Literature Survey of Two-Step Methane-syngas-methanol

Processes

Group 4David Bigelow, Sean Coluccio, Luke Rhodes, Peguy Touani

February 5, 2015CHBE 446 0201

Background

CH4 + H2O → 3 H2 + CO

CO + 2 H2 → CH3OH

• The production of synthesis gas from methane produces three moles of hydrogen gas for every mole of carbon monoxide, while the methanol synthesis consumes only two moles of hydrogen gas per mole of carbon monoxide.

Background cont.

• To deal with the excess hydrogen, CO2 is injected in the methanol reactor where it forms methanol and water

CO2 + 3 H2 → CH3OH + H2O

Reactors and Catalysts

• There are two types of reactors used today: adiabatic and isothermal

• Carbon monoxide and hydrogen react over a catalyst to produce methanol

• Catalyst:

1. Zn/Cr2O3 at high pressure and temperature with impure syngas

2. Cu/Zn/Al2O3 are widely use today and is used at lower conditions

Step 1: Conversion of Methane to Syngas

• Preparation of Synthetic gas typically accounts for 50-75% of the total capital cost of a Gas-to-Liquid (GTL) plant

• Steam Reformation (SR) has been used for decades and forms a hydrogen rich syngas

• Catalytic Partial Oxidation (CPOX) is a newer technology that oxidizes methane to form syngas

Steam Reformation

• Methane is contacted with steam over a heated catalyst at

high pressures and temperatures to produce a high

hydrogen content syngas

• Requires large heat exchangers and a large initial

investment

• Strict heat balance requirements which makes it hard to control and difficult to

scale down to a small size

Catalytic Partial Oxidation

• Methane is reacted with oxygen over a catalyst bed to yield

syngas at a 2:1 hydrogen ratio

• Operated at moderate pressures (0.5 - 4 MPa) which is compatible with downstream

processes

• Easier to control and manipulate reactor sizing

• Newer technology that lacks research in comparison to

steam reformation

Step 2: Methanol Synthesis from Syngas

• CO + 2H2 ↔ CH3OH

• The original methanol synthesis process was operated at high temperature and pressure

• Methanol is now generally synthesized using a slightly different reaction, which has the addition of CO2 as a reactant

• Modern plants will also use the heat produced from the methanol synthesis for the steam reformation reaction

Reactors

• Two main types of reactors are used today, adiabatic and isothermal

• Adiabatic reactors generally use injection of cooled syngas, whether it is fresh or recycled

• Isothermal reactors are continuously cooled, though generally from another source, and operate similarly to heat exchangers

• Both types of conventional reactors utilize fixed bed catalysts

• The Liquid Phase Methanol Synthesis process is used less often and utilizes slurry reactors instead of conventional fixed bed reactors

Reactor Examples

http://www.zeogas.com/files/83939793.pdf

Lurgi Methanol Converter (Isothermal)

Linde Isothermal Reactor

http://www.linde-india.com/userfiles/image/File/Linde%20Isothermal%20Reactor.pdf

Reactor Examples Cont.

http://www.topsoe.com/sites/default/files/topsoe_methanol_coal_based_plants.ashx_.pdf

Topsoe Collect, Mix, Distribute Converter (Adiabatic)

Reactor Examples Cont.

http://www.gasification.org/uploads/eventLibrary/gtc9807p.pdf

Slurry Reactor

Catalysts

• The first catalyst used was Zn/Cr2O3 at high pressure and temperature with impure syngas

• In 1966 a Cu/Zn/Al2O3

catalyst began seeing use, and allowed operation at much lower conditions

• This Cu/Zn/Al2O3 catalyst is still used today, and remains the popular choice for methanol synthesis

Conclusion

• Two step process of:1. Conversion Methane to Syngas

2. Methanol Synthesis from Syngas

• Varying forms of operation• Most reactors use similar, using small range of

catalysts

• Preferable for medium to large scale processes

References• M. Lyubovsky, S. Roychoudhury, R. LaPierre. “Catalytic partial oxidation of

methane to syngas at elevated pressures. Catalysis Letters. Vol. 99, Nos. 3-4, February 2005.

• http://bioweb.sungrant.org/Technical/Bioproducts/Bioproducts+from+Syngas/Methanol/Default.htm

• http://www.syngaschem.com/syngaschem