friday 3/5/20021 metallocene catalyzed liquid-pool polymerization in a continuous hsr dpi # 114...

$: Friday 3/5/20021 Metallocene Catalyzed Liquid-Pool Polymerization in a Continuous HSR DPI # 114 Mohammad Al-haj Ali DCP\IPP Groups Chemical Engineering$
Friday 3/5/2002 1

Metallocene Catalyzed Liquid-Pool Metallocene Catalyzed Liquid-Pool Polymerization in a Continuous HSRPolymerization in a Continuous HSR

DPI # 114DPI # 114

Mohammad Al-haj AliMohammad Al-haj Ali

DCP\IPP Groups

Chemical Engineering Department

Industrial Polymerization Processes

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Quality Assurance of a Polypropylene Reactor Quality Assurance of a Polypropylene Reactor During Continuous Production and Product During Continuous Production and Product

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Presentation Outline:Presentation Outline: The mechanism of polypropylene polymerization.

1) The catalyst system.

2) Polymerization steps.

Development of expected MWD function.

1) Instantaneous MWD.

2) Derivation of instantaneous MWD function.

Factors affecting MWD.

1) Catalytic System.

2) Polymerization Parameters.


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Grade transition strategies.

1) Factors affecting grade transition policies.

2) Grade transition approaches.

3) Optimization problem formulation.

4) Objective function.

5) The method of solution.

What is next.

Friday 3/5/2002 4

Catalyst System:Catalyst System:The catalyst system used in this work is: rac-Me2Si[Ind]2ZrCl2/MAO/TIBA

1- Metallocene Catalyst:

rac-Me2Si[Ind]2ZrCl2

Me2Si ZrCl 2


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Catalyst System:Catalyst System:

2- Cocatalysts:

a- MAO

b- TIBAAl

R C

H

R

R

C

C

C

HH

H

HH

H

H

H

R=

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The Mechanism of Propylene Polymerization:The Mechanism of Propylene Polymerization:

1- Initiation

MCl2

Me

AlO+ MMe2

Me

AlO

Me

AlO

-

MMe2

Me

M

+

+ +


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2- Propagation:

Me

M+

RMe

RM+

R +

M

nR

M+

R


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2- Propagation:


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2- Propagation:


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3- Termination:

a-Transfer with Hydrogen:

H2

+

M

nR+

+

M H

nR+

b- Transfer with Monomer:

+

+

M

nR+

nR

+

M Me


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Development of Expected MWD Function:Development of Expected MWD Function:Instantaneous MWD:

The method of instantaneous MWD relies on the big difference in time scale for

the polymerization reactor and the polymers life time.

The instantaneous MWD of polyolefins with single-type catalyst:

)jqexp(jqy 2dj

Schulz-Flory distribution function assumptions:

1- All chain propagating species have the same kinetic parameters.

2- The probability of chain termination does not depend on chain length.

3- polymerization reactions are carried out at constant monomer concentrations.


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Development of Expected MWD Function:Development of Expected MWD Function:

Derivation of instantaneous MWD function:

1- Propagation reaction

MPkrPMP jpp1jj

2- Transfer reactionsa- transfer with hydrogen:

j2HtHt*

j2j P]H[krCMHP22

b- transfer with monomer

jMtMt*

jj MPkrCMMP 3- Deactivation

jddjj PkrDMP


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Derivation of instantaneous MWD function

The production rate of active and dead polymers:

dMt2Ht

jdMt2HtMj

jdjMtj2Htj1jppj

N

1iik,ik

kMk]H[kT

P]kMk]H[k[R

PkMPkP]H[k)PP(MkR

rR

2

2

2


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By using QSSA for the active polymer

1qp

pPP

MkT

Mkp

MPkP]MkT[

1jj

p

p

1jpjp

MkkMk]H[k

kMk]H[kq

pdMt2Ht

dMt2Ht

2

2


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)jqexp(TqPR

P)jqexp(qP

pq

PP

P)jqexp(pP

PpP

tMj

tj

1t

11

j

11j

j


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21n

1j

n

1j1j

1jt

tdj

1jMjM

MjMdj

qq!ndj)jqexp(j

dj)jqexp(j)jqexp(j

)jqexp(TjqP

)jqexp(TjqPy

RjM

RjMy


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)jqexp(jqy 2dj

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Factors Affecting MWD:Factors Affecting MWD:

1- Catalytic System:

a- Catalyst type.

b- Cocatalyst.

c- Catalyst / Cocatalyst

2- Polymerization Parameters:

a- Hydrogen concentration.

b- Reaction temperature.

c- Reaction time.


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1- Hydrogen concentration

Low H2

High H2


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1- Reaction temperature

Low T

High T


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1- Reaction time

No effect is found for time in MWD:

1- Naofumi & Mizunuma, 1998

2- Chien & Wang, 1990.


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Grade transition strategies:Grade transition strategies:

Desirable grade transition policy, takes the following points into account:

Time.

Plant safety.

Polymer instantaneous properties.


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D ynamic S imulations U isng D ynamicKinetic & P rocess M odel

u s in g co rro la tio n m o d els fo r p o lym er p ro p erties u s in g m o re co m p licated k in etic m o d els

S olving D ynamic M odel-B ased O ptimizationP rob lem

G rade T ransition A pproach es

Requires an extensive trial & error

Can not represent PDI Consider all polymer properties


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Optimization problem formulation

uplow

uplow

oo

fo)t(u

x)t(xx

u)t(uu

x)t(x

)]t(x),t(u[fdt

dx

0)]t(x),t(u[c.t.s

]t,t[t)]t(x),t(u[Fmin


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dt))PDITPDI

PDIT)t(PDI(*t*w)

TMWMW

TMW)t(MW(*t*w(F

f

o

t

t

2

0t2

2

n0t,n

nn1


Objective function


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The method of solution

s

1jijiji )t(a)t(U

Control Vector ParameterizationControl Vector Parameterization

time

ij


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0)a(h

0)a(g.t.s

)a(Fmin

ij

ij

ija ij

Applying U(t) in the original optimization problemgives:


The method of solution


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What is Next:What is Next:

1-1- Formulation of the second optimal strategy for grade transition of Formulation of the second optimal strategy for grade transition of

Polyolefins using Polyolefins using Barrier ApproachBarrier Approach . .

2- 2- Experimental model validation of the batch mode of the HSR model, Experimental model validation of the batch mode of the HSR model,

and producing bimodal PP theoretically and experimentally.and producing bimodal PP theoretically and experimentally.


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http://www.animfactory.com/animations/science/chemistry_physics/caffeine_molecule_md_wht.gif



Friday 3/5/2002 28



)jqexp(p)qexp(p

q)p(Ln)p(Ln1p

q1p)1(p1q

P)jqexp(pPjPpP

j

11

11j

j

friday 3/5/20021 metallocene catalyzed liquid-pool polymerization in a continuous hsr dpi # 114...

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