Department of Chemical Engineering – Faculty of Engineering Modeling and Control of Molecular Weight Distribution in a Liquid-phase Polypropylene Reactor Dr. Mohammad Al-haj Ali Department of Chemical Engineering – Faculty of Engineering King Saud University 07-11-2006

Motivation Producing tailor-made polypropylenes, by using a single reactor

Motivation MWD = g (T,H2) Rp = h (T,H2)

Project phases to develop a predictive kinetic model for propylene polymerization in liquid pool. to improve the understanding of the relationship between polypropylene molecular weight and MWD and hydrogen concentration in liquid propylene as well as model this dependency. to study the optimal grade change of polypropylene. to perform a feasibility study of the optimal broadening of MWD. to build hollow shaft reactor set-up.

Experimental set-up 5.0 L batch reactor. Ziegler-Natta catalyst: Max. operating Pressure = 60 bar. Liquid and gas polymerization reactions. Ziegler-Natta catalyst: MgCl2/TiCl4/phthalate – AlEt3/Silane

Experimental Results Reproducibility Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, hydrogen added = 150 mg

Effect of reactor filling on polymerization kinetics Run T, °C Catalyst, mg Cocatalyst mg Donor, mg H2, mg Yield, kg/gcat. hr Filling degree 1 70 3.78 500 30 12.6 H 2 1040 50 15.6 T 3 150 59.8 4 82.5

Effect of reactor filling on polymerization kinetics Run T, °C Catalyst, mg Cocatalyst, mg Donor, mg H2, mg Yield, kg/gcat. hr Filling degree 3 70 3.78 500 30 150 59.8 H 4 1040 50 82.5 T 5 80 1.54 120 52.5 6 119.8

Kinetics and Molecular weight distribution Experimental recipe: Liquid-pool polymerization in a fully-filled reactor. Different hydrogen amounts. 0.0 mg - 2500 mg Hydrogen Different reaction temperatures. 60 °C - 80 °C

Kinetics: hydrogen and temperature effects T = 70 °C Run H2, mg X*10-3 X=CH2/Cm tr, min Rpo, kg/gcat. hr kd, hr-1 1 0.0 60 16.1 0.34 2 25 0.24 62.5 0.80 3 150 1.44 47 121.6 1.19 4 250 2.47 45 145.1 1.50 5 1000 9.94 139.6 1.93 6 2500 26.7 30 125.9 2.81

Kinetics: hydrogen and temperature effects

Kinetics: hydrogen and temperature effects

Kinetics: modeling

Molecular weight distribution

Process model

Optimal Grade Transition Objective function: Solution methods: Pontryagin’s Minimum Principle Simultaneous method Control Parameterization technique

Optimal Grade Transition Control Parameterization technique

Optimal Grade Transition Pontryagin’s Minimum Principle

Optimal Grade Transition

Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor Objective function:

Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor

Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor

Hollow Shaft Reactor Minimum dead volume. Can be modeled as CSTR. 2.0 L reactor. Max. operating Pressure = 250 bar Max. operating Temperature = 250° C Minimum dead volume. Can be modeled as CSTR.

Hollow Shaft Reactor Monomer supply unit

Catalyst injection unit Hollow Shaft Reactor Catalyst injection unit

Hollow Shaft Reactor The reactor

Hollow Shaft Reactor Experimental results

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Polymerization Mechanism Initiation Propagation

Polymerization Mechanism Propagation

Dormant site theory

Dilatometry Pressure-drop dilatometry

Dilatometry Pressure-drop dilatometry

Pressure-drop dilatometry Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, H2 = 150 mg Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, H2 = 1000 mg Extrapolated H2, mg 0.0 50 250 1000 M1 1.85 1.57 1.62 3.10 M2 2.01 1.99 2.05 4.80 1000 3.2 4

Compensation dilatometry

Molecular weight distribution

Molecular weight distribution

Molecular weight distribution

Design of Control Scheme

Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller = 0

Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller

Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller

Design of Control Scheme

Design of Control Scheme

Design of Control Scheme

Design of Control Scheme

Optimal Broadening of MWD Batch mixing of two polypropylene samples