Phase Separator Monomer Recycle Supercritical Polymerization
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Solution Overview
Problem
Current polymerization processes for producing commercially useful propylene-rich polymers with high molecular weight and high crystallinity under supercritical conditions face challenges in achieving efficient and economical separation of monomers from polymers, while also recycling low molecular weight components effectively, with existing systems often requiring high capital investment and energy consumption.
Innovation Solution
A process involving dense fluid homogeneous polymerization systems where olefin monomers with three or more carbon atoms are contacted with catalyst compounds and activators at temperatures above the crystallization temperature and pressures between 10 MPa and 200 MPa, followed by pressure reduction to form a two-phase mixture for efficient separation and recycling of low molecular weight components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional separation processes are used to separate monomers from polymers in supercritical polymerization, then separation can be achieved, but capital investment and energy consumption increase significantly
Solution Approach 1:
The invention utilizes phase transition of the polymer from dissolved state in supercritical monomer to precipitated state upon pressure reduction. The polymer precipitates when the system transitions from supercritical phase to subcritical phase, enabling automatic separation without additional energy-intensive separation equipment. This resolves the contradiction by using natural phase transition instead of conventional high-energy separation processes.
Solution Approach 2:
The invention changes the pressure parameter from supercritical conditions (above critical pressure) to subcritical conditions (below critical pressure) to trigger phase separation. By controlling pressure as the key parameter, the system automatically separates polymer and monomer phases, eliminating the need for complex separation equipment and reducing both capital investment and energy consumption.
2Stability of the object's composition
If high pressure is maintained to keep polymer in solution, then homogeneous polymerization is achieved, but separation of polymer from monomer becomes difficult
Solution Approach 1:
The invention dynamically changes the pressure condition from constant high pressure (supercritical) to reduced pressure (subcritical) after polymerization. This dynamic pressure adjustment allows the system to first maintain homogeneous polymerization under supercritical conditions, then automatically separate phases under subcritical conditions, eliminating the need for complex continuous separation equipment.
Solution Approach 2:
The invention performs polymerization completely under supercritical homogeneous conditions first, then applies pressure reduction as a preliminary action to trigger phase separation. This preliminary pressure reduction causes polymer precipitation and automatic phase separation, simplifying the overall separation system while maintaining homogeneous polymerization benefits.
3Productivity
If temperature is increased to maintain monomer in liquid phase, then polymerization proceeds, but polymer may crystallize and complicate separation
Solution Approach 1:
The invention creates different local conditions for monomer and polymer: monomer remains in liquid or supercritical phase while polymer precipitates as solid. This local quality difference allows polymer to separate from monomer even at elevated temperatures, avoiding polymer crystallization complications while maintaining high polymerization productivity.
Solution Approach 2:
The invention utilizes differential phase transitions of monomer and polymer upon pressure reduction. While monomer transitions to liquid or remains supercritical, polymer transitions to solid precipitate. This differential phase behavior enables easy separation without polymer crystallization issues, maintaining high productivity while simplifying separation.
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 enables the production of propylene-rich polymers with high molecular weight and crystallinity while reducing capital investment and energy consumption by efficiently separating monomers from polymers and recycling low molecular weight components, thereby optimizing product separation and monomer recovery.
Implementation Method 1
reducing the pressure of the polymerization medium below the cloud point pressure to form a two-phase mixture comprising a polymer-rich phase and a monomer-rich phase
Implementation Method 2
contacting in one or more reactors, in a dense fluid homogeneous polymerization system, olefin monomers having three or more carbon atoms at a temperature above the crystallization temperature of the polymerization system and a pressure between 10 MPa and 200 MPa
Data Source
AI summary
A process for polymerizing olefins, comprising the steps of: (a) contacting in a dense-fluid-homogeneous-polymerization system (“PS”), >30 wt % C3+ olefins with: catalyst, activator, 0-50 mol % comonomer, and 0-40 wt % diluent/solvent, at a temperature > PS Tc and a pressure no lower than 1 MPa below the PS cloud point pressure and <200 MPa; (b) forming a reactor effluent comprising polymer-monomer mixture; (c) optionally heating the mixture (b); (d) collecting the mixture (b) in a separation vessel; (e) reducing the pressure to form a two-phase mixture where the pressure in the reactor is 7-100 MPa higher than the pressure in the separation vessel and the temperature in the separation vessel is > the polymer or above 80° C., whichever is higher; (f) separating the monomer-rich phase from the polymer-rich phase; (g) recycling the separated monomer-rich phase and recovering polymer from the polymer-rich phase.