How is Methanol Made?
Methanol can be made from a wide array of feedstocks, making it one of the most flexible chemical commodities and energy sources available today. To make methanol, you need first to create synthesis gas, which has carbon monoxide and hydrogen gas as its main components.
While natural gas is most often used in the global economy, methanol has the distinct advantage of 'polygeneration' - whereby methanol can be made from any resource that can be converted first into synthesis gas. Through gasification, synthesis gas can be produced from anything that is or ever was a plant. This includes biomass, agricultural and timber waste, solid municipal waste, and a number of other feedstocks.
In a typical plant, methanol production is carried out in two steps. The first step is to convert the feedstock natural gas into a synthesis gas stream consisting of CO, CO2
O and hydrogen. This is usually accomplished by the catalytic reforming of feed gas and steam. Partial oxidation is another possible route. The second step is the catalytic synthesis of methanol from the synthesis gas. Each of these steps can be carried out in a number of ways and various technologies offer a spectrum of possibilities which may be most suitable for any desired application.
Conventional steam reforming is the simplest and most widely practiced route to synthesis gas production:
+ 3 H2
O -> CO + CO2
+ 7 H2
CO + CO2
+ 7 H2
-> 2 CH3
OH + 2 H2
This process results in a considerable hydrogen surplus, as can be seen.
If an external source of CO2 is available, the excess hydrogen can be consumed and converted to additional methanol. The most favorable gasification processes are those in which the surplus hydrogen is “burnt” to water, during which steam reforming is accomplished through the following partial oxidation reaction:
-> CO + 2 H2 -> CH3OH
CH4 + O2 -> CO2 + 2 H2
The carbon dioxide and hydrogen produced in the last equation would then react with an additional hydrogen from the top set of reactions to produce additional methanol. This gives the highest efficiency, but may be at additional capital cost.
Unlike the reforming process, the synthesis of methanol is highly exothermic, taking place over a catalyst bed at moderate temperatures. Most plant designs make use of this extra energy to generate electricity needed in the process.
This is just the most common of a number of ways to produce methanol from readily available and abundant feedstocks. For more information on how methanol is made from other resources, see our Renewable Methanol