N°656 / PC
TOPIC(s) : Alternative solvents / Renewable carbon / Biomass conversion / Valorization of waste
Functional Nanocrystalline Cellulose Produced Directly From Lignocellulosic
Biomass Using Recyclable Formic Acid
AUTHORS
ZHANG Yongchao / TIANJIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, DAGUNAN ROAD 1038,HEXI
DISTRICT, TIANJIN
Guoyu TIAN / TIANJIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, TIANJIN UNIVERSITY OF SCIENCE
AND TECHNOLOGY, TIANJIN
Yongchao ZHANG / TIANJIN UNIVERSITY OF SCIENCE AND TECHNOLOGY, TIANJIN UNIVERSITY OF
SCIENCE AND TECHNOLOGY, TIANJIN
Menghua QIN / TAISHAN, #525, YINGBIN AVENUE, TAIAN
YINGJUAN FU / QILU UNIVERSITY OF TECHNOLOGY, #3501 UNIVERSITY ROAD, CHANGQING DISTRICT,
JINAN
Corresponding author : Zhaojiang WANG / [email protected]
PURPOSE OF THE ABSTRACT
Nanocrystalline cellulose (NCC) has caught the worldwide attention with many applications and the potential for a
multibillion-dollar industry. conventionally, NCC is prepared from cellulose source material, and wood pulp is
normally used, by the acid hydrolysis commonly using sulfuric or hydrochloric acid. The main concern with using
mineral acid hydrolysis is the difficulties in economic acid recovery (approximately 9 kg H2SO4/kg NCC using
sulfuric acid) and the requirement for disposal of a large amount of salt (approximately 13 kg Na2SO4/kg NCC)
from acid neutralization. Here we report the production of NCC by hydrolysis using organic acids (formic acid) and
lignocellulosic biomass (poplar wood) in two-step reaction, i.e. organosolv fractionation of wood and the
subsequent acid hydrolysis of wood pulp. Under the optimized conditions of organosolv fractionation at 130°C for
60 min of cooking, with a solvent ratio of 85:15 (v:v), wood:solvent ratio of 1:7, a relatively pure cellulose pulp (
88% cellulose, 5% lignin, 7% hemicellulose) was obtained with remarkable yield of 56%. Because formic acid is
weaker than the typical inorganic acid and its boiling point is lower (100.8 ºC), mechanocatalysis was
implemented for preparation of NCC from wood pulp by using a high-shear homogenizer at 12000 rpm in a
interrupted hyper-pulse mode. The mechanocatalysis process allowed a rapid isolation of NCC from wood pulp
with a higher yield of 61.3% at a lower formic acid concentration of 80%, a lower temperature of 90 ºC, and a
shorter reaction time of 20 min. The resultant NCC surface contained formyl groups which facilitate
functionalization and dispersion in aqueous processing. Further, results indicated that the formyl groups can be
easily removed by simple hot water boiling or dry heating at elevated temperatures, which raised the interesting in
composite processing. The low strength (high pKa) of formic acid also resulted in NCC with longer lengths of
approximately 1654±35 nm and higher crystallinity (81.2% crystallinity index) than those produced using mineral
acids (77.3% crystallinity index). The diluted formic acid from organosolv fractionation, mechanocatalysis, and
washing of NCC was recovered and concentrated by phase transfer reactive extraction using tertiary amines as
reactant with 98.3% yield. Adducts of formic acid and tertiary amines can be thermally cleaved into free formic
acid and tertiary amine and therefore serve as an intermediate in the recovery of formic acid. The ability to
recover the formic acid using a conventional and commercially proven method makes formic acid uniquely suited
for sustainable and green production of cellulose nanomaterials. The resultant NCC with removable formyl groups
and large aspect ratio are excellent for bio-composite applications.
FIGURES
FIGURE 1
FIGURE 2
figure 1
schematic flow diagram of experiments for integrated
nanocrystalline cellulose, sugars, and lignin
production through organosolv fractionation and
mechanocatalysis process with full recovery of formic
acid.
KEYWORDS
nanocrystalline cellulose | organosolv fractionation | mechanocatalysis | formic acid
BIBLIOGRAPHY
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[2] Li, Bin, et al. Cellulose nanocrystals prepared via formic acid hydrolysis followed by TEMPO-mediated
oxidation. Carbohydrate polymers 133 (2015): 605-612.
[3] Fujimoto, Tetsuya, et al. Reaction of cellulose with formic acid and stability of cellulose formate. Journal of
Polymer Science Part C: Polymer Letters24.10 (1986): 495-501.