CO2-Switchable Hydrophilicity Solvents for Distillation-Free Separation
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Solution Overview
Problem
Existing volatile organic solvents (VOS) pose health, safety, and environmental risks due to flammability, toxicity, and high energy consumption in distillation processes, and alternative solvents like ionic liquids and supercritical CO2 are difficult to separate from products without using volatile organic solvents, defeating their purpose.
Innovation Solution
Development of anionic switchable hydrophilicity solvents (ASHS) that can reversibly switch between hydrophobic and hydrophilic states using CO2, allowing easy separation from products without distillation by forming biphasic mixtures with water, using carboxylic acids and water-soluble bases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If volatile organic solvents (VOS) are used for industrial processes, then productivity and ease of operation are improved, but health and safety risks increase due to flammability and toxicity
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by using carboxylic acids with specific pKa values (3-7) and controlling the pH through addition of base. This parameter change transforms the solvent from a flammable VOS to a non-flammable ASHS system while maintaining solvent functionality. The switchable hydrophilicity parameter is controlled by pH, allowing the system to transition between hydrophobic (solvent mode) and hydrophilic (aqueous mode) states.
Solution Approach 2:
The patent utilizes phase transition of the carboxylic acid between hydrophobic (neutral form) and hydrophilic (anionic form) states through pH control. In the hydrophobic state, the ASHS functions as an organic solvent for reactions and extractions. In the hydrophilic state, it forms biphasic mixtures with water, enabling easy separation. This phase transition eliminates the need for distillation and removes flammability risks.
2Loss of substance
If distillation is used to remove or recycle VOS, then solvent recovery is achieved, but energy consumption increases
Solution Approach 1:
The patent replaces energy-intensive distillation with pH-controlled phase transitions. By adding base to increase pH, the carboxylic acid converts to its anionic form and becomes hydrophilic, forming a biphasic mixture with water. This allows the ASHS to separate from the organic phase through simple decantation or phase separation, eliminating the need for thermal distillation and significantly reducing energy consumption.
Solution Approach 2:
The patent replaces the thermal/mechanical separation process (distillation) with a chemical control mechanism (pH adjustment). Instead of using heat and mechanical vaporization to separate solvent from product, the system uses chemical pH control to trigger hydrophilicity changes and phase separation, substituting a chemical control system for a thermal-mechanical separation system.
3Object-affected harmful factors
If nonvolatile organic solvents like ionic liquids are used to replace VOS, then flammability risks are reduced, but separation from products becomes difficult
Solution Approach 1:
The patent introduces dynamic switchability to the solvent system. Unlike static nonvolatile solvents like ionic liquids, the ASHS can dynamically change its hydrophilicity properties through pH adjustment. The carboxylic acid can switch between hydrophobic (for product dissolution) and hydrophilic (for water-miscibility and separation) states, providing operational flexibility that static nonvolatile solvents lack.
Solution Approach 2:
The patent changes the hydrophilicity parameter of the solvent by adjusting pH. At low pH (acidic conditions), the carboxylic acid remains in its neutral hydrophobic form. At high pH (basic conditions), it converts to the anionic hydrophilic form. This parameter change enables the solvent to transition from a state where it dissolves organic products to a state where it separates from water, solving the separation problem.
4Object-affected harmful factors
If less volatile solvents are used to decrease flammability, then safety is improved, but energy required for distillation increases
Solution Approach 1:
The patent uses pH-controlled phase transitions to replace thermal distillation. The carboxylic acid undergoes a chemical transformation from neutral to anionic form through base addition, which triggers a physical phase transition from hydrophobic to hydrophilic state. This allows separation from the organic phase without heating, eliminating the energy penalty associated with distilling high-boiling-point solvents.
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
ASHS provide a safer, energy-efficient alternative to VOS by eliminating the need for distillation, reducing health and environmental risks, and enabling easy separation and recovery, while maintaining low flammability and toxicity.
Implementation Method 1
the water-soluble base deprotonates the carboxylic acid and converts the carboxylic acid to its anionic water-soluble form
Implementation Method 2
when the aqueous solution is contacted with CO2 at one of the one or more selected temperatures, the anionic form of the carboxylic acid is protonated
Implementation Method 3
a carboxylic acid, wherein the carboxylic acid is a water-immiscible liquid in its neutral form, and is water-soluble in its anionic form
Implementation Method 4
forming an organic phase comprising the carboxylic acid in its neutral form
Data Source
AI summary
Anionic switchable hydrophilicity solvents (ASHS) that can be reversibly converted between hydrophobic and hydrophilic forms are described. The ASHS comprise a carboxylic acid, a water-soluble base, water, and addition and removal of an acidic gas (CO2) effects the conversion between the hydrophobic and hydrophilic forms. A system and method for forming the ASHS are described, as well as applications utilizing the ASHS, including a method for separating a selected substance from a mixture, a method of removing gas from polymeric foam, and a method of extracting a hydrophobic material from a solid that is at least partially coated by the hydrophobic material.