Acrylic Acid Benzoic Acid Separation via Crystallization
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Solution Overview
Problem
The separation of acrylic acid and benzoic acid from product gas mixtures in partial heterogeneously catalyzed gas phase oxidation processes is energy-intensive and inefficient, particularly due to the high boiling point of acrylic acid and the formation of benzoic acid as an undesirable byproduct, which complicates purification and affects the quality of polymers used in applications like water superabsorbents.
Innovation Solution
A process involving thermal separation followed by crystallization, where components with lower boiling points than benzoic acid are removed, allowing benzoic acid to crystallize out from the liquid phase, resulting in a high depletion coefficient that ensures minimal incorporation into acrylic acid crystals, thereby achieving efficient separation of benzoic acid from acrylic acid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal separation processes are used to separate acrylic acid from benzoic acid, then separation efficiency is improved, but energy consumption increases significantly
Solution Approach 1:
The invention utilizes the phase transition of benzoic acid from liquid to solid state through controlled cooling to achieve separation from acrylic acid. By reducing the temperature of the liquid phase mixture to below the melting point of benzoic acid (122°C), benzoic acid crystallizes out while acrylic acid remains in the liquid phase, enabling separation without energy-intensive distillation processes.
Solution Approach 2:
The invention changes the temperature parameter of the system to enable selective crystallization. By controlling the temperature to be below 122°C but above the freezing point of acrylic acid, benzoic acid precipitates as crystals while acrylic acid remains dissolved, achieving separation based on differential solubility and phase behavior.
2Quantity of substance
If conventional thermal separation is used, then acrylic acid can be separated, but benzoic acid contamination in the final product increases
Solution Approach 1:
The invention extracts benzoic acid from the mixture by inducing its crystallization and separating the solid crystals from the liquid phase containing acrylic acid. The crystallized benzoic acid is removed as a solid precipitate, leaving the acrylic acid in the liquid phase with minimal contamination, thereby improving product purity.
Solution Approach 2:
By exploiting the phase transition of benzoic acid to solid state through cooling, the invention achieves selective removal of benzoic acid while keeping acrylic acid in the liquid phase, ensuring high purity of the recovered acrylic acid product.
3Device complexity
If crude C3 precursor compound is used directly, then process complexity is reduced, but benzoic acid byproduct formation increases
Solution Approach 1:
The invention converts the harmful effect of butadiene impurities (which cause benzoic acid formation through Diels-Alder reactions) into a beneficial separation opportunity. By allowing benzoic acid to form and then selectively crystallizing it out, the process transforms an unwanted byproduct into a separable solid phase, enabling the use of crude feedstocks while maintaining product purity.
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 method allows for the quantitative separation of benzoic acid from acrylic acid, reducing energy consumption and improving the purity of acrylic acid for polymer production, as evidenced by a depletion coefficient of ≥15, which indicates minimal benzoic acid incorporation into acrylic acid crystals, facilitating the production of high-quality superabsorbent polymers.
Implementation Method 1
the acrylic acid and the benzoic acid together with others lighter and heavier than acrylic acid boiling components of the product gas mixture are converted from the product gas mixture into a liquid phase P
Implementation Method 2
the separation of the benzoic acid from the acrylic acid from the liquid phase P* is carried out in such a way that the benzoic acid crystallizes from the acrylic acid from the liquid phase P*
Data Source
AI summary
A method of separating acrylic acid-containing acrylic acid and benzoic acid in a product gas mixture from a partial oxidation, in which the acrylic acid and the benzoic acid are first converted into a liquid phase, components lighter than benzoic acid and acrylic acid are boiled away by means of thermal separation methods, and the acrylic acid is separated by crystallization from the remaining liquid phase.