The kinetic studies are as follows:

(1) Stoichiometric analysis (can be omitted in the case of single reaction):

So linerarly independent reactions and conversion degrees.

(2) Thermodynamic analysis (can be skipped in the case of single irreversible reaction iin nisothermal conditions):

Then equlibrium constant /s, equlibrium conversion degree /s and reaction enthalpy / ies (nonisothermal conditions).

(3) Determination of kinetic curves (reaction rate /s vs. concentration or concentrations vs. time)

The different innitial concentrations of substrates, different constant or not temperatures, various flow rates (tubular type reactor) etc. are needed.

(4) Derivation of the form of kinetic equation /s and the determination of the values of kinetic parameters (differential method, integral method which needs mass balance equation /s)

You suggested to realize (3) - and then what - interpolation, aproximation, neural networks?

A few examples:

one kinetic equation for SO3 synthesis - many plants around the world,

one kinetic equation for NH3 synthesis - many plants around the world etc.

So instead of one kinetic equation and many installations, one unit with one catalyst and then one installation in one chemical plant?

The ancient man did not need models to light a fire, but we need equations to extinguish it.

Regards,

PS About how RG users understand the term "kinetic model" I will write another time. MG

Yes, both science and engineering. Models decrease the amount of research data required for a stable production. Also models can warn of potential danger.

Thank you, Miroslaw.

I am abreast of. Sorry, I will wait for several explanations and will answer then. I hope, the engineers will understand me.

Regards.

Dear Mirosław,

I would be interested to discuss what a "kinetic model" term means. This deserves a separate discussion. Could you please to post a question on this subject?

No, this is the same question.

Please, Miroslaw, formulate here your opinion on the term "kinetic model". May be, it is differing from the commonly accepted one.

OK.

I start with that I do not like the terms model, mathematical modelling and computer simulation. I sometimes and not only sometimes use them, but I prefer using the terms equation, mathematical description and solution of the equation. I do not like the term rate eqution and I try not to use it.

For me, the kinetic model is the same as the kinetic equation, that is, it is the relationship between the rate of reaction and the temperature and concentration of the reactants. For me, and not only do I think, the form of the kinetic equation should not depend on the type of reactor used and the values of process parameters used. It may, however, depend on the type of catalyst. The form of the kinetic equation should not depend on the transport phenomena. I mean here inter and intra particle diffusion. The value of the pre-exponential factor (inter particle diffusion) and the pre-exponential factor and activation energy (intra particle diffusion) will obviously change. They may also change the values of sorption parameters as in L-H kinetic equation. It is said that kinetic parameters are falsified by transport phenomena. Of course, no "extra terms" can be added to the kinetic equation, taking into account the influence of transport phenomena. One can, of course, but to balance equations. Unfortunately, many people mix the meaning of terms: kinetic equation, rate equation, process rate, balance equation and also reaction order. No matter whether we deal with chemical reactions, biomass growth, sorption phenomena (adsorption, desorption, drying, hydration, drag release etc.), structural changes of material during shearing, etc. the terms kinetic equation and mass balance equation have the same meaning. The same as relaxation time in many phenomena. Example (reversible adsorption): dq / dt = k (qe-q) - for me mass balance equation, r = k (qe-q) - for me kinetic equation for reversible adsorption, r = dq/dt - for me adsorption rate, but r = k(qe-q)2 - for me it is not kinetic equation ........... but it might be rate equation.

Regards

Thank you, Dear. Miroslaw,

Now, we can continue our amusements. I believe that your issue is capable of attaching more importance to them.

I will write a little about it, but not today.

Regards,

OK! Dear Miroslaw,

I see, you argue as a chemical engineer, who consider kinetic equations just as kinetic models which are applicable for the unique aim of simulation of chemical processes and for forecastings the connections between the productivities, on the one hand, and the distribution of the temperatures and concentrations in reactors, on the other hand. Isn't it? It is, in my opinion, the quite natural requirement of an engineer to a kinetic equation. Dear Farid Benyahia writes approximately the same.

But some researchers, when writing "kinetic model", write about a system of chemical equations, which, by their opinion, should be stated in order to deduce the equation for the reaction rate dependence on the temperature and concentration only. As you, I think, know, different researchers, on frequent occasions, invent very different systems of chemical equations (they usually term such systems "mechanisms") for any reaction and dispute which of them is better.

