Transcript POLYRED

Nigerian Academy of Engineering
June 2013
Some Engineering Opportunities and
Challenges when Producing Polymer
Materials from Oil and Gas
by
W. Harmon Ray
University of Wisconsin - Madison
Dept. of Chemical Engineering
W. Harmon Ray
Vilas Research Professor Emeritus
US National Academy of Engineering (Class of 1991)
OUTLINE
INTRODUCTION
FUNDAMENTALS
PROCESS DESIGN AND OPERATIONS
» General Considerations
» Production in Nigeria
LOW VOLUME PRODUCTION
CONCLUSIONS
Background; Polymer Production Basics (Worldwide & Nigeria)
INTRODUCTION
Polymers in our Automobiles
Body Exterior
Impact PP
Body Interior
Coatings
Electrical/Electronics Fuel Tanks
Polyacetal
HDPE
Powertrain
Safety Glass
Polyvinylbutyral
Polymers in our Clothing
• Dacron Polyester (PET)
• Nylon 66 (HMD/AA)
(Polyethylene Terephthalate) (Hexamethylene diamine/Adipic acid)
• Lycra Spandex
• Polypropylene (PP)
• Gore-Tex (Polytetrafluoroethylene)
Polymers in Food Packaging
Polyethylene & ethylene copolymers
(LDPE, LLDPE, EVA)
Polystyrene (PS)
Polyethylene Terephthalate (PET) &
High-density Polyethylene (HDPE)
Polymers in Everyday Life
Nylon/Polyesters
Nylon/ABS
PolyTFE
Polyformaldehyde
ABS/HIPS/PP
PS/PC
HDPE/PP/PVC
Copolymers of Styrene, Methacrylates, Acrylates, Epoxies.
Solvent borne, Latex emulsion, Powder coat.
ABS/HIPS/PC
(Particle size distribution and particle morphology are critical)
Polymers in Protective Apparel
No melting point;
Nomex
stable beyond 350 C
(Poly-metaphenylene
isophthalamide)
Liquid Crystal
Polymers
Kevlar (aromatic nylon)
(Poly-paraphenylene
terephthalamide)
Worldwide Scale of Polymers: ~ 300 Million tons/yr
Some Polymer Production in Nigeria
High Density and Linear Low Density Polyethylene:
• Sclairtech (Nova Chem) HDPE/LLPDE (1-butene)
250,000 tons/yr (Port Harcourt)
• Methanol to Olefins Project underway to add
400,000 tons/yr of HDPE (Port Harcourt)
Polypropylene:
• Spheripol (Basell) PP homopolymer/High Impact PP
95,000 tons/yr (Port Harcourt)
• Older PP Plant 35,000 tons/yr (Warri)
• Methanol to Olefins Project underway to add
400,000 tons/yr of PP (Port Harcourt)
Bottle Grade Polyethylene Terephthalate (PET):
• Buehler Two Stage Solid State Process
75,000 tons/yr (Port Harcourt)
_________________________
Business Monitor International (Jan 2013)
Special Chem Industry News (July 2012)
Annual Cost of Polymer Imports to Nigeria in 2010
High Density Polyethylene (HDPE)*:
$85 Million
Low Density Polyethylenes (LDPE/LLDPE)*: $376 Million
Other Polyethylene*:
$38 Million
Polypropylene (PP, all types)*:
Polyethylene Terephthalate (PET)*:
Polyvinyl Chloride (PVC)*:
Polystyrene (PS, EPS)*:
$150 Million
$45 Million
$125 Million
$13 Million
All Imports of Synthetic Polymers ~ $1 Billion/yr
_________________________
*United Nations Commodity Trade Statistics
Separation
Cracking
Purification
Purification
Catalytic Conversion
Methanol to Olefins
Dr.K.R.Krishnamurthy (2009)
Ethylene and Propylene Production
Project Currently underway in Nigeria
Dr.K.R.Krishnamurthy (2009)
Zeolite Catalysts for Olefins from Methanol
For Ethylene
For High Propylene yield
Polymerization Kinetics and Mechanisms
FUNDAMENTALS
Polymerization Kinetics
Fundamental Kinetic Mechanisms
Polycondensation
Addition Polymerization
Living
Catalyzed
Uncatalyzed
Chain Terminated
Ionic/Group Transfer
Ionic
