Process development of lignin depolymerization

Photocatalytic modification and depolymerization of lignin

 

Renewable raw materials provide natural lignin, which is attractive for the development of new biomaterials and, above all, for the production of aromatic fine chemicals. The biopolymer - a main component of vascular-forming plants, especially the wood of trees - is present in a composite structure with cellulose and hemicellulose and is one of the three most abundant organic compounds on earth. Around 55 million tonnes of it are produced as a by-product of pulp production per year. Only around two percent of the lignin obtained is currently used as a material; the rest is used thermally due to its relatively high calorific value.

Therefore, within subproject 4, a photocatalytic process for the splitting and modification of lignin will be implemented in order to advance the use of the natural substance as an additive and biomaterial.

Compared to other catalytic cleavage reactions, photocatalysis is a particularly energy-efficient and health-safe method. Since lignin is a large, widely branched polymer with many different structural features, direct research on this natural product is very complex. In order to better understand the processes during photocatalytic cleavage, smaller model lignin compounds are synthesized and analyzed in advance. T

he aim of the sub-project is to apply the knowledge gained from these model splits to ever larger models in order to achieve a gradual approximation to the actual lignin. The now known cleavage products of lignin can either be isolated directly and used as materials or they can be given further chemical modifications and thus new properties. Due to the mild reaction parameters of a photochemical reaction and the reagents used, a more selective splitting is expected than with other methods.

In addition to all the positive aspects of this green chemistry, this would have a promising side effect, namely the simplification of the subsequent isolation and purification processes of the separated fine chemicals and a reduction in the associated costs.