Aqueous-Phase Reforming of Bio-Oil Model Compounds Over Pt-Re/C

While fast pyrolysis bio-oil is an inexpensive liquid fuel derived from lignocellulosic biomass, the quality of bio-oil is poor partially due to its high content of oxygenated species, which included various acids, alcohols, aldehydes, ketones, sugars, guaiacols, syringols furans, and furfurals.  These species can be divided into water soluble and insoluble compounds, with the water soluble species coming primarily for the carbohydrate portion of the biomass.  Aqueous-phase reforming (APR) is a potential approach to convert these highly oxygenated compounds to H₂ and mono-functional species that can be subsequently upgraded to hydrocarbons.  However, a myriad of reactions will occur when APR is applied to the soluble portion of bio-oil, so there is a need to perform model compound studies to better understand the reaction system.  As a starting point, we conducted APR of ethanol over Pt-Re/C at 250 °C.  H₂, CO₂, CH₄, C₂H₆, acetaldehyde, ethyl ether, ethyl acetate, acetic acid were main products.  Additionally, acetaldehyde, acetic acid and formic acid were employed as reactants for APR, to provide information on the reaction pathways over Pt-Re/C.  Flux analysis on the ethanol reaction system was made to determine the reaction pathway and relative rates (v₁-v₈) for each step, which is shown in Figure 1.

Figure 1.  The reaction pathway for aqueous phase reforming of ethanol over Pt-Re/C.