Cellulose Oxidation at Medium Consistency Using Nitroxyl Catalyst
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Solution Overview
Problem
Current methods for catalytic oxidation of cellulose at low consistency are inefficient and costly due to high water consumption, energy demands, and environmental concerns related to bromine compounds used as activators, which also lead to side reactions and corrosion issues.
Innovation Solution
Performing the oxidation at medium consistency (above 6% by weight) using a heterocyclic nitroxyl radical catalyst, such as TEMPO, with chlorine dioxide or tertiary amine activation, and sodium hypochlorite as the main oxidant, allowing for efficient mixing and temperature control through circulation of the reaction medium, reducing the need for bromide and minimizing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If oxidation is performed at low consistency (1-4%), then good mixing is achieved, but water consumption increases and production costs rise
Solution Approach 1:
The patent changes the consistency parameter from conventional low values (1-4%) to medium values (6-15%), fundamentally altering the process conditions. This parameter change allows the system to achieve both good mixing and reduced water consumption, as the medium consistency provides sufficient material concentration for efficient reaction while requiring less water than low consistency processes
2Ease of operation
If intensive mixing is applied to ensure efficient mixing at low consistency, then mixing efficiency improves, but energy consumption increases and temperature rises above optimum range
Solution Approach 1:
By changing the consistency parameter to medium range (6-15%), the patent eliminates the need for intensive mixing. The medium consistency naturally provides adequate mixing characteristics, allowing conventional mixing equipment to operate at lower energy consumption levels while maintaining optimal temperature control without excessive heating
3Productivity
If sodium bromide is used as activator to accelerate the reaction, then reaction rate increases, but environmental harm increases and corrosion problems occur
Solution Approach 1:
The patent extracts and removes sodium bromide from the reaction system, eliminating the source of environmental harm and corrosion problems. The reaction rate acceleration function previously provided by bromide is replaced by alternative activators such as sodium chloride or calcium chloride, which do not generate harmful bromine compounds
Solution Approach 2:
The patent introduces alternative activators (sodium chloride, calcium chloride) that serve as intermediaries to facilitate the oxidation reaction without the harmful effects of bromide. These substitute activators mediate between the oxidant and cellulose, providing the necessary reaction acceleration while avoiding environmental and corrosion issues
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 approach enhances selectivity and reduces energy consumption, maintains optimal temperature, and avoids excessive heating, resulting in a more efficient and environmentally friendly process for producing nanofibrillar cellulose with improved properties.
Implementation Method 1
catalytic oxidation of cellulose using a heterocyclic nitroxyl radical as catalyst
Implementation Method 2
oxidation of the C-6 hydroxyl groups of the cellulosic β-D-glucopyranose units to carboxylic groups
Implementation Method 3
a main oxidant is used to bring oxygen to the reaction series and convert the nitroxyl compound back to the oxidized form
Implementation Method 4
with chlorine dioxide or tertiary amine activation
Data Source
AI summary
Cellulose is oxidized catalytically using a heterocyclic nitroxyl radical as catalyst, main oxidant acting as oxygen source, and an activator of the heterocyclic nitroxyl radical. The oxidation is performed in a reaction medium which is at medium consistency of cellulosic pulp, which is above 6%, more preferably equal to or higher than 8%, and most preferably in the range of 8-12%. The reaction medium is mixed in a reactor through circulation of the reaction medium back to the reactor.