Conventional CNC process is based on the use of ~65% aqueous sulfuric acid leading to difficult purification procedures, high water consumption, and poor yields. To tackle these problems, our group has recently introduced a method that utilizes HCl vapor or pressured HCl gas. Here, we describe a full, improved production process of CNCs by combining HCl gas hydrolysis and TEMPO-mediated oxidation. The degree of polymerization was successfully reduced from 2160 to 220 with a CNC yield of &gt;80% while TEMPO-oxidation provided carboxylic charges on the CNC surface, resulting in a stable dispersion. Wide Angle X-ray Scattering (WAXS) indicated that the crystallinity index increased from 45% to 61%, i.e., a ~30% increase, which may play a role in the high yield of CNCs. It appears that HCl gas hydrolysis on BC is faster and more efficient than on plant-based fibers. A highly porous structure of the freeze-dried BC is also more accessible to cavitation during sonication when dispersing the CNCs. In terms of sustainability, the benefits of the new process can be outlined in three categories: (i) &gt;50% higher yield of CNCs than with the usual liquid/solid procedure, (ii) BC can be prepared from, e.g., sugars in food waste, minimizing the exploitation of forest resources, and (iii) dry gaseous acid can be easily recycled and the water consumption is greatly minimized because of the simple purification procedure of CNCs. Indeed, the full recovery of aqueous acid has prevented the sustainable, large scale use of acid in hydrolysis of cellulose in the past. Furthermore, the thermal stability of carboxylic groups should be higher than those of sulfate groups which are the norm for charged groups on CNCs.

High yield process to bacterial cellulose nanocrystals

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.