Cellulose Recycling with Two-Step Solvent Dissolution
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Solution Overview
Problem
Existing methods for recycling cellulose from textiles are inefficient, costly, and use hazardous chemicals, lacking a simple and effective process for dissolving and recycling cellulose from feedstocks.
Innovation Solution
A process involving a two-step solvent system with a cyclic amide as the first solvent and a protic ionic liquid comprising an acid and a base, maintaining specific temperatures and times to dissolve cellulose effectively, while separating polyester prior to cellulose dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional organic solvents or water are used to dissolve cellulose, then the process is simple and safe, but cellulose remains insoluble due to intermolecular hydrogen bonding
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by using ionic liquids with specific cations (imidazolium, pyridinium, ammonium) and anions (acetate, halides, cyanides) that can disrupt cellulose intermolecular hydrogen bonding. The ionic liquid structure and composition are optimized to achieve both solubility and environmental safety
Solution Approach 2:
The patent employs composite solvent systems combining ionic liquids with conventional organic solvents or water. This composite approach leverages the solubility-enhancing properties of ionic liquids while maintaining the simplicity and safety of conventional solvents, achieving both improved solubility and process simplicity
2Productivity
If Viscose process is used to produce cellulose fibres, then fibres can be produced, but highly toxic carbon disulfide must be used
Solution Approach 1:
The patent replaces the toxic carbon disulfide reagent with ionic liquids that are non-toxic and environmentally benign. The ionic liquids achieve the same function of dissolving cellulose to enable fibre production without the harmful effects of carbon disulfide, converting a harmful process into a safe one
Solution Approach 2:
The patent uses ionic liquids that can be easily regenerated and reused multiple times in the fibre production process. The solvent system is designed to be economically viable with minimal loss and regeneration costs, replacing the need for continuous input of toxic chemicals
3Productivity
If Lyocell process is used to dissolve cellulose, then fibres can be produced, but N-methylmorpholine N-oxide requires stabilising additives and has economic problems
Solution Approach 1:
The patent extracts and eliminates the need for stabilising additives by using inherently stable ionic liquid systems. The ionic liquids themselves provide the necessary stability for cellulose dissolution and fibre production without requiring additional chemical additives, simplifying the process and reducing costs
Solution Approach 2:
The patent copies the successful fibre production capability of the Lyocell process using ionic liquids that mimic its functionality but without its economic and complexity drawbacks. The ionic liquid system achieves similar or superior results with simpler and more economical operations
4Productivity
If ionic liquids are used to dissolve cellulose, then dissolution efficiency is improved, but solvent removal and regeneration becomes more complex
Solution Approach 1:
The patent utilizes phase transition properties of ionic liquids, particularly their ability to transition between different physical states or solubility regimes, to facilitate easy removal and regeneration. The ionic liquids can be regenerated through simple processes such as evaporation, filtration, or phase separation, reducing the complexity of solvent recovery
Solution Approach 2:
The ionic liquid system is designed to be self-regenerating through simple processes that require minimal external intervention. The solvent automatically separates from the dissolved cellulose under controlled conditions, and can be regenerated in situ without complex external equipment or processes
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 achieves efficient and cost-effective cellulose dissolution with non-hazardous solvents, reducing processing time and energy consumption, and selectively dissolving cellulose without damaging other polymers.
Implementation Method 1
treating the cellulose-containing treated solids with a cyclic amide solvent system to dissolve the cellulose and form a solution containing dissolved cellulose
Implementation Method 2
The ionic liquid is used to dissolve the cellulose to give a solution containing dissolved cellulose
Data Source
Figure 1
AI summary
The present invention provides a process for separating cellulose from a feedstock, comprising the steps of: a) wetting the cellulose with a first solvent system to form wet cellulose; b) contacting the wet cellulose with a second solvent system to form a mixture; c) maintaining the mixture at a first temperature for a first period of time; d) maintaining the mixture at a second temperature for a second period of time to dissolve the cellulose; and e) removing the first and second solvent system containing the dissolved cellulose.