Glycolic Acid Purification via Vacuum Rectification and Cooling Crystallization
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Solution Overview
Problem
Current methods for glycolic acid separation and purification, particularly those using molecular rectification and crystallization, face challenges such as equipment complexity, high energy consumption, low separation efficiency, and the introduction of impurities in bio-based routes, leading to poor purification outcomes.
Innovation Solution
A rectification-crystallization coupling process utilizing bio-based platform compound molecules and a device comprising a vacuum rectification column and crystallization kettle, where crude glycolic acid is concentrated and then crystallized under controlled conditions to achieve high-purity glycolic acid, overcoming polymerization issues and optimizing process parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If molecular rectification is used for glycolic acid separation, then separation can be achieved, but the operation becomes complicated, equipment investment increases, and separation efficiency decreases
Solution Approach 1:
The patent segments the separation process into two distinct stages: rectification concentration (to achieve ≥70 wt.% concentration) and cooling crystallization (to achieve high-purity separation). This segmentation allows each stage to be optimized independently, avoiding the complexity of single-stage molecular rectification while maintaining high separation efficiency.
Solution Approach 2:
The patent changes the operating parameters from conventional atmospheric distillation to vacuum rectification (reducing pressure to prevent polymerization), and from simple filtration to controlled cooling crystallization with specific temperature profiles (cooling rate 0.3-1.0°C/min). These parameter changes enable effective separation without requiring complex molecular rectification equipment.
2Manufacturing precision
If conventional rectification and crystallization equipment and parameters are used, then the process can be simple, but the separation and purification effect of glycolic acid is poor
Solution Approach 1:
The patent optimizes specific parameters: rectification pressure (0.05-0.2 MPa), feed temperature (20-50°C), cooling rate (0.3-1.0°C/min), and stirring rate (200-500 r/min). These parameter optimizations significantly improve purification effect (91.5-99.1% purity) while keeping the equipment design relatively simple and easy to manufacture.
Solution Approach 2:
The patent implements a continuous coupled process where rectification concentration feeds directly into cooling crystallization without intermediate storage. This continuous operation maintains optimal conditions throughout the process, improving purification effectiveness while avoiding the need for complex batch-to-batch transfer equipment.
3Quantity of substance
If glycolic acid is concentrated without proper vacuum rectification control, then concentration can be achieved, but polymerization occurs and separation efficiency decreases
Solution Approach 1:
The patent creates a vacuum environment (inert atmosphere) during rectification concentration to prevent oxidative polymerization of glycolic acid. This vacuum condition allows concentration to proceed without the harmful polymerization reactions that would otherwise occur at atmospheric pressure, maintaining both concentration effectiveness and separation efficiency.
Solution Approach 2:
The patent performs vacuum rectification concentration as a preliminary step before cooling crystallization. By pre-concentrating the glycolic acid to ≥70 wt.% under vacuum conditions, the subsequent crystallization step operates on a more concentrated feed, improving overall separation efficiency and reducing the energy required for the crystallization stage.
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 method results in high-purity glycolic acid with a purity of 91.5-99.1%, improving separation and purification efficiency while being cost-effective and environmentally friendly, with a device design that simplifies operations and enhances market prospects.
Implementation Method 1
the crude glycolic acid solution may be concentrated in a rectification column using vacuum rectification technology
Implementation Method 2
The rectification column may have a feed temperature of 30° C., a plate number of 25, a reflux ratio of 0.32, a bottom temperature of 60° C., and an absolute pressure of 0.29 MPa
Implementation Method 3
the obtained concentrated solution of the glycolic acid may be crystallized in the crystallization kettle at −15° C. under a cooling rate of 0.5° C./min
Implementation Method 4
cooling crystallization and filtration may be conducted on the concentrated solution to obtain high-purity glycolic acid crystals
Data Source
AI summary
The present disclosure belongs to the technical field of separation and purification of glycolic acid, and in particular, to a method and device for separation and purification of glycolic acid by a rectification-crystallization coupling process and use. Bio-based platform compound molecules are used as raw materials to synthesize the glycolic acid, and the obtained crude glycolic acid is separated and purified using the rectification-crystallization coupling process to obtain high-purity glycolic acid. The method initiates system separation and purification under a new glycolic acid synthesis route, which has the difficulty that the glycolic acid is easy to polymerize during concentration, so there are technical barriers to equipment design of vacuum rectification and adjustment of process parameters. In addition, during crystallization, there are technical barriers to equipment design of a crystallization kettle and adjustment of process parameters.