1. Polypropylene PGC Applications

2. Polypropylene Plant
A mixture of propylene plus a second compound called a co-monomer
Chemical used for the co-monomer varies depending on the desired properties
Ethylene, butene, or hexene
Typical polypropylene plant design with the chemical reactions are done in two stages

3. Reactors 1st Stage – Slurry Reactor 2nd Stage – Co-monomer Reactor
Polymer-grade propylene enters the first reactor along with the catalyst
Hydrogen is also added to control the size of the polymer molecule and sets the overall melting point of the final product
Slurry – an inert diluent compound such as hexane or butane is added
2nd Stage – Co-monomer Reactor
Chemically-active mixture leaves the first reactor and enters the second reactor
Fresh propylene and the co-monomer are added to finish the reaction process

4. Flash Tank
Finished polymer leaves the second reactor, along with the diluent and any unreacted components and enters a flash tank
Unreacted monomers and diluent vaporizes and leaves the top of the vessel
The polymer settles out the bottom to be extruded into plastic sheets or pellets

5. Diluent Recovery System and Stripper
Separate the diluent from any unreacted monomers
The diluent is recycled back to the feed of the reactor
The unreacted propylene and co-monomer enter a stripper where they are separated from each other
The propylene is recycled to the feed of the first reactor and the co-monomer is recycled to the feed of the second reactor

6. Typical Polypropylene Plant
GC #7
GC #6
GC #5
GC #1
GC #2
GC #3
GC #4

7. Improving Polypropylene Performance with PGC’s
It is critical that the quality of the plastic be high and consistent
To insure this high quality, it is important that the ingredients fed into the polymer reactor be tightly controlled
GC #1, GC #2, GC #3, and GC #4 are used to provide live feedback on the quality of the feed streams
GC #1 – Propylene feed quality
GC #2 – Diluent feed impurities
GC #3 – Hydrogen feed impurities
GC #4 – Propylene / Co-monomer feed impurities

8. Additional Measurements
Flash Tank Measurements
Feedback to the control system on how the reactions are progressing in the reactors is common through measuring the flash tank off-gases
Unreacted components can indicate the quality of reactions occuring
Monitor the recycle streams
Diluent recycle stream
Propylene recycle stream

9. PGC Analysis Summary GC # Stream Components Measured
Measurement Objective 1
Propylene Feed
C2, C3, MA, PD
Propylene feed purity 2
Diluent feed
Hydrocarbons
Diluent feed purity; exact components vary with diluent used 3
Hydrogen feed
Hydrogen feed purity 4
Co-monomer feed
Co-monomer feed purity; exact components vary with co-monomer used 5
Flash tank off-gas
H2, C3=, comonomer
Feedback to control system on reaction kinetics 6
Diluent recycle
Monitor impurities recycled with the diluent 7
Propylene recycle
H2, comonomer
Monitor impurities recycled with the propylene

10. GC #1 and GC #4 – Example 1

11. GC #1 and GC #4 – Chromatogram

12. GC #1 and GC #4 – Example 2

13. GC #1 and GC #4 – Chromatogram 1

14. GC #1 and GC #4 – Chromatogram 2

15. GC #1 and GC #4 – Chromatogram 3

16. GC #5 – Example

17. GC #5 – Chromatogram

18. GC #6 and GC #7 – Example

19. GC #6 and GC #7 – FID, Stream 1

20. GC #6 and GC #7 – FID, Stream 2

21. GC #6 and GC #7 – FID, Stream 3

22. GC #6 and GC #7 – TCD, Stream 1

23. GC #6 and GC #7 – TCD, Stream 2