Bio-based feedstock is an urgent needed energy source worldwide. Cellulose, being the most abundant renewable biopolymer in the world, has attracted much attention due to its fascinating structure and promising properties. Traditionally, cellulose is extracted from wood through the Kraft pulping process, which poses environmental hazards in the air and water because of using toxic chemicals. Therefore, efficient extraction of cellulose with no hazards emission is necessary.

Prof. LI Huiquan and his group from Institute of Process Engineering, Chinese Academy of Sciences developed an effective cellulose extraction method from wood chip in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl).

In the present study, four kinds of wood species pine, poplar, Chinese parasol, and catalpa wood chips were used to extract cellulose. Results showed that pine was the most suitable wood species for cellulose extraction with ILs. Its cellulose extraction rate reached as high as 62% under optimized conditions and the cellulose content as high as 85% when DMSO/water was used as the precipitant. The dissolution process can be clearly observed by hot stage optical microscopy. 13C CP/MAS NMR, FTIR, XRD, and SEM were used to analyze the cellulose-rich extracts of pine. Results show that IL dissolves pine wood by destroying inter- and intramolecular hydrogen bonds between lignocelluloses. After extraction, AmimCl can be easily recycled and reused.

The study not only realized a green process of cleanly extracting cellulose from wood under mild conditions, but also provided a new approach for utilizing biomass resources. The results presented here make the proposed technology highly promising for future applications.

This work has been published on Bioresource Technology.

cellulose extraction from wood chip in 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid. (Image by IPE)