Chemical Kinetics - Science topic

I don't think it is possible to optimize the number of stages as it is automatically generated based on the column design and operating conditions. Trial and error is recommended in your case. Have scenarios of + and - 10% of each operating variable (temp, pressure, RR,... etc) then check out the process performance to compare between these scenarios. For the reactive stages, I think you can initially assume, for example, 5, 10, 15 and 25 reactive stages, then compare the reactive distillation performance. I wish you the best.

Elbatoul Benidris please check your inbox

Yes,it can

Pareto Chart is a normal plot originally plotted from your data obtained. The standardized effects of the chemical kinetics process will be compared to showcase which process parameters that singly or interactively assisted the process.

See minitab tutorial pdf.

Hope it is helpful. Good luck

Send your email address to me, dgamble@ns.sympatico.ca. I can send my published comments about second order kinetics.

Best regards,

Donald Gamble

In fact, it is actually a bit unusual that with regard to gas-liquid absorption, no names of scholars have been assigned to particular equilibrium curves and their corresponding mathematical functions, other than William Henry.

While the chemical equilibrium is strictly dictated by thermodynamics, the kinetics expressions depend on the type of catalyst (these reactions are usually catalysed) and may vary from one another. Some typical expressions can be found in Chemical Engineering Journal (2007), 134(1–3), 138–144. https://doi.org/10.1016/j.cej.2007.03.051

The study of combustion is important to optimize the design and operating parameters of a combustor. The combustion between the fuel and air involves the conversion of the chemical energy of the species to heat energy. Complete combustion is desirable to get the maximum thermal efficiency out of it. Incomplete combustion is not desirable as it emits hazardous unburnt hydrocarbon as well as CO2, NOx, etc to the environment.

I think you might mean DRM 19 CHEMKIN files.

You can download it by googling it.

If you cannot find it, give me your email address, and I'll send it to you.

Toyese Oyegoke, Of course, browning, presumably food, is not an elementary reaction. There we can deal with the oxidation of various food components, enzymatic reactions and a slow loss of water. Structural and texture changes may also occur. One can, obviously, try to describe the kinetic curves (degree of browning vs. time) with known functions and on this basis infer the order of the process (treated as a single step), but one need to have reliable data. But if the changes in the degree of browning are small, as the author of the question writes, such calculations will be unreliable. And one more thing. In such a situation, the use of the term apparent activation energy does not make sense.

But you should specify the M-Ln complex( like Ru (III) bpy3 / Rh complex ) as well as quencher ( like Fe ( H2O)6 or Iodide ion , I - ) complying Stern - Volmer kinetics .The standard fluremetric data is to be analysed for correlation coefficiant ( r ) lies

in between or less than 1. This data analysis signifies a linear with relevant value of r proves the co-ordination number of metal M like Ru , Rh complexes are hexa-co-ordinated ( n=6) .

Thank you very much for your answer. I am still not practical with Aspen Plus since I focused for a lot of time on Aspen Hysys, I will try to insert the design specification you suggest. I am working at 15bar and 950°C, the molar fraction of hydrogen that i would eliminate is 10^-7.

I will reach you out is any help is needed.

Thank you and wish you the best

Asya

According to the link provided above, one may be tempted to suggest a simple combustion test case involving hydrogen oxidation to validate the "in-house" developed chemical kinetics CFD code. Thanks.

Okay, thank you Sudesh Kumar !

Dear Tawney Knecht

As reported by Nayim Sepay , these two reactions are pH-depended. Besides, the esterification of phenol is lower than that of alcohol because of the lower nucleophilicity of the hydroxyl group that results from the participation of oxygen lone pair with the aromatic resonance.

Regards,

Regardless of the subject, questionnaires can be developed by the researcher with what he/she considers important or can come from other researchers (I.e., benchmarks).In general, the first contact with the social click you research must be suave, and empathic so that you get to know about them. Stress and distrust can bother students, for instance.Info about the Likert scale can be found here:

https://www.scribbr.com/methodology/likert-scale/

You can also use Excel (please, refer to the enclosed file), Matlab, Origin, Scilab, R and online sites to process data related to questionnaires.

Set aside your algorithms and calculations for a few minutes and test the following nonlinear regression curves.

You can also estimate the parameters well.

Regardless of whether we use nonlinear regression or one of the many graphical methods, e.g. L-B, E-H or Merino, nothing will change because the number of points is too small to determine reliables values of two parameters. Additional kinetic tests should be performed for rate limiting substrate concentrations below 2.5 and above 15.