What is your opinion on the significance of such schemes for understanding of the real mechanisms of catalytic reactions and on the usefulness of such schemes for the real engineering?

These researchers usually believe that the kinetic equations deduced from such schemes (on frequent occasions, with some additional approximations) supplemented with equations of diffusion and equations of the heat transmission should be used for simulation of contact catalytic reactors. Such a method leads to the necessity of solution of the system of partial differential equations with all amenities of these procedures.

What is your opinion, maybe, it would be more useful to have experimental real unit tube filled with a real catalyst or an experimental shelf with such a catalyst at a chemical plant, interested in a prosess under study, and to determine the map of the catalyst productivity under different ambient conditions with no kinetic model and as a real function of kinetic dependences, heat conduction, and diffusion.

Thanks, Mirosław.

To continue the discussion and to avoid misunderstanding, we must define each term very clearly.

The term "rate equation." My definition:

The rate equation or rate law for a chemical reaction is an equation that links the reaction rate with the concentrations or pressures of the reactants and constant parameters. The rate law can be obtained experimentally or deduced from a sequence of "elementary" steps.

I disagree with you that "the kinetic model is the same as the kinetic equation."

" balance equation" or the "mass balance equation."

I disagree that " the terms kinetic equation and mass balance equation have the same meaning." For me " the mass balance equation" is the same as the reaction stoichiometry. "The mass balance equation" should be included in the rate law, but it does not determine the rate law.

Victor, at this time I agree with you that

" when writing "kinetic model", write about a system of chemical equations, which, .... should be stated in order to deduce the equation for the reaction rate dependence on the temperature and concentration only."

For me, the kinetic model is the sequence of "elementary" chemical reactions," with values of rate constants assigned for each reaction. This leads to a system of differential equations, which often can't be solved to give the reaction rate law. This system of differential equations under given initial conditions (concentrations, temperature, etc) can be solved numerically to predict the time profile of reactants, products and all intermediates.

What is an elementary reaction in the kinetic model? For me, this is the reaction which can be written as a uni- or bimolecular reaction. In other words, the reaction for which the rate law is determined by the reaction stoichiometry.

The kinetic model is NOT the synonym of the reaction mechanism.

The term "reaction mechanism" is rather vague. This is a separate question which deserves a separate discussion.

I'll appreciate your comments on my definitions.

Hi,

It's an interesting question. The catalytic practice needs to be modeled. The developed model will describes the reaction rate and the optimum operating conditions. It is used by scientists and engineers. The developed models is a mean for comparison between catalysts and used technologies. The improvements of kinetic reaction or ciharacteristcs of catalysts need models. Its a big question. We can say several pages without finishing.

with my best wishes!

Dr. Adel Oueslati

Interesting disscusion. As a practical matter; the mass balance is applied to the reactor design. The balance will change depending on the size and type of reactor, residence time, etc. A CSTR design may, very well, have a different mass balance than a plug flow design or a batch. For continuous processes the mass balance and reactor design will vary till the production goal / specification is achieved. The kinetic equation is used for the design to calculate the concentrations for each design basis. For instance ....

More later...

"Models" are almost never 100% correct but they are often very useful. Ancient man was able to harness the power of fire without knowing the chemistry of combustion. Similarly many current operators are able to run chemical plants and refineries without a very detailed knowldge of the reacrions taking place in their units. So no - good models are not absolutely necessary in order to accomplish great achievements.

However, it is much easier to understand how to optimize a unit's performance if you have a good model that material balances (both overall and elemental) and this sort of model is actually surprisingly rare, in oprating plants.

Correctly accounting for reaction stoichiometry, kinetics and reaction equilibrium is very useful for those designing chemical process plants mostly because it eliminates a lot of the poor choices.

There are curently neural network systems with no basic knowledge of kinetics or equilibrium that can achieve similar or even better results than more detailed kinetic models so I suppose it isn't actually necessary to have models based on good science aslong as you don't stray too far from places you have already been to.

A wise man once said "all models are wrong but most models are useful". There is great danger in beieving you know more than you actually do about how a plant operates. But is still useful to understand as much as you possibly can.

