Ionic Liquid Separation for Olefin Polymerization Recycle
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Solution Overview
Problem
The recycling of comonomers in olefin polymerization plants is inefficient, especially when saturated and unsaturated hydrocarbons are present, leading to high losses and increased costs due to difficult separation and disposal, which is exacerbated when using alternate catalyst systems like Ziegler-Natta and metallocene catalysts.
Innovation Solution
A process involving the polymerization of olefins in a reaction mixture, followed by separating polyolefins, removing gaseous components to obtain a liquid fraction, treating this fraction with ionic liquids to isolate unsaturated hydrocarbons, and recycling them back to the reactor after optional purification, allowing for efficient separation and reuse of comonomers regardless of catalyst type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If comonomer recycling is attempted using conventional separation methods, then some comonomer recovery is achieved, but separation efficiency is poor due to close boiling points of saturated and unsaturated hydrocarbons
Solution Approach 1:
The invention changes the physical-chemical parameters of the separation system by using ionic liquids with specific properties (low vapor pressure, tunable polarity, selective solubility) instead of conventional volatile solvents. This parameter change enables effective separation of comonomers from saturated hydrocarbons based on differential solubility rather than boiling point differences, directly resolving the technical contradiction between comonomer recovery and separation difficulty
Solution Approach 2:
The invention introduces ionic liquids as an intermediary substance that mediates the separation process. The ionic liquid acts as a selective solvent that preferentially dissolves unsaturated hydrocarbons (comonomers) while leaving saturated hydrocarbons in the raffinate phase, enabling efficient comonomer recovery without the separation difficulties associated with conventional methods
2Reliability
If recycle streams containing polar catalyst components are used with metallocene catalysts, then catalyst deactivation occurs, but excluding these components reduces recycle efficiency
Solution Approach 1:
The invention uses ionic liquids as an intermediary separation medium that selectively extracts unsaturated hydrocarbons from the recycle stream while leaving polar catalyst components in the raffinate phase. This intermediary separation step protects the metallocene catalyst from deactivation by polar contaminants while maintaining high comonomer recycle efficiency, resolving the contradiction between catalyst reliability and productivity
Solution Approach 2:
The invention segments the recycle stream into distinct phases through ionic liquid treatment: a comonomer-enriched phase that can be safely recycled to the reactor, and a polar component-containing phase that is discarded or treated separately. This segmentation allows selective recovery of valuable comonomers while removing catalyst poisons, simultaneously improving both catalyst activity and recycle efficiency
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 process enhances recycling efficiency, reduces costs, improves polymerization control, and allows for the use of different catalyst systems by effectively separating and purifying unsaturated hydrocarbons, thereby minimizing waste and environmental impact.
Implementation Method 1
treating the liquid fraction with at least one ionic liquid to obtain a fraction containing unsaturated hydrocarbons
Implementation Method 2
Treating the liquid fraction with at least one ionic liquid to obtain a fraction containing unsaturated hydrocarbons
Data Source
Figure 1
AI summary
The invention relates to a process for the polymerization of olefins comprising the comprising the steps of a. Polymerizing olefins in a reaction mixture comprising monomers, diluent, processing aids to prepare a product stream comprising polyolefins, monomers and diluent; b. Removing the polyolefins from the product stream to obtain a purge stream; c. Removing gaseous components from the purge stream to obtain a liquid fraction; d. Treating the liquid fraction with at least one ionic liquid to obtain a fraction containing unsaturated hydrocarbons; e. Recycling the fraction containing unsaturated hydrocarbons to the reaction mixture, optionally after purification of said fraction containing unsaturated hydrocarbons. The invention also relates to an olefin polymerization system comprising a polymerization reactor, a purge vessel, a vent gas recovery and an ionic liquid separator for separating liquid alkenes from liquid alkanes, wherein the liquid alkenes which are separated from the alkanes in the ionic liquid separator can be recycled to the polymerization reactor.