Liquid-Liquid Extraction of Diolefins Using Cyclic Dialkylcarbonates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solvent extraction and purification methods for diolefins from complex hydrocarbon mixtures are inefficient due to high solvent requirements, complex distillation processes, and the use of toxic solvents, which result in high costs and operational challenges.
Innovation Solution
A process utilizing a polar solvent solution comprising cyclic dialkylcarbonates, such as ethylene carbonate and propylene carbonate, in a liquid-liquid extraction method with counter-current extraction and re-extraction steps, reducing the number of theoretical stages and solvent flow rates while maintaining high separation quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extractive distillation is used to separate diolefins from hydrocarbon mixtures, then separation can be achieved, but the solvent flow rate must be much higher than the load flow rate (typically a ratio of 10), the number of plates must be high (typically more than 50 real plates), and the reflux rate is important, resulting in heavy investment and operating costs
Solution Approach 1:
The patent changes the fundamental separation mechanism from vapor-liquid equilibrium (distillation) to liquid-liquid equilibrium (extraction). This parameter change allows separation based on differential solubility in immiscible solvents rather than volatility differences, enabling effective separation with fewer theoretical stages and lower solvent-to-feed ratios
Solution Approach 2:
The patent introduces an immiscible solvent system (polar and non-polar solvents) as an intermediary to facilitate separation. The solvent acts as a mediating phase that selectively dissolves target compounds, enabling separation without requiring direct vapor-liquid contact and reducing the need for complex distillation equipment
2Manufacturing precision
If extractive distillation is used to separate diolefins from hydrocarbon mixtures, then separation can be achieved, but the solvents used are very toxic (e.g., N-MethylPyrrolidone and DiMethylFormamide), the use of which we seek to limit today
Solution Approach 1:
The patent replaces persistent toxic solvents with a solvent system that can be easily separated and regenerated. The immiscible solvent pair allows for simple phase separation and recycling, reducing the environmental burden and toxicity concerns associated with traditional extractive distillation solvents
Solution Approach 2:
The patent changes the solvent selection criteria from requiring high boiling point and chemical inertness (traditional extractive distillation) to requiring immiscibility and selective solubility (liquid-liquid extraction). This parameter change enables the use of less toxic, more environmentally friendly solvent systems
3Productivity
If liquid-liquid extraction with polar and non-polar solvents is used, then the number of theoretical stages can be reduced, but the solvents must have low mutual solubility and sufficient density difference to allow rapid phase separation
Solution Approach 1:
The patent optimizes the solvent pair selection to achieve the right balance between extraction efficiency and phase separation ease. By carefully selecting solvents with appropriate polarity differences and density contrasts, the process achieves both reduced theoretical stages and facile phase separation in the decanter
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 the number of theoretical stages and solvent flow rates, achieving high-purity diolefins with improved separation efficiency and lower operational costs, and allows for the separation of diolefins from complex hydrocarbon mixtures with reduced risk of degradation.
Implementation Method 1
Instead of taking advantage of the difference in solubility of C 4 and/or C 5 hydrocarbons depending on the degree of unsaturation between a liquid phase and a vapor phase (as is the case in extractive distillation) to carry out the separation, we take advantage of the difference in solubility as a function of the degree of unsaturation between two liquid phases.
Implementation Method 2
These solvents must also have a sufficient difference in density to allow rapid phase separation within a decanter, the polar solvent being a priori denser than the apolar solvent.
Data Source
Figure 1
AI summary
The invention relates to an absorbent solution comprising at least one polar solvent chosen from cyclic dialkylcarbonates and also to a process for the liquid-phase extraction of the diolefins contained in a feedstock of hydrocarbons having various degrees of saturation.