Methane Conversion to Methanol by Platinum Catalysts

By: Sean W. Hanley

Cl

Pt

Cl Cl

ClCl

Cl

2-

O

H

H

H

2+

N N

N N

Pt

Cl

Cl

Pt

Cl

Cl

Pt

Cl

Cl

Cl

Cl

Pt

H3N

H3N

Cl

Cl

Cl

Pt

Cl

ClCl

K-

2+

K-

Platinum Catalysts

Cl

Pt

Cl Cl

ClCl

Cl

2-

O

H

H

H

2+

N N

N N

Pt

Cl

Cl

Pt

Cl

Cl

Pt

Cl

Cl

Cl

Cl

Pt

H3N

H3N

Cl

Cl

Platinum (II)

Chloride

(bpyrm)PtCl2

PtCl2

H2PtCl6

(NH3)2PtCl2

All of these catalyst have been studied to see which catalyst has the best percent yield of methanol with the least amount of catalytic death. (bpym)PtCl2 with oleum has been recently found to have 72% yield. This catalyst will be the major catalyst looked at. This reaction has the most hope in industry but also a crucial problem arises. Past catalysts have had 40% yield using mercury which is not environmentally friendly.

Cl

Pt

Cl

ClCl

K-

2+

K-

K2PtCl4

Overall Reactions

CH4 + 2H2SO4 CH3OSO3H 2H2O SO2++(bpyrm)PtCl2

CH3OSO3H H2O H2SO4+ + CH3OH

Overall Reaction

Hydrolysis Reaction

220C

Application Reaction

H2O CO2+ +CH3OH 6H+ + 6e-

Catalytic Interaction

Platinum (II) Platinum (IV)

Catalytic interaction mechanism to form methanol

Activating step of methane

Catalytic Interaction cont.

Suggested mechanism for the oxidation step

Catalytic Interaction cont.

CH3OSO3H H2O H2SO4+ + CH3OHFinal product then undergoes hydrolysis and turns into methanol

Purposed mechanism for functionalization step

Overall Proposed Mechanism

Different Solvent Interactions

• H2SO4 Sulfuric Acid

– Concentrated Sulfuric Acid– Dilute Sulfuric Acid

• HF/SbF5 – Causes Fluorination rather then oxidation of methane

• Methanol and H2O Interacts with catalyst- causing catalytic death

Using Different Catalysts

• (bpym)PtCl2 soluble and good interaction with sulfuric acid

• PtCl2 and PtO2 insoluble in H2O or other organic solvents

• PtCl4, K2PtCl4, and H2PtCl6 soluble but not compatible with sulfuric acid

• This leads us to believe only (bpym)PtCl2 is the only catalyst that works

• Yet Ionic Liquids allow these other catalysts to dissolve readily upon heating

Ionic Liquids (IL)

N

N

+

CH3

1-methylimidazolium

N

HN

+imidazolium

N

N

+

CH3

CH3

1,3-dimethylimidazolium

1-methylpyrazoliumN

NH+

CH3

NH

NH+

Pyrazolium

1,2-dimethylpyrazolium

N

N

CH3

CH3

+

NH +

Pyridinium

1,2,4-trimethylpyrazolium

N

N

CH3

CH3

+

H3C

Ionic Liquids Interactions

Ionic Liquids Interactions Cont.

• Better percent yield (Concentration) from the Ionic Liquids then with (bpym)PtCl2 by itself

• Ionic liquids are more water-tolerant• “Green” Chemistry due to low volatility

and good thermal stability

N

N

+

CH3

1-methylimidazolium

Pt

Cl

Cl

Applications• Industry applications to produce natural

gas to liquid products in milder conditions (T < 300oc)

• Use in hydrogen cars to produce a hydrogen yielding reaction from methanol

• Safer fuels

• Environmentally

friendly reaction

Batteries

Cell Phones

• You need only 2ml of fuel to ensure power for 20 hours operation of an MP3 audio player. Toshiba is actually running field tests with mobile phones at this moment.

Problems Facing Industry

• (bpym)PtCl2 is extremely sensitive to small amounts of water present in the reaction

• Methanol is very hard to extract from the sulfuric acid/ water solution

• There is also severe inhibition from the sulfuric acid/ water solution- causing catalytic death

Future Experiments

• Differing acids may lead to a more accessible way of extracting Methanol as a product

• Using Ionic Liquids to create a higher yield in less concentrated sulfuric acid

• Different Platinum catalysts that are more water-tolerant

Highlights

• (bpym)PtCl2 is a very good catalyst at producing methanol approximately 70% yield

• The problems are that methanol is very hard to extract from the sulfuric acid/ water solution

• HF/SbF5 is not a reasonable system to convert methane to methanol

• Ionic liquids increase yield and are more water-tolerant

• Realize how this catalyst could be used to further Hydrogen “Car” applications

References

• Cheng, J.; Li, Z.; Haught. M.; Tang. Y. Chem. Commun. 2006, 4617

• Kua, J.; Xu X.; Perenia, R. A.; Goddard, W. A., III. Organometallics 2002, 21, 511.

• Kua, J.; Goddard III, W. J. Am. Chem. Soc. 1999, 121, 10928

• Seidel, S.; Seppelt, K. Inorg. Chem. 2003, 42, 3846

• http://www.fuelcells.org/

Questions???

• Cool Website Link to See Fuel Cells

• http://www.utcpower.com/fs/com/Videos/UTCPower.wmv