Thermodynamic Analysis of Hydrogen Production from Oxidative Steam Reforming of Ethanol

A thermodynamic analysis of ethanol oxidative steam reforming was carried out with a Gibbs free energy minimization method. The addition of oxygen lowers the enthalpy of the system and favors the heat recycle. Thermal-neutral (TN) conditions are obtained, at which the heat released from exothermic reactions makes up exactly for the requirement of the endothermic reactions. At three temperatures, 700, 900, and 1100 K, the ratios of H2O/EtOH and O2/EtOH for making up TN conditions are estimated, and the equilibrium moles of hydrogen, methane, carbon monoxide, and carbon are examined. 900 K is favorable for hydrogen production where the maximum equilibrium mole of hydrogen appears, with coke and methane being suppressed effectively. For the non-TN operations, a detailed calculation is presented on a range of reaction conditions, i.e., temperature of 700–1100 K and H2O/EtOH and O2/EtOH feed ratios in 1.0–10.0 and 0.0–0.9, respectively. Hydrogen is favored at low O2/EtOH ratio, high H2O/EtOH ratio, and 900 K. Methane is not favored at high temperatures and high O2/EtOH and H2O/EtOH ratios. Carbon monoxide increases with the increase of temperature. Carbon formation can be avoided by adjusting the reaction condition in a reasonable range.