A great deal of my work is just playing with equations and seeing what they give. Paul Dirac (1902-1984)

ANALYSIS OF ETHYLENE/1-OLEFIN COPOLYMERS MADE WITH ZIEGLER-NATTA CATALYSTS BY DECONVOLUTION

OF GPC-IR DISTRIBUTIONS

João BP Soares, Saeid Mehdiabadi Department of Chemical and Materials Engineering

University of Alberta, Edmonton, AB, Canada

Boping Liu, Keran Chen State Key Laboratory of Chemical Engineering

East China University of Science and Technology, Shanghai, China

International Symposium on GPC/SEC and Related Techniques September 26-29, 2016, Amsterdam, Netherlands

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Acknowledgements

Mr Keran Chen Professor Boping Liu State Key Laboratory of Chemical Engineering East China University of Science and Technology Shanghai, China

Dr Saeid Mehdiabadi Department of Chemical and Materials Engineering University of Alberta Edmonton, AB, Canada

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Deconvolution of GPC-IR distributions identifies the minimum number of active sites on Ziegler-Natta catalysts.

This method also estimates the apparent kinetic constants for activation, propagation, deactivation, and comonomer incorporation of each site type.

Summary

Site Mn (103) SCB/1000C

1 3 29.6

2 12.5 11.3

3 37 6.2

4 112 4.2

5 350 3.4

Introduction Method GPC-IR Kinetics Conclusions

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Ziegler-Natta polyolefins have broad molecular weight and chemical composition distributions.

Problem Formulation

Log MW

W

SCB

Log MW

W

SCB

It should look like this,

but it looks like this,

A reasonable explanation is that there are 2 or more site types, each making polymer with the distribution on the left of the slide.

PDI = 2

PDI > 4

Introduction Method GPC-IR Kinetics Conclusions

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Multiplicity of Active Site Types

1 2 3

0.880.91

0.930.95

0.980

20

40

60

80

100

0.00

1.38

2.75

4.13

FA

w(l

ogr,

FA)

log r

1

2 3

1 2

3

Hypothesis: Different polymer populations are made on each site type

Introduction Method GPC-IR Kinetics Conclusions

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Methodology

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

3 4 5 6 7

SCB/

1000

C

w log

MW

log MW

j 1 2 3 4 5 m 0.0378 0.1800 0.4333 0.2674 0.0815 Mn 7 400 23 900 64 900 164 000 507 000

SCB/1000C 7.05 1.98 1.10 0.99 0.99

BF 0.0143 0.0040 0.0022 0.0020 0.0020

Minimize Σ [(GPC-IR)exp – (GPC-IR)pred]2

Introduction Method GPC-IR Kinetics Conclusions

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Polymerization System

ethylene

MFM

α-olefin

GCA

• 250 mL SS autoclave reactor

• 90 oC polymerization temperature

• 7 bar ethylene

• 2, 4, or 6 g 1-hexene

• 10, 20, 40, 60 min polymerization time

• H2 used a chain transfer agent

Introduction Method GPC-IR Kinetics Conclusions

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Polymerization Kinetics

2.0 g 1-Hexene

10 min

20 min

40 min 60 min

Introduction Method GPC-IR Kinetics Conclusions

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Deconvolution Assumptions

• Sites of different types make polymer populations with the same Mn and SCB/1000 C.

• The changes in Mn and SCB/1000C for the whole polymer result from differences in the polymerization kinetics of the distinct site types. Distinct site types have different

activation/propagation/deactivation rates that affect the properties of the whole polymer.

Introduction Method GPC-IR Kinetics Conclusions

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GPC-IR Deconvolution 2.

0 g

1-He

xene

Introduction Method GPC-IR Kinetics Conclusions

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Deconvolution Results

2.0 g 1-Hexene

Site Mn (103) SCB/ 1000C

1 3 29.6

2 12.5 11.3

3 37 6.2

4 112 4.2

5 350 3.4

The fraction of polymer made in high-Mn sites increases

The fraction of polymer made in low-Mn sites decreases

Introduction Method GPC-IR Kinetics Conclusions

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Results for Other 1-Hexene Concentrations

