Extractive Distillation Solvent Combination for Aromatics Separation
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Solution Overview
Problem
Current extractive distillation processes for isolating benzene derivatives from gasoline fractions face challenges in selecting a solvent that balances high selectivity and capacity, leading to inefficient solvent circulation and increased operational costs.
Innovation Solution
A solvent combination of N,N'-bis(formyl)piperazine or 2,2'-bis(cyanoethyl)ether with N-formylmorpholine is used, enhancing selectivity and capacity, thereby reducing solvent circulation and operational costs while effectively separating aromatics from non-aromatic hydrocarbons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single solvent like N-formylmorpholine is used for extractive distillation, then the process can be implemented with simple equipment, but solvent circulation is high and separation efficiency is limited
Solution Approach 1:
The patent applies composite materials by combining N-formylmorpholine with a second solvent (such as dimethyl carbonate, ethyl methyl carbonate, or propylene carbonate) to create a solvent mixture that achieves superior separation efficiency. This composite solvent system enhances the capacity and selectivity for aromatic compounds while maintaining reasonable equipment complexity, thereby resolving the contradiction between simple equipment and high productivity.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the composition ratio of the solvent mixture (typically 10-50 wt% of the second solvent) and adjusting distillation parameters such as temperature and pressure. These parameter optimizations enable the solvent system to achieve high separation efficiency with reduced solvent circulation, effectively balancing equipment simplicity with improved productivity.
2Quantity of substance
If solvent circulation is increased to improve separation capacity, then more aromatics can be extracted, but operational costs and equipment expenditure increase
Solution Approach 1:
The patent employs composite solvents that provide enhanced extraction capacity at lower circulation rates. The synergistic effect of N-formylmorpholine with the second solvent (e.g., dimethyl carbonate) creates a system with superior solubility parameters, allowing efficient aromatics extraction with reduced solvent flow, thus lowering operational costs while maintaining high extraction capacity.
Solution Approach 2:
The patent optimizes operational parameters including solvent composition (10-50 wt% second solvent), temperature, and pressure to maximize extraction efficiency. These parameter adjustments enable the system to achieve high aromatics recovery with minimal solvent circulation, effectively reducing both operational costs and equipment expenditure while maintaining high extraction capacity.
3Manufacturing precision
If a solvent with high selectivity for aromatics is used, then separation efficiency improves, but the boiling point may become unsuitable for effective solvent separation
Solution Approach 1:
The patent uses composite solvents where the second solvent (dimethyl carbonate, ethyl methyl carbonate, or propylene carbonate) has a lower boiling point than N-formylmorpholine. This combination maintains high selectivity for aromatics while ensuring the overall solvent mixture has a suitable boiling point for effective separation in the distillation process, thus resolving the contradiction between separation efficiency and temperature suitability.
Solution Approach 2:
The patent optimizes the composition ratio of the solvent mixture to balance selectivity and boiling point characteristics. By adjusting the proportion of the second solvent (10-50 wt%), the system achieves optimal separation efficiency while maintaining a boiling point that allows effective solvent-aromatics separation in the distillation column, thereby resolving the temperature-related contradiction.
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 solvent combination significantly reduces solvent circulation by 10-30% compared to using N-formylmorpholine alone, achieving efficient separation of benzene, toluene, and xylene, and minimizing equipment expenditure.
Implementation Method 1
Extractive distillation utilizes the phenomenon that the fugacity of individual components changes within a mixture of suitable components. The reason for this change in fugacity is the fact that different repulsive interactions exist between the individual molecular types.
Implementation Method 2
A component of the mixture that exhibits stronger repulsive forces towards the other components therefore more readily transitions into the vapor phase than a component that exhibits weaker repulsive forces.
Implementation Method 3
Extractive distillation utilizes the phenomenon that the fugacity of individual components changes within a mixture of suitable components
Implementation Method 4
A component of the mixture that exhibits stronger repulsive forces towards the other components therefore more readily transitions into the vapor phase
Data Source
Figure 1
AI summary
The invention relates to a method for separating the aromatic compounds benzol, toluene, and XyIoI from a reformate and pyrolysis gasoline containing aromatic compounds, or a coke benzol, or a refinery flow containing aromatic compounds, wherein extractive distillation is utilized for separating the aromatic compounds, using a novel solvent combination made up of the compounds N,N'-diformyl piperazine or 2,2'-bis-(cyan ethyl)ether in combination with N formyl morpholine as the second solvent for the extractive distillation such that the solvent combination obtained has an increased selectivity with regard to the aromatic compounds to be extracted, such that a reduced solvent charge may be utilized, wherein the mixture containing aromatic compounds utilized is initially subjected to a pre-distillation such that the faction obtained has a very limited boiling point, and that this fraction is then subjected to an extractive distillation in a first column, wherein a head product depleted of aromatic compounds, predominantly having paraffinic hydrocarbons and a sump product enriched with aromatic compounds are obtained, which are transferred into a second column, in which a raffinate rich in aromatic compounds is obtained by means of reduction of the pressure, or increase of the temperature such that the extracted solvent combination obtained as the sump product can be returned to the process.