1. Thermodynamics in the production and purification of methanol from methane Jacob Hebert, Michael McCutchen, Eric Powell, and Jacob Reinhart (Group 6)

2. Thermodynamics Review - Topics Important Terms & Concepts Models in CHEMCAD Partial Oxidation Steam Reforming Water-Gas Shift Methanol Synthesis Methanol Purification

3. Important Concepts Gibbs energy (G, ΔG): denotes what happens spontaneously, and to what degree Enthalpy (H, ΔH): relates to sensible heat Entropy (S, ΔS): commonly referred to as “disorder”, universal entropy always increases Chemical equilibrium (matters most at long time scales and/or fast reactions!)

4. Significance of the Thermodynamic Model There are many models allowing for good approximations in a variety of situations These models account for the non ideality which arise when chemical interactions cause unexpected effects.

5. The Selection Process Factors to be considered include: – Intermolecular bonding – Pressure and Temperature of the reaction – Phase separation – Molecular weights (for hydrocarbons)

6. Choosing our model Hydrocarbon C 5 or lighter H 2 present Polar or Hydrogen bonding Sour Water H 2 present Electrolytes T < 250 K P < 200 bar T < 250 K γ i experimental data P < 350 bar P < 4 bar T < 150ºC Two Liq phases Need more experimental data Select model that gives best fit to data Use G-S Use B-W-R or L-K-P Use P-R or R-K-S Use R-K-S Use G-S 0<T<750K Use G-S or P-R Use NRTL or UNIQUAC Use Wilson, NRTL or UNIQUAC Use electrolyte Use sour water system Use UNIFAC to estimate interaction parameters Start Y Y Y Y Y Y Y Y Y Y Y N N N N N N N N N N N Y N Y N Y N Towler, G., & Sinnott, R. (2008). Chemical engineering design principles, practice and economics of plant and process design. Amsterdam: Elsevier/Butterworth-Heinemann.

7. Steam Reforming CH4 + H2O -> CO + 3H2 Affected by temperature (higher temperature favors the reaction) Affected by pressure (lower pressure favors the reaction) Very endothermic reaction Ali, M. S., Zahangir, S. M., Badruddoza A. Z. M., Haque M. R. (n.d.) A Study of Effect of Pressure, Temperature, and Steam/Natural Gas Ratio on Reforming Process for Ammonia Production. Journal of Chemical Engineering 23 1995-2005 http://www.banglajol.info/index.php/JCE/ar ticle/view/5565

8. Partial Oxidation – Methane and oxygen feed to reactor at 2:1 for methanol synthesis preparation – Three different reactions can take place during partial oxidation A) CH 4 + 0.5O 2  CO + 2H 2 ΔH = -38kJ/mol B) CH 4 + 2O 2  CO + 2H 2O ΔH = -803kJ/mol C) CO + H 2 O ↔ CO 2 + H 2 ΔH = -41kJ/mol – Choose reaction conditions to maximize Reaction A and minimize Reactions B and C

9. Partial Oxidation: Reaction Enthalpies http://www.bjb.dicp.ac.cn/jngc/2004/2004-04-191.pdf

10. Partial Oxidation: Temperature Effect http://www.bjb.dicp.ac.cn/jngc/2004/2004-04-191.pdf

11. Partial Oxidation: Pressure Effect Despite excess feed oxygen, all oxygen was consumed, indicating a lack of inhibition for total oxidation Increase in moles of gas molecules inhibit partial oxidation at increasing pressure Reduced conversion at high pressure can be compensated for by operating at higher O:C ratios http://www.bjb.dicp.ac.cn/jngc/2004/2004-04-191.pdf Methane conversion at different pressures and different O:C ratios

12. Water-Gas Shift John Kitchin, using values from the NIST Webbook http://matlab.cheme.cmu.edu/2011/12/12/water-gas-shift-equilibria-via-the- nist-webbook/ Chang, T., Rosseau, R. W., Kilpatrick, P. K., (1986). Methanol Synthesis Reaction: Calculations of Equilibrim Conversions Using Equations of State. Ind. Eng. Chem. Process Des. Dev. 25 477-481. CO + H2O -> CO2 + H2 Slightly exothermic, but G and H vary with temperature Low temperatures favor forward reaction Pressure affects the reaction (even if it appears it should not)

13. Methanol Synthesis temperature dependent, much like most other reactions CO + 2H -> CH3OH exothermic reaction strongly pressure dependent due to the reduction in total moles (high pressure favors the forward reaction) Chang, T., Rosseau, R. W., Kilpatrick, P. K., (1986). Methanol Synthesis Reaction: Calculations of Equilibrim Conversions Using Equations of State. Ind. Eng. Chem. Process Des. Dev. 25 477-481.