Site Mn (103) SCB/ 1000C

1 3.5 39.6

2 13 17.5

3 36 13.7

4 101 10.9

5 290 10.4

Site Mn (103) SCB/ 1000C

1 3 35.1

2 12.0 13.8

3 35 9.5

4 107 7.6

5 318 6.2

4.0 g 1-Hexene 6.0 g 1-Hexene

Introduction Method GPC-IR Kinetics Conclusions

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1-Hexene Incorporation per Site Type

Introduction Method GPC-IR Kinetics Conclusions

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Investigating Site Type Kinetics

Description Chemical Equation Rate Constant

Activation ka

Propagation kp

1st Order Deactivation kd

0PAlC →+

1+→+ rr PMP

rdr DCP +→

Introduction Method GPC-IR Kinetics Conclusions

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Effect of kp

0

0.5

1

1.5

2

2.5

3

3.5

0 500 1000 1500 2000 2500 3000 3500 4000

Mon

omer

Upt

ake

(mol

/s)

Polymerization Time (s)

Introduction Method GPC-IR Kinetics Conclusions

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Effect of kd

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 500 1000 1500 2000 2500 3000 3500 4000

Mon

omer

Upt

ake

(mol

/s)

Polymerization Time (s)

Low kd

High kd

Introduction Method GPC-IR Kinetics Conclusions

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Effect of KA

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 500 1000 1500 2000 2500 3000 3500 4000

Mon

omer

Upt

ake

(mol

/s)

Polymerization Time (s)

Medium KA

High KA

Introduction Method GPC-IR Kinetics Conclusions

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Polymer Yield in a Semi-Batch Reactor

0

1000

2000

3000

4000

5000

6000

7000

0 500 1000 1500 2000 2500 3000 3500 4000

Tota

l Mon

omer

Con

sum

ptio

n (m

oles

)

Polymerization Time (s)

kd = 1.5×10-3 s-1

Ywhole = Σ Yi

High kd

Introduction Method GPC-IR Kinetics Conclusions

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Partitioning the Polymer Among Active Sites

Whole polymer

t = 20 min

Introduction Method GPC-IR Kinetics Conclusions

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Ethylene Homopolymerization Yield per Site Type

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100

Mas

s (g

)

Time (min)

Site1 Exp. Site2 Exp. Site3 Exp. Site4 Exp. Site5 Exp.

Introduction Method GPC-IR Kinetics Conclusions

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Ethylene Homopolymerization Site Kinetics

Introduction Method GPC-IR Kinetics Conclusions

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Copolymer Yield per Site Type: 2.0 g 1-Hexene

Introduction Method GPC-IR Kinetics Conclusions

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Copolymerization Site Kinetics: 2.0 g 1-Hexene

Introduction Method GPC-IR Kinetics Conclusions

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Copolymer Yield per Site Type

4.0 g 1-Hexene 6.0 g 1-Hexene

Introduction Method GPC-IR Kinetics Conclusions

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Copolymerization Site Kinetics

4.0 g 1-Hexene 6.0 g 1-Hexene

Introduction Method GPC-IR Kinetics Conclusions

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0

2

4

6

8

Homopolymer6.0g 1-C64.0g 1-C6

Ka

(min

-1)

Site 1 Site 2 Site 3 Site 4 Site 5

2.0g 1-C6

1-Hexene increases Ka

Introduction Method GPC-IR Kinetics Conclusions

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0.00

0.02

0.04

0.06

0.08

0.10kp

(min

-1)

Site 1 Site 2 Site 3 Site 4 Site 5

Homopolymer6.0g 1-C64.0g 1-C62.0g 1-C6

1-Hexene increases kp of low Mn sites but decreases kp of high Mn sites

Introduction Method GPC-IR Kinetics Conclusions

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0.0

0.1

0.2

0.3

0.4

0.5kd

(min

-1)

Site 1 Site 2 Site 3 Site 4 Site 5

Homopolymer6.0g 1-C64.0g 1-C62.0g 1-C6

1-Hexene increases kd

Introduction Method GPC-IR Kinetics Conclusions

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What is this information good for?

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Concluding Remarks

• GPC-IR deconvolution can: • Quantify the MWD x SCB/1000 C evolution of

polyolefins made with multiple-site catalysts (Ziegler-Natta and Phillips).

• Assign Mn and SCB for different site types. • Estimate apparent Ka, kp and kd for each site type.

• We must be aware that our conclusions will depend on

the hypotheses we made during data analysis.

Introduction Method GPC-IR Kinetics Conclusions

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