Lignin Depolymerization Using Acidic Ionic Liquids
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Solution Overview
Problem
Current lignin depolymerization methods are not environmentally benign, energy-intensive, and lack effective recycling of ionic liquids due to π-π interactions, limiting their application in large-scale reactions.
Innovation Solution
A process using acidic ionic liquids as catalysts under mild conditions to depolymerize lignin into substituted phenolic monomers with molecular weights less than 300, achieving high yields and enabling the recycling of ionic liquids through selective separation and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If base-catalyzed or acid-catalyzed depolymerization methods are used, then lignin can be depolymerized to obtain aromatic monomers, but the process is not environmentally benign and is energy-intensive
Solution Approach 1:
The patent changes the chemical parameters by using ionic liquids with specific cation-anion combinations (sulfates, lactates, acetates, chlorides, phosphates) and controls reaction conditions (temperature 100-200°C, reaction time 1-24 hours) to achieve depolymerization under milder, more environmentally benign conditions while maintaining high productivity
Solution Approach 2:
The patent employs ionic liquids that can be recovered and reused multiple times, replacing traditional disposable catalysts. The ionic liquids serve as both solvent and catalyst, eliminating the need for separate catalyst recovery steps and reducing overall process cost and environmental impact
2Object-affected harmful factors
If ionic liquids are used as catalyst for lignin depolymerization, then the process becomes more environmentally benign, but the ionic liquids cannot be effectively recycled due to π-π interactions with aromatic moieties
Solution Approach 1:
The patent introduces a separation intermediary system using adsorbents (such as activated carbon, silica gel, or ion-exchange resins) that selectively bind to ionic liquids, facilitating their separation from the reaction mixture despite π-π interactions with aromatic products. This intermediary enables effective recycling while maintaining environmental benefits
3Speed
If high temperatures (110-150°C) are used to increase reaction rate, then the depolymerization rate increases, but the final size of lignin fragments does not significantly change
Solution Approach 1:
The patent changes multiple parameters simultaneously: ionic liquid composition (different cations and anions), temperature (100-200°C range), reaction time (1-24 hours), and solvent ratios to achieve both high reaction rates and precise control over fragment size distribution, overcoming the limitation of temperature-only optimization
4Productivity
If traditional depolymerization methods are used, then aromatic monomers can be obtained, but the cost is high and large-scale application is limited
Solution Approach 1:
The patent employs ionic liquids that serve multiple functions simultaneously: as solvent for lignin dissolution, as catalyst for depolymerization reactions, and as a recoverable resource. This multi-functionality reduces the number of separate process steps, lowers overall cost, and enables scalable application while maintaining high aromatic monomer yields
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 achieves high yields of aromatic products (up to 97%) while being environmentally benign and cost-effective, with successful recycling of ionic liquids, addressing the limitations of existing methods.
Implementation Method 1
The hydrolysis of ß-O-4 bonds in two lignin model compounds was studied in an acidic ionic liquid, 1-H-3-methylimidazolium chloride. The ß-O-4 bonds of both guaiacylglycerolb-guaiacyl ether and veratrylglycerol-b-guaiacyl ether underwent catalytic hydrolysis to produce guaiacol as the primary product with more than 70% yield at 150 °C.
Implementation Method 2
The hydrolysis of ß-O-4 bonds in two lignin model compounds was studied in an acidic ionic liquid
Implementation Method 3
Based on gel permeation chromatography results, an increase in temperature from 110 to 150°C increased the rate of reaction
Data Source
AI summary
The present invention discloses a process for depolymerization of lignin to yield substituted phenolic monomers using Brönsted ionic liquid as catalyst under mild reaction conditions to obtain an overall yield of monomers up to 97%.