Thank you Professor Frank T. Edelmann for the great insight. sure, I'll go through the mention linked. well, from your expertise, will you please suggest some potential materials which can show desired chemistry. Thanks

Toyese Oyegoke when we are talking about your question and particularly the catalyst which always lowers the energy of the transition state for the reaction - in this case any reaction you can assume.The difference between the transition state energy and the other part that is the reactant energy is the main ACTIVATION ENERGY and this is very important to understand, Lowering of this energy which means lowering of transition state energy also ensures and lowers the activation energy for sure

The "feasibility" of one reaction depends on thermodynamic factors and kinetic factors. When thermodynamics are feasible, then kinetic factors become the main impact we consider.

When we consider the Eyring Equation,

κ = K ( kT / h )exp (–Δ G ‡ / kT)

the Eyring Equation, developed by Henry Eyring in 1935, is based on transition state theory and is used to describe the relationship between reaction rate and temperature. It is similar to the Arrhenius Equation, which also describes the temperature dependence of reaction rates.

Two aspects should be calculated: about enthalpy and entropy.

ΔGº = ΔHº – TΔSº

Most of the time, someone consider activation enthalpy factors to estimate the reaction "feasibility" temperature. However, more accurately, the influence of activation entropy should be consideredespecially when the activation entropy is relatively large. For example, some enzyme similar-catalyzed reactions, they can occur at low temperatures even the activation enthalpy were large.

Another important thing that needs to be considered is that, in addition to the common calculation errors in DFT calculations, it often does not represent the true situation in the reaction, such as the solvation effect. Given a large or small activation energy in the DFT calculation, it does not mean that the reaction will never happen or happen, but may be caused by some factors in the calculation.

From the published literature, by comparing the calculated results with the experimental results, the results of 29 to 39 kcal/mol you gave is possible.

Pls see references of

Activation energy makes sense here for each stage separately. Exponential functions with different bases and/or exponents cannot be added together.

Giovanni Barone, Activation energy only makes sense for elementary reactions/processes. The value you determined is not the activation energy.

Each water has a capacity to dissolve any solute. After reaching such level, the water is saturated. Thus, it is not surprizing to see high TDS water has lower capacity to dissolve NaCl, compared low TDS one

If one go literally to what you wrote, one can think that you mean fuel blending. But, as one know, the rate at which such mixtures are formed does not affect their properties. So you probably mean something else, e.g. the mechanism of the combustion process of fuel mixtures in the engine. You should be clear about this. As for the composition, it is best to use mass fractions here.

Please use this link: http://www.thinks.chemphys.ru/shiny/Redir/

A lot of information can be useful.

Best of luck

Dear Oykum Unal I found your technical question really interesting, although I'm not a proven expert in this field. Even though this does perhaps nor answer you question directly, you might find some very useful information in the following PhD thesis entitled

DEVELOPMENT OF AMMONIUM PERCHLORATE BASED SOLID PROPELLANT

The thesis can be freely downloaded as pdf file from the internet. As in your case, the studied propellant consisted of a mixture of ammonium perchlorate as oxidizer, aluminum (Al) as fuel and hydroxy-terminated polybutadiene (HTPB) as binder.

Good luck with your research! 👍

Amylopectin restricts restricts starch from becoming plastic-like therefore, HCl serves to change its properties.

Thank you for sharing idea Madhukar Baburao Deshmukh

I suppose you are talking about normal octadecane (n-C18H38).

You may try several engineering models for a reasonable temperature range up to about 600 K to 700 K. Although there are no extensive data measurements for this fluid. The one-parameter friction theory model: https://doi.org/10.1016/S0378-3812(00)00474-X, combined with the Peng and Robinson EoS can give you some reasonable pvT, viscosity, and phase behavior estimations. This approach can also be extended to thermal conductivity.

But for most of the temperature range you are looking at, the octadecane will certainly be degraded. I even doubt you will have any CH4 left at all, as it starts decomposing at about 1000 K.  

So, you need to first figure out what compounds you will have left.

But, at such temperatures, you are likely only to have some light gases and C. For the fluid phase, a simple model that may be useful to consider would be the one by Chung et al.:

I would start here.

If heterogeneities existed in the protolith, tectonic transposition can be a major factor. e.g.

Myers, J., 1978. Formation of banded gneisses by deformation of igneous rocks. Precambrian Res. 6, 43–64. doi:10.1016/0301-9268(78)90054-2.

