Process for catalytically oxidising cellulose paste
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Solution Overview
Problem
Existing cellulose oxidation processes for producing microfibrillated cellulose from unbleached cellulose pulp are costly and environmentally impactful due to the use of sodium bromide and generate toxic organohalides, and they require separate delignification steps that increase energy consumption and effluent treatment costs.
Innovation Solution
A catalytic oxidation process using chlorine dioxide and a heterocyclic nitroxyl radical to simultaneously delignify and oxidize cellulose fibers, eliminating the need for separate delignification steps and reducing the use of sodium bromide, with a pH and temperature-controlled reaction to minimize environmental impact and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sodium bromide is used in the catalytic oxidation process, then the oxidation of cellulose fibers is effective, but toxic organohalides are formed and effluent treatment costs increase
Solution Approach 1:
The invention extracts and removes sodium bromide from the catalytic oxidation system, replacing it with an alternative oxidizing system that does not generate toxic organohalides, thereby eliminating the harmful byproducts while maintaining oxidation effectiveness
Solution Approach 2:
The invention uses a disposable oxidizing system (sodium hypochlorite combined with heterocyclic nitroxyl radical) that does not require regeneration through harmful intermediate steps, eliminating the need for sodium bromide and avoiding organohalide formation entirely
2Ease of manufacture
If separate delignification steps are performed before oxidation, then unbleached cellulose pulp is effectively processed, but energy consumption and effluent treatment costs increase
Solution Approach 1:
The invention merges the delignification and catalytic oxidation steps into a single integrated process where chlorine dioxide performs both functions simultaneously, eliminating the need for separate processing stages and reducing overall energy consumption
Solution Approach 2:
The invention employs chlorine dioxide as a multi-functional reagent that simultaneously delignifies the unbleached cellulose pulp and activates the heterocyclic nitroxyl radical for catalytic oxidation, replacing multiple specialized reagents with one universal agent
3Reliability
If multiple processing steps are used for delignification and oxidation, then complete fiber treatment is achieved, but process complexity and production time increase
Solution Approach 1:
The invention combines multiple processing functions (delignification, catalyst activation, and oxidation) into a single reaction step using chlorine dioxide and heterocyclic nitroxyl radical, simplifying the process flow while maintaining treatment effectiveness
Solution Approach 2:
The invention performs preliminary delignification action through chlorine dioxide before oxidation, preparing the cellulose fibers in advance for effective catalytic oxidation in the same reaction medium, thereby eliminating subsequent separate treatment steps
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
The process reduces costs and environmental impact by integrating delignification and oxidation in a single step, minimizing effluent volume and energy use, facilitating the production of microfibrillated cellulose on an industrial scale.
Implementation Method 1
induce in the reaction medium at least a partial delignification of the unbleached cellulose pulp by reaction between the lignin and the chlorine dioxide
Implementation Method 2
induce a catalytic oxidation of the cellulose fibers by the heterocyclic nitrosonium cation
Implementation Method 3
oxidizing the hydroxyl groups present at C-6 to carbonyl groups, and then to carboxyl groups
Implementation Method 4
TEMPO-red is oxidized by hypobromite to reform TEMPO-ox
Data Source
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AI summary
The invention relates to a process for catalytically oxidising an unbleached cellulose paste, comprising the following steps: supplying to a reactor an unbleached cellulose paste; supplying a heterocyclic nitroxyl radical; supplying chlorine dioxide, in molar excess in relation to the heterocyclic nitroxyl radical, in order to cause the heterocyclic nitroxyl radical to be activated by the chlorine dioxide, and at least partial delignification of the unbleached cellulose paste by reaction between the lignin and the chlorine dioxide; supplying a hypochlorite so as to cause a catalytic oxidation of the cellulose fibres; recovering, at the end of the catalytic oxidation of the cellulose fibres, the oxidised cellulose fibres which are at least partially delignified. The process according to these features advantageously combines the delignification of an unbleached cellulose paste and the catalytic oxidation of the cellulose fibres.