No, Dear Dr. Rick Manner,

So-called “models” (if to understand under this term the imaginary system of chemical equations which allegedly describes the intimate mechanism of a catalytic process when it proceeds in a so-called kinetic region and even isn’t influenced by mass-transfer, heat-transfer, and different spatial heterogeneities) are scarcely useful for the catalytic science, because there was no example when an imaginary mechanism was proved solidly in the sequel and because any imaginary model orientates incorrectly the later researchers and leads to futile discussions and scarcely is a better means of creation or optimization of a real industrial process as compared with the means proposed by me above as the illustration to this question.

It is known that the F. Haber - C. Bosch process was developed more than a century ago with no model and its main parameters are today the same or almost the same as they had been stated in 1913. The processes of the ethylene oxide catalytic production (T. Lefort, SFCG), stereospecific polymerization (G. Natta – K.Ziegler), methanol production from hydrogen and carbon oxides (F.Haber), and many other processes were developed with no models and produce chemical products under the same conditions as before with no models; speaking more exactly, the model is by itself and the process is by itself.

To understand the real mechanism of any catalytic process, studies of chemisorption and desorption of the components of reaction mixture and studies of intermediate states are necessary (see, for example, CH3OH synthesis in a review https://www.researchgate.net/publication/235355092_Mechanisms_of_methanol_synthesis_from_hydrogen_and_carbon_oxides_at_Cu-Zn-containing_catalysts_in_the_context_of_some_fundamental_problems_of_heterogeneous_catalysis).

The delusions, to which the attempts to guess the reaction mechanisms basing on kinetic data can lead, are seen from

https://www.researchgate.net/publication/235343211_Paradox_of_Heterogeneous_Catalysis_Paradox_or_Regularity

A wide complex of the theoretical and practical problems of heterogeneous catalysis is considered in the review paper

https://www.researchgate.net/publication/307920182_Energetic_homogeneity_of_thermally_stabilized_metal_and_metal-oxide_surfaces_new_oscillation_theory_of_catalysis_OTCAT_and_unification_of_catalytic_mechanisms , were the oscillation theory of catalysis is also presented and its practical applications are considered.

All these papers are available by these addresses at the ResearchGate site.

Dear Victor,

I do not have a Phd only an SM from MIT and over 35 years experience developing useful correlations ( sometimes referred to as models) for the refining industry and using them to improve reinery performance and create a basis for monitoring of catalyst deactivation.

It appears that we live in different worlds with a very different focus on what is important and what is not. My emphasis has been in Hydrotreating, Hydrocracking and Steam Methane Reforming processes but I have also developed correlations (that often look like models) for Naphtha Isomerization, Catalytic Reforming, Fisher-Tropsch, Delayed Coking, Transalklation/Isomerization of Xylenes, Methanol production, methanol to gasoline/diesel and several other processes. I can assure you that all of these models/correlations are useful. They are often fit for purpose and sometimes not very rigorous. I expect you have a different definition of useful that leads to our difference of opinion.

Many academics believe they have developed a rigorous understanding of simple reaction systems like steam methane reforming or isomerization but they are often actually sophisticated correllations. This information is often very useful but can lead to problems if it is misinterpretted or extrapolated improperly.

The real world is often quite complex and shortcuts must be are taken to predict effects of process changes. In my experience these "models" are often quite useull and lead to significant operational improvement opportunities at refineries and chemical plant. They are extremely useful but they are not completely accurrate.

I expect that your definiton of a good model is quite different than mine because your models have a very diferent purpose than mine. You are trying to creae a more rigorous fundemental understanding of the chemistry. That is well beyond the scope of my efforts to build useful tools that help refineries to operate more profitably by understaning the impact of operational changes on current yields as well as projected future yields.

As indicated in several answers, it is necessary to specify what we mean by "model". If, as specified by Rick, we speak about a correlation between numerous experimental observations, a model is certainly useful. The answer is less obvious if we adopt a more fundamental point of view. In every case, it is necessary to accept that a model is not the reality but a momentary, simplified and imperfect representation of the reality. Alfred Korzybski wrote, " A map is not the territory. " A map is nevertheless useful.

