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Lignin, degradation and analysis
The project involves study on the comprehensive approach to lignin utilization for production of valuable chemicals that may serve as renewable replacements of petrochemicals. The key technical issues essential for success of the whole project are addressed in three technical and one non-technical tasks.
Task 1 on lignin degradation is split into two technical subtasks.
Task 1a: Lignin biochemical degradation.
This process has been known for decades; the participating microorganisms and enzymes have been identified and characterized. Both the plant biomass and isolated lignin (after the separation of readily digestible carbohydrates) can be partially converted to water-soluble products using either fungi or bacteria. However, this process is far from practical realization because of the uncertainty with the product composition.
Task 1b: Lignin thermal decomposition.
This process also has been attempted for decades at 300-500 oC at high pressures in aqueous or protic solvents, i.e., under sub- or supercritical conditions. However, this process is known to produce large amounts of coke and tars, and also low-value gas-phase products; thus, its practical implementation remains questionable. Cokes and tars are produced due to re-polymerization of lignin degradation products to form even more recalcitrant polymers. The team seeks several solutions of this re-polymerization problem including the use of product-altering catalysts and multiple-step processes. In addition, the use of a novel scalable flow reactor will accommodate the tar formation, with its subsequent conversion to useful elemental carbon based materials.
Task 2. Analysis of lignin and its decomposition products.
This key task is designed to provide the basis for success of the other technical tasks. Lignin is an irregular polymer, so its chemical analysis is complicated. But even the products of lignin degradation, either biochemical or thermal, are not that easy to identify and quantify. This is because the "workhorse" of modern chemical analysis, gas chromatography, is not well-suited for the analysis of oligomers, significant intermediate and final products of lignin decomposition. Many previous studies report the analysis of only a very small fraction of products, i.e., GC-elutable phenolic monomers. The BioCon team sets out to address this problem by developing reliable and comprehensive analytical protocols and providing important feeds to Tasks 1 and 3.
Task 3. Separation and utilization of lignin decomposition products.
Chemical engineers will develop methods of separation and isolation of valuable chemical products of lignin decomposition. NDSU chemists and experts in polymers and coating materials will develop synthetic routes and practical steps for conversion of some low-value phenolic/aromatic products into more valuable chemicals and by-products, e.g., monomers for polymer synthesis.
Task 4 is a non-technical task supporting the Dakota BioCon mission with educational and outreach activities. Fellowships and stipends for graduate students have been given. Graduate students and faculty have been participating in a wide array of outreach activities targeting both high schools and tribal colleges.