And illustration in

Ramsay, J.G., Graham, R.H., 1970. Strain variation in shear belt. Can. J. Earth Sci. 7, 786–813. doi:10.1139/e70-078.

I believe the exchange current density is at "zero" overpotential. Tafel equation relates current density to some over potential but it does not offer any insights about exchange current density when overpotential is zero.

Yurii V Geletii out of curiosity, would chrono-amperometry be useful here? The idea there is to provide a periodic modulation of the over-potential and monitor the response current decay while the overpotential is zero?

Kafia Oulmi Thank you for the recommendations.

Here is link visit this channel

The energy gap between HOMO and LUMO also helps to describe the chemical behavior and electrical properties of molecules, with lower energies indicating higher reactivity and lower stability

this depends on which type of ligand used

How to apply Langmuir adsorption isotherm. A complete guidance ..

How to apply Freundlich adsorption isotherm. A complete guidance

Pseudo first order kinetic model.a complete step by step process..

Freundlich adsorption isotherm a complete guidance

… Read more

The skeletal mechanism is a detailed mechanism considering both sensitivity and flux analyses where as the reduced mechanism to consistently over predict the temperature .

Hi,

Like other molecules, the kinetics of drugs adsorption can be presented using various existing models. These are some of the articles related to adsorption of emerging contaminants conducted by my team for your future references, if applicable.

ATENOLOL SEQUESTRATION USING ACTIVATED CARBON DERIVED FROM GASIFIED GLYRICIDIA SEPIUM, October 2020, Arabian Journal of Chemistry 13:7544–7557

DOI: 10.1016/j.arabjc.2020.08.029

Amino-functionalised silica-grafted molecularly imprinted polymers for chloramphenicol adsorption, May 2020, Journal of Environmental Chemical Engineering 8(5):103981

DOI: 10.1016/j.jece.2020.103981

Ordered mesoporous carbons originated from non-edible polyethylene glycol 400 (PEG-400) for chloramphenicol antibiotic recovery from liquid phase, January 2015, Chemical Engineering Journal 260:730-739

DOI: 10.1016/j.cej.2014.09.010

Riboflavin adsorption onto multi-modal mesoporous carbon synthesized from polyethylene glycol 400, January 2013, Chemical Engineering Journal s 215–216:297–305,

DOI: 10.1016/j.cej.2012.10.031

Regards,

Azam

Heterogeneous catalysis the phase of catalysts differs from that of the reactants or products. On the other hand homogeneous catalysis the catalyst is soluble forms a homogeneous mixture with the reactants . The common feature in both types of reactions reaction occurs at the surface .The rate depends upon the amount of the reactants and nature of the substrate. Sterically crowded substrates may undergo the reactions less readily in both the cases.

and products and ... the surface.

Good day everyone. i am required to develop a model for gas hydrate calculation can anyone assist me on how to do it

Dear Sumit.

I would recommend to get in touch with the Hanson lab in Stanford. They have done lots of laser spectrosopy in shock tubes, in paticular detection of H2O. On their website (hanson.stanford.edu) you will find the PhD thesis of Hejie Li from 2007 where you can find details on the 1392/1398 nm absorption lines. In a later paper (J. Phys. Chem A, 2010, 114, 18: 5718-27) they measured time histories of H2O in a shock tube using 2550.96 nm (this might tell you already something).

I hope that helps,

Wolfgang

Engelbert Buxbaum, Well, we will discuss it one each other.

There is "linear regression". There are minimization methods with the objective function in the form of one of fit measures, commonly called "nonlinear regression". I still do not know what is "linearizing regresion". By changing the coordinate system, a straight line can be obtained from the data in the form of a curve, but it is not a linear transformation or a linearization. Likewise, they are not a linear transformation of L-B, Hanes-Woolf or Eadie-Hofstee transforms, or taking log. So you did not convince me of the sense of using such a term.

You have your favorite method and I have mine. You had interesting experiences with NM, me with ML. Among other, I used it to solve two-point boundary value problems for ODE, to minimize G (equilibrium composition of reaction mixtures), or to determine the parameters of kinetic equations. As I wrote earlier, ML can be used for any function, whether in the form of a formula or an algorithm. I also used NM (2nd step) in conjunction with the Monte Carlo method (1st step) and the FPD method (3rd step) called MINUITL from the CERN numerical program library.

You ask for chi². There used to be an ML routine in the CERN library with a built-in SRE (sum of relative errors) instead of SSD. But with chi² I did not see. Regards,

Navid Jamali Hi, I am facing a similar problem as you. I am using NHDF cells for MTT assay. During my cell density optimization, I got an absorbance value of 0.6 even with 40,000 cells/well (100ul). They are untreated and I allowed them to grow in the 96-well plate for 24 hours. Do you mind sharing how did you troubleshoot this problem?

