Abstract
Neutron scattering methods were employed to study the microscopic structure and dynamics of Bio Crude Oils (BCOs) and their lignin fractions. The structure of the carbonaceous aggregates was investigated using Small Angle Neutron Scattering to reveal a fractal hierarchy as well as a growth of the aggregates as the aging of the BCO proceeds. Elastic Neutron Scattering measurements indicate that BCO liquid phase, comprised of water and other hydrogenated molecular liquids, is in a state of extreme confinement. Quasi-Elastic Neutron Scattering yields information on the molecular motions, indicating that long range translational diffusion is suppressed and only localized dynamics take place on the tens of picosecond time range. The obtained results provide quantitative information on the molecular activity, as aging proceed, in these reactive materials of relevance as potential renewable energy sources.
Highlights
The energetic scenario depicted by most analysts and Kyoto agreement on CO2 emissions control require the development of new fuels based on renewable sources
This contribution does not provide any benefit to the final fits in all other samples probably because this fraction of larger objects precipitates out of the sample at longer times or it is covered by the scattering of the growing fractal assembly
Values of S and Df are greater than the ones reported in the literature on a batch of Bio Crude Oils (BCOs) produced by VTT starting from different biomass and production plant (Fratini et al, 2006) indicating that the lignin aggregates formed in the present case are more clustered and have a denser structure
Summary
The energetic scenario depicted by most analysts and Kyoto agreement on CO2 emissions control require the development of new fuels based on renewable sources. BCOs are formed by a large number of organic compounds, mainly carboxylic acids, carbohydrates and lignin derivatives, together with a variable amount of water Some of these organic compounds are very reactive and seem to be the main responsible for the aging process (Bridgwater, 2008). The possibility to correlate the aggregation between pyrolytic lignin into clusters with the evolution of the BCOs chemical and physical properties was disclosed This is of great importance in the formulation of pyrolysis fuels with long-term stability. Dynamic neutron scattering techniques offer the unique capability to measure the single particle dynamics of the hydrogen atoms in the system over length scales of the order of the Ångstrom and time scales ranging from few picoseconds to nanoseconds This microscopic mobility of the liquid species is indicative of the activity in the system. A comparison with the dynamics of the diverse lignin fractions is carried out as well
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