A simple correlation is useful only under the conditions where it was established. A model can suggest new experiments for, maybe, improve these conditions. A model so conceived is useful but is not a mechanism. To look for a mechanism is a matter of fundamental research. The utility of the fundamental research is never obvious in the short term but we always observed that it is useful in the long term, sometimes for reasons to which we had not thought initially.

Dear All,

In last days, I get several letters, in which it is written that it is impossible to download my papers from the ResearchGate site. Indeed, it appears that a number of my catalytic papers became invisible for the visitors of the site. I returned the papers at the site, and they are now available. I ask you to inform me if the error recommences.

Dear All,

The Guy's remark is rather timely. Thank you, Dear Guy.

I should elucidate the content of the question. It doesn't cover the case considered by Rick.

I would like to discuss the "kinetic model" as a means of description of the kinetics and mechanisms of catalytic processes, which is aimed at the transition from laboratory studies of catalytic reactions to the simulation of industrial processes and reactors and to optimization of the working processes.

Some researchers use the following procedure for transition from laboratory studies of a catalytic process to simulation of an industrial process and reactor or to optimization of an industrial process.

(1) Laboratory experiments aimed at obtaining the data on the reaction rates at different concentrations and temperatures of reacting mixtures (in the kinetic regime, when neither diffusion nor heat conduction influence the reaction rate);

(2) Fabrication of a "kinetic model" (a system of equations of intermediate chemical reactions leading to formation of the product) in such a way that the kinetic equation deduced algebraically from this model could describe approximately the experimental results (on frequent occasions, with additional approximations);

(3) Use of the equation thus deduced for simulation of the process under study under industrial conditions or for optimization of the process.

Does the catalytic practice have a need for such “kinetic models” and if “yes” does just the science or just the engineering have a need for such “models”?

Would it be better to use another procedure, which is described by me above in the elucidation to the initial question, namely, it would be more useful to have an experimental unit real tube filled with a catalyst or an experimental shelf with a catalyst at the chemical plant and to determine the map of the catalyst productivity under different ambient conditions with no models?

There is an example.

Tolman et al have built the "kinetic model" of industrial cyclohexane oxidation to adipic acid, which improved the process:

Tolman, C. A.; Druliner, J. D.; Nappa, M. J.; Herron, N.; Alkane Oxidation Studies in Du Pont's Central Research Department; in (1989), 303–60, Activation and functionalization of alkanes, Edited by C. Hill, Wiley, Chichester, ISBN 0-471-60016-4

Victor,

Now you completely reformulated your original question. Plz, clarify what is " another procedure, which is described by me above in the elucidation to the initial question."

Breaking out of the discussion for two days makes it very difficult to turn it on now. In my statement I referred to how I understand the term kinetic equation. I also pointed to the most important, in my opinion, the feature of kinetic equation, namely that the form of a kinetic equation should be invariant to the conditions of kinetic study. The only exception is a catalyst used, which, through the influence of the chemical reaction mechanism, can change, though not necessarily, the form of a kinetic equation. If we refer to reactions in flow heterogeneous systems, it is best to conduct research in the so-called kinetic region. However, this is not always possible. The reduction of the catalyst particles results in an increase in flow resistance in the bed. In turn, the increase in reactant flow through bed causes a decrease in conversion. etc. Ideally, the kinetic equation would reflect the mechanism of chemical reactions. Unfortunately, in the case of macrokinetic study, where in the laboratory reactor we determine the concentration of reactants as a function of time or space time is not possible. I mean mechanism of chemical reaction, not inhibiting effects or sorption phenomena (eg. Vanden Busche and Froment kinetic equations for methanol synthesis). Of course, we can consider the of so-called molecular level. Then, instead of several kinetic equations, r = r (c, T) (their number depends on the number of linearly independent reactions) we will get several, several dozen or several hundred equations. These will be differential equations with equally large number of unknown parameter values.

It is important to remember that to describe industrial processes, kinetic equations are most commonly used in the smallest possible number and in the simplest possible form. Preferably in the form of a power monomial for the irreversible reaction and of power binomial for reversible reaction. The chemical reaction mechanism can then be forgotten. Such are usually the requirements of industry guys.

It is also important to note that any kinetic equations (the values of their parameters) obtained in laboratory conditions must be verified in industrial conditions.

