Lignin Extraction via Depressurisation and Organic Acids
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Solution Overview
Problem
Traditional methods for extracting lignin from biomass, such as sulfate and sulfite pulping processes, face challenges like sulfur contamination, alkaline degradation, and condensation reactions that reduce yield and increase costs, while acidic processes harm cellulose and hemicelluloses, leading to inefficient lignin extraction and carbohydrate losses.
Innovation Solution
A method involving a reactor vessel where lignocellulosic biomass is treated with a primarily aqueous solution containing water and an organosolv, with pressure reduced to create an oxygen-starved environment, minimizing condensation reactions by maintaining the reaction mixture below 0.8 bar absolute pressure and heating to 70-250°C, and adding an extraction chemical like sodium hydroxide to solubilize lignin effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional alkaline pulping processes are used to extract lignin, then lignin extraction is achieved, but condensation reactions increase molar mass and reduce extraction efficiency
Solution Approach 1:
The patent changes the chemical parameters by using organic acids (acetic acid, formic acid) instead of traditional alkaline pulping chemicals. This parameter change prevents condensation reactions while maintaining lignin extraction efficiency, as the acidic environment suppresses the condensation reactions that would otherwise increase lignin molar mass and reduce extraction efficiency.
Solution Approach 2:
The patent creates an inert environment by using organic acid solutions that prevent oxidative condensation reactions. The acidic medium acts as an inerting agent that prevents the unwanted condensation reactions between lignin units, thereby maintaining extraction efficiency without the need for additional inert gas atmospheres.
2Productivity
If alkaline conditions are used in pulping processes, then lignin extraction is facilitated, but carbohydrate degradation and peeling reactions occur
Solution Approach 1:
The patent fundamentally changes the pH parameter from alkaline to acidic by using organic acid solutions. This parameter reversal prevents the carbohydrate degradation and peeling reactions that are characteristic of alkaline pulping processes, while still enabling effective lignin extraction through the solubilizing action of the acidic organic solution.
3Quantity of substance
If acidic sulfite pulping is used to extract lignin, then sulfur-free lignin is produced, but cellulose and hemicelluloses are degraded
Solution Approach 1:
The patent modifies the acidic environment by using organic acid solutions (acetic acid, formic acid) instead of strong inorganic acids. This parameter modification maintains the ability to produce sulfur-free lignin while significantly reducing the harmful effects on cellulose and hemicelluloses, as the organic acid system is less aggressive toward carbohydrate structures.
4Loss of time
If pulping chemicals are added at the beginning of the process, then extraction is initiated early, but unwanted degradation and condensation reactions occur
Solution Approach 1:
The patent performs preliminary action by pre-heating the organic acid solution to the extraction temperature before contacting it with the biomass. This preliminary heating step ensures that when the chemicals contact the biomass, the extraction can proceed efficiently at optimal temperature without allowing time for unwanted degradation and condensation reactions to occur during the mixing phase.
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 significantly reduces lignin condensation and carbohydrate hydrolysis, enabling up to 99% lignin separation from cellulose with comparable or better cellulose yield and sheet strength, and produces a high-purity lignin extract with reduced chemical consumption and processing time.
Implementation Method 1
reducing the pressure in the reactor vessel below 0.8 bar absolute pressure, preferably below 0.5 bar absolute pressure, more preferably below 0.2 bar absolute pressure, to provide an oxygen starved environment
Implementation Method 2
adding at least one extraction chemical, which comprises a base or an acid, to the reaction vessel when the extraction temperature is reached and extracting lignin from the biomass to the liquid phase of the reaction mixture
Implementation Method 3
keeping the reaction mixture in a predetermined extraction temperature of 70 - 250 °C
Data Source
Figure 1
AI summary
The invention relates to a method for removing lignin from lignocellulosic biomass. The method comprises feeding of lignocellulosic biomass and a first aqueous solution into a reactor vessel, the lignocellulosic biomass and the first aqueous solution forming a reaction mixture; reducing the pressure in the reactor vessel below 0.8 bar absolute pressure, preferably 0.5 bar absolute pressure, more preferably below 0.2 bar absolute pressure; keeping the reaction mixture in a predetermined extraction temperature, and adding at least one extraction chemical, such as base or acid, to the reaction vessel and extracting lignin from the biomass to the liquid phase of the reaction mixture.