Premium quality fuels and chemicals from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading

Biomass in the form of pine wood was pyrolysed in an externally heated fluidised bed pyrolysis reactor with nitrogen as the fluidising gas. A section of the freeboard of the reactor was packed with zeolite ZSM-5 catalyst. The pyrolysis oils before and after catalysis were collected in a series of condensers and cold traps. In addition, gases were analysed off-line by packed column gas chromatography. The composition of the oils and gases were determined before and after catalysis in relation to process conditions. The oils were analysed by liquid chromatography followed by gas chromatography/mass spectrometry. The results showed that the oils before catalysis were highly oxygenated, after catalysis the oils were markedly reduced in oxygenated species with an increase in aromatic species, producing a premium grade gasoline type fuel. The gases were CO2, CO, H2, CH4, C2H4 and C3H6 and minor concentrations of other hydrocarbon gases. After catalysis the concentration of CO2 and CO were increased. Detailed analysis of the upgraded oils showed that there were high concentrations of economically valuable chemicals. However, biologically active polycyclic aromatic species were also present in the catalysed oil, which increased with increasing catalyst temperature.