Cellulose Ester Production via Supercritical CO2 Drying
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cellulose processing faces challenges in fiber opening and downstream chemistry due to sheet hardness and moisture content inconsistencies, which affect the efficiency of acetylation and product quality, particularly when using standard attrition equipment and water, leading to uneven drying and reagent consumption issues.
Innovation Solution
A process involving moistening cellulose sheet stock to a water content of 20-50%, attriting it to a wet pulp, flash drying to a floccule with 4-8% moisture, and esterifying to produce a cellulose ester product, which maintains even moisture and minimizes fiber damage, allowing for environmentally friendly processing without additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If water is used for fiber-opening step, then green chemical process is provided, but water consumes acetylation reagent acetic anhydride leading to inefficient consumption
Solution Approach 1:
The invention extracts and removes water from the cellulose substrate before the acetylation reaction by using supercritical carbon dioxide as a drying agent. This extraction of water prevents it from consuming the acetic anhydride reagent, thereby resolving the contradiction between using water for green processing and maintaining reagent efficiency.
Solution Approach 2:
Supercritical carbon dioxide acts as an intermediary substance that facilitates the removal of water from cellulose without directly participating in the acetylation reaction. This mediator enables the process to benefit from both water-based fiber opening (green chemistry) and efficient reagent consumption in the subsequent acetylation step.
2Quantity of substance
If drying attempts are made to improve processing for downstream chemistries, then moisture content is reduced, but under dried, over dried, or unevenly dried product is produced
Solution Approach 1:
The invention changes the physical state and properties of the drying agent by using supercritical carbon dioxide, which allows for precise control of drying parameters. By adjusting pressure and temperature to maintain supercritical conditions, the process achieves uniform moisture removal without the problems of conventional drying methods, resolving the contradiction between moisture reduction and drying uniformity.
3Ease of operation
If standard attrition equipment is used, then fiber opening is performed, but sheet hardness limitations restrict processing capability
Solution Approach 1:
The invention replaces the mechanical attrition process with a chemical/physical treatment using supercritical carbon dioxide. This substitution eliminates the need for mechanical force to overcome sheet hardness, allowing the processing of harder cellulose sheets that would be incompatible with standard attrition equipment while still achieving effective fiber opening.
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 ensures consistent and reliable moisture content, reduces fiber damage, and enhances the compatibility of cellulose with downstream chemistries, such as esterification, while producing high-quality cellulose ester products like cellulose acetate with controlled acetyl value and intrinsic viscosity.
Implementation Method 1
moistening a cellulose sheet stock to a water content in a range from about 20% to about 50%
Implementation Method 2
flash drying said wet pulp to a floccule of cellulose having a moisture content from about 4% to about 8%
Implementation Method 3
esterifying the floccule of cellulose to provide a cellulose ester product
Data Source
AI summary
Processing of cellulose, and more particularly, fiber opening and downstream processing and chemistry are provided. A process includes moistening a cellulose sheet stock to a water content in a range from about 20% to about 50%, attriting the moistened cellulose sheet to a wet pulp, flash drying the wet pulp to a floccule of cellulose having a moisture content from about 4% to about 8%, and esterifying the floccule of cellulose to provide a cellulose ester product.