Dear sir,
We are performing a reaction which involves nitration of 4-Hydroxy-2-trifluoromethyl pyridine in the Conc.sulfuric acid medium& fuming nitric acid added successively at 0°C and heated to 80°C to form compound 2-nitro-4-trifluoromethyl-phenol.
For the scheme please refer to attachment "kinetics.png".
I have completed with finding the rate constant and reaction order,However I am not able to estimate Enthalpy of the reaction(-ΔHr) to find the total heat production or heat generation as mentioned in the equations below.
I have extracted the data from Mettler toledo RC1e, and I would like to mention that I had summed up the individual Qr,so i got the heat generation in the Watts(W), and I multiplied that total watts with the corresponding time to convert into Kilo-joules.
The total heat generated Qrx (kilo-joules) is not matching with the Corresponding RC1e Heat generation value.
And I want to plot those individual qr values w.r.t time to generate Qrx vs time Curve.
Hence I would request your advice on how to go forward.
Further I would like to request from you any other similar case study which you can share.
Please refer to the excel sheet and final report attached for further clarification.
Kind Regards,
Raghu Perumalla,
Process Safety Engineer,
Scale Up Facility,
TCG Lifesciences Pvt Ltd,
Kolkata,India.
Arjun Chaudhuri,
M.Sc ( Bio Chemical Engineering )
Technical University of Delft,
The Netherlands.
I recommend that you use HSC Chemistry software to estimate the reaction enthalpy as a function of temperature.
All what you have to do is to enter the equation the cited in your message into the HSC Chemistry software and also enter the range of temperatures of interest. the program will calculate all the thermodynamics parameters including the reaction enthalpy, Gibbs Free Energy, and the Entropy for the reaction. It will also give your the reaction rate constant.
Hope this helps answer your question.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, United Kingdom
Might I suggest politely that this is less of a research-directed question and more of an industrial-processing + methods-of-data-analysis-directed question. As such, within the limits of the forum here, it may be inappropriate. Also, anticipating that results are benefiting a for-profit venture, the question is certainly even more inappropriate here.
That being said, I can kindly offer to consult with further advice off-line.
Can you summarize the problem for us? What is the calculated heat of reaction and how different is it from the measured value? What procedure are you using to measure the heat release?
I recommend that you use HSC Chemistry software to estimate the reaction enthalpy as a function of temperature.
All what you have to do is to enter the equation the cited in your message into the HSC Chemistry software and also enter the range of temperatures of interest. the program will calculate all the thermodynamics parameters including the reaction enthalpy, Gibbs Free Energy, and the Entropy for the reaction. It will also give your the reaction rate constant.
Hope this helps answer your question.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, United Kingdom
Dear Raghavandra, If I understand your question correctly you have used the Mettler RC1 to accurately record temperature rise as a function of time and calculate the amount of heat required for that temperature rise to occur and this does not match the calculated heat of reaction (Qrx) from literature similar to the source Prof Khalil sited. The first thing to do is recheck the literature to make sure you understand the heat of reaction correctly. Also you should make sure that you are looking at both the literature and experimental values properly and that you are accounting for any vaporization that may also be occurring as the process temperature rises. The impact of heat of vaporization could potentially be large. I hope this helps.
One addition place where researchers sometimes go wrong is using the heat of reaction at standard condition instead of adjusting it to actual conditions. This could be important if the heat capacity of your reactants is significantly different than the heat capacity of your products. To correctly calculate temperature rise at given reactor temperature above the standard temperature where heat of reaction is known (usually 25 C) you need to cool the reactants to the standard temperature calculate the heat of reaction, add the heat from cooling the reactants and the heat of reaction and heat the reaction products to by adding the heat from cooling the reactants and the heat of reaction together and using product heat capacity to calculate the temperature rise from standard conditions to actual reactor outlet temperature. I hope this helps.
If used is the mixed acid (HNO3+H2SO4) you have two reactions at the same time. The obtained result contains: total heat due to reactions = heat of nitration + heat of dilution.
Dear Sir, note that the heat due to aromatic nitration is relatively large in comparison to the dilution heat.
Small systems tend to lose heat more than the scaled up plant. So heat removal can be underestimated in the scale up.
In your description I believe the multiplication of watts by time interval should be done in small segments before the addition is done. In your description if multiplication is only done once, then the average watts not the total watts, should be multiplied by time.
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