Thermodynamic comparison between bio-oil and ethanol steam reforming

The thermodynamic analysis of the steam reforming (under catalytic steam reforming conditions) of a simulated bio-oil (composed of model compounds of components in a real bio-oil) and of ethanol is performed by minimization of Gibb's free energy method with Pro II-Simsci® 8.3 software, and their results are compared. At the equilibrium conditions both oxygenated feeds are completely converted, with H2, CO2, CO and CH4 being the only significant gaseous products. Coke formation is observed below 700 °C for low steam/carbon (S/C) molar ratios (below the stoichiometric value). H2 yield, which is very similar for both reforming processes (with small differences only for S/C < 2), increases with S/C ratio and goes through a maximum with temperature, being higher than 90% for S/C > 5 and in the 540-640 °C range. Above 600-650 °C (depending on the S/C molar ratio), the energy requirement for steam reforming of ethanol is slightly higher that for bio-oil steam reforming. These results evidence the viability of the joint valorisation of bio-oil and bio-ethanol by means of steam reforming.