catalytic conversion of pyrolytic vapors of woody biomass
Résumé
For thousands of years, pyrolysis has been applied for charcoal production but it is only during the last 30 years that fast pyrolysis was developed. The concept is the rapid heating of biomass at moderate temperatures around 500°C with short reaction times of up to 2 seconds in an oxygen-free environment to optimize the yield of liquids. Pyrolytic bio-oils contain a significant amount of reactive oxygenated species and they have to be stabilized and deoxygenized to be compatible with traditional fuels. Catalytic pyrolysis is an approach that allows a partial deoxygenation before vapor condensation.
To produce upgraded bio-oils, a semi-continuous pyrolysis experiment on lab-scale was developed. It consists of a quartz tube containing two porous frits. The first retains the wood and char, while the second holds the catalyst. This reactor is placed inside a cylindrical oven. Beech wood chips are introduced into the top part of the reactor by means of a solid powder dispensing system (Parimix). A flow of nitrogen of 500 mL/min inerts the biomass injector and drives pyrolysis vapors through the catalyst fixed bed (catalyst-to-biomass ratio of 1:10). At the reactor exit a condenser collects the bio-oil at 4°C. This condenser is followed by an electrostatic trap to capture the very fine oil droplets and to protect the micro-GC used for on-line gas analysis.