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 A great deal of my work is just playing with equations and seeing what they give. Paul Dirac (1902-1984)
Acknowledgements Dr Saeid Mehdiabadi Mr Keran Chen Professor Boping Liu State Key Laboratory of Chemical Engineering East China University of Science and Technology Shanghai, China Department of Chemical and Materials Engineering University of Alberta Edmonton, AB, Canada 2/30
Summary 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. Site M n (10 3 ) SCB/10 00C 1 3 29.6 2 12.5 11.3 3 37 6.2 4 112 4.2 5 350 3.4 3/30
Problem Formulation Ziegler-Natta polyolefins have broad molecular weight and chemical composition distributions. It should look like this, but it looks like this, W SCB Log MW W SCB PDI = 2 Log MW PDI > 4 A reasonable explanation is that there are 2 or more site types, each making polymer with the distribution on the left of the slide. 4/30
Multiplicity of Active Site Types Hypothesis: Different polymer populations are made on each site type 100 1 2 1 3 w(logr,fa) 80 60 40 20 1 2 3 3 2 0 0.00 1.38 2.75 4.13 0.88 0.91 0.93 0.95 0.98 log r FA 5/30
Methodology 0.9 5 0.8 4.5 Minimize Σ [(GPC-IR) exp (GPC-IR) pred ] 2 w log MW 0.7 0.6 0.5 0.4 0.3 0.2 4 3.5 3 2.5 2 1.5 1 SCB/1000C 0.1 0.5 0 3 4 5 6 7 0 log MW j 1 2 3 4 5 m 0.0378 0.1800 0.4333 0.2674 0.0815 M n 7 400 23 900 64 900 164 000 507 000 SCB/1000C 7.05 1.98 1.10 0.99 0.99 F 0.0143 0.0040 0.0022 0.0020 0.0020 B 6/30
Polymerization System 250 ml SS autoclave reactor 90 o C polymerization temperature 7 bar ethylene 2, 4, or 6 g 1-hexene 10, 20, 40, 60 min polymerization time H 2 used a chain transfer agent ethylene MFM GCA α-olefin 7/30
Polymerization Kinetics 2.0 g 1-Hexene 10 min 20 min 40 min 60 min 8/30
Deconvolution Assumptions Sites of different types make polymer populations with the same M n and SCB/1000 C. The changes in M n 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. 9/30
GPC-IR Deconvolution 2.0 g 1-Hexene 10/30
Deconvolution Results The fraction of polymer made in high-m n sites increases 2.0 g 1-Hexene Site M n (10 3 ) SCB/ 1000C 1 3 29.6 2 12.5 11.3 3 37 6.2 4 112 4.2 The fraction of polymer made in low-m n sites decreases 5 350 3.4 11/30
Results for Other 1-Hexene Concentrations 4.0 g 1-Hexene 6.0 g 1-Hexene Site M n (10 3 ) SCB/ 1000C Site M n (10 3 ) SCB/ 1000C 1 3 35.1 2 12.0 13.8 3 35 9.5 4 107 7.6 5 318 6.2 1 3.5 39.6 2 13 17.5 3 36 13.7 4 101 10.9 5 290 10.4 12/30
1-Hexene Incorporation per Site Type 13/30
Investigating Site Type Kinetics Description Chemical Equation Rate Constant Activation C + Al P 0 k a Propagation P r + M Pr +1 k p 1 st Order Deactivation P r Cd + Dr k d 14/30
Effect of k p 3.5 3 Monomer Uptake (mol/s) 2.5 2 1.5 1 0.5 0 0 500 1000 1500 2000 2500 3000 3500 4000 Polymerization Time (s) 15/30
Effect of k d 1.8 1.6 Low k d 1.4 Monomer Uptake (mol/s) 1.2 1 0.8 0.6 0.4 0.2 High k d 0 0 500 1000 1500 2000 2500 3000 3500 4000 Polymerization Time (s) 16/30
Effect of K A 1.8 1.6 High K A Medium K A 1.4 Monomer Uptake (mol/s) 1.2 1 0.8 0.6 0.4 0.2 0 0 500 1000 1500 2000 2500 3000 3500 4000 Polymerization Time (s) 17/30
Polymer Yield in a Semi-Batch Reactor 7000 6000 Y whole = Σ Y i Total Monomer Consumption (moles) 5000 4000 3000 2000 k d = High 1.5 10k -3 s -1 d 1000 0 0 500 1000 1500 2000 2500 3000 3500 4000 Polymerization Time (s) 18/30
Partitioning the Polymer Among Active Sites t = 20 min Whole polymer 19/30
Ethylene Homopolymerization Yield per Site Type 4 3.5 3 Mass (g) 2.5 2 1.5 1 Site1 Exp. Site2 Exp. Site3 Exp. Site4 Exp. Site5 Exp. 0.5 0 0 20 40 60 80 100 Time (min) 20/30
Ethylene Homopolymerization Site Kinetics 21/30
Copolymer Yield per Site Type: 2.0 g 1-Hexene 22/30
Copolymerization Site Kinetics: 2.0 g 1-Hexene 23/30
Copolymer Yield per Site Type 4.0 g 1-Hexene 6.0 g 1-Hexene 24/30
Copolymerization Site Kinetics 4.0 g 1-Hexene 6.0 g 1-Hexene 25/30
1-Hexene increases K a Ka (min -1 ) 8 6 4 2 Site 1 Site 2 Site 3 Site 4 Site 5 0 2.0g 1-C6 4.0g 1-C6 6.0g 1-C6 Homopolymer 26/30
1-Hexene increases k p of low M n sites but decreases k p of high M n sites kp (min -1 ) 0.10 0.08 0.06 0.04 0.02 Site 1 Site 2 Site 3 Site 4 Site 5 0.00 2.0g 1-C6 4.0g 1-C6 6.0g 1-C6 Homopolymer 27/30
1-Hexene increases k d kd (min -1 ) 0.5 0.4 0.3 0.2 Site 1 Site 2 Site 3 Site 4 Site 5 0.1 0.0 2.0g 1-C6 4.0g 1-C6 6.0g 1-C6 Homopolymer 28/30
What is this information good for? 29/30
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 M n and SCB for different site types. Estimate apparent K a, k p and k d for each site type. We must be aware that our conclusions will depend on the hypotheses we made during data analysis. 30/30
31/30