And another note. Kinetic equations are not solved - as they are written in Wikipedia. Kinetic equation/s are part of mass balance equation/s (right side) and only after supplementing with other equations (many types) can it be used in practice. Such a mathematical description of the process, some scientists call the kinetic model. Not me.

Regards,

Dear Yurii,

This is probably some misunderstanding. I have not written that the mass balance equation is the same as the kinetic equation or the kinetic model. The kinetic equation is a part of mass balance equation for chemical reaction (accumulation - (input - output) = chemical transformation) and in my opinion the most important.

You use rate equation or rate low I prefer kinetic equation or kinetic model.

Regards,

Dear Miroslaw,

You write: "... the form of a kinetic equation should be invariant to the conditions of kinetic study. The only exception is a catalyst used, which, through the influence of the chemical reaction mechanism, can change, though not necessarily, the form of a kinetic equation".

Indeed, in the ideal case, the form of a kinetic equation for any reaction at the same catalyst could be invariant to the conditions of kinetic study. However, unfortunately, today there are no catalytic reaction, for which is consensus relative to the kinetic equation. The problem of the ways to the reveal the ideal kinetic equations is in the cross point of a number of the problems of the theory of catalysis. The review paper by S.W. Weller, "Kinetics of heterogeneous catalytic reactions", Catal Rew. 1992, 34 (3), 227 is the encyclopaedia of these problems and the review paper by V.E. Ostrovskii and E.A. Kadyshevich, "Energetic homogeneity of thermally stabilized metal and metal-oxide surfaces, new oscillation theory of catalysis (OTCAT) , and unification of catalytic mechanisms", J.Therm. Anal. Calorim., 2017, 127, 319-350 proposes solutions of a majority of these problems. This paper is available at the ResearchGate site by the address Article Energetic homogeneity of thermally stabilized metal and meta...

Victor asked:

"Would it be better to use another procedure, which is described by me above in the elucidation to the initial question, namely, it would be more useful to have an experimental unit real tube filled with a catalyst or an experimental shelf with a catalyst at the chemical plant and to determine the map of the catalyst productivity under different ambient conditions with no models? "

-------------

Unfortunately catalyst contacting/ effectiveness factor is much poorer in a lab scale pilot plant fixed bed reactor so it would be difficult to use much of the information you would get from a pilot reactor with varying feed rates. Unit upsets would also be diffifult to replicate.

Comercial reactors are typically built robustly enough to operate contiuously for several years with minimal loss of yield as the catalyst deactivates. It is also usually desirable to coordinate turnaround of several interdependent units at the same time (eg Hydrogen producing and Hydrogen consuming units shut down together). Turnaround scheduling depends on many factors and is often independent of the performance of an individual unit.

However there are indeed some chemical plant facilities that routinely operate pilot plants or smaller comercial units to help evaluate projected yields altenate feed stocks.

Dear Victor,

I used the word "should". Theory is not always reflected in practice. We discuss, however, whether mathematical models, and in particular kinetic models (for me kinetic equations) are needed. In my opinion - yes - because they shorten the design time. But they also cost a lot. I mean here, of course, the correct kinetic equations, not the so-called kinetic equations.

Regards,

Dear Miroslaw, Dear All,

You again mix up the terms "equation" and "kinetic model",

The question covers empirical "kinetic model" that is

" the imaginary system of chemical equations which allegedly (with no sufficient proofs of their validity) hypothetically describes the intimate mechanism of a catalytic process" and the question has the following content: whether such an empirical model is needed.

The question doesn't contain the term "equation" . About equation a special tolk could be.

Dear Victor,

To begin with, generally about kinetic equations - as I understand it. The kinetic equation usually takes the form of a power monomial or binomial (homogeneous system) or a hyperbolic function (heterogeneous systems). The form of the equation is determined on the basis of experiments by the differential or integral method using the assumed norm (objective function) in form of RMS, average relative error etc. which we minimize. The effects of temperature, influence of initial substrate concentrations and, possibly, influence of concentrations of selected products (inhibiting effects of products) are taken into account in the studies. In case of reaction A ==> ... we investigate the effect of initial concentration of A, and in case of reaction A + B ==> ....... we will perform experiments at least for several molar ratios B / A. The most common mistake made here is to conduct the experiment for one molar ratio. For example 2: 1 and then the conclusion - the second order reaction with respect to A and B or 20: 1 and then the conclusion - the first reaction order with respect A. This may be, but it does not have to be.