Living Free Radical
Free Radical
Trans Metal Catalysis
Trans Metal Catal
Addition Polymerization Kinetics
R• + M
H
P1•
H
C
C
Y
Pn•+ A
kf / k r
j
•
Pn+1
H
kpij
C
Propagation
Pni •+ Mj
H
Dn +C
H
Transfer to dormant state
H
C
C
Y
Termination (incl. chain transfer)
ktc
Pn + Pm
Dn+m / Dn+Dm
• •
Pn• + T
k tf
X
H
Dn +
P1•
• X & Y are functional groups
with specific properties
• Monomer addition at each step is
statistical based on kpij and
M1/M2 ratio
• The chain length is also
statistical depending on
relative rates of initiation,
propagation, and termination
or
CH2
CH
X
CH2
•
CH
Y
H
ßR •
ki
C
I
kd
H
Initiation
Molecular Weight Distributions
Number average = Mn
Viscosity average
Weight average= Mw
Polymer mass
For “narrow”
distribution of
Mw/Mn=2,
σ= Mn !!
Polydispersity:
Mw/Mn=2 - 20
for commodities;
as low as 1.1 for
some specialities
Chain length
Molecular weight
MWD’s are usually very Broad!
Distributions with Multiple Monomers
Composition
Distribution
(% of each
Monomer in each
Polymer chain)
Random (most common)
Alternating
Block
Graft
Syndiotactic, Isotactic, or Atactic addition
is equivalent to having different comonomers!
Sequence Length
Distributions
(% 1’s, 2’s, 3’s, ...
in a row for each
monomer):
• controls crystal
structure and
total crystallinity
• controls chain
stiffness
• related to material
strength, elasticity,
etc.
• controls side chain
functionality for
surface properties,
cross-linking, etc.
Key to control of Polyethylene properties --> Branching
Ethylene Unbranched Polyethylene (rare)
Short-chain Branched PE
Short and Long-chain Branched PE
LDPE
HDPE
&
LLDPE
• For high pressure LDPE, short and long-chain branches are formed naturally
and are controlled by reaction conditions (temperature and pressure).
• For HDPE and LLDPE, short-chain branches are formed by copolymerization
with α-olefins such as butene, hexene, or octene. No long-chain branching
occurs except with special catalysts allowing polymer chains to be inserted.
Branching Distributions
Examples:
Distributions:
• Short chains
per 1000 C
• Branch sequence
- long runs vs
short runs
- concentrated in
long chains vs
short chains
• Long chains
per 1000 C
• Morphology of
Long chains:
- generations
- gel formation
Linear molecule
ca. 4 to 10 short side chains
per 1000 C - atoms
High-Density Polyethylene
HDPE
Very High Pressure
Low-Density Polyethylene
LDPE
Both short and long-chain branching
Linear Low-Density
Polyethylene - LLDPE
Linear molecule
ca. 10 to 35 short side chains
per 1000 C – atoms
With Special
Catalysts
Short Chain Branching influences degree of
Crystallinity in Semi-Crystalline Polymers
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
Why be interested in crystallinity effects?
– Monomer S swells amorphous polymer, not crystals
– Crystallites act like “tie” segments in polymer networks
– Polymer properties depend on crystal and tie molecule size distributions
Effect of Long-Chain Branches on Polymer Viscosity
Branched
Viscosity (Poise)
106
Linear
104
102
10-2
100
102
104
Shear Rate γ (Sec-1)
Alteration of viscosity-shear rate
behavior due to the presence of
long branches.
General Considerations; Polymer Production in Nigeria
PROCESS DESIGN &
OPERATIONS
Making polymers at low cost and in quantity –
polymerization process issues
• Batch, semi-batch or continuous process?
