According to Arrhenius equation, k = A*exp(-Ea/RT), I would like to know the value of A (Arrhenius constant) and Ea (activation energy). Because I use Aspen Plus software to simulate the production process in chemical engineering. For example, I need to have A and Ea of the following reactions: 1) Ethylen react Chlorua to form Dichlo ethane (C2H4Cl2).
2) Oxidation methanol to folmandehyt HCHO.
3) Steam cracking Ethane to Ethylen and Hydrogen.
4) Methy tert buthyl ether MTBE from iso_buthane.
In the above 4 reactions, to calculate reaction rate constant (k) according the different temperature (T), we need to know the value of A and Ea. So From which I can search these constant?
Best regards,
Thank for your answer,
The method that you presented I have know through subject "Kinetics". However, I need the value of A and Ea for a particular reaction. Herein, in above 4 reactions, I need these constant for calculating reaction rate constant (k) at known temperature.
This is important in simulating chemical engineering process by Aspen Plus software according to I am known
Best regards,
Dear Dang Nguyen Thoai,
in order to simulate these reactions you are looking for the freuqency factor and activation energy of the reactions you listed in your original post.
There are two ways to find them. One is to perform experiments in a lab study and determine the parameters in the way Pushpa Jha suggested. This simple approach will not work for every kind of kinetics in that simple way, but the basic idea is numerical fitting of your experimental data to your idea of a kinetic model.
The second way is to look into literature and figure out wheteher or not somebody already investigated the reactions you are interested in. I am quite confident, that there is some data, you just need to find it via a literature study.
Regards,
André.
Dear Prof. Marc R Roussel, Prof. Andre Reiger and Prof. Pushpa Jha,
Thank for all of your interested answers. I have understood more details about this problems.
I also would like to receive such good comments from you in the next time
Best wishes and Best regards,
Great question.
Normally, to evaluate the constants in Arrhenius equation, you need to have experimental data, then you could do a log plot in which the lnA is the intercept and E/R is the gradient.
Otherwise, you could look into literature to see if the same reaction has been ran before where you can get them. Aspen plus will normally tittle lnA as pre-exponential factor.
Hope that helps.
Firstly, you need to calculate the conversion x of reaction with time, then from the following equation calculate k,
dx/dt=k(1-x)^n, n order of reaction n=1,2,3 ... (curve fitting)
by draw ln dx/dt against (1-x) you can calculate the value of k from the slope.
after that draw lnk vs 1/T to get activation energy (slope) and A intercept.
lnk=lnA-E/RT
Note you need at least two temperature for your reaction to get two value for K.
I am certain that these reactions are not simple or elementary reactions, and of course they are catalytic processes especially eq. 1, 2 & 4. Thus, the parameters you are interested in are surely going to be a function of the activity and physicochemical properties of catalysts that are employed.
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