Nothig mixed. I consistently use the term kinetic equation - as a result of kinetic studies (macrokinetic). But what you call the kinetic model, I call the mathematical model of the process. Remember, however, that 30 years ago, the term model and modeling was rarely used.

Besides, the kinetic equation is derived from the experiment, so, of courese, it can be called an empirical equation.

Regards,

Dear Miroslaw,

Allow me to ask you, whether you simulated ever any industrial reactor.

I by no means want to offend you, but, the fact of the matter is that my answer to you should be dependent on your experience.

Dear Victor,

Yes. At the end of the 1980s, I belonged to a small scientific team, who was involved in the optimization of the methanol synthesis process at the Nitrogen Plant in Chorzów. The team leader was Professor Skrzypek. It was a muti-bed tubular reactor with cold gas injection. It was about choosing the amount of catalyst in each bed and the amount of cold gas to increase the amount of methanol produced per year. Besides, I participated in the verification of the mathematical model describing the oxidation process of o-xylene to phthalic anhydride (experiments in the pilot scale reactor in Nitrogen Plant in Kędzierzyn). I was also in a team that studied the kinetics of the synthesis of 2-ethylhexyl phthalate for Nitrogen Plant in Kędzierzyn. It was about eliminating by-products that had an adverse effect on the color of ester.

As you have noted, I am not speaking about modeling and simulation of the processes in industrial scale reactors, but only on macrokinetic studies in laboratory and description their results - without them, however, you can not simulate any process in industrial reactors.

Regards,

Dear Victor Ostrovskii and all.

I can only say in Russian: - « Мамы разные нужны, Мамы всякие важны.»

Interpretation of the experiment depends on the qualification of the experimenter, his objectivity, voluntarism and the volume of experimental data. It is possible to represent the bimolecular mechanism as a sum of exponentials with good accuracy.

The proposed topic can be discussed indefinitely.

Yours faithfully, Ivan Ivanovich Dolgov

Уважаемый Victor Ostrovskii и все, все.

Я могу сказать только на русском языке:- « ..Мамы разные нужны, Мамы всякие важны..».

Интерпретация эксперимента зависит от квалификации экспериментатора, его объективности, волюнтаризма и объёма экспериментальных данных. Можно бимолекулярный механизм представить как сумму экспонент с хорошей точностью.

Предложенная тема может обсуждаться бесконечно.

Искренне Ваш, Иван Иванович Долгов.

Dear Ivan Ivanovich!

Уважаемый Иван Иванович,

Говоря по-русски, как ни крути, на самом деле механизм реакции такой, какой он есть и никакой другой. Бывает так, что из разных механизмов можно вывести одно и то же уравнение. Мы это продемонстрировали. Бывает даже так, что одно и то же кинетическое уравнение для стационарной каталитической реакции можно вывести, выдумав, что поверхность неоднородна или считая ее однородной, какой она есть на самом деле. Это мы тоже доказали.

Но знание истинного механизма реакций, протекающих стационарно на поверхностях твердых тел, важно не только для описания кинетики какого-то каталитического процесса при определенных условиях, но также - для понимания теории твердого тела и ее приложений не только к явлению катализа, т.к. природа едина в законах ее проявления и все знания о природе должны быть объединены общими законами, применимым к различным ее проявлениям.

Я уверен, что надо стремиться к познанию реальных сущностей природных явлений, а не конструировать представления о них на основе "моделей", хотя последнее и было характерно для прошлого века, особенно - для его второй половины, что привело к массе псевдотеорий.

I am sure that it is necessary to aspire to the cognition of the real essences of the natural phenomena rather than to construct notions of them on the basis of "models", though the last was characteristic for the previous century, especially, for its second half and led to a majority of pseudo-theories.

С уважением и наилучшими пожеланиями.

Виктор Островский.

А мамы разные нужны и разные важны, так же, как и нужно, чтобы было побольше поэтов хороших и разных.

В.О.

Dear Victor, Dear Ivan,

Russian language - why not Polish.