• In solution/melt or multiphase suspension, emulsion,
or dispersion?
• Can we scale-up (heat removal, mixing, mass transfer)
to produce the polymer we made in the lab?
• Can we control the process in order to obtain
reproducible quality?
• Will the costs of production be low enough?
• More than 85% of all polymer production is by
Exothermic Addition Polymerization! Can we control the
reactor temperature and prevent process runaway?
• Will the process be safe and friendly to
the environment?
Thermal Parameters for Addition Polymerization Dynamics
Monomer
Ethylene
Propylene
1-Butene
Isobutylene
1,3-Butadiene
Isoprene
Styrene
alpha- Methylstyrene
Vinyl chloride
Vinylidene chloride
Tetrafluoroethylene
Acrylic Acid
Acrylonitrile
Maleic Anhydride
Vinyl acetate
Methyl acrylate
Methyl methacrylate
Methacrylic acid
Butyl acrylate
Heat of
Poly
Kcal /Mol
25.9
20.1
19.9
11.5
17.4
17.9
17.4
8.4
17.2
17.4
38.9
16.0
18.3
14.1
21.0
18.6
13.4
18.6
18.6
Pure Mon
Conc
mol/lit
14.2
12.3
10.6
10.6
11.5
10.0
8.7
7.7
14.6
12.5
15.2
14.6
15.2
15.3
10.8
11.1
9.4
11.8
7.0
A Major Design and Control Problem!
Adiab.
Temp Rise
C
1609
850
647
395
589
496
398
173
803
655
1447
464
774
491
519
452
260
488
310
DTad =
(-DH p )Mf
rC p
Heat Removal
Duty
Kcal /Kg
922
476
355
204
322
263
167
71
275
180
390
222
344
144
244
216
134
216
145
Polymerization Reactors
Features
• Single phase Solution (liquid or supercritical fluid)
• Multiphase with particle in liquid or gas dispersion
• Heat removal by wall cooling, recycle cooling or
evaporative cooling
To recycle
Product
Catalyst
Monomer
Hydrogen
C
W
TC
Polymer
Some Polymer Production in Nigeria
High Density and Linear Low Density Polyethylene:
• Sclairtech (Nova Chem) HDPE/LLPDE (1-butene)
250,000 tons/yr (Port Harcourt)
• Methanol to Olefins Project underway to add
400,000 tons/yr of HDPE (Port Harcourt)
Polypropylene:
• Spheripol (Basell) PP homopolymer/High Impact PP
95,000 tons/yr (Port Harcourt)
• Older PP Plant 35,000 tons/yr (Warri)
• Methanol to Olefins Project underway to add
400,000 tons/yr of PP (Port Harcourt)
Bottle Grade Polyethylene Terephthalate (PET):
• Buehler Two Stage Solid State Process
75,000 tons/yr (Port Harcourt)
_________________________
Business Monitor International (Jan 2013)
Special Chem Industry News (July 2012)
Dupont/Nova Sclairtech HDPE/LLDPE Solution Process
(Polyethylene Process used at Port Harcourt Plant)
Flexible process: products
range from clear film (ρ=0.91)
to bottles (ρ=0.96)
(1-Butene
or
1-Octene)
(Transition Metal)
(Cyclohexane)
Reactor
Adiabatic
to 300 C,
140 bar.
