For biomass gasification to be effective, some difficult problems associated with tars must be overcome.
One of these is the lack of a way to quantitatively analyze all of the gravimetric tar components with a single
analytical device. Therefore, gravimetric tar components have been identified and their yields have been
measured with a combination of two or more devices. However, a simple and practical analytical method is
required for process development and pilot-scale testing. Here, we propose a practical method of
gravimetric tar analysis that reflects the gravimetric tar reaction scheme and is suitable for industrial
use. We applied this method to gravimetric tars produced by secondary biomass tar thermal cracking
experiments. This method uses both ultimate analysis and 1H NMR analysis. Ultimate analyses showed
that the h/c molar ratio of the gravimetric tars decreased with increasing secondary thermal cracking
temperature. 1HNMRanalyses showed that the hydrogen distribution depended on the thermal cracking
temperature: as the temperature was increased, the number of aliphatic hydrogens decreased and the
number of aromatic hydrogens increased. Analysis of the chemical shifts of 1H NMR peaks of the main
biomass tar components in a reference material showed that the components could be separated into
monocyclic aromatics and polycyclic aromatics at a threshold chemical shift of 7.4 ( 0.1 ppm. From these
results, we proposed a modified reaction scheme and converted the hydrogen distributions obtained by
1H NMR analysis to carbon distributions. Even though gravimetric tar yields decreased with increasing
thermal cracking temperature, the yields of polycyclic aromatics were almost constant and were
independent of thermal cracking temperature. The yields of monocyclic aromatics decreased with
increasing thermal cracking temperature, whereas the yields of monocyclic aromatics in the volatile
organic compound fraction increased. The yields of monocyclic aromatics were almost constant at
temperatures below 1073 K. Thus, the occurrence of ring-opening reactions was negligible below
1073 K. Decomposition of monocyclic aromatics started at temperatures above 1173 K. Dealkylation
reactions were accelerated at temperatures above 1073 K.
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