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

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

Effect of potassium on the mechanisms of biomass pyrolysis studied using complementary analytical techniques

Complementary analytical methods have been used to study the effect of potassium on the pyrolysis mechanisms of cellulose and lignocellulosic biomasses. Thermogravimetry, calorimetry, high-temperature 1H NMR spectroscopy (in situ and real-time analysis of the fluid phase formed during pyrolysis), and water extraction of quenched char followed by size-exclusion chromatography coupled with mass spectrometry have been combined. Potassium impregnated in cellulose suppresses the formation of anhydrosugars, reduces the formation of mobile protons, and gives rise to a mainly exothermic signal. The evolution of mobile protons formed from K-impregnated cellulose has a very similar pattern to the evolution of the mass loss rate. This methodology has been also applied to analyze miscanthus, demineralized miscanthus, miscanthus re-impregnated with potassium after demineralization, raw oak, and Douglas fir. Hydrogen mobility and transfer are of high importance in the mechanisms of biomass pyrolysis