Continuous process for the controlled ozonolysis of organsolv lignin in a solvent consisting of short chain carboxylic acids or short chain carboxylic acid/water mixtures to yield aromatic monomer products including vanillin.
The ozonolysis can replace current wet oxidation process for converting valorizing lignin. The ozonolysis products include 4-hydroxy- benaldehyde and vanillin along with other monomers that can be used as a specialty chemicals or precursors for liquid fuels and other products. Over 1.5 billion tons of lignin are derived from industrial and agricultural process each year. The bulk of this lignin is currently burned as low value solid fuel. About 1% of the lignin is processed to produce specialty products including vanillin, a valuable fragrance and flavoring additive. Approximately 1,500 tons/year of vanillin is produced from lignin via a wet chemical caustic oxidation process. The current wet oxidation process wastes a large portion of the lignin and produces a hazardous waste stream.
This technology can replace the currently used wet oxidation methods for producing vanillin and other aromatics from lignin. It could be expended to process a larger portion of the available lignin feed and to provide low molecular aromatics as a platform for conversion to polymers, fuels and other products.
How it works:
Lignin is dissolved in a liquid organic acid or organic acid water solution and treated with ozone generated by electrochemical reaction. The ozone preferentially attacks olefinic bonds linking the aromatic groups in the lignin. The extent of reaction is controlled by adjusting the residency time, temperature and solvent system to preserve the aromatic rings while producing good yields of monomers.
- An underutilized agricultural material is converted to higher valued products
- The feedstock is renewable and the products can replace fossil oil derived materials
- Over oxidation of the lignin is controlled and monomer yields are optimized via modification of process conditions.
Why it is better:
- Process is clean and does not produce corrosive waste stream.
- There is no catalyst to recover
The ozonolysis process could be extend to treat other forms of lignin in addition to the organosolv lignin. Treatment of ligonocellulose materials may also be possible.