Thermodynamic analysis of hydrogen production for fuel cells from oxidative steam reforming of methanol

摘要

A thermodynamic analysis of hydrogen production from oxidative steam reforming (OSR) of methanol has been carried out by a Gibbs free energy minimization method. The equilibrium yields of hydrogen, carbon monoxide, methane and coke as a function of H_2O/Me0H ratio (0.0-10.0), O_2/MeOH ratio (0.0-1.0), and temperature (200 ℃, 400 ℃, 600 ℃, 800 ℃) at 0.1 MPa are investigated. Methanol can be fully converted at any H_20/Me0H and O_2/Me0H ratio in the condition range evaluated. Methane is the main product at low temperatures (200 ℃, 400 ℃), while hydrogen and carbon monoxide become dominant products with the increase of the temperature. 600 ℃ is favorable for hydrogen production at which the highest hydrogen yield appears. Carbon monoxide yield increases monotonically with the increase of the temperature and shows its maximum at 800 ℃. An increase of the H_2O/MeOH ratio leads to a preference for hydrogen production as well as an inhibition of the formation of carbon monoxide, methane and coke. The major contribution of adding oxygen is lowering the energy supply and suppressing the potential of coke formation at low H_2O/Me0H ratio. However, the total oxidation of methanol tends to dominant in this case. For the purpose of producing hydrogen-rich gas, no oxygen addition is preferred. The favorable operation window is obtained as 600 ℃, H_2O/MeOH ratio = 6.0-8.0 and O_2/MeOH ratio = 0. Under this optimal condition, 2.77-2.84 mol/mol methanol hydrogen yield and 0.13-0.17 mol/mol methanol carbon monoxide yield with trace amount methane (0.0070-0.017 mol/mol methanol) can be achieved without the risk of carbon deposition.