Copyrolysis of wood biomass and synthetic polymers mixtures. Part II: characterisation of the liquid phases

The copyrolysis of wood biomass-polyolefins was carried out in a rotating autoclave. At 400 degreesC, more than 50% (in mass) of final products are found in the liquid phase for a 1:1 (in mass) mixture. The obtained liquids are separated in a distillable liquids fraction and in an extracted liquids fraction. The first fraction can be fully characterised by gas chromatography/mass spectrometry. Only olefins, paraffins and some aromatics (benzene, toluene and xylene), issued from the polymers, are found in this fraction. The origin of the polymer plays the most important role in the chemical composition of this fraction. Some interactions with the solid issued from thermal degradation of the biomass are evidenced, for example by the presence of 2-alkenes with 3n carbon atoms. In the heavy liquids fraction, more than 80% (in mass) of the products are heavy olefins or paraffins. Schematically, we can explain the results of the copyrolysis experiments by: the biomass, whatever its origin, leads to solid, water and gas; polymer leads to liquid and gaseous olefins and paraffins; at a temperature lower than 400 degreesC, the biomass reacts and during the pyrolysis at 400 degreesC the formed solid evolves to act as a radical donor; assisted by radicals from biomass, polymer chain scission leads to the production of the light liquids; if the presence of biomass has an influence on the chemical composition of final products (particularly the light liquids fraction) their origin has, in general, only a limited effect. (C) 2002 Elsevier Science B.V. All rights reserved.