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601078: Chemical Thermodynamics, Environment & Sustainability
Home-Based Coursework Assignment in Chemical Thermodynamics
Assessment set: September 29, 2021
Assessment due in: November 3, 2021 at 2 p.m. GMT
This assessment comprises one question on Chemical Thermodynamics.
You are requested to answer ALL parts of this question.
Please upload your answers (in .pdf format) to Canvas by the deadline.
Chemical thermodynamics in the manufacture of methanol
Methanol (CH3OH) is used to manufacture a large number of important
chemicals, such as formaldehyde (HCHO) which is employed in the
manufacture of a variety of polymers; methyl-tertiary-butylether
((CH3)3OCH3), which has been used as a lead-free anti-knocking agent in
petrol; acetic acid (CH3CO2H), etc. Annual production of methanol has been
increasing: from 3.3 MTe/yr in 1982,1 to 20 MTe/yr in 1991.2
Methanol is manufactured using synthesis gas (a mixture of carbon monoxide,
CO, and hydrogen, H2) through the following chemical equilibrium.
CO(g) + 2H2 (g)←
⎯⎯⎯⎯→CH3
OH (g)
Thermodynamic data (standard enthalpies of formation, ΔHf
0
, absolute
entropies, S0
, and heat capacities (CP) at 298 K) corresponding to the five
chemical species in the above chemical reactions are given in Table 1 below.3
Table 1: Thermodynamic quantities for the
reacting gases involved in the manufacture of methanol.
3
Species ΔHf
0
/kJ mol-1 S0
/J mol-1 K-1 CP/J K-1 mol-1
CO(g) -110.5 197.7 29.1
H2(g) 0.0 130.7 28.8
CH3OH(g) -201.5 239.8 43.9
(a) Use the data in Table 1 to calculate the following.
(i) The enthalpy change for the reaction, under standard
conditions. Comment on your answer.
(2 marks)
(ii) The standard entropy change for the reaction. Comment on
your answer.
(2 marks)
(iii) The standard Gibbs energy change for the reaction, under
standard conditions. Comment on your answer.
(2 marks)
(iv) The equilibrium constant for the reaction equilibrium, under
standard conditions. Comment on your answer.
(2 marks)
2
(v) The change in the heat capacity at constant pressure for the
chemical reactions, under standard conditions.
(1 mark)
(b) Assuming that the constant pressure heat capacities are
independent of temperature, use your answers to part (a) to
calculate the equilibrium constant for the reaction at 225, 300 and
450 o
C, at standard pressure. Comment on your results.
(6 marks)
(c) There are three types of conditions used for methanol manufacture:
• high pressure: 250-300 atm; 300-450 o
C using ZnO-Cr2O3 catalysts
• medium pressure: 150 atm; 300 o
C using ZnO-CuO catalysts
• low pressure: 50 atm; 225 o
C using Cu-ZnO-Al2O3 catalysts.
Assume your industrial reactor has a feed of synthesis gas in the
stoichiometric ratio 1 CO : 2 H2. Using your answers to (b), give
your reasoning as to which of the three types of conditions you
would recommend for operations. You must show all your
calculations used to justify your decision.
[HINT: Assume the gases obey Raoult’s law and that fugacity
coefficients can be neglected. You may it useful to use an
online cubic equation solver, such as
https://keisan.casio.com/exec/system/1181809414 (accessed
on September 19, 2021).]
(10 marks)
References
1. G. T. Austin, Shreve’s Chemical Process Industries, 5th edn., McGraw-Hill, New York,
1984.
2. R. Perrin, J.-P. Scharff, Chimie Industrielle, 2nd edn., Dunod, Paris, 2002.
3. Data taken from D. R. Lide (ed.), CRC Handbook of Chemistry and Physics, 76th
edn., CRC Press, Boca Raton, Fl., 1995.
601078_ChemThermo2021CORRECTED
APA
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The post Chemical thermodynamics in the manufacture of methanol Methanol (CH3OH) is used to manufacture a large number of important chemicals, such as formaldehyde (HCHO) which is employed in the manufacture of a variety of polymers; methyl-tertiary-butylether ((CH3)3OCH3), which has been used as a lead-free anti-knocking agent in petrol; acetic acid (CH3CO2H), etc. Annual production of methanol has been increasing: from 3.3 MTe/yr in 1982,1 to 20 MTe/yr in 1991.2 Methanol is manufactured using synthesis gas (a mixture of carbon monoxide, CO, and hydrogen, H2) through the following chemical equilibrium. CO(g) + 2H2 (g)← ⎯⎯⎯⎯→CH3 OH (g) Thermodynamic data (standard enthalpies of formation, ΔHf 0 , absolute entropies, S0 , and heat capacities (CP) at 298 K) corresponding to the five chemical species in the above chemical reactions are given in Table 1 below.3 appeared first on Apax Researchers.
