Quantitative insights into the fast pyrolysis of extracted cellulose, hemicelluloses and lignin

Abstract

The transformation of lignocellulosic biomass into bio-based commodity chemicals is technically possible. Among thermochemical processes, fast pyrolysis, a relatively mature technology that has now reached the commercial level, produces a high yield of an organic-rich liquid stream. Despite the recent efforts in elucidating the degradation paths of biomass pyrolysis, the selectivity and recovery rates of bio-compounds remain low. In an attempt to clarify the general degradation scheme of biomass fast pyrolysis and provide a quantitative insight, this study has combined the use of fast pyrolysis micro-reactors, spectrometric techniques and mixtures of unlabelled and Carbon-13 enriched materials. The first stage of the work reported aimed at selecting the type of reactor to ensure control of the pyrolysis regime. The comparison of chemical fragmentation patterns of 'primary' fast pyrolysis volatiles detectable by GC-MS between two small scale micro-reactors has shown the inevitable presence of secondary reactions. In a second stage, liquid fractions also made of 'primary' fast pyrolysis condensables have been analysed by quantitative liquid-state 13C-NMR providing a quantitative distribution of functional groups. The compilation of those results into a map that displays the distribution of functional groups according to the individual and main constituents of biomass confirmed the origin of individual chemicals within fast pyrolysis liquids.