Change in molecular structure of flash pyrolysis tar by secondary reaction in a fluidized bed reactor

The effect of the secondary vapor-phase reaction on the molecular structure of flash pyrolysis tar was studied in a fluidized-bed reactor where the temperatures of the dense bed and the freeboard were independently controlled. Although the tar yield and its ratio to the total volatile yield were affected by the temperature of both the bed and the freeboard, the H/C ratio of the tar was determined only by the freeboard temperature. The number-based distribution of -CH₂-groups attached to aromatic rings and its change by the dealkylation were each evaluated as a function of temperature for each homologous series having the same aromatic ring structure.