Res time
~ 30 min
1 or 2
Reactors
Meyers, R.A. “Handbook of Petrochemical Production Processes”
Soares, J.B.P. & T.F.L. McKenna “Polyolefin Reaction Engineering”
Dupont/Nova Sclairtech HDPE/LLDPE Solution Process
Some Possible Products
Mol Wt (chain length)->
VLDPE
LLDPE
HDPE
(Crystallinity)
OTHER POLYETHYLENE PROCESSES
LDPE AUTOCLAVE REACTOR
Monomer
•
Adiabatic reactor
•
190 to 270 °C
•
2000 to 3000 bar (supercritical fluid)
•
10 to 20 % conversion
•
DuPont type (L/D = 2 - 4)
•
10 to 120 sec residence time
•
Initiator
TC
T
Reactor temperature is controlled
by the amount of initiator in the feed
Products
POLYMERIZATION vs DECOMPOSITION
Reaction Rate, mol/lt-sec
10+06
10+04
Decomposition vs Polymerization
• Heat of Rxn 40% larger
• Activation Energy 900% larger
• Runaway starts at T ~ 300C
with fast reaction w/o initiator
10+02
1
Polymerization
10-02
10-04
10-06
10-08
110
190
270
350
430
Temperature, °C
510
CONTINUATION AND STABILITY DIAGRAM
EFFECT OF RESIDENCE TIME ON TEMPERATURE - PERFECT MIXING MODEL
Temperature, °C
3000
STABLE
It would be practically impossible
to operate a reactor with this small
operating window, and yet these
reactors actually operate! ??
1000
UNSTABLE
300
STABLE
UNSTABLE
STABLE
100
0
100
200
300
Residence Time, sec
400
500
Evidence of Imperfect Feed Mixing
Simple compartment
models
are adequate to explain curves
of initiator consumption in
LDPE
autoclave
reactors
(Marini and Georgakis, 1984)
van der Molen et al. (1982)
Initiator Consumption, g/kg polymer
Experiments show that
changing feed location, velocity,
or agitator design will strongly
affect initiator efficiency!
0.10
0.09
0.08
IMPERFECT
MIXING
Imperfect
Mixing
0.07
0.06
0.05
200
Perfect
Mixing
220
240
260
280
300
Temperature, °C
Carlos Villa
MIXING INTENSITY = RECYCLE RATIO
EFFECT OF RESIDENCE TIME ON TEMPERATURE - IMPERFECT MIXING MODEL
300
100
500
50
R = 10
Temperature, °C
250
200
QR = RQO
QF
Good reactor design involves
understanding and controlling
the degree of imperfect mixing
I
QR
III
II
QO
150
100
50
150
250
350
Residence Time, sec
450
Computational Fluid Mechanics (CFD) combined with
Compartment Models allow detailed information
decomp active (shaded region)
Exit Temperature (K)
580
A
540
B
Contours of Radical Conc. x 107 mol/L
Temp. rise: 0.65 K/ppm
C
55.4
out
27.6
in
500
300 ppm TBPOA feed
460
420
0.00
0
Ncompart
CFD results
Stable
A: 1
Unstable B: 3
Limit point C: 100
400
200
600
Initiator Feed Fraction (ppm)
Temp. rise: 4.67 K/ppm
3.41
out
1.71
in
0.00
30 ppm TBPOA feed
• Decomp active at temperatures above about 560 K;
modeled using approach of Zhang et al. (1996)
Tfeed = 360 K (87 °C); 200 rpm stirring rate; t = 32 sec
Ethylene & Molten Polymer
Vented to the Neighborhood 
Decomp
Safety Equipment
Title
Emergency
Relief Valves
LDPE
Reactor
Emergency
Relief Valves
Consequences of LDPE Decomp
• Burnt and molten polymer rains down on the
surrounding area, leading to possible difficulties
inside the plant, but also coats the employees cars
in the parking lot, and dumps material on neighbors
• A large ethylene cloud on a windless day could be
ignited by flames from other equipment inside the
plant or on neighboring properties. In this case the
explosion can damage other equipment leading
to leaks that can ignite and cause a fire or the
release of toxic chemicals.
• If the ethylene cloud moves safely away from the
plant to an open area, it can be ignited with a flare.
Heterogeneous Catalytic Processes
for Polyolefins
Fluidized Bed Reactors
(Union Carbide (now Univation),
BP, and in-house technology)
- the most widely used
process for making catalytic
polyethylene products
(high density (HDPE) and
linear low density (LLDPE)
Polyethylene)
Gas Phase Fluidized Bed Polyethylene Process
Microscale
Pkn,i*
+
Mj
kpij
Pkn+1,j* (Growth of a polymer chain)
Mesoscale
C2H4
Catalyst
Macroscale
Inlet Stream
Catalyst
Cocatalyst
Poison
Hydrogen
The particle size distribution
(PSD) depends on:
• the PSD of the original
catalyst support,
• the catalyst activity kinetics,
Polymer Particle
• the residence time distribution
Purge
of the reactor
The particle is the micro-reactor
Cooler inside the fluidized bed which is
the macro-environment.
