Understanding the relationship between catalytic pyrolysis conditions and hydrogen production by aqueous phase reforming of the water-soluble fractions of bio-oils

The valorization to H2 of real aqueous fractions of bio-oil (AFBs) from catalytic pyrolysis of woodchips was carried out by aqueous phase reforming (APR). Notable gas yield (23 mmol/gTOCo) and H2 concentration (46 mol%) were achieved, with values among the best published for the APR of real biorefinery streams. The reforming of AFBs was favoured by a high concentration of levoglucosan and low proportion of acids and ketones, with acetone and acetic acid being the most refractory compounds to APR. Relationships between the pyrolysis conditions and the H2 production obtained by APR were assessed, with more favourable results when the pyrolysis was carried out under the most severe conditions of those studied, i.e. 0.30 catalyst/biomass ratio and 500 degrees C in the catalytic step. H2 production increased to 32 mmol/gTOCo when 0.04 wt% formic acid was added to the reaction medium, showing that this strategy can overcome the low reforming ability of some AFB components. The Pt catalyst showed good stability after 3 consecutive reaction cycles, displaying only a slight decrease in TOC conversion and CCgas, but a moderate decrease in H2 production and gas concentration. The loss of activity was ascribed to cumulative adsorption of high molecular weight compounds and oligomers on the catalyst surface.