Devolatilization of conventional pyrolysis oils generated from biomass and cellulose

Weight loss curves in the air at a heating rate of 5 K/min up to 600 K are measured for liquids generated from the conventional pyrolysis of wood particles (beech and fir), bark, several agricultural residues (straw, olive husks, and nut shells), and cellulose. An aqueous fraction (fraction A), collected from ice-cooled condensers and corresponding to about 70-76% of the total liquid, and a muddy phase (fraction B), which, except for cellulose, appears as a superficial layer above the water scrubbers, are examined. Fraction A, consisting mainly of water; carbohydrates; furans; and, in the case of wood/biomass samples, phenols, guaiacols, and syringols, produces a small amount of solid residues (about 15-20%, dry liquid basis), but for cellulose, where a yield of about 40% is obtained. The global devolatilization rates are well-predicted by a mechanism comprising three parallel first-order reactions with comparable values of the kinetic parameters. Higher yields of solid residues (26-35%, dry liquid basis) are observed for fraction B, consisting of phenolic compounds and presumably extractives and high-molecular-weight species. Although the same global mechanism can also be applied, the kinetic parameters are significantly different from those estimated for fraction A and more affected by the origin of the samples.