5_1-Methanol-le-2008

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Page 1: 5_1-Methanol-le-2008

Methanol from synthesis gasMethanol from synthesis gas

Applications of methanolApplications of methanolProduct (in w.%) 1988 1996 2005Formaldehyde 39 35 38Acetic acid 6 7 11Methyl halides 7 7 7MTBE 12 27 20Dimethyl terephthalate 3 2 2Methyl amines 4 4 4Methyl methacrylate 3 3 4Solvents 9 4 4Others 17 11 13Sum (in mio t/a) 17,3 24,3 32,1

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Methanol from syngasMethanol from syngas(ΔH = -92 kJ/mol)

(ΔH = -50 kJ/mol)

CO + H2O ⇌ CO2 + H2 (ΔH = -41 kJ/mol)

• Several side-products that are thermodynamically more stable than methanol.

• As the reactions are exothermic➜ Good temperature control in the

reactor important.

• The catalyst needs to be active and selective towards methanol

CO + 2H2 ⇌ CH3OH

CO2 + 3H2 ⇌ CH3OH + H2O

Mechanism of methanol formationMechanism of methanol formation

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Methanol synthesis mechanismMethanol synthesis mechanism

Rate determining step

Cu/ZnO/AlCu/ZnO/Al22OO33 catalystscatalysts

H2 H2 : H2O = 1 : 3 H2 : CO = 95 : 5

CuO (wt %) > 55ZnO (wt %) 21-25Al2O3 (wt %) 8-10

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Equilibrium CO conversion to methanolEquilibrium CO conversion to methanol

Zn/Cr2O3

Cu/ZnO/Al2O3

Synthesis gas for methanol productionSynthesis gas for methanol production

• Optimum H2/CO ratio : 2– Lower ratio: increased production of by-products– Higher ratio: excess hydrogen needs to be purged

• A small amount of CO2 increases the catalyst activity

ATR

Module M = 2 = H2 – CO2

CO + CO2

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Purification of syngas

Low concentrations of impurities, such as sulfur (especially newer catalysts are very sensitive against poisoning)

The feed (syngas) purification section may consist of the following steps:

• Hydrogenation • Chlorine Absorption • Sulphur Absorption • Trace removal of Sulphur (final purification)

Industrial processesIndustrial processes

• ICI/LINDE – low pressure process• Lurgi – low pressure process• BASF – high pressure process• UK – Wesseling high pressure process

Desulfurization

Methanol product

Distillation

Methanol synthesis

Compression

Cooling

ReformingNatural

gas

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Types of reactors used for efficient coolingTypes of reactors used for efficient cooling

•(a) Cooling with water bath; (b)cooling with water coils; (c) cooling with cold feed;(d) feed gas quench; (e) feed–effluent heat exchange by periodic flow reversal;

(f) lateral flow; (g) fluidised bed.

Linde/ICI low pressure synthesisLinde/ICI low pressure synthesis

Boiler feed waterGas

Steam

Circulating water

Circulating water Gas exit

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Linde/ICI Linde/ICI –– low pressure synthesislow pressure synthesis• Temperature 240 – 260 °C• Pressure 50 – 100 bar• Catalyst Cu-Zn-Al-Oxides

→ catalyst is very sensitive against poisoning and requires very low concentrations of impurities.

99.9% MeOH

The Lurgi The Lurgi –– low pressure processlow pressure process• Temperature: 250 – 260 °C• Pressure: 50 – 80 bar• Catalyst: modified CuO-ZnO catalyst• Reactor type: multi-tubular reactors Mega methanol plants

(5000 tons/d)

Syngas is partially converted in the 1st

reactor and is sequentially fed to the 2nd

where the cooling medium is cold syngas

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BASF BASF –– high pressure processhigh pressure process

• Temperature: 320 – 380 °C• Pressure: 340 bar• Catalyst: ZnO-Cr2O3 (Zn:Cr ratio: 70:30)

Catalyst is very resistant against poisons in low concentrations→ long life time (several years)

• Very short residence time to avoid side reactions (1-2 sec) • Low conversions per one single pass (12-15%)• At several inlets along the reactor cold feed is added to control

the temperature.

UK UK –– Wesseling high pressure processWesseling high pressure process

• Temperature: 350°C• Pressure: 300 bar• Catalyst: ZnO-Cr2O3

→ similar conditions like in the BASF process

Difference:Lower partial pressure for CO (13 bar) used:• Reactor can be built from steal as Fe(CO)5 is not produced• Purity of methanol very good

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New industrial developmentsNew industrial developments

Company Catalsty Temperature (°C) Pressure (bar)

Haldor-Topsøe CuO-ZnO-Cr2O3 230-260 100-150

Vulcan ZnO-Cr2O3 270-330 150-250

Pritchard CuO Unknown 100-250

Catalyst & Chemical Inc.

CuO-ZnO-Al2O3 240-250 100-250

BASF CuO-ZnO-Al2O3 200-350 50-250

Mistubishi Gas Chemical

CuO + promoters 200-280 50-150

Methanol production with medium pressure processes

Methanol synthesis slurry processMethanol synthesis slurry process

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Methanol future

Reducing the cost of production by installing “Mega”production facilities using asraw material low-cost natural gas is opening up new promising areas for methanoluses as a motor fuel, gasoline additive, feedstock for chemical synthesis, sourceof carbon for protein production

New applications of MeOH for the production of• Ethylene and/or propylene, MTP• Dimethyl ether as a substitute for diesel fuel• Liquid fuels (substitute of gasoline or raw material for gasoline production

MTG process • Hydrogen or feed material for power generating systems or• Use in integrated schemes combined with an ammonia/urea complex• Methanol consumption for fuel cells to be used in automobiles, for power

generation and portable equipment is bound to increase in the near future.