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ethanol eh-ph diagram help


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I need to check e-ph diagram for ethanol. I calculated many reactions in excel myself and I want to check it with the software. But I dont know how to use the software effectively. I guess it is becuse I am new with the software. I actually calculated many reactions involving C2H5OH(l), CH4(gas), CO2(gas), H2(gas), O2(gas), CO3[-2][aq], HCO3-[aq], H+ and OH-. Can I obtain e-pH diagram of ethanol and also methanol with all those ionic species.where to start. I appreciate any help. SOme of the reactions are as follows;


25 ºC and 1 atm

E0(V)= -DG0/nF

DG0rx,298.15 (J/[mol)

1. 6H2(g) + 2HCO3[-] (aq) D C2H5OH(l) + 3H2O(l) + 2OH[-](aq)




-27267, -29455 Ref[2]

2. 6H2(g) + 2CO3[-2] (aq) DC2H5OH(l) + H2O(l) + 4OH[-](aq)



14704, 12426 Ref[2]

3. 2H2(g) + CO3[-2] (aq) + CH4(g) D C2H5OH(l) + 2OH[-](aq)



4. CH4(g) + CO2(g) + 3/2H2(g) + e-D C2H5OH(l) + OH[-] (aq)



5. CH4(g) + CO2(g)+ 3H2O(l) +4e-D C2H5OH(l) + 4OH[-](aq)




6. CH4(g) + CO2(g) + 2H2(g) + 1/2O2(g) + 2e- D C2H5OH(l) + 2OH[-](aq)



7. CO2(g)+ 1/2O2(g) + 2e-D CO3[-2] (aq)



8. CO2(g)+ 3H2(g) + 2e-D CH4(g) + 2OH[-](aq)



9. 2CO2(g) + 4H2(g) + 2e-D C2H5OH(l) + 2 OH[-](aq)



10. 2CH4(g) + 1.5O2(g) + 2e- D C2H5OH(l) + 2OH[-] (aq)



11. CH4(g) + CO2(g) + H2O(l) + H2(g) + 2e- D C2H5OH(l) + 2OH[-](aq)




12. CO2(g) + CH4(g) + 3H2(g) + 3/2O2(g) + 4e-D C2H5OH(l) + 4OH[-](aq)



13. 2CO3[-2] (aq) + 16H+ + 12e-D C2H5OH(l) + H2O(l)









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You'll want to use Act2 to make an Eh-pH diagram. If you're interested in ethanol or methanol, you should load a thermo dataset containing those species into the program. The thermo.com.V8.R6+.tdat dataset installed with the GWB contains info for both of these species.

If you draw an Eh-pH diagram for HCO3- using that dataset, you'll find that methane is the predominant species under reducing conditions. Your best bet is to disable all of the redox coupling reactions involving carbon except for that between ethanol and HCO3-. To do so, just go to Config - Redox Couples... and in the pulldown that says "select with" choose Carbon, then hit decouple>>. Next, find the couple for Ethanol/HCO3- and re-enable that by hitting << couple.

There are a few different minerals or aqueous species in equilibrium with ethanol, such as "C" or 1-Pentanol(aq) that take precedence over the ethanol, but you can remove them from the diagram by suppressing them from the Config - Suppress dialog.

For more information on Act2, please see section 5, Using Act2, in the GWB Essentials Guide. For info on the thermo datasets included with the software and redox coupling reactions, please see sections 2.3, Thermodynamic datasets, and 2.4, Redox couples, respectively, in the GWB Essentials Guide.

Hope this helps,

Brian Farrell

Aqueous Solutions LLC

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Hello Brian,


Thanks for your help. I was able to plot E=pH diagram involving HCO3-, CH4. CO3-- and CO2. I have another problem with reading and constructing the data. My purpose is actually to see all the reactions in the same E-pH diagram if possible. By doing that I want to get a better understanding of ethanol decomposition mechanisms with respect to E and pH. I actually calculated all the reaction Gibbs energies given in the table.

​The most favorable reaction in terms of Gibbs energy is

C2H5OH(l) + 4OH[-](aq) D CH4(g) + CO2(g) + 3H2O(l) +4e-

I can not get this equilibrium line with the module. Am I doing something wrong? Is it metastable?


​the other most favorable reactions are as follows:


1- C2H5OH(l) + H2O(l) + 4KOH(s) D 6H2(g) + 2K2CO3(s)

2- C2H5OH(l) + 2 OH[-](aq) D 2CO2(g) + 4H2(g) +2e-

3- C2H5OH(l)+ 2OH[-](aq) D CH4(g)+ CO2(g)+ H2O(l) + H2(g)+2 e-

My problem is how I can show the equilibrium line between ethanol and CH4, CO2, H2 together. For example the reaction number 3 above. How can I represent the equilibrium line in he diagram for reaction 3. I mean according to E=pH diagram the right side of the equilibrium line must be the zone where CH4, CO2, H2 are stable and the other side must be ethanol. Similarly for number 2 above. I can not get ethanol equilibrium with CO2 and H2 together.

Thanks for any help

diagrams are in attached file.

best wishes.



Muhsin IDER


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