Nanocellulose Fiber Preparation via Ozone Depolymerization
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Solution Overview
Problem
Current methods for producing nanocellulose fibers are inefficient in terms of energy consumption and often require the use of chlorine-containing bleaching agents, which are costly and environmentally harmful, and existing oxygen-based bleaching processes degrade fibers and leave residual lignin, necessitating additional processing steps.
Innovation Solution
A process involving an aqueous slurry with ozone or cellulase enzymes, or a combination of both, is used to partially depolymerize cellulosic materials, followed by comminution, achieving significant energy efficiency and reducing the need for chlorine-based bleaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chlorine-containing bleaching agents are used, then effective delignification is achieved, but equipment corrosion and environmental harm occur
Solution Approach 1:
The patent employs ozone, a strong oxidant, as the primary bleaching agent to replace chlorine-containing agents. Ozone effectively delignifies pulp while avoiding the corrosion and environmental harm associated with chlorine. The process uses ozone at controlled concentrations (0.5-5% v/v) to achieve efficient delignification without the harmful side effects of traditional chlorine-based bleaching.
Solution Approach 2:
The patent utilizes hydrogen peroxide as a supplemental bleaching agent that decomposes into water and oxygen, leaving no harmful residues. This short-lived chemical provides effective bleaching action during the process but disappears completely after treatment, avoiding equipment corrosion and environmental contamination associated with persistent chlorine compounds.
2Object-affected harmful factors
If oxygen-based bleaching agents are used, then chlorine use is reduced, but fiber degradation and residual lignin occur
Solution Approach 1:
The patent combines multiple bleaching mechanisms by integrating ozone oxidation with hydrogen peroxide treatment and mechanical refining. This multi-stage approach merges chemical delignification with physical fiber separation to achieve complete lignin removal while preserving fiber strength, overcoming the limitations of single-method oxygen-based bleaching.
Solution Approach 2:
The patent applies ozone pretreatment to the pulp before mechanical refining. This preliminary oxidation weakens the lignin-cellulose bonds and prepares the fiber structure for more efficient mechanical separation, enabling complete delignification while minimizing the energy required for subsequent refining and preserving fiber integrity.
3Manufacturing precision
If multiple refining passes are used to produce nanocellulose, then fiber size is reduced, but energy consumption increases
Solution Approach 1:
The patent applies chemical pretreatment with ozone and hydrogen peroxide before mechanical refining. This preliminary action partially degrades the lignin and weakens fiber bonds, preparing the material for more efficient mechanical size reduction. As a result, fewer refining passes are needed to achieve nanocellulose dimensions, significantly reducing total energy consumption while maintaining manufacturing precision.
4Manufacturing precision
If TEMPO oxidation is used to liberate nanofibrils, then fiber separation is improved, but chemical modification and handling problems occur
Solution Approach 1:
The patent uses ozone, a strong oxidant, to achieve fiber separation and nanofibril liberation without the extreme chemical modifications caused by TEMPO. Ozone oxidation provides sufficient fibril separation while maintaining more natural fiber surface properties, avoiding the need for cation neutralization and simplifying downstream handling and processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process reduces energy consumption by at least 20% and minimizes the use of chlorine, resulting in improved properties of cellulose nanofibers such as porosity, smoothness, opacity, brightness, and strength, while being environmentally friendlier.
Implementation Method 1
treating the cellulosic material with an aqueous slurry containing a depolymerizing agent selected from (a) ozone at a charge level of at least about 0.1 wt/wt % for generating free radicals in the slurry
Implementation Method 2
treating the cellulosic material with an aqueous slurry containing a depolymerizing agent selected from (b) a cellulase enzyme at a concentration from about 0.1 to about 10 lbs/ton
Data Source
AI summary
A scalable, energy efficient process for preparing cellulose nanofibers is disclosed. The process employs a depolymerizing treatment with one or both of: (a) a relatively high charge of ozone under conditions that promote the formation of free radicals to chemically depolymerize the cellulose fiber cell wall and interfiber bonds; or (b) a cellulase enzyme. Depolymerization may be estimated by pulp viscosity changes. The depolymerizing treatment is followed by or concurrent with mechanical comminution of the treated fibers, the comminution being done in any of several mechanical comminuting devices, the amount of energy savings varying depending on the type of comminuting system and the treatment conditions. Comminution may be carried out to any of several endpoint measures such as fiber length, % fines or slurry viscosity.