Synthesis of Cellulose Nanoparticles from Lignocellulosic Feedstock: A Roadmap

Kalavathy Rajan1,2, Angele Djioleu1,2, Elizabeth Martin1,3, and Jin-Woo Kim1,2

1Bio/Nano Technology Laboratory, Institute for Nanoscience & Engineering; 2Department of Biological & Agricultural Engineering; 3Arkansas Institute of Nanoscale Materials Science and

Engineering; University of Arkansas, Fayetteville, AR

ABSTRACT Cellulose, when deconstructed to nano-crystalline particles, finds a variety of applications from drug delivery to

material engineering owing to its unique physicochemical properties. Cellulose can be extracted from lignocellulosic biomass, an inexpensive and renewable feedstock, which contains cellulose in the ranges of 35 to 50%. There are different methods available for the production of cellulose nanoparticles from lignocellulosic biomass namely, I) biological delignification, II) chemical pulping, III) mechanical diminution, IV) dissolution and V) integrated synthesis and chemical modification. These methods are used to fractionate the lignocellulosic biomass and extract the cellulose fibers, which are then processed further to produce cellulose nano fibrils or cellulose nanocrystals. Each method has its own advantages and disadvantages and can be customized to fit the end user requirements. Lignocellulose is a complex polymer and it often necessitates combining two or more of the above-said fractionation techniques in order to improve the yield of cellulose nanoparticles. This presentation provides a road map for the deconstruction of lignocellulosic biomass to cellulose nanoparticles and a comparison of the feasibility and suitability of each of the production processes.

CASE Annual Meeting 2016

November 24–25, 2016 Little Rock, AR, USA

BACKGROUND & SIGNIFICANCE

Strategies to synthesize CNC from woody biomass will pave way for production of value added cellulosic co-products from forestry residues

DELIGNIFICATION STRATEGIES SUMMARY & CHALLENGES

The complex matrix of lignocellulose warrants a combined utilization of mechanical and chemical treatments and advanced fractionation techniques to obtain a suitable end product

MECHANICAL STRATEGIES

Center for Advanced Surface Engineering

Tunicates

Algae

Municipal solid waste

Woody biomass

Herbaceousbiomass

Cellulosic feedstock

Sources: NASS, USDA, 2012; Arkansas Energy Office, AEDC. http://arkansasenergy.org/energy-sources/biomass

14.1

2.8

2.7

0.24

0.14

0.11

0 5 10 15

Forestry residues

Municipal solid waste

Rice residues

Corn residues

Wheat residues

Cotton residues

Arkansas state renewable biomass sources (2013)

Million dry ton/ year

Lignocellulose is a renewable feedstock for the production of high-value cellulosic products like Cellulose Nano-Crystals (CNC). CNC has some unique properties such as, elastic modulus of 110-220 GPa similar to that of 302 stainless steel, tensile strength of 7500-7700 MPa, which is twice as much as that of Kevlar and density of 1.6 g/cm3, which is lighter than 302 stainless steel (Brinchi et al., 2013). CNC are rigid rod-like particles of variable dimensions; CNC from hardwood, for example, will have a dimension of 140-150 x 4-5 nm (Habibi et al., 2010). CNC are liquid crystalline and show birefringence (Moon et al., 2011). And since it is biodegradable and non-toxic, CNC find a variety of useful applications such as, “green” structural composites, rheology modifiers, barrier films, electro-optic devices, tissue scaffolds, contrast agents, etc. (Sinha et al., 2015).

Fig. 1A- Natural sources of cellulosic feedstock Fig. 1B- Renewable feedstock available in Arkansas for the production of value-added cellulosic co-products

Renewable sources of lignocellulosic feedstock grown in Arkansas are southern pine, hardwoods, rice and corn residues, etc. (Fig. 1B). Woody biomass are the largest sources of cellulosic feedstock and in Arkansas, the timber product output was reported to be 489 million cu. ft. (USDA Forestry service, 2009), which roughly translates to 60 million tons of cellulose per annum. There are a few studies on the production of CNC from bleached wood pulp and even fewer that focus on the production of CNC from woody feedstock. Conversion of woody biomass to CNC is a painstakingly long process and this study has strived to summarize the various production pathways.

Solid state fermentation of loblolly pine chips with white rot fungus (Trametes versicolor)

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Control 30 days

White rot fungi, like Trametes versicolor, are known to disrupt the surface lignin of woody biomass by virtue of secreting lignin-degrading enzymes like, polyphenol oxidases and lignin peroxidases. Thus it results in enriching the cellulose content of woody biomass by 18-20%. Pros: “Green” technology, consumes less energy and capital Cons: Time consuming, inconsistency in fungal growth

Biological delignification

Changes in loblolly pine chips composition after 30 days of incubation with Trametes versicolor fungi. Substrate carbohydrate concentration determined by HPLC analysis. Averages & standard deviation, n=3.