Emulsion Phase
Bubble Phase
Product
Monomers
Heterogeneous Catalytic
Olefin Polymerization
Breakup of catalyst and
growth of polymer particle
(TEM showing catalyst
fragments inside
polymer microparticles)
Metal catalyst (TiCl4, Cr, Zr, etc)
supported on SiO2
12 g/g-cat
108 g/g-cat
880 g/g-cat
30 nm
Chakraborti, S.,A.K. Datye, & N. J. Long,
J. Catalysis, 108, p 444 (1987)
Kakugo, M., H. Sadatoshi, & J. Sakai,
Catalytic Olefin Polymerization, T. Keii &
K. Soga,Editors; Elsevier (1990), pp 345-354
Multistage Fluidized Bed Polyethylene Process
Comonomer
Comonomer
Particle Growth Behavior
Surface
area
3.5
3
9
dp/dc
2.5
2
4
1.5
1
1
0.5
0
0
2
4
Yield
(g pol/g cat)
6
8
10
Fluidized Bed Particle Temperatures
3
Temperature difference DT [C]
10
Melted
Quasi-steady state
particle temperature,
fully activated
2
10
Polymer melting
1
10
Direct injection,
fast activation
Dynamic particle
temperature
15C temp rise
Prepolymerization
or slow activation
dpmin
0
10
50
dcat
100
200
300
400
500
800
1000
Particle diameter dP [mm]
Sticky particles adhere to the reactor wall and attract more particles.
After some buildup, the polymer sheets on the wall fall down and
disrupt the fluidization, causing the entire polymer bed to melt.
Polymer Product Images
Particles overheating and
sticking to reactor walls or
agglomerating:
chunks
observed
Good operation: freeflowing powder; no chunks
observed
Consequences of Particle Melting
• Overheated polymer particles melt and stick to the reactor
walls forming sheets of solidified PE.
• Eventually these sheets fall down and block the gas
circulation so that remaining particles are no longer
fluidized, and melt together.
• The inside of the reactor becomes one large
mass of solidified Polyethylene!
• There is no reactor runaway danger because the reaction
essentially stops when the polymer mass limits monomer
diffusion to the encapsulated catalyst.
• The process must be shut down for weeks to allow the
reactor to be cleaned out; this involves small charges of
dynamite and the use of chain saws to break apart and
then remove many tons of polyethylene from the reactor.
Liquid Slurry Polyethylene Reactors
Hexene, Qm2
Ethylene
Qm1
Isobutane Solvent
QS
Catalyst (Cocat.)
Qcat, (Qcoc)
CW
Inputs
CW
CW
CW
CW
Outputs
CW
F
CW
Stirred Tank
Loop RTD & CSTR RTD at high recirculation rates; only need
CSTR model to represent both types of reactors
Heat transfer area per unit volume (A/V) is larger in loops.
Heat transfer coefficient (h) is also larger in loops (but varies
with recirculation rate)
Tanks can remove less heat per unit volume and thus have
lower productivity per unit volume
Formosa Plastics 550 Million lb/yr
ChevronPhillips HDPE/LLDPE loop
reactors, Point Comfort, TX
(photo from Formosa Plastics)
180
1
PE melting pt.
Liquid boiling pt.
140
120
100
B
80
Hopf points
Limit Points
Stable States
Unstable States
A
60
40
0
2000
4000
6000
8000
Residence time of catalyst (sec)
h/h0*(A/V) = 65 cm2/L, fcatfeed = 3x10-5
10000
A
B
0.8
0.6
0.4
0.2
0
0
2000
4000
6000
8000
Residence time of catalyst (sec)
10000
h/h0*(A/V) = 65 cm2/L, fcatfeed = 3x10-5
• Unstable steady states can exist for a wide
range of residence times!
