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Many types of chemical pathways aimed at representing the primary process of biomass degradation have been published. These models include or ignore the possibility of the existence of an intermediate "Active" species or state. The purpose of this paper is to gather theoretical results and experimental observations intended to open the discussion on the possible existence and nature of such an intermediate.

The results of the modelling of the chemical and thermal behaviour of biomass undergoing a pyrolysis decomposition are first given. Simple experimental and visual observations associated with theoretical considerations based on heat transfer measurements lead then to the conclusion that the overall reaction is similar to a fusion with production of an intermediate liquid species. From kinetic rate constants derived from literature, it appears that it is not necessary to take into account such a liquid in thermogravimetric analysis (TGA) experiments, but that it cannot be ignored in high temperature ablative pyrolysis conditions.

At the end of the paper, a discussion is conducted on the possible chemical natures of these liquids, the evolved vapours and the condensed pyrolysis oils formed in a pyrolysis process. It is concluded that the primary liquids could be composed of dimers and higher oligomers derived from cellulose and lignin, while the vapours would be mainly monomers and monomer fragments from the cracking of oligomers in the liquid phase.

Additional information

Authors: LEDE J, Laboratoire des Sciences du Genie Chimique, CNRS - ENSIC - LSGC, Nancy (FR);LÈDÈ J, Laboratoire des Sciences du Génie Chimique, CNRS - ENSIC - LSGC, Nancy (FR);DIEBOLD J P, National Renewable Energy Laboratory, Golden (US);PEACOCKE G V C, Bio-Energy Research Group, Aston University, Birmingham (GB);PISKORZ J, RTI - Resource Transforms International Ltd, Waterloo, Ontario (CA)
Bibliographic Reference: A chapter in "Fast Pyrolysis of Biomass: a handbook, Volume 1", EUR 18913. CPL Press, 1999. 194pp. 35 pounds sterling
Availability: Available from: CPL Press, Liberty House, The Enterprise Centre, New Greenham Park, Newbury, RG19 6HW, UK Tel: +44-1635-817408 Fax: +44-1635-817409 Email:
ISBN: 1-872691-07-2
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