Methanol Economy - Methanol Production For A Methanol Economy

Methanol Production For A Methanol Economy

The methanol needed in the methanol economy can be synthesized not only from a wide array of carbon sources including still available fossil fuels and biomass but also CO₂ emitted from fossil fuel burning power plants and other industries and eventually even the CO₂ contained in the air.

Today methanol is produced exclusively from methane through syngas. Although conventional natural gas resources are currently the preferred feedstock for the production of methanol, unconventional gas resources such as coalbed methane, tight sand gas and eventually the very large methane hydrate resources present under the continental shelves of the seas and Siberian and Canadian tundra could also be used. Besides methane all other conventional or unconventional (tar sands, oil shale,etc.) fossil fuels could be utilized to produce methanol.

Besides the conventional route to methanol from methane passing through syngas generation by steam reforming combined (or not) with partial oxidation, new and more efficient ways to produce methanol from methane are being developed. These include:

• Methane oxidation with homogeneous catalysts in sulfuric acid media
• Methane bromination followed by hydrolysis of the obtained bromomethane
• Direct oxidation of methane with oxygen
• Microbial or photochemical conversion of methane

The use of methane or another fossil fuel for the production of methanol using all the above mentioned synthetic routes has a potential drawback: the emission of the greenhouse gas carbon dioxide CO₂. To mitigate this, methanol can be made through ways minimizing the emission of CO₂. One solution is to produce it from syngas obtained by biomass gasification. For this purpose any biomass can be used including wood, wood wastes, grass, agricultural crops and their by-products, animal waste, aquatic plants and municipal waste. There is no need to use food crops as in the case of ethanol from corn, sugar cane and wheat.

Biomass → Syngas (CO, CO₂, H₂) → CH₃OH

More importantly, methanol can also be produced from CO₂ by catalytic hydrogenation of CO₂ with H₂ where the hydrogen has been obtained from water electrolysis. Methanol may also be produced through CO₂ electrochemical reduction, if electrical power is available. The energy needed for these reactions in order to be carbon neutral would come from renewable energy sources such as wind, hydroelectricity and solar as well as nuclear power. In effect, all of them allow free energy to be stored in easily transportable methanol, which is made immediately from hydrogen and carbon dioxide, rather than attempting to store energy in free hydrogen.

CO₂ + 3H₂ → CH₃OH + H₂O

CO₂ +2H₂O + electrons → CO + 2H₂ (+ 3/2 O₂) → CH₃OH

The necessary CO₂ would be captured from fossil fuel burning power plants and other industrial flue gases including cement factories. With diminishing fossil fuel resources and therefore CO₂ emissions, the CO₂ content in the air could also be used. Considering the low concentration of CO₂ in air (0.037%) improved and economically viable technologies to absorb CO₂ will have to be developed. This would allow the chemical recycling of CO₂, thus mimicking nature’s photosynthesis.