14. Final Step: Separation One of the most important steps where thermodynamics plays a role. The goal is to minimize energy loss These losses are due to mixing as well as heat and mass transfer Thermodynamic properties and phase equilibrium are notoriously hard to predict in methanol, water, and hydrocarbon mixtures.

15. Distillation Differing boiling points among the species allows for a flash drum followed by distillation Two distillation columns are used to separate water and methanol In a perfect system the thermodynamics would be controlled by heaters and coolers with appropriate duties at each stage of the columns, main issue is the cooling of mixture exiting at high temperature Thermodynamically distillation is a good separation process but care must be taken to specify proper column specifications in order to avoid unnecessary complications.

16. Simple Example http://www.scielo.br/scielo.php?pid=S0104-66322008000100021&script=sci_arttext

17. Hydrate formation At specific temperatures and pressures hydrate formation can occur within the stream Hydrates are solid crystalline compounds that are created by natural gas compounds occupying the empty lattice positions in a water structure http://www.esrf.eu/UsersAndScience/Publicati ons/Highlights/2009/materials/mat09

18. Azeotropes No Azeotropes in data for methanol, water, and hydrocarbons The closest azeotropic mixture is ethanol and water Care must always be taken when dealing with separating a mixture that no azeotropes exist.

19. Pressure Swing Adsorption An easier separation process that deals with gases, thermodynamically favored Separates a gaseous species based off of the molecular affinity for absorbent materials High pressure adheres the gas to solid surface and low pressure it is released Very useful cleaning catalysts for hydrocarbons are zeolites http://www.gazcon.com/sw13931.asp

20. References - Models Towler, G., & Sinnott, R. (2008). Chemical engineering design principles, practice and economics of plant and process design. Amsterdam: Elsevier/Butterworth-Heinemann.

21. References – Water Gas Shift and Methanol Synthesis Bustamante, F., Enick, R., Rothenberger, K., Howard, B., Cugini, A., Ciocco, M., Morreale, B. (2002). Kinetic Study of the Reverse Water Gas Shift Reaction in High- Temperature, HIgh-Pressure Homogeneous Systems. Fuel Chemistry Division Preprints 47(2), p. 663-664 Daza, Y. A., Kent, R. A., Yung, M. M., Kuhn, J. N. (2014). Carbon Dioxide Conversion by Reverse Water-Gas Shift Chemical Looping on Pervoskite-Type Oxides. Ind. Eng. Chem. Res. 53, 5828-5837. Park, S., Joo, O., Jung, K., Kim, H., Han, S. (2001). Development of ZnO/Al2O3 catalyst for reverse-water-gas-shift reaction of CAMERE (carbon dioxide hydrogenation to form methanol via a reverse-water-gas-shift reaction) process. Applied Catalysis A: General 211 p. 81-90 Chang, T., Rosseau, R. W., Kilpatrick, P. K., (1986). Methanol Synthesis Reaction: Calculations of Equilibrim Conversions Using Equations of State. Ind. Eng. Chem. Process Des. Dev. 25 477-481. Kitchin, J. (2011) “Water Gas Shit Via the NIST Webbook”. http://matlab.cheme.cmu.edu/2011/12/12/water-gas-shift-equilibria-via-the-nist- webbook/

22. References POX and Steam Reforming Ali, M. S., Zahangir, S. M., Badruddoza A. Z. M., Haque M. R. (n.d.) A Study of Effect of Pressure, Temperature, and Steam/Natural Gas Ratio on Reforming Process for Ammonia Production. Journal of Chemical Engineering 23 1995-2005 http://www.banglajol.info/index.php/JCE/article/view/5565 Lyubovsky, M., Roychoudhury, S., & LaPierre, R. (2005). Catalytic partial “oxidation of methane to syngas” at elevated pressures. Catalysis Letters. doi:10.1007/s10562-005-2103-y Zhu, Q., Zhao, X., & Deng, Y. (2004). Advances in the Partial Oxidation of Methane to Synthesis Gas. Journal of Natural Gas Chemistry, 13, 191-203. Retrieved from http://www.bjb.dicp.ac.cn/jngc/2004/2004-04-191.pdf

23. References - Separations Demirel, Dr Y., "Retrofit of Distillation Columns Using Thermodynamic Analysis" (2006). Papers in Physical Properties. Paper 6. http://digitalcommons.unl.edu/chemengphysprop/6 http://digitalcommons.unl.edu/chemengphysprop/6 Lide, D.R., and Kehiaian, H.V., CRC Handbook of Thermophysical and Thermochemical Data, CRC Press, Boca Raton, FL, 1994. http://chemistry.mdma.ch/hiveboard/picproxie_docs/000506 293-azeotropic.pdf http://chemistry.mdma.ch/hiveboard/picproxie_docs/000506 293-azeotropic.pdf