Noble Metal Based Bimetallic Catalysts for the Catalytic Hydrotreatment of Phenolic Model Components for (Pyrolytic) Lignins
Lignins and pyrolytic lignins are considered to be interesting renewable sources for the production of important aromatic chemicals like benzene, toluene, xylene (BTX), and phenolic compounds. Catalytic hydrotreatment using supported metal catalysts has proven to be an interesting technology for this conversion. However, as lignins are highly cross-linked polymers with a large number of linkages between the aromatic nuclei, it is very challenging to obtain information about the reaction pathways occurring during the catalytic hydrotreatment process. The use of model components instead of real lignins provides valuable insights into the reactivity of the different bonds in the lignin structure. With this knowledge, the selectivity towards the target aromatics or phenolics can be optimised through proper catalyst design and selection. This review gives an overview of the use of bimetallic noble metal based supported catalysts for the catalytic hydrotreatment of lignin-derived model components. Such bimetallic catalysts are of high interest as the interaction between the two metals modifies the geometric and electronic properties, and this can lead to improved catalytic activity, selectivity and stability.