Methanol

Production

Today, synthesis gas is most commonly produced from the methane component in natural gas rather than from coal. Three processes are commercially practiced. At moderate pressures of 1 to 2 MPa (10–20 atm) and high temperatures (around 850 °C), methane reacts with steam on a nickel catalyst to produce syngas according to the chemical equation

Related Topics:
Methane - Natural gas - Reacts - Steam - Syngas - Chemical equation

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:CH4 + H2O → CO + 3 H2

Related Topics:
CH₄ - H₂O - CO - H₂

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This reaction, commonly called steam-methane reforming or SMR, is endothermic and the heat transfer limitations place limits on the size of the catalytic reactors used. Methane can also undergo partial oxidation with molecular oxygen to produce syngas, as the following equation shows:

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:CH4 + 0.5 O2 → CO + 2 H2

Related Topics:
CH₄ - O₂ - CO - H₂

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this reaction is exothermic and the heat given off can be used in-situ to drive the steam-methane reforming reaction. When the two processes are combined, it is referred to as autothermal reforming. The ratio of CO and H2 can be adjusted by using the water-gas shift reaction,

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:CO + H2O leftrightarrow CO2 + H2,

Related Topics:
CO - H₂O - CO₂ - H₂

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to provide the appropriate stoichiometry for methanol synthesis.

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The carbon monoxide and hydrogen then react on a second catalyst to produce methanol. Today, the most widely used catalyst is a mixture of copper, zinc oxide, and alumina first used by ICI in 1966. At 5–10 MPa (50–100 atm) and 250 °C, it can catylize the production of methanol from carbon monoxide and hydrogen with high selectivity

Related Topics:
Copper - Zinc oxide - Alumina - ICI - 1966

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:CO + 2 H2 → CH3OH

Related Topics:
CO - H₂

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It is worth noting that the production of synthesis gas from methane produces 3 moles of hydrogen for every mole of carbon monoxide, while the methanol synthesis consumes only 2 moles of hydrogen for every mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where it, too, reacts to form methanol according to the chemical equation

Related Topics:
Mole - Carbon dioxide - Chemical equation

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:CO2 + 3 H2 → CH3OH + H2O

Related Topics:
CO₂ - H₂ - H₂O

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Although natural gas is the most economical and widely used feedstock for methanol production, other feedstocks can be used. Where natural gas is unavailable, light petroleum products can be used in its place. The South African firm Sasol produces methanol using synthesis gas from coal.

Related Topics:
Petroleum - South Africa - Sasol - Coal

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