• Reactor design and operation procedures must
avoid these unstable operating conditions!
Rp, kg poly/(g cat-hr)
160
Ethylene Conversion
Reactor Temperature, °C
Titanium Catalyst: Effect of Residence
Time on Loop Reactor Stability
12
10
8
6
4
2
0
0
Half-life = 30 min
2000
4000
time, sec
6000
Reactor Temperature, °C
Titanium Catalyst: Example of Sustained
Oscillations Possible in the Loop Reactor
200
180
160
140
120
100
80
60
40
20
PE Melting Pt.
Liquid boiling pt.
New Steady-State
0
9000
18000
time, sec
27000
36000
fcatfeed = 3.0x10-5, h/h0*(A/V) = 65 cm2/L
Disturbance: change from t=7200 sec to t=3600 sec after 5000 sec.
Large oscillations in temperature cause both solvent boiling
point and polymer melting point to be exceeded.
Period of oscillation is ~2500 sec (~40 min).
Consequences of Oscillatory Operation
• Melting polymer particles would coagulate and create
large chunks of polymer which could plug the tubes and
foul the impeller – leading to a stagnant mass. In the
melted particles and chunks, the catalyst would no longer
have access to diffusing monomer so the polymerization
would stop.
• Removing the mass of polymer and cleaning the reactor
would require a major shutdown and cleanup effort.
Some Polymer Production in Nigeria
High Density and Linear Low Density Polyethylene:
• Sclairtech (Nova Chem) HDPE/LLPDE (1-butene)
250,000 tons/yr (Port Harcourt)
• Methanol to Olefins Project underway to add
400,000 tons/yr of HDPE (Port Harcourt)
Polypropylene:
• Spheripol (Basell) PP Homopolymer/High Impact PP
95,000 tons/yr (Port Harcourt)
• Older PP Plant 35,000 tons/yr (Warri)
• Methanol to Olefins Project underway to add
400,000 tons/yr of PP (Port Harcourt)
Bottle Grade Polyethylene Terephthalate (PET):
• Buehler Two Stage Solid State Process
75,000 tons/yr (Port Harcourt)
_________________________
Business Monitor International (Jan 2013)
Special Chem Industry News (July 2012)
Polypropylene
Isotactic PP
(crystalline)
*
*
*
*
*
*
*
*
*
*
*
*
Syndiotactic PP
(crystalline)
*
*
*
*
Atactic PP: random methyl groups and no crystallinity
• Commercial homopolymer Polypropylene is mostly isotactic with
some small sections of the chain atactic (from insertion errors).
The material density lies between that of LDPE and HDPE.
• Other Polypropylene products can be copolymers with ethylene
to produce lower density (less rigid) materials or even an ethylene propylene amorphous rubber material.
• “Impact Polypropylene” is a well-mixed physical mixture of isotactic
polypropylene and ethylene-propylene rubber.
Thermal Parameters for Addition Polymerization Dynamics
Monomer
Ethylene
Propylene
1-Butene
Isobutylene
1,3-Butadiene
Isoprene
Styrene
alpha- Methylstyrene
Vinyl chloride
Vinylidene chloride
Tetrafluoroethylene
Acrylic Acid
Acrylonitrile
Maleic Anhydride
Vinyl acetate
Methyl acrylate
Methyl methacrylate
Methacrylic acid
Butyl acrylate
Heat of
Poly
Kcal /Mol
25.9
20.1
19.9
11.5
17.4
17.9
17.4
8.4
17.2
17.4
38.9
16.0
18.3
14.1
21.0
18.6
13.4
18.6
18.6
Pure Mon
Conc
mol/lit
14.2
12.3
10.6
10.6
11.5
10.0
8.7
7.7
14.6
12.5
15.2
14.6
15.2
15.3
10.8
11.1
9.4
11.8
7.0
A Major Design and Control Problem!
