, Aviation and Technology
{{DEFAULTSORT:Yablonsky, Grigoriy
Living people
American chemical engineers
20th-century American mathematicians
21st-century American mathematicians
Saint Louis University mathematicians
Jewish scientists
1940 births
Soviet chemists
20th-century chemists
Soviet mathematicians
Washington University in St. Louis faculty