Dynamics & Control Processes Modeling and Control of Molecular Weight Distribution in a Liquid-phase Polypropylene Reactor Mohammad Al-haj Ali, Ben Betlem, Günter Weickert & Brian Roffel Research groups Dynamics & Control Processes -Industrial Polymerization Processes - Faculty of Science and technology University of Twente 11/11/2005

Dynamics & Control Processes 2 Project goals Producing tailor-made polypropylenes, including bimodal grades, by using a single reactor

Dynamics & Control Processes 3  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 develop a simple and efficient nonlinear model-based control scheme.  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.  to develop a predictive kinetic model for propylene polymerization in liquid pool.

Dynamics & Control Processes 4 Experimental set-up 5.0 L batch reactor. Max. operating Pressure = 60 bar. Liquid and gas polymerization reactions. Ziegler-Natta catalyst: MgCl 2 /TiCl 4 /phthalate – AlEt 3 /Silane 6 wt % TiCl 4

Dynamics & Control Processes 5 Experimental Results Reproducibility Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, hydrogen added = 150 mg

Dynamics & Control Processes 6 Effect of reactor filling on polymerization kinetics RunT, °C Catalyst, mg Cocatalyst mg Donor, mg H 2, mg Yield, kg/g cat. hr Filling degree H T H T

Dynamics & Control Processes 7 RunT, °C Catalyst, mg Cocatalyst, mg Donor, mg H 2, mg Yield, kg/g cat. hr Filling degree H T T H Effect of reactor filling on polymerization kinetics

Dynamics & Control Processes 8 Kinetics and Molecular weight distribution Experimental recipe: fully-filled  Liquid-pool polymerization in a fully-filled reactor.  Different hydrogen amounts. 0.0 mg mg Hydrogen  Different reaction temperatures. 60 °C - 80 °C

Dynamics & Control Processes 9 RunH 2, mgX*10 -3 t r, minR po, kg/g cat. hrk d, hr Kinetics: hydrogen and temperature effects T = 70 °C

Dynamics & Control Processes 10 Kinetics: hydrogen and temperature effects

Dynamics & Control Processes 11 Kinetics: modeling

Dynamics & Control Processes 12 Molecular weight distribution

Dynamics & Control Processes 13 Process model

Dynamics & Control Processes 14 Design of Control Scheme

Dynamics & Control Processes 15 Design of ControlScheme Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller = 0

Dynamics & Control Processes 16 Design of ControlScheme Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller

Dynamics & Control Processes 17 Design of ControlScheme Design of Control Scheme Nonlinear Multivariable Controller: Generic model control (GMC)-based controller

Dynamics & Control Processes 18 Design of ControlScheme Design of Control Scheme

Dynamics & Control Processes 19 Design of ControlScheme Design of Control Scheme

Dynamics & Control Processes 20 Design of ControlScheme Design of Control Scheme

Dynamics & Control Processes 21 Optimal Grade Transition Objective function: Solution methods: 1.Pontryagin’s Minimum Principle 2.Simultaneous method 3.Control Parameterization technique

Dynamics & Control Processes 22 Optimal Grade Transition Control Parameterization technique

Dynamics & Control Processes 23 Optimal Grade Transition Pontryagin’s Minimum Principle

Dynamics & Control Processes 24 Optimal Grade Transition

Dynamics & Control Processes 25 Optimal Broadening of MWD Batch mixing of two polypropylene samples

Dynamics & Control Processes 26 Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor Objective function:

Dynamics & Control Processes 27 Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor

Dynamics & Control Processes 28 Optimal Broadening of MWD Broadened polypropylene produced in the continuous reactor

Dynamics & Control Processes 29 Hollow Shaft Reactor  2.0 L reactor. Max. operating Pressure = 250 bar Max. operating Temperature = 250° C  Minimum dead volume.  Can be modeled as CSTR.

Dynamics & Control Processes 30 Monomer supply unit Hollow Shaft Reactor

Dynamics & Control Processes 31 Hollow Shaft Reactor Catalyst injection unit

Dynamics & Control Processes 32 The reactor Hollow Shaft Reactor

Dynamics & Control Processes 33 Experimental results Hollow Shaft Reactor

Dynamics & Control Processes 34

Dynamics & Control Processes 35 Pressure-drop dilatometry H 2, mg M1M M2M Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, H 2 = 150 mg Experimental conditions: T = 70 °C, mass of catalyst = 3.78 mg, mass of cocatalyst = 1000 mg, H 2 = 1000 mg Extrapolated