Kraft lignin successfully degraded using a "green" oxidizer
1 March 2023
The demand for vanillin vastly outstrips the natural resources of this flavoring agent. A chemical process is thus used to produce the required large quantities of vanillin from petroleum, which is far less expensive than obtaining the substance from fermented genuine vanilla pods. Another alternative is to make vanillin from lignin, a waste product of the wood pulping industry. A team led by Professor Siegfried Waldvogel of Johannes Gutenberg University Mainz (JGU) has now managed to further enhance their method of electrochemical production of vanillin from lignin in that they employ a "green" oxidation method for this purpose. This degrades Kraft lignin, a supposed worthless byproduct, to release vanillin. "We are confident that our sustainable, environmentally-friendly process can contribute towards an even larger scale production of vanillin," Professor Siegfried Waldvogel pointed out. The results of their research have been published in Angewandte Chemie International Edition.
High-quality vanillin can be produced from the waste material lignin
Many of the foods and drinks we consume contain vanillin as an additive, while the perfume and pharmaceutical industries also require the flavoring. Every year, several tens of thousands of tons of the substance are thus generated by chemical means. This requires mostly fossil raw materials and the process gives rise to toxic waste products. "We can avoid these problems by making vanillin from lignin, a component of wood," said Waldvogel. "The electrochemical process we have now been working on for nearly 15 years enables us to obtain high-quality vanillin from the renewable resource wood employing an eco-friendly method."
Lignin has long been used as a source of vanillin. The corresponding commercial process employs copper as a catalyst, which requires a complex and expensive purification of the resultant end product. In contrast, direct exposure of the raw material to an electrical current working as oxidizer is inherently less detrimental, more cost-effective, and does not result in the production of waste. Kraft lignin is needed for the sustainable production of vanillin. This is a waste product of the paper industry that is then thermally exploited in order to generate electricity. Caustic soda is used as a solvent and, at the commencement of the reaction, a freshly electrolyzed peroxodicarbonate solution is supplemented with the lignin solution. "The yield we achieve with this process can be up to 6.2 percent by weight of lignin used, which is an outstanding result," emphasized Waldvogel. Moreover, the carbonate used is a necessary make-up chemical for the operation of cellulose plants. This means that there are various options for a technical solution of combining the process with the operation of a biorefinery.
Different projects designed to promote eco-friendly production processes
Professor Siegfried Waldvogel of the JGU Department of Chemistry is spokesperson of the SusInnoScience – Sustainable Chemistry as the Key to Innovation in Resource-efficient Science in the Anthropocene – research focus at Mainz University. SusInnoScience focuses on the development of sustainable chemical innovations that will contribute to a circular economy and help circumvent the use of fossil raw materials. Waldvogel and his team collaborate with various related groups. Among other things, they are part of the international LIBERATE consortium exploring the commercial opportunities of the conversion of low-cost lignin feedstock. The EU is funding LIBERATE with EUR 10 million.