Thermodynamic study of the CO2 valorization in the combined steam-dry reforming of bio-oil into syngas

Abstract

This work studies the thermodynamics of the combined steam-dry reforming (CSDR) (with H2O and CO2 as reactants) of bio-oil as an efficient route for the syngas production from biomass and CO2 valorization. The calculations are performed by Gibb's energy minimization with software AVEVA ProII, considering a mixture of 6 typical compounds in a raw bio-oil (acetic acid, hydroxyacetone, 2-methoxyphenol, furfural, ethanol, acetone), in the conditions: 300–900 ºC; CO2/carbon (CO2/C) ratio in the fed, 0.5–5; steam/carbon (S/C) ratio in the fed, 0.5–3. The syngas yield and composition (H2/CO ratio), CO2 conversion, and reduction of CO2 emissions compared to steam reforming (SR) have been calculated. The heat reaction study has allowed to determine the operating conditions in thermoneutral regime. The syngas yield > 99% of the stoichiometric value is achieved above 700 ºC for any feed composition, with positive CO2 conversion when suitable combinations of S/C and CO2/C ratios are used (the higher the S/C the higher the CO2/C ratio required). At 900 ºC with S/CO2/C= 0.5/0.5/1, 99.9% syngas yield is attained with 48% CO2 conversion and 49% reduction of CO2 emissions compared to SR, with the lowest energy requirement, but with low H2/CO ratio (0.84) in the syngas. H2/CO= 1 (interesting for the synthesis of fuels and chemicals) can be achieved with positive CO2 conversion (2.7–26% range depending on feed composition), but H2/CO= 2 leads to negative CO2 conversions due to the high S/C ratio required. The results indicate good prospects for the development of bio-oil CSDR technology, combining the objectives of sustainable syngas production and decarbonization.