Isoidide Purification via Epimerization and Selective Adsorption
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Solution Overview
Problem
The commercial production of isoidide is hindered by the high cost of its synthetic precursor, iditol, and the complexity of separating isohexides through fractional distillation due to their close boiling points, as well as the formation of unwanted by-products during the dehydration of sorbitol to isosorbide, which complicates the purification process and results in impure monomer feedstocks for polymerization.
Innovation Solution
A method involving the epimerization of incompletely purified isosorbide containing sorbitans, which skips rigorous purification steps, allowing certain by-products to remain, enabling the production of monomer-grade isoidide with reduced downstream separation and purification costs, using a process that includes ultrafiltration, ion exclusion, ion exchange, and activated carbon treatment to achieve isoidide with high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fractional distillation is used to separate isohexides, then separation is achieved, but the process becomes complex and costly due to close boiling points
Solution Approach 1:
The patent extracts and removes unwanted by-products (sorbitans, dimers, oligomers) from the isosorbide feedstock before epimerization using selective adsorption and filtration methods. This pre-purification approach eliminates the need for complex post-reaction distillation to separate isohexides, as the problematic components are removed upfront, simplifying the overall separation process while maintaining high purity.
Solution Approach 2:
The patent performs preliminary purification of isosorbide by removing sorbitans and other by-products before the epimerization reaction. This advance removal of impurities that would interfere with subsequent separation steps prevents the formation of complex mixtures, thereby avoiding the need for complex fractional distillation and reducing process complexity.
2Manufacturing precision
If rigorous purification steps are applied to isosorbide, then high purity is achieved, but production costs increase and heat-sensitive isosorbide is exposed to excessive heat
Solution Approach 1:
The patent replaces thermal separation methods (distillation requiring high heat exposure) with mechanical/chemical separation methods including selective adsorption on activated carbon, ion exchange resins, and membrane filtration. These methods achieve high purity removal of sorbitans and by-products without subjecting heat-sensitive isosorbide to excessive heat, thereby reducing energy loss and preserving isosorbide integrity.
Solution Approach 2:
The patent changes the separation parameters from thermal-based (temperature-dependent distillation) to chemical-based (pH-dependent ion exchange, adsorption affinity, molecular size filtration). This parameter change enables effective purification of heat-sensitive isosorbide at ambient or mild temperatures, minimizing heat exposure and associated energy losses while maintaining high purity.
3Ease of manufacture
If iditol is used as the synthetic precursor for isoidide, then isoidide can be produced, but the production cost becomes prohibitively high
Solution Approach 1:
The patent uses inexpensive, readily available isosorbide as a feedstock instead of costly iditol. Although isosorbide contains unwanted by-products (sorbitans), these can be effectively removed using low-cost purification methods (activated carbon, ion exchange resins). This approach substitutes an expensive precursor with a cheap one, reducing production costs while achieving the desired isoidide product through subsequent epimerization.
Solution Approach 2:
The patent converts the previously harmful presence of sorbitans and by-products in isosorbide feedstock into a benefit by developing efficient, low-cost removal methods. The abundance and low cost of isosorbide (even with impurities) becomes advantageous when combined with selective, inexpensive purification techniques, ultimately making isoidide production more economical than using pure but expensive iditol.
4Manufacturing precision
If isosorbide is fully purified before epimerization, then feedstock purity is high, but the purification process becomes complex and costly
Solution Approach 1:
The patent selectively extracts and removes only the critical unwanted components (sorbitans, dimers, oligomers) from isosorbide using targeted purification methods. Rather than attempting complete purification through complex multi-step processes, the invention focuses on removing specific interfering substances that affect epimerization efficiency and product quality, thereby achieving sufficient feedstock purity with simpler, less costly procedures.
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 allows for the cost-effective production of high-purity isoidide by reducing the need for distillation and minimizing heat-sensitive isosorbide exposure, achieving yields of up to 58% isoidide with significant reductions in sorbitan content and operational costs, while maintaining high purity suitable for polymer applications.
Implementation Method 1
an aqueous solution of isosorbide is subjected to epimerization in the presence of hydrogen under the influence of a catalyst comprising ruthenium on a support
Implementation Method 2
epimerization in the presence of hydrogen under the influence of a catalyst comprising ruthenium on a support
Implementation Method 3
activated carbon treatment to achieve isoidide with high purity
Implementation Method 4
ion exchange, and activated carbon treatment to achieve isoidide with high purity
Data Source
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AI summary
Methods are provided for the conversion of isosorbide to isoidide, wherein the isosorbide contains sorbitan impurities. The impurities in the isosorbide subjected to epimerization are converted to hydrodeoxygenation products. A method for synthesizing isoidide, comprising, providing an isosorbide containing one or more sorbitans; and, epimerizing the isosorbide to form an epimerization product comprising isoidide and hydrodeoxygenation products.