Methanol / Insight

Synthesis gas is produced from the methane contained in natural gas. At moderate pressures of 10-20 bar and high temperatures (about 850 °C), methane reacts with water vapour with a nickel catalyst to produce syngas according to the formula: CH4+H2O⟶CO+3H2

This endothermic reaction is commonly called SMR (steam methane reforming). Methane can also be partially oxidised with molecular oxygen to produce syngas, as the following equation shows: 2CH4+O2⟶2CO+4H2

This reaction is exothermic and the heat generated can be used in situ for the SMR reaction. When the two reactions are combined, the process is called autothermal reforming. The ratio of CO to H2 can be adjusted to a certain extent by the water gas shift reaction: CO+H2O⟶CO2+H2

and provide the correct stoichiometry for the methanol synthesis reaction. Carbon monoxide and hydrogen then react in a second catalytic reactor, producing methanol. Today, the most widely used catalyst is a mixture of copper, zinc oxide and alumina, used for the first time in 1966 by Imperial Chemical Industries. At pressures of 50-101 bar and temperatures of 250 °C, the catalytic reaction produces methanol with high selectivity: CO+2H2⟶CH3OH

The catalytic reaction model:

The production of synthesis gas from methane produces 3 moles of hydrogen per mole of carbon monoxide, whereas methanol synthesis consumes only 2 moles of hydrogen per mole of carbon monoxide. . One way to use the excess hydrogen is to inject carbon dioxide into the methanol synthesis reactor, where the following reaction also occurs: CO2+3H2⟶H2O+CH3OH
Although natural gas is the cheapest and most widely used raw material, other raw materials can also be used. Coal is increasingly being used as a raw material for methanol production, particularly in China. Moreover, the maturity of current biomass technologies also makes methanol production possible.

  • Adsorption
  • Surface reaction
  • Desorption
  • Catalyst regeneration