Thermodynamic analysis of formic acid synthesis from CO2 hydrogenation

Thermodynamic calculations for CO₂ hydrogenation to formic acid has been analysed by using Virial state equation which contains only the Second Virial Coefficient. On the assumption that the number of moles of CO₂ is n_CO2 = 1 and the molar ratio of H₂ to CO₂ is n_H2/n_CO2 = n, effects of reaction temperature, pressure and n(H₂)/n(CO₂) on equilibrium compositions in system were studied. The results showed that: while n=1, the CO₂ equilibrium conversion increases along with the increasing of temperature and pressure. And when p=10MPa, between the range of n=1 to 5 the higher ratio of n(H₂)/n(CO₂) is profitable to the reaction of formic acid synthesis from CO₂. However, to CO₂ = H₂ → HCOOH which was thermodynamically unfavorable not only needed higher temperature and higher pressure, priority would be given to this reaction was to disrupt the control of thermodynamic equilibrium. In addition, a suitable catalyst was needed to make an efficient transformation from CO₂ to formic acid possible.