Lignin is a by-product of the pulp paper industry, with around 100 million tonnes produced each year - most of which ends up being incinerated for energy.
Harnessing the potential of this by-product - the largest renewable source of aromatic carbon on Earth - as a feedstock for bio-based chemicals has been hampered due to lignin’s complex polymeric structure, which makes it difficult to process.
Now researchers at the US Department of Energy’s Lawrence Berkeley National Laboratory have developed a process which they said converts kraft lignin, a particularly tough form of the material, into benzylamines, an important ingredient in the production of a range of products including pharmaceutical ingredients, dyes, fertilisers, and pesticides.
Benzylamines are traditionally manufactured using benzyl chloride, a petroleum-derived compound, which requires large energy inputs to produce. The researchers say that their new route is more environmentally friendly as well as scalable.
Publishing their work in Chemical Engineering Journal, the research team, led by Chang Dou, principle engineer at Berkely Laboratory’s Advanced Bioprocess Development Unit, compared three alcohol solvents - methanol, ethanol, and isopropanol, in combination with formic acid in the presences of a ruthenium on carbon catalyst to produce alkyl guaiacols, a lignin-derived monomer. Reactions using methanol, formic acid and the ruthenium catalyst achieved the highest yields. The monomers were then transformed into phenolic benzylamines.
“The running joke in the industry is that you can make anything but money from lignin,” said Dou. “We’ve shown that even the most stubborn industrial lignin can be upgraded into valuable chemical building blocks.”
Ning Sun, staff scientist at Berkely Laboratory’s Advanced Bioprocess Development Unit noted : “While different types of solvents impacted yields, the product distribution – the ratio of products that are degenerated – remained largely the same across all solvents. However, different catalytic reagents affected the types of products that [could be made]. This suggests that solvent choice primarily governs yield, whereas catalyst selection is critical for steering toward desired chemical product.”
To analyse the economics of this route, the researchers collaborated with the Joint BioEnergy Institute and found that using methanol as the solvent performed best at larger scales. However, it was concluded that the inclusion of catalytic reagents did not have a significant enough impact on benzylamine yields to justify using them in the process.
Sun added: “This moves us beyond a largely academic exercise toward a more practical, scalable and economically relevant chemical manufacturing strategy.”
The researchers conclude that the study establishes a scalable, bio-based pathway for producing benzylamines from commercial kraft lignin valorisation, offering a sustainable alternative to petrochemical-based benzylamines.
Further reading:
- Bioeconomy boost as Europe unveils three new initiatives
- New project seeks to create sustainable bio-based polymers
- Location can impact sustainability of bio-based building materials
Visit Blog