Chemical delignification Pulping process using caustic or acid sulfite reactions is commonly used in the paper industry for the extraction

of cellulose. Pulp yields are in the range of 80% of the theoretical maximum. During pulping the lignin molecules are depolymerized, chemically substituted and solubilized under acidic or alkaline conditions. After pulping, bleaching of wood pulp is required in order to remove the intractable lignin residues, if any, and bleaching agents such as, chlorine, oxygen, hydrogen peroxide, etc., are used under alkaline conditions. Pros: High purity. Cons: Time consuming, requires high chemical input and complicated downstream processing

EXPERIMENTAL SET-UP

CITED WORKS

2000 nm

A.  TEM image of nanocellulose from cotton obtained by enzymatic hydrolysis and ultrasonication at 20 kHz. Bittencourt et al. 2008. https://www.hielscher.com/ultrasonic-production-of-nano-structured-cellulose.htm

B.  TEM image of nanocellulose from hardwood obtained by high pressure homogenization at 30,000 psi using a microfluidizer. Tien et al. 2016, Carbohydrate Polymers 136, 485-492

C.  TEM image of freeze dried Avicel®. Fortunati et al. 2012. Polymer degradation and stability, 97(10), 2027-2036 D.  TEM image of ball-milled wheat straw cellulose. Nuruddin et al. J. Appl. Polym. Sci. DOI: 10.1002/APP.42990

•  Brinchi et al.,2013. Carbohydrate polymers. 94(1):154-169 •  Habibi et al., 2010. Chemical review. 110(6):3479-3500 •  Moon et al., 2011. Chemical society reviews. 40:3941-3994 •  Sinha et al., 2015. Journal of Biosystems Engineering. 40(4):373-393

A.  Ultrasonication for dispersion of individual cellulose fibril B.  Microfluidizer- It is a high pressure homogenization technique where the

cellulose fibrils are passed through a microfluidic pathway (30-50 µm) that creates high shear and facilitates fiber separation and size reduction.

C.  Cryo-crushing- Uses lyophilization to enhance fiber fracture and size reduction.

D.  Ball-milling- Fractures the cellulose fibers at the amorphous regions. Increases mechanical strength and promotes fibrillation.

E.  Mechanical pulping- Fractionation of cellulose from woody biomass using heat and mechanical energy. Uses stone grinding mills and disc refiner plates. Pros: High yield. Cons: High energy input, low grade pulp

Strong acids like concentrated sulfuric and hydrochloric acid under controlled conditions can dissolve the amorphous cellulose and hemicellulose, to yield crystalline cellulose fibers. Milder acids like formic, acetic, peracetic and performic acids can be used to fractionate hemicellulose and acid soluble lignin regions. Enzymes like endo- and exo- cellulases and xylanases can be used to hydrolyze the amorphous cellulose and hemicelluloses.

Lignocellulose or Cellulose fiber

Acid hydrolysis

CNCEnzymatic hydrolysis

Solvent extraction

Ionic liquids

Chemical diminution

Dissolution Chemicals can be used to dissolve and fractionate either lignin (ethanol, methanol) or the carbohydrates (1-

ethyl-3-methylimidazolium acetate, N,N- dimethylacetamide, dimethylsulfoxide, persulfate) from woody biomass. Pros: Less energy consumption. Cons: Requires advanced fractionation and additional purification.

38 42

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Original HC ext. pine

Ext. Kraft pulp 1500

% T

otal

sol

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Lignin Hemicellulose Cellulose

Loblolly pine sawdust

Hemicellulose extraction Kraft delignification

Loblolly pine pulp 1 g 0.84 g 0.37 g

•  Hemicellulose extraction o  0.5% H2SO4, 160 °C, 1 h

•  Kraft delignification o  170 °C, effective alkalinity 24%,

sulfidity 66%, H factor 1500 o  Carbohydrate composition was

determined by HPLC

Cellulose fiber Chemical/enzymatic depolymerization

Mechanical disruption/ refining

Physico-chemical fractionation

Chemical Diminution/ Dissolution

CNC

Advanced fractionation Size exclusion

Lignocellulose Cellulose nanoparticles

TEM image of commercially purchased CNC. Print Mag: 119,000 X @ 7 in. Source: Dr. Martin, UAF.

100 nm

CHEMICAL STRATEGIES