I come across many reactions like A + B --> products.
How to consider "products" as a species and solve the kinetics in simulation/modelling, as such the reaction is unbalanced by logic of chemistry.
Products are the species formed from chemical reactions. During a chemical reaction reactants converted into products after going through a high energy transition state. This results in the consumption of the reactants and yielding of produts.
Hi, its not generalized. There are reactions where products itself is mentioned as species. https://kinetics.nist.gov/kinetics/ReactionSearch?r0=74828&r1=3352576&r2=0&r3=0&r4=0&p0=-10&p1=0&p2=0&p3=0&p4=0&expandResults=true&
how can this reaction be handled in modelling? how to add "product" as a species.
Hi there,
Additionally to Fache Axel answer please check the paper: A Kinetic Study of OH Radical Reactions with Methane and Perdeuterated Methane by James R. Dunlop & Frank P. Tully.
Best
It is usually a shortcut to prevent listing all of the numerous product. Fischer-Tropsch is an example of a reaction (2. H2 + CO => products) that is sometime described this way. In this case product is an entire distribution of products ranging from CH4 to C50+
Lumping all components formed in a chemical reaction into a pseudo-species "products" is possible, if differentiation of all product species is not relevent. For the particular case of solving kinetics in modeling and simulation this simplification can only be made, if no product species is involved in the kinetic equation. The error of assuming that product species are not relevant in the kinetic expression is acceptable for many reactions, therefore this assumption is often reasonable.
It should also be considered that by lumping all product species, one loose information on product distribution, which is the main interest in many cases, though. Therefore, this simplification is mainly used in CRE textbooks or in an early stage of reactor model development.
Robert Güttel thanks for your response.. I have a question. In that case, how to balance thte mass of the species in kinetic simulation?
That is the weakness of lumping: The mass balance of components requires information on the product composition, which is not accessible after lumping. One might use average values for the products, such as molar mass or density. Those average values, however, depend on the composition, which is not known after lumping. The mass balance consequently contains errors. Therefore it is probably more meaningful to go for molar balances assuming constant density or flow rate (note that appropriate assumptions depend on the specific problem).
In general the applicability of lumping always depends on the accuracy required, which is defined in the problem statement. Therefore it has to be clear, which kind of assumptions are appropriate (e.g. constant density, flow rate, etc.). Furthermore, none of the products should affect the kinetics of the involved reactions.
Please also keep in mind that your question is rather generic and can't be answered in general, as the answer always depends on the specific problem.
Robert Güttel I Understand.. will come with more specific problem.
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