Global vision from the thermodynamics of the effect of the bio-oil composition and the reforming strategies in the H2 production and the energy requirement

Abstract

The yield of H2 and by-products and the heat duties in the reforming of different oxygenates in bio-oil (acids, ketones, aldehydes, phenols and saccharides) have been compared by means of thermodynamic analysis, focusing on steam reforming (SR), oxidative steam reforming (OSR) and autothermal reforming (ATR) as alternatives. The study is performed by minimization of Gibb's energy method with ProII-Simsci® 10.1 software and has been extended for a wide range of conditions (temperature, steam/carbon (S/C) and O2/C ratios, and inert gas addition). The results of products yield and heat duties of SR are slightly different with oxygenates of different nature, and S/C = 5 and 610–644 °C range are the most suitable conditions for attaining high equilibrium H2 yield (90–92%) without excessive penalty in energy requirements. At S/C = 1.5, the inert addition increases slightly hydrogen yield and decreases coke formation, but this effect is not significant for S/C ratios above 5. Original correlations are proposed to predict the maximum yield of H2 and byproducts and the optimum temperature for the SR of oxygenates, from the values of the C/S ratio in the feed and the H/C, O/C and O/H ratios characteristic of the oxygenates composition. At 630 °C, ATR regime is achieved with a different O2/C ratio for the oxygenates, in the 0.12–0.22 range (aldehydes < acids ≈ phenols < ketones), and with H2 yield of 83–77%.