Acrylic Acid Recovery From Acid Water by Solvent Extraction
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Solution Overview
Problem
Existing processes for recovering acrylic acid from gas phase oxidation result in significant losses due to the presence of acrylic acid in acid water, which is not effectively recovered, leading to reduced overall yield and increased costs.
Innovation Solution
An additional extraction stage using a second solvent is introduced to separate and recover acrylic acid from acid water, followed by a stripping column to further purify the acrylic acid, with temperature adjustments and solvent selection to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional absorption and condensation processes are used to recover acrylic acid from gas phase oxidation, then the basic separation is achieved, but significant acrylic acid losses occur in the acid water stream
Solution Approach 1:
The patent applies extraction by introducing a second solvent (such as dimethyl phthalate or diethyl phthalate) to selectively extract acrylic acid from the acid water stream. This extraction stage separates acrylic acid from the aqueous phase, reducing losses from conventional absorption-condensation processes while managing the complexity through targeted chemical separation.
Solution Approach 2:
The patent utilizes temperature adjustments and solvent selection to enhance extraction efficiency. By optimizing operational parameters such as temperature and solvent-to-feed ratios, the process maximizes acrylic acid recovery while controlling process complexity through parameter optimization rather than additional equipment.
2Manufacturing precision
If acrylic acid is absorbed from gas stream with high-boiling hydrophobic solvent, then selective absorption is achieved with water vapor remaining in gas phase, but acrylic acid remains in acid water after condensation
Solution Approach 1:
The patent introduces a second solvent as an intermediary substance to transfer acrylic acid from the acid water phase. This intermediary solvent selectively extracts acrylic acid from the aqueous stream, maintaining the selectivity of the original absorption process while eliminating the loss of acrylic acid in the acid water discharge.
3Productivity
If additional extraction stage with second solvent is introduced to recover acrylic acid from acid water, then overall yield improves by up to 2%, but energy consumption increases
Solution Approach 1:
The patent optimizes energy consumption by adjusting operational parameters such as temperature and solvent flow rates in the extraction stage. Through parameter optimization, the process achieves improved overall yield while minimizing the energy penalty associated with the additional extraction operation.
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 significantly reduces the acrylic acid content in acid water to below 1% by weight, improving overall yield by up to 2% and reducing energy consumption, while extending plant operation time and lowering energy costs.
Implementation Method 1
a) feeding the aqueous phase (4*) of the acid water (4) drawn off from the condensation stage that has been obtained in the phase separation vessel (B1) to an extraction stage (K7) in which acrylic acid present in the acid water (4) is extracted with a second solvent (5)
Implementation Method 2
b) feeding the acrylic acid-comprising extract (6) to a stripping column (K8) in which the acrylic acid is removed from the second solvent (5) with cycle gas (8)
Implementation Method 3
in the condensation stage, the gas mixture is condensed, and a condensed phase of the gas mixture is drawn off as acid water (4)
Implementation Method 4
in an absorption stage (K2), the acrylic acid is absorbed from the reaction mixture (1) from the gas phase oxidation with a first solvent (3)
Data Source
AI summary
The present invention relates to a process for recovering acrylic acid which is obtained by catalytic gas phase oxidation of propene,wherein, in an absorption stage (K2), the acrylic acid is absorbed from the reaction mixture (1) from the gas phase oxidation with a first solvent (3) and is drawn off for distillative purification, and a gas mixture from the absorption stage (K2) is passed onward to a condensation stage,wherein, in the condensation stage, the gas mixture is condensed, and a condensed phase of the gas mixture is drawn off as acid water (4) and is subjected to a phase separation operation in a phase separation vessel (B1),comprising the steps ofa) feeding the aqueous phase (4*) of the acid water (4) drawn off from the condensation stage that has been obtained in the phase separation vessel (B1) to an extraction stage (K7) in which acrylic acid present in the acid water (4) is extracted with a second solvent (5),b) feeding the acrylic acid-comprising extract (6) to a stripping column (K8) in which the acrylic acid is removed from the second solvent (5) with cycle gas (8), wherein the second solvent (5) removed is fed back again after the acrylic acid has been stripped out in the extraction stage (K7),c) feeding the acrylic acid-laden cycle gas (9) to a stripping cycle gas scrubber (K5) in which the acrylic acid is removed from the cycle gas with the first solvent stream (10) fed to the stripping gas scrubber (K5) and transferred into the first solvent (3), andd) feeding a first portion of the acrylic acid-laden first solvent (3) back to the absorption stage (K2).The present invention further relates to a corresponding plant for recovery of acrylic acid.