The article Radomir I Slavchov shared are good

I would like to thank to Prof. Karaman for his explanation and the references.

We experienced several barierless TS in calculations of organic radicals binding weakly Br. radicals. In some cases this was apparently not due to thermochemical corrections (as reported in some references known to us) but due to an entropy penalty for some of the intermediates. We would like to understand the phenomenon (if not resulting from a method artifact) better, hence I am grateful for any hint.

It will depend on the shape of your DTG curves. The peaks (and shoulders) will show you the temperature range for the main pyrolysis reactions. Most biomass materials have 300 - 600 degC as the main pyrolysis temperature range.

Through the assumed reactions pathways and their final products and kinetics rates parameters. For global two step reactions, it the reaction rate of the CO oxidation will the rate-limiting or controlling rate for the CO2 emission. Same thing if you have other small radicals in your mechanism. Conduct a sensitivity study to determine which reaction(s) are the important ones for the emission species being investigated.

Dear Etienne Testard,

in 2019 Krishna Prasad Shrestha et al. presented a paper on this topic ( ) and further also on Methanol and Ethanol combustion. Maybe his reaction mechanism can help you to get better results.For my calclations with Methane and hydrogen mixtures the mechanism worked quite well

Combustion Science and Technology

DOI: 10.1080/00102202.2019.1606804

and

Fuel 261

DOI: 10.1016/j.fuel.2019.116349

I guess you mean effective values. Then not only porosity, but a tortuosity factor is needed. It is better, however, to measure yourself.

Tania Avianda Gusman When we observe the transformation (crystal growth) of our molecules in a polarized optical microscope, we capture every moment at transformation. For example, every 1 sec or 30 sec etc (the choice is ours depending on the speed of crystal growth), we capture one image. With collections of images at fixed duration, we now have a bunch information about (1) average crystals size (in micrometer usually) which can be calculated using the software given by the microscope and (2) time (in seconds or minutes). The constant rate of growth can be calculated by plotting at least seven data points (the more the merrier) of (1) divided by (2). Please also note that the magnification settings and calibration shall be adjusted well for accurate calculation. Hope this helps.

Please send me your mail or you whatsapp number . I will explain you as completely.

Hi Elena,

Thank you very much for your detailed answer.

All the best for your future research.

Melanie

Hello, i do not know how a quasi 1d analysis of pulse jet should look like. Since there are pulses of combustion you would need a proper time resolved solver. Due to the nature of the different phases you would need to resolve chemistry in transients, though you need a fast solver which could adapt its time step size. Even if you are able to write (or use an existing solver in Matlab) for ODEs it will be very slow. Depending on which model (reaction mechanism) you are going to use to model the fuels it will very likely become very very slow. So slow that you can not do any model development with this.

I admit they i never modelled a pulse jet myself, but my knowledge is based on modelling flames, engines and furnaces in different models from 0D to 3D. I also worked with difference solvers a lot. If you want to solve chemistry on the fly, is strongly suggest you use an already developed chemistry solver. Writing your own will need all your worktime and you will have no time working on the actual model.

Thanks all

Roh,

I'm happy you find your answer. But note that everybody is free to answer as they desire. It is up to you to decide which one work for you. Their answers are also valuable but might not point out what you meant. Then simply ignore them. They may be of interest to other people who have a similar question in the future.

Good luck.

Sorry, in my answer I vorgot the C₀ . The correct formula is:

C=C₀ exp-(Q/kT).

C₀ is not temperature dependent and is defined by the local change of entropy if 1 vacancy is formed. C₀ should be taken from experimental literature, since it is not easy to calculate theoretically.

Activation energy for a sintering is a system property, namely: the energy barrier which system must overcome to start sintering process. In the discussed case, obviously, the estimated activation energy is a combination of surface/grain boundaries/volume diffusion activation energies of the mentioned materials system.

On the other hand, densification is a sintering result. So, is sintering parameters permitted to overcome the energetic barrier, a sintering process was initiated and then resulted in a certain final density.

Taken into account the mentioned above, I do not see any contradiction between high activation energy and high sintered density, if sintering process was adjusted and optimized specially to the mentioned materials system.

