Title: Cellulose Molecular Dissolution and its Effect in Processing of Porous Materials, Emulsification and Enzymatic Hydrolysis
Presenter: Professor Yachin Cohen, Department of Chemical Engineering, Technion-Israel Institute of Technology
Abstract: Cellulose is the most abundant renewable material in nature, and significant quantities are available as waste sludge of the paper industry. Yet only a minute of fraction of its annual natural production is utilized as raw material for fabrication of synthetic products, or as source for biofuel production. Its processing requires harsh solvents or procedures considered to be detrimental to the environment and are increasingly regulated. The use of ionic liquids (IL) as “green” solvents has attracted significant attention due to unique properties such as stability, low toxicity and non-volatility. Our current research achieved two basic discoveries: using mixtures of an ionic liquid and a polar organic solvent we show that the cellulose molecules are dissolved essentially as individual chains. This was evident from neutron and x-ray scattering patterns augmented by cryo-transmission electron microscopy imaging. Furthermore, the dissolved cellulose chains readily form a unique encapsulation coating in oil-in-water or water-in-oil emulsions. This indicates that individual cellulose chains have an amphiphilic character. The cellulose cating exhibits a continuous amorphous structure which differs significantly from the nano-crystalline nature of the cellulose coating in Pickering emulsions. These newly discovered characteristics lead to potential applications in several directions, such as utilisation of native cellulose as a unique coating for functional hydrophobic molecules (e.g. pharmaceuticals, phase-change materials, etc) and cellulose aerogels having amorphous (non-crystalline) structure that exhibit amphiphilicity, which may be beneficial in applications as novel adsorbents. Furthermore, we show that cellulose hydrogel particles in aqueous suspension exhibit significantly higher rates of glucose production in enzymatic decomposition, relative to other pretreatment effects. In particular, the hydrolysis rate of cellulose-coated emulsions can be three orders of magnitude faster than that of microcrystalline cellulose. Similar practical results were obtained by cellulose dissolution in cold aqueous NaOH solutions (7%wt. at -10C). This process was applied successfully to waste sludge of a local paper industry. The use of cellulose-coated emulsions in enzymatic hydrolysis and subsequent fermentation and esterification may impact on achievement of a sustainable bio-fuel process.
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