Lyocell Ionic Liquid Recycling by Water Removal Without Solubility Loss
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Solution Overview
Problem
Existing ionic liquids used in the Lyocell process for producing cellulose fibers face issues with hydrolysis in the presence of water, leading to degradation and loss of solubility, which complicates the recycling and reuse of these solvents.
Innovation Solution
The use of guanidinium-based ionic liquid, [mTBDH][OAc], which exhibits high hydrolytic stability even in the presence of water, allowing for effective recovery and recycling by adjusting the acid-to-base ratio and removing water through thermal processes, maintaining solubility and spinning properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ionic liquids are used in the Lyocell process, then cellulose dissolution and spinning are achieved, but hydrolysis occurs in the presence of water leading to degradation and loss of solubility
Solution Approach 1:
The patent changes the chemical parameters of the ionic liquid by selecting specific guanidinium-based cations with appropriate pKa values and matching them with suitable anions. This parameter optimization ensures high hydrolytic stability while maintaining cellulose solubility and spinning performance throughout the recycling process.
Solution Approach 2:
The patent employs composite ionic liquid systems consisting of guanidinium cations combined with specific anions (acetate, formate, propionate, or their mixtures). This composite approach creates a synergistic effect where the cation provides hydrolytic stability and the anion maintains solubility, resolving the contradiction between stability and solubility maintenance.
2Loss of substance
If water is removed from the ionic liquid to enable recycling, then recovery efficiency improves, but thermal degradation may occur
Solution Approach 1:
The patent optimizes thermal parameters by controlling the water removal process under mild conditions (low temperature and reduced pressure). This parameter control prevents thermal degradation of the ionic liquid while efficiently removing water to enable recycling, thus improving recovery efficiency without compromising thermal stability.
3Stability of the object's composition
If acetic acid is added in excess to maintain solubility, then cellulose dissolution is improved, but the complexity of the recycling process increases
Solution Approach 1:
The patent changes the compositional parameters by allowing a controlled excess of acetic acid (up to 30 mol%) in the ionic liquid system. This parameter adjustment maintains excellent cellulose solubility and spinning behavior while the simplified water removal process handles the excess acid, actually reducing overall process complexity compared to strict stoichiometric control.
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 enables almost loss-free recovery and recycling of [mTBDH][OAc], preserving its ability to dissolve cellulose and maintain excellent spinning behavior, even with up to 30% excess acetic acid and residual water, thus supporting continuous production of high-strength cellulose fibers.
Implementation Method 1
dissolution of a cellulose substrate in an ionic liquid consisting of the superbase cation 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium [mTBDH]+ and an anion
Implementation Method 2
recovering the ionic liquid by removing water
Data Source
AI summary
According to an example aspect of the present invention, there is provided a process for the production of a cellulose filaments or films, comprising the steps of dissolving a cellulose substrate in an ionic liquid consisting of the superbase cation 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium [mTBDH]+ and an anion to produce a solution forming a spinning dope, said anion being derived from an acid which is present at a stoichiometric excess to the superbase, extruding the spinning dope through a spinneret in a coagulation bath containing water to form filaments or films from the solution, withdrawing ionic liquid in an aqueous mixture with water from the coagulation bath, recovering the ionic liquid [mTBDH][OAc] from the aqueous mixture by removing water and optionally recycling the recovered ionic liquid to the dissolution step.