Heterogeneous and homogeneous reactions of pyrolysis vapors from pine wood

To maximize oil yields in the fast pyrolysis of biomass it is generally accepted that vapors need to be rapidly quenched. The influence of the heterogeneous and homogeneous vapor-phase reactions on yields and oil composition were studied using a fluidized-bed reactor. Even high concentrations of mineral low char (till 55 vol %) appeared not to be catalytically active. However, the presence of minerals, either in biomass or added, does influence the yields, especially by the occurrence of vapor-phase charring/polymerization reactions. Contradictory, in the absence of minerals, homogeneous vapor-phase cracking reactions were dominant over polymerization/charring reactions (400–550°C, 1–15 s). With increasing vapor residence time, the oil yield reached an asymptotic value, which decreased with temperature. At a vapor temperature of 400°C no decrease in oil yield was observed, but dedicated analysis showed that homogeneous vapor to vapor reactions had occurred.