(717a) Oxidative Degradation of Lignin to Value Added Products

More, A. - Presenter, Auburn University
Jiang, Z., AC-PABE

Kraft lignin
obtained from paper and biofuel productions is currently being used as energy,
however it can be further converted to value added products thereby making
sustainable bio-refinery. Oxidative degradation of lignin produces low
molecular weight phenolic compounds which are high value added chemicals. However,
the current challenge of this process is to selectively control and improve the
yield of these phenolic compounds. In addition to phenolic compounds,
dicarboxylic acids are also produced by fragmentation of aromatic ring of
lignin. The goal of this research is to deepen the fundamental understanding of
factors governing the oxidative degradation processes of kraft lignin and integrate
it to current pulp and paper industry. This will be done by experimental study
of different reaction conditions, oxidizing and stabilizing agents, lignin
source and reactor configurations. The products were detected using high
performance liquid chromatography using RI and UV detectors and verified with
gas chromatography mass spectrometry. This approach is focused on analyzing
factors improving the yield of low molecular weight phenolic compounds. Hydrogen
peroxide is of the most widely used bleaching agent in the pulp and paper
industry. Hence, the use of hydrogen peroxide as an oxidizing agent improves
the economic viability of integrating the process to pulp and paper industry. The
study conducted showed that hydrogen peroxide treatment of kraft lignin can be
carried out at a comparatively low severity of reaction conditions compared to
oxygen. The preliminary results indicate that experiments carried out under
certain conditions generate low molecular weight phenolic compounds in yields
of 1-2 % and carboxylic acid fragments in yields of 15-20%. These compounds are
essentially phenolic aromatic aldehydes such as vanillin, syringaldehyde,
vanillic acid and carboxylic acids such as oxalic and formic acids. These
preliminary results indicate that there is a scope of improving low molecular
weight phenolic aldehydes and carboxylic acids yield. Also, the techno-economic
feasibility of the process makes it suitable to further deepen the fundamental
understanding of factors governing the peroxide degradation processes. Lignin
model compound study will be performed under similar conditions to further
develop the reaction scheme. This study will also include addition of aromatic
ring preserving agents such as α-tocopherol. Finally, the method to
selectively generate low molecular weight phenolic compounds from kraft lignin
will be proposed. The resultant process then will be integrated to pulp and
paper industry which will help in diversifying the products portfolio for a
sustainable bio-refinery.


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