Improved yield of carbon fibres from cellulose and kraft lignin

Abstract

To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48–51%). No difference in the mechanical properties of the produced CF was observed.

Mesoporous Carbon Microfibers for Electroactive Materials Derived from Lignocellulose Nanofibrils

“…Up to 70 wt% lignin was successfully wet spun into fibres with the assistance of TOCNF. This is also the highest ratio reached using ionic liquid dissolved lignin as dopes (Ma et al 2015;Bengtsson et al 2018). On the other hand, LCNF from mechanical treated wood retaining the native wood composition (lignin 28%, cellulose 36% and hemicelluloses 29%) was applied for ligninbased fibre production.…”

Hydrothermal base catalysed treatment of Kraft lignin - time dependent analysis and a techno-economic evaluation for carbon fibre applications

“…For the LMW fraction + pH 2, when t ret = 16 min, a faint T g can be determined at 123°C, suggesting that the LMW is not acting as a plasticiser due to there being very little difference between the T g of LMW and this sample. Bengtsson et al co-spinning of KL and cellulose as a polymer blend (Bengtsson et al, 2018). This would lower carbon content, but can increase linearity and thus stability of the resulting fibre.…”

Hardwood versus softwood Kraft lignin – precursor-product relationships in the manufacture of porous carbon nanofibers for supercapacitors

“…4 Together with its high degree of aromaticity and its high carbon content (>60%) lignin is an ideal candidate for the preparation of porous carbons with good yield, which is a distinct difference to other biopolymers, such as cellulose, hemicellulose or chitosan. 5 The reactions during the Kra process yielding new structural arrangements (building units and linkages) and chemical compositions of Kra lignins have been the focus of several research works in the past. [6][7][8][9] In particular, advanced spectroscopic and rigorous analytical methods give more and more insights into the diverse structural arrangements of various Kra lignins.…”