Adiab.
Temp Rise
C
1609
850
647
395
589
496
398
173
803
655
1447
464
774
491
519
452
260
488
310
DTad =
(-DH p )Mf
rC p
Heat Removal
Duty
Kcal /Kg
922
476
355
204
322
263
167
71
275
180
390
222
344
144
244
216
134
216
145
Basell Spheripol Loop-FBR Polypropylene/Impact PP Process
The Port Harcourt Process
PURGE
Hydrogen
Ethylene
CW
Propylene
Catalyst
(TiCl4 - MgCl2)
Cocatalyst
STEAM
N2
( Al - Alkyl )
Prepolymerization
Finishing
Fluidized Bed Reactor
Loop Reactors (liquid propylene)
70 o C , 35 - 40 atm
E/P Rubber produced in PP particles
80 oC , 20 atm
Liquid Propylene Slurry
Loop Reactor - the most
widely used process for
making Polypropylene
OTHER POLYPROPYLENE PROCESSES
Some Polypropylene Processes
Features
FBR
Horizontal
Stirred Bed
Particles
• PP/catalyst particles
• Multiphase liquid or
gas dispersions
• Heat removal by surface,
recycle or evaporation
• multiple reactors for
complex products
Catalyst
1st REACTOR
Gas + particles
To recycle
Vertical
Stirred Bed
Product
Catalyst
Monomer
Hydrogen
Loop
Gas + particles
Liquid
+
particles
Product
CW
TC
Polymer
Basell Spherizone Polypropylene Reactor
2002
• More Uniform Product
for layered copolymer
• Bimodal MWD in a
single reactor
• blocky copolymer for
catalysts with long
chain lifetimes
• single reactor rather than
two for complex products
Some Polymer Production in Nigeria
High Density and Linear Low Density Polyethylene:
• Sclairtech (Nova Chem) HDPE/LLPDE (1-butene)
250,000 tons/yr (Port Harcourt)
• Methanol to Olefins Project underway to add
400,000 tons/yr of HDPE (Port Harcourt)
Polypropylene:
• Spheripol (Basell) PP Homopolymer/High Impact PP
95,000 tons/yr (Port Harcourt)
• Older PP Plant 35,000 tons/yr (Warri)
• Methanol to Olefins Project underway to add
400,000 tons/yr of PP (Port Harcourt)
Bottle Grade Polyethylene Terephthalate (PET):
• Buehler Two Stage Solid State Process
75,000 tons/yr (Port Harcourt)
_________________________
Business Monitor International (Jan 2013)
Special Chem Industry News (July 2012)
POLYETHYLENE TEREPHTHALATE
(POLYESTER) PROCESSES
Polycondensation (Chain Addition) Kinetics
Primary Polycondensation Polymers:
• Polyesters (e.g., Polyethylene Terephthalate (PET))
2 ~~-OOC--
--COOCH2CH2OH
~-OOC--
• Polyamides (e.g. Nylon 66)
~~~~NH2 + HOOC~~~~
Pn + Pm
Pn + Pm
kf
kr
kredis
+ HOCH2CH2OH
~~~~NHOC~~~~ + H2O
Pn+m + Condensate
Pn+m-r + Pr
--COOCH2CH2 -~~
Chain building
Redistribution
(Does not build polymer but returns
CLD to the Flory distribution)
Polyethylene Terephthalate (PET) & Reagents
Terephthalic Acid
Ethylene Glycol
Polyethylene Terephthlate (PET)
Molecular Weight & Chain Length Distributions - Polycondensation
Polycondensation
(polyester, polyamide,
epoxy, polycarbonate, etc.)
For many condensation polymers
equilibrium limitations allow only very
short chains in a closed system
without condensate removal
Polycondensation (growth)
kf
Pn + Pm « Pn +m + Condensate
kr
Redistribution (CLD adjustment)
kredis
Pn + Pm ® Pn +m -r + Pr
• Reactions occur only between
polymer molecules; a “living”
polymerization.
