Chinese and foreign scientists have made progress in the high-value utilization of all components of biomass

Recently, Wang Chenguang, a researcher at the Guangzhou Institute of Energy Research, Chinese Academy of Sciences, cooperated with Bert F. Sels, a professor at the University of Leuven in Belgium, to make important progress in the high-value utilization of all components of biomass. The study was published online in ACS-Catalysis as a long article.

Gentle oxidation is a promising biomass catalytic conversion technology that converts lignocellulosic biomass into high-value chemicals and cellulose materials. However, in this process, the dissolution conversion of carbohydrates and the polycondensation and degradation of lignin and monophenols limit the improvement of overall carbon efficiency.

Based on the traditional oxygen-alkali papermaking lignin removal process, the researchers proposed a catalytic oxidative separation strategy based on the idea of preferential utilization of lignin, and applied it to the separation of lignocellulose components, while oxidizing lignin into high value-added monophenols.


Lignocellulose catalytic oxidative separation strategy. Photo courtesy of Wang Chenguang

It was found that the low-cost nano-copper oxide particles (CuO NPs) under mild conditions showed excellent catalytic oxidative separation properties, inhibiting cellulose hydrolysis while catalyzing the oxidation of lignin to aromatic aldehydes and ketones, and the carbon efficiency of high value-added monomers and materials (cellulose) obtained by this method reached 80%. Among them, lignin is converted into aromatic monomers (mainly vanillin and syringaldehyde), with a conversion rate of up to 48.6 wt%.

Through the two-step experiment and model reaction of “separation-oxidation”, it is found that CuO NPs can efficiently catalyze the cleavage of C-C bonds and C-O bonds of the side chains of lignin phenylpropane, promote the conversion of methylene quinone radicals of lignin oxidation intermediate to the target product aromatic aldehyde ketones, and make the monophenol yield exceed the theoretical value (based on the content of β-O-4 bonds). Hemicellulose is selectively converted to oxalic acid-based water-soluble small molecule fatty acids. 80% of cellulose is retained as a white solid residue (cellulose purity up to 95%).

It is proved by model reaction and 13C NMR that the strong complexation of copper cations with hydroxyl groups on the glucose chain of cellulose and oxygen atoms of pyran rings is the main reason for inhibiting cellulose hydrolysis.

The catalytic oxidative separation strategy proposed in this study is generally applicable to the catalytic conversion of woody and herbaceous biomass, which provides a guiding idea for the gentle and high-value utilization of biomass in the future, and further promotes the transition from fossil economy to a more sustainable bioeconomy using biomass to produce chemicals. (Source: China Science News Zhu Hanbin)

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