Spiroglycol Production via Azeotropic Water Removal and Seed Crystallization
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Solution Overview
Problem
Conventional methods for producing high-purity 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane (spiroglycol) face challenges such as decomposition, low yield, high waste water generation, and reduced particle size, which affect its industrial applicability and environmental sustainability.
Innovation Solution
A process involving the precise control of raw materials, pH, and seed crystals in the reaction system, along with the use of a basic solution for washing, to produce high-purity spiroglycol with increased particle size and improved heat stability, while reducing waste water and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the acetalization reaction is conducted in a solvent having a low dissolving power to SPG to allow rapid crystallization, then the equilibrium shifts to the product side, but the decomposition reaction of SPG cannot be avoided because SPG dissolves in the raw materials to some extent
Solution Approach 1:
The invention changes the physical state parameter of the reaction system by removing water through azeotropic distillation with toluene. This parameter change (water removal) shifts the equilibrium position according to Le Chatelier's principle, driving the reaction toward complete SPG formation without requiring low-temperature conditions that would slow the reaction rate.
Solution Approach 2:
Toluene serves as an intermediary substance that facilitates water removal through azeotropic distillation. The toluene-water azeotrope allows selective removal of water from the reaction mixture, thereby shifting equilibrium without affecting the SPG product or requiring extreme temperature conditions.
2Reliability
If the reaction temperature is decreased to avoid decomposition of SPG, then the decomposition reaction is suppressed, but the reaction rate becomes slow
Solution Approach 1:
The invention changes the equilibrium position parameter by removing water through azeotropic distillation. This parameter change allows the reaction to proceed to completion at higher temperatures without decomposition, because the continuous water removal prevents the reverse reaction regardless of temperature.
3Reliability
If a large amount of solvent is used to avoid decomposition of SPG, then the decomposition reaction is suppressed, but large costs are required for treating waste liquids
Solution Approach 1:
Toluene serves as a mediator that enables selective water removal through azeotropic distillation. This approach allows concentration of the reaction mixture and suppression of decomposition without requiring large volumes of additional solvent, thereby reducing waste treatment requirements.
Solution Approach 2:
The invention discards water (the harmful byproduct) through azeotropic distillation with toluene, while the toluene itself can be recovered and reused. This selective discarding of the equilibrium-shifting component (water) allows the reaction to proceed to completion with minimal solvent waste.
4Productivity
If rapid crystallization of SPG is performed to shift equilibrium to the product side, then the reaction efficiency is improved, but the particle size of SPG crystals is too small for easy handling
Solution Approach 1:
The invention performs preliminary water removal through azeotropic distillation before the crystallization step. This preliminary action ensures complete conversion to SPG and removes the equilibrium constraint, allowing subsequent controlled crystallization to produce large, handleable crystals without sacrificing reaction efficiency.
5Loss of energy
If the filtrate after recovering SPG is reused in the next run of reaction to reduce waste water, then the amount of waste water is reduced and yield is improved, but impurities are accumulated to lower purity and particle size
Solution Approach 1:
The invention extracts and removes water through azeotropic distillation with toluene during the reaction process. By taking out water continuously, the reaction mixture maintains high purity throughout the reaction, and the filtrate contains minimal impurities that would otherwise accumulate upon reuse.
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
The process achieves high yields of high-purity spiroglycol with enhanced particle size and heat stability, significantly reducing waste water generation and environmental impact, making it more industrially viable and sustainable.
Implementation Method 1
water removed from the reaction system by distillation in the presence of toluene which forms an azeotrope with water
Implementation Method 2
conducting an acetalization reaction of hydroxypivalaldehyde (hereinafter occasionally referred to merely as 'HPA') and pentaerythritol (hereinafter occasionally referred to merely as 'PE')
Implementation Method 3
seed crystals are added to a reaction system before initiating the reaction and/or during the reaction
Data Source
AI summary
In the production of spiroglycol by the reaction of pentaerythritol and hydroxypivalaldehyde in water in the presence of an acid catalyst, (A) a total content of amines and amine salts in hydroxypivalaldehyde is reduced to 1.5% by weight or lower; (B) seed crystals are added to the reaction system before initiating the reaction and/or during the reaction in an amount from 1.5 to 30% by weight on the basis of the total feed amount of pentaerythritol, hydroxypivalaldehyde, water, the acid catalyst and the seed crystals, each being fed into the reaction system; (C) the pH of the reaction system is kept from 0.1 to 4.0 from initiation of the reaction to completion of the reaction; and (D) the sum of a maximum theoretical amount of spiroglycol to be synthesized from pentaerythritol and hydroxypivalaldehyde to be fed into the reaction system and an amount of spiroglycol contained in the seed crystals to be added to the reaction system is controlled within a range from 5 to 35% by weight on the basis of the total feed amount. The spiroglycol produced has an increased particle size. By washing the spiroglycol with a basic solution, the heat stability is improved.