Two-Stage Solvent Extraction for Diol Purification
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Solution Overview
Problem
The production of di, tri, or polyhydric alcohols, such as 2-alkyl-1,3-propanediols, is hindered by the presence of organic by-products like formals and organometallic salts, which interfere with crystallization, cause fouling in equipment, and reduce process capacity, due to their high concentrations in mother liquids.
Innovation Solution
The method involves using high boiling solvents like diisopropyl ether, 2-ethylhexanol, or 2-propylheptanol in a two-stage extraction process, where the mother liquid is first extracted in a high boiling solvent to remove organic by-products, and then the extract is re-extracted in water, allowing for solvent recycling and energy-efficient recovery of the solvents, thereby reducing the amount of by-products and improving process efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional production methods are used without extraction, then the process is simpler, but organic by-products accumulate causing crystallization interference and equipment fouling
Solution Approach 1:
The patent applies extraction to remove organic by-products (formals, acetals) from the mother liquid. A solvent is contacted with the mother liquid to form an extract phase containing the by-products, which is then separated and discarded, while the raffinate phase containing the purified alcohol is retained for further processing. This directly removes harmful substances without complicating the overall production process.
Solution Approach 2:
The patent introduces a solvent as an intermediary substance to facilitate the removal of organic by-products. The solvent acts as a mediator that selectively dissolves formals and acetals from the mother liquid, enabling their separation without directly interacting with or complicating the main alcohol production process.
2Object-affected harmful factors
If extraction process is implemented to remove by-products, then crystallization and equipment performance improve, but process complexity increases
Solution Approach 1:
The patent segments the extraction process into distinct operational stages: solvent contact with mother liquid, phase separation, extract removal, and raffinate retention. This segmentation allows each step to be optimized independently and simplifies the overall process control while effectively removing by-products.
Solution Approach 2:
The patent utilizes parameter changes in the solvent system to achieve selective extraction. By selecting solvents with specific properties (boiling point, solubility characteristics) and controlling extraction conditions, the process efficiently separates by-products while maintaining simplicity in operation.
3Loss of energy
If high boiling solvents are used for extraction, then energy efficiency improves through reduced evaporation, but solvent recovery requires more energy input
Solution Approach 1:
The patent exploits phase transitions for solvent recovery. The high boiling solvent is recovered through controlled phase change from liquid to vapor and back, utilizing its thermal properties to enable energy-efficient recovery while minimizing losses during the extraction process.
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 the amount of linear and cyclic formals, improves process capacity, and prevents fouling by effectively separating organic by-products, leading to increased efficiency and reduced energy consumption in the production of di, tri, or polyhydric alcohols.
Implementation Method 1
extracting the mother liquid in at least one high boiling solvent
Implementation Method 2
a liquid solvent which dissolves little water and is of low solubility in said aqueous phase
Implementation Method 3
extracting the extract in water, obtaining a water phase comprising organic by-products
Implementation Method 4
separating the phases and recovering trimethylolpropane from the solvent phase
Data Source
AI summary
Disclosed is a method for extraction in a process for production of a 2-alkyl-l,3-propanediol, 2,2-dialkyl- 1,3 -propanediol, 2-alkyl-2-hydroxyalkyl-l,3-propanediol or 2,2-dihydroxialkyl- -1,3-propanediol. Said method comprises the steps of (i) feeding a mother liquid, obtained in a process for synthesis of a said di, tri or polyhydric alcohol, at a controlled mass flow to a first extraction unit, (ii) extracting said mother liquid in said first extraction unit in at least one high boiling solvent effective in extracting organic by-products, (iii) obtaining a raffmate and an extract comprising said solvent and organic by-products, (iv) recycling said raffmate to said process, (v) feeding at a controlled mass flow obtained extract to a second extraction unit, (vi) extracting said extract in water, (vii) obtaining a water phase comprising said organic by-products and a solvent phase, and (viii) recycling said solvent phase.