Kishan Kasundra presented on methanol synthesis from industrial CO2 sources. Two case studies were analyzed: direct CO2 to methanol (d-CTM) and synthesis gas to methanol (sg-CTM). The d-CTM process consumed more utilities and CO2 per ton of methanol but emitted slightly more CO2. The sg-CTM process optimized methanol production at high hydrogen-carbon ratios and was less resource intensive. Both achieved high methanol yields but differed in raw material use and carbon emissions. The presentation concluded the sg-CTM route may be preferable due to lower resource use and carbon emissions per ton of methanol produced.
3. INTRODUCTION
The green-house effect is caused by the release of carbon dioxide into the atmosphere from
different power and chemical plants.
Conversion of CO2 to methanol is recognized as one of the most promising processes to reduce
the atmospheric CO2 level.
Moreover, using methanol as a fuel allows one to reduce the emissions of undesirable toxic
products such as unburned hydrocarbon, CO and NOx.
Methanol is used extensively in the plastics industry and also as solvents in the pharmaceutical
industry.
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Based on reaction mechanisms of the CO/CO2/H2 conversion to methanol, three overall reactions
(Bussche and Froment, 1996) occur over Cu/ZnO/Al2O3 catalysts:
(1) Methanol decomposition: CO + 2H2 ↔ CH3OH
(2) Water shift gas: CO2 + H2 ↔ CO + H2O
(3) Methanol steam reforming: CO2 + 3H2↔ CH3OH + H2O
In addition to reactions (1), (2) and (3), other two reactions may occur (Eliasson et al., 1998):
(4) CO2 + 4H2 ↔ CH4 + 2H2O
(5) CO + 3H2 ↔ CH4 + H2O
Reactions (4) and (5) indicate that methane formation is the main obstacle limiting the production
methanol.
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CASE STUDY -1: An analysis of methanol production route via CO2
hydrogenation by Rita M. B. Alves, Camila F. R. Machado
Figure 1: CO2 hydrogenation
7. RESULTS:
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Table presents simulation results concerning the utilities consumption per ton of methanol:
Consumption/ton of methanol d-CTM
Vapour (ton/ton) 1.26
Cooling water(m3/ton) 101.18
Electricity (GJ/ton) 3.36
Reactor conditions: T = 245 °C, P = 80 bar
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Table shows the relevant factors of production for the d-CTM processes as methanol yield,
consumption of H2 and CO2, and CO2 emission
Factor d-CTM
Methanol Production 464kta
H2 consumption 99.04kta
CO2 consumption 664.8kta
Syngas consumption -
CO2 emission 19.02 ton CO2eq/h
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Case d-CTM:
In this case, the influence of pressure and H2/CO2 (N ratio) on the following parameters were
investigated:
(1) Methanol production in kg/h
(2) CO2 conversion
(3) Selectivity to MeOH
(5) Water production in kg/h
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Figure 3: different behaviours of (a)CO2 conversion, (b)selectivity to MeOH,(c) MeOH production and
(d)water production for a set of N ratios and pressures
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Table: Behaviour of MeOH production, MeOH selectivity, CO2 conversion and water production due the
variation of pressure and N parameter of the d-CTM process
12. CASE STUDY 2: Methanol production route via synthesis gas by Olah,
George A. Beyond
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Figure 4: Synthesis gas
14. RESULTS:
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Table presents simulation results concerning the utilities consumption per ton of methanol:
Consumption/ton of methanol sg-CTM
Vapour (ton/ton) 0.30
Cooling water(m3/ton) 67.93
Electricity (GJ/ton) 1.34
Reactor conditions: T = 245 °C, P = 80 bar
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Table shows the relevant factors of production for the sg-CTM processes as methanol yield,
consumption of H2 and CO2, and CO2 emission
Factor sg-CTM
Methanol Production 464kta
H2 consumption -
CO2 consumption -
Syngas consumption 536 kta
CO2 emission 15.56 ton CO2eq/h
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Case sg-CTM
In this case, the influence of pressure and M ratio(H2-CO2/CO+CO2) on the following parameters
were investigated:
(1) Methanol production in kg/h.
(2) CO2 conversion.
(3) Selectivity to MeOH
(4) CO conversion
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Figure 6: different behaviours of (a)methanol production, (b)CO conversion, (c)methanol selectivity
and (d)CO2 conversion for a set of M ratios and pressures
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Table: Behaviour of CO conversion, CO2 conversion, MeOH selectivity and MeOH production due
the variation of pressure and M parameter of the sg-CTM process
19. CONCLUSION:
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There are at least two paths for methanol synthesis using syngas or a mixture of H2 and CO2 as
raw material.
d-CTM process presents more consumption of utilities as vapor, cooling water and electricity
per ton of methanol production compared to sg-CTM.
d-CTM process emits 19.02 ton CO2 equivalent per hour against an emission of 15.56 ton CO2
equivalent per hour for sg-CTM.
Regarding the consumption of raw material, d-CTM process is more demanding compared to
sg-CTM .
The production of methanol through the sg-CTM process is maximized at high M parameter
but in the studied pressure range remains unchanged.
20. REFERENCES:
Turton, R., Bailie, R.C., Whiting, W.B., Shaeiwitz, J.A., 2016. Analysis, Synthesis, and Design
of Chemical Processes, third ed. Prentice Hall, Upper Saddle River, New Jersey
Olah, George A. Beyond, Oil and Gas:The Methanol Economy,Angew.Chem., Int. Ed., 44, 2017
Behrens M., Felix, Kasatkin I., Kühl S., Hävecker M., Abild-Pedersen F., Zander S., Girgsdies
F., Kurr P.,Kniep B., Tovar M., Fischer R. W.,Nørskov J. K.,Schlögl R.,The Active Site of
Methanol Synthesis over Cu/ZnO/Al2O3, Industrial Catalysts, vol. 336, 18 may, 2017
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