Today, CO2 is added up to 30% of the total carbon in syngas (Aresta and Dibenedetto, 2007). The addition of CO2 in the
CO/H2feed significantly improves the methanol yield and the
energy balance. CO2 is directly converted to methanol without
a preliminary reduction to CO (Saito et al., 1996). To facilitate methanol synthesis, the CO in syngas is converted to CO2
through the water-gas shift (WGS) reaction:
CO+H2O↔CO2+H2 H25
◦C=−41 kJ/mol (4)
Reactions represented by Eqs.(3) and (4)are exothermic. The
overall reaction for methanol synthesis is given by the sum of
these reactions:
CO+2H2↔CH3OH H25
◦C=−90.5kJ/mol (5)
The theoretical single-pass CO conversion is limited to∼20%
under commercial operating conditions (Strelzoff, 1970; von
der Decken et al., 1987). Today, this process is well established
and several companies such as Lurgi, Topsoe and Mitsubishi
offer commercial technology solutions.