4-Hydroxybenzoic Acid Purification via Segmented Crystallization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing 4-hydroxybenzoic acid face challenges in achieving high purity and yield, often requiring lengthy crystallization steps that compromise either purity or yield, leading to unintended coloring.
Innovation Solution
A multi-step process involving acid precipitation, re-dissolution, and cooling crystallization stages, with reuse of waste liquids as solvents, and the use of activated carbon as an adsorbent to enhance purity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the crystallization step is extended to increase purity, then the purity of 4-hydroxybenzoic acid is improved, but the productivity decreases due to longer processing time
Solution Approach 1:
The crystallization process is divided into multiple sequential crystallization steps (first crystallization, second crystallization, third crystallization) rather than one long crystallization. Each step progressively increases purity while limiting the time required for each individual step, thereby resolving the contradiction between achieving high purity and maintaining productivity.
2Manufacturing precision
If the crystallization step is extended to increase purity, then the purity of 4-hydroxybenzoic acid is improved, but the yield decreases and coloring occurs
Solution Approach 1:
The purification process is segmented into multiple crystallization steps with intermediate handling. This segmentation allows progressive purification without excessive loss of product at each step, and prevents prolonged exposure conditions that cause coloring, thereby maintaining both high purity and acceptable yield.
Solution Approach 2:
The process includes preliminary acid precipitation steps before the crystallization sequence. These preliminary actions remove impurities early in the process, reducing the burden on subsequent crystallization steps and preventing the need for excessively long crystallization times that would reduce yield and cause coloring.
3Loss of substance
If waste liquids are reused as solvents, then the loss of substance is reduced, but the manufacturing precision may be affected by accumulated impurities
Solution Approach 1:
The process systematically reuses waste liquids from each crystallization step as solvents for subsequent crystallization steps. This recovering approach minimizes substance loss while the multi-step crystallization process ensures that accumulated impurities do not compromise the final product purity, as each step progressively removes impurities.
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 produces 4-hydroxybenzoic acid with high purity and reduced coloring at a high yield, utilizing waste liquids as solvents to optimize the process and activated carbon to remove impurities effectively.
Implementation Method 1
a first acid precipitation step of mixing a starting material liquid containing a metal salt of 4-hydroxybenzoic acid and water with an acid to precipitate a first post-acid-precipitation crystal of 4-hydroxybenzoic acid
Implementation Method 2
a first cooling crystallization step of mixing the second post-acid-precipitation crystal with a first aqueous solvent and subsequently performing cooling crystallization to precipitate a first post-crystallization crystal of 4-hydroxybenzoic acid
Implementation Method 3
adding an adsorbent to the solution
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An object of the present invention is to provide a method for producing 4-hydroxybenzoic acid, which is capable of producing 4-hydroxybenzoic acid having high purity and less coloring at a high yield. The method for producing 4-hydroxybenzoic acid of the present invention includes: a first acid precipitation step of mixing a starting material liquid containing a metal salt of 4-hydroxybenzoic acid and water with an acid to precipitate a first post-acid-precipitation crystal of 4-hydroxybenzoic acid; a re-dissolution step of mixing the first post-acid-precipitation crystal with a basic solvent to obtain a solution in which the first post-acid-precipitation crystal is re-dissolved, and adding an adsorbent to the solution; a second acid precipitation step of mixing the solution after the re-dissolution step with an acid to precipitate a second post-acid-precipitation crystal of 4-hydroxybenzoic acid; and a first cooling crystallization step of mixing the second post-acid-precipitation crystal with a first aqueous solvent and subsequently performing cooling crystallization to precipitate a first post-crystallization crystal of 4-hydroxybenzoic acid, and separating the first post-crystallization crystal and a first waste liquid.