Dual catalyst-sorbent role of dolomite in the steam reforming of raw bio-oil for producing H2-rich syngas

The dual role that low-cost dolomite plays as a catalyst and CO2 sorbent in the steam reforming of raw bio-oil has been studied. The reactions were performed in a continuous regime at 700 degrees C and steam/carbon ratio of 3. The results show that calcined dolomite is a feasible catalyst for producing a H-2-rich syngas from raw bio-oil, with efficient CO2 retention and positive impact on the CO2 global emissions balance. Reforming of oxygenates (mainly acids, alcohols and aldehydes) and cracking/hydrogenation of poly-substituted phenols are prevailing reactions during the effective CO2 capture, catalyzed by the CaO and MgO in the dolomite. Consequently, around 40% of bio-oil is converted into a CO2-free syngas with H-2 and CO concentrations above 65 vol% and below 20 vol%, respectively, whereas the liquid product is primarily composed of phenol and alkyl-phenols. Products composition changes along reaction by two causes: i) saturation of dolomite by CaO carbonation, which drastically changes the liquid product composition leading to the formation of aromatics by alkyl-phenols hydrodeoxygenation (HDO), activated by the CaCO3 and Fe impurities; ii) coke deposition which involves a progressive decrease in H-2/CO ratio (6-2.5 in 4 h) by deactivation of steam reforming and water-gas-shift reactions.