Technology offer: Chemical raw materials from wood

Given the constant increase in the world’s population and the decline in fossil raw material reserves, the recovery of renewable raw materials is one of the key issues for the future. However, the aim is not only to fulfill long-term energy demand through the use of alternative, renewable, climate-friendly energy sources. Substances known as aromatics, which have been produced from oil up to now, are needed for the manufacture of thousands of everyday materials and are found, in drugs, coloring agents, plastics, and epoxy resins, among other things. And although it is possible to obtain these crucial synthesis components from wood, the conversion of wood into aromatic compounds was thus far only possible under technically sophisticated and uneconomic conditions. Researchers from the Max Planck Institut (MPI) für Kohlenforschung have now developed a method, with the help of which aromatics from wood can be made available for use as raw materials in a simple and cost-effective way.
Image: Laboratory process for the isolation of lignin from wood

The scientists’ starting point is lignin, a complex biopolymer stored by trees and bushes in their cell walls to give them stability. Up to 30% of the mass of woody plants consists of the strongly linked chain molecules, which must be deliberately dismantled into their components to be made available for further use. Although chemists could already separate these polymers into smaller units with the help of acids and high temperatures, the result was an unusable mixture of oxygenated compounds that were very difficult to separate. The majority of the aromatic compounds were also converted into other more hydrogen-rich products through subsequent conversion with hydrogen. As a result, they were no longer available for further use. For this reason, lignin, which is produced in large volumes in various technical processes like paper production, was to date usually incinerated for the purpose of energy generation rather than being used as a raw material for chemical synthesis components.

The MPI researchers have now developed a depolymerization process, with the help of which the biopolymer lignin can be decomposed into aromatic components. Through the combined use of two commercially available catalysts (Raney nickel and Zeolith B), several chemical reactions, which produce the desired aromatic compounds directly, have now been coupled for the first time. This means that important synthesis components like benzene, toluene, xylene (BTX) and other related substances can be obtained in one step. According to a recent study by Frost & Sullivan on the potential of lignin as a raw material, the estimated annual market value of BTX aromatics will be approximately USD 122 billion in the year 2020. The new MPI process could help to enable the production of BTX from renewable sources in a cost-effective way using simple technical means.

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