You can use any band based on the chemical groups that do not show changes during any chemical reactions or physical reactions. However, majority of the IR bands are the contributions from multiple groups and, thus, tend to change the intensity by either chemical reactions or physical structural changes. Aliphatic CH stretching bands, in the region of 3000-2800 cm-1, are usually very stable as the potential energy distribution of these bands are nearly 99% pure. In the case of PU, you have relatively well isolated 2972 cm-1 band. However, PIR lacks this band. Yet, there are multiple bands between 2950 and 2850 cm-1 that appear to be relatively stable. Ideally, you should curve resolve these heavily overlapped bands (there are at least three bands, maybe 4) to be more accurate, but by measuring the height (absorbance), you can obtain quasi-quantitative comparison. Use the intensity of one of the band (the one near 2850 cm-1 might be good) and divide the absorbance of the band you want to compare to normalize the intensity then compare the normalized intensity of two different conditions, such as different reaction times.

It depends. It might be good because the degradation rate does not decrease in the course of reaction

Hi,

When the surface area of reactants is increased, the frequency of collision between the reactant particles is also increased. Greater the surface area, higher will be the rate of reaction.

Best regards

Conventional water softeners are actually ion exchangers which “swap” sodium for calcium and magnesium.

There are attempts to extrapolate the CALPHAD method to low temperatures. See for example 10.1016/j.calphad.2012.01.003 and 10.1016/j.calphad.2016.09.001

Dear Kishore Ragi

Inventing of the artificial chemistry is definitely to be avoided if we want our models to have any relation to the real atmosphere. This problem was discussed by Heymann (2010): Lumping, testing, tuning: The invention of an artificial chemistry in atmospheric transport modeling (Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics)

The paper was published in the special issue dedicated to modeling and simulation in the atmospheric and climate sciences and the text is available on request in the RG system.

Considering the complexity of the problem it is indeed very wise to perform first the detailed kinetic studies (both theoretical and experimental) followed by the rational compression of the chemical mechanism. In this area I would like to suggest Sportisse (2000): Reduction of Chemical Kinetics in Air Pollution Modeling., J. Comp. Physics, Vol 164, issue 2, p 354–376

The reality of chemical modeling is that some atmospheric chemistry models still use the outdated lumping methods. It is indeed an excellent idea to revisit these problems.

Hi Lili,

Jose is correct, TeraChem is likely the best bet if you want GPU acceleration, however speed alone shouldn't dictate what program you use. One major concern is cost: TeraChem, Gaussian, Vasp and QChem are not free and your institution likely has a subscription already to one of these. Another thing you should be concerned about is if your chosen program has the functionals implemented that you would like to study, if you're just doing B3LYP or something of that nature you won't have to do much research but if you're looking for a more exotic functional you should make sure it's there first before purchasing.

Additionally, there are other ways to speed up a DFT calculation than GPU acceleration. I don't know much about TeraChem, but I do know Orca is a free computational chemistry program with methods implemented to speed up DFT and post-HF calculations. The resolution of identity approximation for both Coulomb and exchange integrals in ORCA significantly speeds up DFT calculations with little to no effect on the accuracy, even though it's not implemented on GPUs. Additionally, in terms of post-HF methods DLPNO, F12, and RI methods are available for MP2, CCSD(T), etc that work to speed up and increase the accuracy of results with smaller basis sets (in the case of F12). These methods may be on TeraChem, I don't know but if they are they would be great with GPUs, but I just wanted to make you aware of other considerations that could help with your decision.

Syed Ali Ammar Taqvi

I've try to replicate the process using Aspen Plus and the result are wrong and I can't find where I was wrong

First Pic (kinetic) show the kinetic that the ref. given and I transfrom them into POWERLAW expression in Aspen Plus (Kinetic Factor = kT^(n)*e^(-E/RT) ) and I've got this (Excel File : Cal) then I run the simulation

I've got result that are wrong (Result (Sim)) and I think it should be about the kinetic. I also include the simulation file hope that you can provide some help for me sir.

For single step elementary reaction, the negative order is NOT possible. This is because the order of such reactions is equal to the molecularity, which is the number of molecules that come together to react in one elementary step.

Thus, the order can be negative only for the complex reaction, with respect to a substance, with undefined overall order. In such case, the negative partial order indicates that that substance participates in a side reaction which:

1- Has higher rate than the complex reaction.

2- Gives a reverse action as compared with the complex reaction, e.a. it produces the reactant(s) of the complex reaction or it consumes the product(s) of the complex reaction.

Thus, as Yurii V Geletii Sir mentioned, that substance will appear as an inhibitor for the complex reaction.

I apologize for the out-of-area answer