I agree that qualifications in laboratory work are very important. It is also important the number of experimental points. In the IChE we have very good lab technician. In the case of kinetic studies of esterification reactions we started from 6-8 kinetic curves in a month (one series), and after one year, there were 6-8 kinetic curves in a week.

By the way - sum of exponetials? concentration with respect ......? , reaction rate with respect ......? ........?

Regards,

OK, please, read english translation.

Dear Ivan Ivanovich, Dear All,

Speaking in Russian, like it or not (here is Russian idiom), the reaction mechanism is such as it is and no other. On frequent occasions, the same kinetic equation for a stationary chemical reaction corresponds to different mechanisms, i.e. can be deduced from different mechanisms.We had demonstrated such examples. On frequent occasions, when using different mechanisms, even any one kinetic equation for a stationary chemical reaction can be deduced just as on the basis of erroneous assumption that the surface is heterogeneous so on the basis of the correct knowledge that it is homogeneous. This also is proved in our works.

But the knowledge of the real mechanism of reactions, going stationary at the solid surfaces, is important not only for description of the kinetics of any catalytic process under some conditions, but also for understanding of the solid bodies theory and its applications not only to the phenomenon of catalysis, becauses nature lives and reveals itself on the basis of the same laws in different situations and all knowledges about natural phenomena should be connected by common laws which are applicable to different its visualizations.

I am sure that it is necessary to aspire to the cognition of the real essences of the natural phenomena rather than to construct notions of them on the basis of "models", though the last was characteristic for the previous century, especially, for its second half and led to a majority of pseudo-theories.

Sincerely,

Best wishes,

Victor Ostrovskii.

Dear Miroslaw,

Thank you for your explanation of your approach to the method of identification of kinetic equations for industrial processes.

We discuss more complicated approaches intended for transfering of the kinetic data obtained in laboratory under so-called kinetic conditions to simulation of industrial apparatuses, namely, the significance of the so-called "kinetic models" termed as a system of equations of intermediate chemical reactions leading to formation of a desired product (this system of reactions includes chemisorption of source substances, surface reactions, and desorption of the product; therewith some of these reactions can be equilibrium and can be combined in one step). My question applies to the frequent cases when these "kinetic models" are obtained empirically with no sufficient proofs by independent (adsorption, calorimetric, spectral, etc.) techniques.

According to the existing practice, researchers try to formulate "kinetic models", which they sometimes name "mechanisms" in such a way that these models are capable of approximate describing their experimental kinetic data.

Especially for you and in the context of your previous issues I repeat:

" Would it be better to use another procedure, which is described by me above in the elucidation to the initial question, namely, it would be more useful to have an experimental unit real tube filled with a catalyst or an experimental shelf with a catalyst at the chemical plant and to determine the map of the catalyst productivity under different ambient conditions with no models?"

If you are interested in the methods of clarification of the real mechanisms of catalytic processes, I could propose you the address of a review paper where a wide bibliography and concrete examples of catalytic reactions are available.

Article Energetic homogeneity of thermally stabilized metal and meta...

Dear Victor,

Thanks for the additional information and a broader explanation of your views on kinetic models. Until now, I did not know your research works, especially those related to the synthesis of methanol on copper catalysts. This is probably because I have never dealt with the physicochemical studies of catalysts. In Institute of Chemical Engineering we do not have such instruments. If we needed, the required tests were performed in the Institute of Catalysis and Surface Chemistry.

Of course, I agree with your view that there is generally no connection between real phenomena on the surface of the catalyst and the usually proposed forms of mathematical models. The macrokinetic study, after the experimental, come down, in fact, to the guessing of the model’s form and the proof, based on the numerical minimization of the assumed norm, that one of the guessed models is the right one. It is rather difficult here, for any unambiguous results.

I also agree that the range of applicability of these models is determined by the range of process parameters used. Thus, no extrapolations are possible.

Going to your suggestion: "an experimental unit real tube filled with a catalyst or an experimental shelf with a catalyst at the chemical plant", I think it is unrealistic. But it seems to me that it should not be treated literally. Rather, you wanted to induce a broader discussion of the uselessness of currently used models and attempts to link them with the mechanism of catalytic reactions.

It is a pity that specialists in surface chemistry did not join the discussion.

Regards,

PS I noticed that in attatched work you used the term "kinetic equation" - usually as me. MG