Recent developments in biomass exploitation are focused on perennial low-input crops such as Miscanthus and cup plants, but also fast-growing trees like Paulownia gain increasing interest. These crops can be cultivated in arid conditions, require low amounts of fertilizer and maintenance and show fast growth. In addition, Miscanthus is able to fix a high amount of terrestrial carbon dioxide and shows high photosynthesis yields.<br/>A catalyst-free organosolv pulping process was applied to cup plant (Silphium perfoliatum), Miscanthus grass (Miscanthus x giganteus), and Paulownia tree (Paulownia tomentosa), resulting in high-purity lignins with no signals for cellulose, hemicellulose or other impurities in two-dimensional heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra. Different biomass particle sizes used for the organosolv pulping (1.6 – 2.0 mm; 0.5 – 1.0 mm; &lt; 0.25 mm) influenced the molecular weight and chemical structure of the isolated lignins. Principal component analysis (PCA) of 1H NMR data revealed a high intergroup variance of Miscanthus and Paulownia lignins, separating the small particle fraction from the larger ones. Furthermore, monolignol ratios identified via HSQC NMR differ significantly: Miscanthus lignins were composed of all three monolignols (guaiacyl (G), phydroxyphenyl (H), syringyl (S)), while for Paulownia and Silphium lignins only G and S units were observed.<br/>Moreover, this contribution presents the use of diffusion-ordered spectroscopy (DOSY) and 1H NMR in combination with multivariate regression for the determination of molecular weight (Mn, Mw) and the polydispersity of organosolv lignin samples. The suitability of the models was demonstrated by cross validation procedures. Furthermore the applicability of the models onto samples from different biomass<br/>origins was investigated.

Extraction of high-purity lignins via catalyst-free organosolv pulping from low-input crops

ACS Spring Meeting 2021

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