• Strong equilibrium limitation,
so condensate is removed to
allow continued chain growth.
Degree of Polymerization
Usually measured by GPC
or Intrinsic Viscosity (IV)
PET Resin Specifications for
Different Products
PET Product
DPn
Polyester Fibers
Soft Drink Bottles
Auto Tire Cords
Intrinsic Viscosity
0.60 dl/g
0.72 dl/g
0.85+ dl/g
Approx.
100
150
200+
PET Direct Esterification Process Flowsheet
(Terephthalic Acid (TPA) and Ethylene Glycol (EG) Feedstock)
Fiber Spinning
EG
TPA
Water
EG
PET
DP = 100
EG
EG
DP = 2-4
1 esterification
240-2600C
3 - 5 bar
7,000-10,000s
PET
DP = 20-30
Prepolymer
2 pre-polycondensation
250-2800C
0.03 bar
5,000-7,000s
DP = 150
3 finishing stage
280-2900C
0.001 bar
10,000-20,000s
Molding
4 solid state stage
200-2400C
1 bar
20,000-90,000s
PET Direct Esterification Process Flowsheet
(Terephthalic Acid (TPA) and Ethylene Glycol (EG) Feedstock)
Fiber Spinning
EG
TPA
Water
EG
PET
DP = 100
EG
EG
DP = 2-4
1 esterification
240-2600C
3 - 5 bar
7,000-10,000s
PET
DP = 20-30
Prepolymer
2 pre-polycondensation
250-2800C
0.03 bar
5,000-7,000s
DP = 150
3 finishing stage
280-2900C
0.001 bar
10,000-20,000s
Molding
4 solid state stage
200-2400C
1 bar
20,000-90,000s
THE MOVING PACKED BED
Polymer Feed
Purge Exhaust
Standard Conditions for PET:
-Temperature about 230oC
-Purge gas is N2
-Residence Time about 3hrs.
-Particle size about 2 mm
Product
Polymer
Purge Gas
Multiphase Polymerization Processes
LOW VOLUME PRODUCTION
PROCESSES
Polymerization in Multiple Phases
Multiple Phase Polymerization Processes
Gaseous Media
Liquid Media
Aqueous
Fluidized
Agitated
Organic
Emulsion
Inverse Emulsion
Dispersion
Inverse Suspension
Suspension
Precipitation
Suspension
Polymerization
monomer
droplets
d=0.1-5 mm
Monomer : Water immiscible
water
Initiator : Oil soluble
Suspending Agents :
1)organic polymers
2) inorganic powders
M / W = 50:50 - 25:75
Each Particle Behaves
as Bulk Reactor
initiator
suspending agent
Advantages:
Low Viscosity, Excellent Temperature Control.
Easy Product Separation and Little Contamination.
Examples: PVC, ABS, Polystyrene, Poly(vinyl acetate)
Particle size distribution is determined by the shear field early in
the batch time - little change thereafter.
MULTICOMPONENT EMULSION POLYMERIZATION
(for convenient polymer synthesis, rubber, latex paints, etc.)
MONOMER
DROPLET
PHASE (5µ)
monomers
MICELLE PHASE
AQUEOUS PHASE
initiator
monomers
oligomers
surfactant
Particle size dist’n
determined by the
kinetics of particle
nucleation and the
residence time
distribution in
continuous reactors
POLYMER PARTICLE PHASE (5-500nm)
monomer
copolymer
live polymer
initiator
Final Remarks; Going on From Here
CONCLUSIONS
Some Final Remarks
• There appear to be great opportunities to produce
large volumes of a broader range of valuable polymers
in Nigeria that would expand the domestic market,
significantly reduce imports, and offer materials for
the export market.
• There are well-regarded and successful polymer
production processes available for license that could
be installed in Nigeria to take advantage of the large
volumes of inexpensive oil, gas, and refined products
available locally.
• Creating and expanding the production of polymers
would allow the expansion of the domestic polymer
processing industry to provide more variety and larger
volumes of polymer consumer products for both
domestic use and export.