Azeotropic Distillation Corrosion Control via Formaldehyde Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for purifying acrylic acid are inefficient due to high levels of formaldehyde, which cause corrosion in distillation equipment and interfere with downstream processes, and existing solutions do not completely address corrosion issues or reduce formaldehyde levels effectively.
Innovation Solution
A method that reduces formaldehyde levels in the aqueous acrylic acid feed stream to less than 0.1% by weight during azeotropic distillation, using copper-based inhibitors and minimizing formaldehyde interaction to prevent formic acid formation, allowing for the use of cost-effective metallurgy in distillation columns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If direct-contact absorption is used to recover acrylic acid from gaseous material stream, then acrylic acid recovery is achieved, but by-products and impurities such as formaldehyde are also captured in the aqueous acrylic acid stream
Solution Approach 1:
The absorption process is segmented into two distinct stages: first, a non-aqueous absorbent (such as phenyl ether or toluene) is used to selectively absorb acrylic acid from the gaseous stream without capturing formaldehyde; second, the absorbed acrylic acid is then transferred to an aqueous phase in a separate step. This segmentation allows recovery of acrylic acid while leaving formaldehyde and many by-products in the gas phase or in separate waste streams.
Solution Approach 2:
A non-aqueous intermediate absorbent is introduced as a mediator between the gaseous acrylic acid stream and the final aqueous product stream. This intermediate absorbent selectively dissolves acrylic acid while being immiscible with water and not absorbing formaldehyde, thus acting as a selective transport medium that separates acrylic acid from harmful by-products before final product formation.
2Manufacturing precision
If conventional azeotropic distillation is used to purify aqueous acrylic acid, then water removal is achieved, but dissolved copper interacts with formaldehyde to form corrosive formic acid
Solution Approach 1:
Formaldehyde is extracted and removed from the aqueous acrylic acid stream prior to the azeotropic distillation step, typically through selective oxidation to formic acid followed by decarboxylation, or through reactive extraction with specific reagents. By taking out formaldehyde before distillation, the subsequent interaction with copper catalysts that would generate corrosive formic acid is prevented.
Solution Approach 2:
A preliminary treatment step is introduced before azeotropic distillation to convert or remove formaldehyde. This preliminary action addresses the formaldehyde issue proactively, preventing the formation of corrosive formic acid during the subsequent distillation process with copper-based catalysts or heat exchangers.
3Manufacturing precision
If multiple purification steps are used to meet final product quality requirements, then acrylic acid purity is improved, but capital investment and operational costs increase
Solution Approach 1:
Multiple purification functions are merged into a single integrated absorption column design. The column combines the absorption of acrylic acid from gas phase, the selective separation from formaldehyde, and the initial concentration step into one unit operation, eliminating the need for separate absorption towers, flash drums, and preliminary distillation columns.
Solution Approach 2:
The non-aqueous absorbent serves multiple functions simultaneously: it selectively absorbs acrylic acid from the gaseous stream, rejects formaldehyde and water, provides a phase separation interface, and enables direct transfer to aqueous phase. This multi-functionality consolidates what would traditionally require multiple separate units into a single versatile process step.
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 approach minimizes corrosion in distillation equipment, reduces polymer formation, and maintains high acrylic acid purity, leading to lower operational costs and extended equipment lifespan.
Implementation Method 1
Purification, or separation of the desired acrylic acid product from other materials in the aqueous acrylic acid stream may be accomplished by one or more well-known and understood processes including distillation, extraction, and/or crystallization. One of the most common of these purification steps is the use of azeotropic distillation to remove water from the aqueous acrylic acid stream.
Implementation Method 2
aqueous acrylic acid is then most typically recovered from the raw gaseous product stream in an absorption tower, wherein a cooled absorbent, such as water or an organic compound (e.g., phenyl ether) directly contacts the gaseous material stream, simultaneously condensing and absorbing various components, including acrylic acid and water
Data Source
AI summary
The present invention relates to reducing corrosion of distillation equipment during azeotropic distillation of (meth)acrylic acid in the presence of dissolved copper, by providing aqueous (meth)acrylic acid having not more than 0.1% by weight formaldehyde, based on the total weight of the aqueous (meth)acrylic acid. The source of the copper may, for example, be copper-based polymerization inhibitors added to the aqueous (meth)acrylic acid and/or distillation equipment.