ROSALIND

Winner of the 2024 call for projects.

The main objective of this proposal is to explore the demethylation of lignin-models, and then real lignins by taking advantages of sono- and photocatalysis approach. Demethylation of lignin fragments or lignins is a reaction of high interest to produce polyphenol derivatives, a family of compounds which is used on a large scale for the manufacture of a wide range of downstream specialty chemicals including antioxidants.

So far, demethylation of lignins has been explored through acid-catalyzed or enzymatic processes:

• Acid-catalyzed processes are robust but, unfortunately, they suffer from a lack of selectivity.
• Enzymatic processes are much more selective but they display several drawbacks such as low reactor productivity and, in some cases, deactivation of the enzymes.

Despite the high interest, so far, the demethylation of lignins on a large scale remains unsolved. The search for cutting-edge technologies capable of demethylating lignins with a higher efficiency is highly expected, but it remains scientifically challenging.

ROSALIND project wishes to explore two alternative activation technologies for lignin demethylation, namely sono- and photocatalysis. The relevance of these two approaches lies in two key aspects:

• The mechanisms involved by these two activation modes are different and complementary.
• They rely on a sustainable source of energy, i.e. photons and acoustic waves.

In photocatalysis: when using supported photocatalyst, energy transfer proceeds either through a non-adiabatic charge transfer from the photocatalyst to the support or involves the formation of reactive oxygen intermediates, which could potentially lead to an oxidative demethylation with the release of the methyl group as formic acid.

In sonochemistry: the demethylation reaction occurs at the liquid cavitation bubble interface, thus inducing hydrothermal cleavage of the O-CH3 bond accompanied with the release of MeOH instead of formic acid.

In terms of methodology:

• Reactions will be first studied on “anisole-like” chemicals such as anisol, syringol, guaiacol.
• The reactions will then be applied to lignin models to:
  • Benchmark these two approaches and explore a potential synergy in associating these two activation approaches.
  • Assess the impact of these alternative activations on other bonds of lignins (i.e. selectivity in terms of side depolymerization/repolymerization of lignins).

The project will be evaluated according to its energy consumption in link to the productivity in reactors as it is an essential criterion to demonstrate the advantages of this approach and is a key environmental / cost factor to endorse transferability to larger scale. This important quantification will be assessed at the end of the project to appraise overall the business capability of our approach. This project represents a great opportunity to achieve selective and in high yield demethylation of real lignins in a competitive way.
 

Project lifetime:
 

2024 - 2028

Scientific manager:
 

François Jérôme (CNRS)

Partner institutions:
 

INRAE, UPJV