Liquefaction of biomass in the presence of phenol and H2O using alkalies and salts as the catalyst

The extent of dissolution of lignocellulosic biomass increased rapidly with the increase in reaction temperature. At higher temperature, i.e. 250 degrees C, 45 min reaction time seemed to be optimum. Compared with aqueous alkali, water was less effective as far as liquefaction of biomass in phenol was concerned. With the increase in catalyst concentration, both residue (%) and combined phenol (%) decreased, while both non-reacted phenol (%) and pH increased. At a phenol : biomass weight ratio of 4 : 6, the residue was lowest, while phenol : biomass ratio of 7 : 3 (wt ratio) offered lowest non-reacted phenol (%), but highest combined phenol (%). During liquefaction reaction, pH changed roughly four to five units. The final pH was always acidic whether the staring pH was alkaline or acidic. The residue (%), combined phenol (%), non-reacted phenol (%) and pH were not the same for different biomass samples. For example, wood meal (birch) gave lowest residue, both wood meal (aspen) and jute fibres offered almost similar residues and ranked second. However, other biomass samples, e.g. thermomechanical pulp (unbleached), kraft pulp (bleached), cotton and kenaf plant meal gave higher residue (%). The effects of various alkalies and salts used as the catalyst on the liquefaction of wood meal (birch) have also been discussed. The reaction conditions, mainly pH and temperature, as well as type of biomass sample, hydrating power and chelating power, particularly for transition metals, of metal ions have a profound influence on the extent of dissolution of biomass in phenol. (C) 1997 Elsevier Science Ltd.