Bubble Column Reactor for Aromatic Acid Oxidation
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Solution Overview
Problem
Existing liquid-phase oxidation systems for dialkyl aromatic compounds face challenges in energy efficiency, production efficiency, and waste minimization, with high energy consumption and capital costs due to mechanical agitation in conventional reactors, and inefficiencies in raw material utilization and impurity management.
Innovation Solution
A continuous process using bubble column reactors with compressed air oxidation in an acetic acid medium, followed by post-oxidation, de-gassing, and digestion units, where energy is recycled and managed through steam generation and water removal, optimizing temperature and catalyst use to enhance product yield and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mechanical agitation is used in continuous stirred tank reactors to maintain uniform concentration and promote oxygen dissolution, then reaction uniformity and oxygen availability are improved, but capital cost and operating cost increase due to expensive motors, bearings, drive shafts, and maintenance requirements
Solution Approach 1:
The patent replaces the mechanical agitation system (motors, drive shafts, bearings) with a gas-phase sparging system that introduces oxygen bubbles into the liquid phase. The rising bubbles provide natural convection and mixing, eliminating the need for complex mechanical agitation equipment while maintaining uniform concentration and oxygen dissolution.
Solution Approach 2:
The patent uses gas-phase oxygen sparging through spargers or diffusers to achieve liquid-phase mixing and oxygen dissolution. The pneumatic introduction of gas bubbles creates hydraulic circulation and convection currents that replace mechanical agitation, reducing device complexity while maintaining reaction uniformity.
2Stability of the object's composition
If mechanical agitation systems are used to maintain uniform reaction medium, then oxygen dissolution and reaction uniformity are improved, but reliability decreases due to mechanical failure and frequent replacement requirements
Solution Approach 1:
The patent eliminates mechanical moving parts by replacing the agitation system with gas-phase sparging. The pneumatic system introduces oxygen bubbles that provide natural mixing through buoyancy-driven convection, removing mechanical components that are prone to failure and requiring replacement, thereby improving system reliability.
Solution Approach 2:
The rising oxygen bubbles self-generate convection currents and mixing action through their natural buoyancy. The system uses the reaction itself (oxygen dissolution and bubble rise) to provide the mixing function, eliminating the need for external mechanical power and improving reliability through a failure-free passive mixing mechanism.
3Productivity
If excess concentration of oxidizable compound is used in liquid phase, then reaction rate may be maintained, but undesirable side-reactions generate impurities and product purity decreases
Solution Approach 1:
The patent employs continuous sparging of oxygen throughout the reaction process, ensuring that oxygen is continuously available in the liquid phase. This continuous supply of oxidant allows the reaction to proceed at optimal rate without needing excess organic substrate, thereby maintaining high reaction rate while preventing side-reactions and preserving product purity.
Solution Approach 2:
The patent changes the physical state and delivery method of oxygen from intermittent or limited supply to continuous gas-phase sparging. This parameter change ensures adequate oxygen concentration throughout the reaction, allowing use of optimal (not excess) oxidizable compound concentration, thus maintaining productivity while preventing impurity formation from side-reactions.
4Manufacturing precision
If insufficient concentration of molecular oxygen is provided in liquid phase, then oxygen availability for reaction is reduced, but side-reactions are minimized; however, reaction rate becomes undesirably slow and productivity decreases
Solution Approach 1:
The patent uses pneumatic sparging to continuously introduce oxygen gas into the liquid phase, creating fine bubbles that maximize gas-liquid interfacial area. This ensures high oxygen dissolution rate and maintains adequate oxygen concentration in the liquid phase, enabling fast reaction rate while preventing oxygen starvation that would cause side-reactions, thus achieving both productivity and purity.
Solution Approach 2:
The patent employs spargers or diffusers with porous structures to generate fine oxygen bubbles. The porous material creates numerous small bubbles with large total surface area, maximizing oxygen transfer to the liquid phase. This ensures sufficient oxygen availability for high reaction rate while maintaining controlled oxidation conditions that prevent side-reactions and preserve 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 approach significantly reduces energy consumption, improves production efficiency, and minimizes waste by integrating energy and materials management, achieving high-quality aromatic dicarboxylic acid production while reducing capital and operational costs.
Implementation Method 1
Agitation of the reaction medium in the reaction zone is provided primarily by the natural buoyancy of gas bubbles rising through the liquid phase of the reaction medium
Implementation Method 2
At least a portion of the molecular oxygen introduced into the reactor as a gas dissolves into the liquid phase of the reaction medium to provide oxygen availability for the liquid-phase reaction
Implementation Method 3
oxidizing a di-alkyl substituted aromatic compound with compressed air in an acetic acid reaction medium in a primary bubble column reactor in the presence of a catalyst
Implementation Method 4
at least a portion of the energy of the off gas comprising steam is collected and employed to drive an air compressor to supply the compressed air to the bubble column primary reactor and the post-oxidation bubble column unit
Data Source
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AI summary
A continuous process for oxidizing a di-alkyl substituted aromatic compound with compressed air in a primary bubble column reactor; including removing a portion of the three phase reaction medium to a post–oxidation bubble column unit supplied with compressed air; separating the post oxidation reaction medium to an overhead gas and an underflow slurry; collecting overhead gases from the oxidation reactors and the de-gassing unit and conducting the combined overhead gases to a water removal column (WRC); transferring the underflow slurry from the de-gassing unit to a digestion unit to effect further oxidation without addition of air to the digestion unit; removing overhead gases to the water removal column; crystallizing the final oxidation slurry; and filtering the slurry on a rotary pressure filter; wherein a portion of the energy of the off gas from the WRC is employed to drive an air compressor to supply the compressed air for oxidation.