Zhao Lei, Mo Yu, Chen Chia-Lung, Amy, Wang Jing-Yuan

(R3C)

R3C-IWWG-NEA International Symposium 14 & 15 Nov 2011

Presented by

Pyrolysis for Waste Plastics Recycling

Agenda

• The advantages and limitations of plastics

pyrolysis process.

• Thermal degradation characteristics of different

waste plastics.

• Lab scale pyrolysis experiments and products

analysis.

Plastics waste pyrolysis

• Conventional petrochemical plastics

are currently consumed at a

staggering global figure of more than

200 million tonnes a year and

continue to increase at a rate above

5%

• Plastics pyrolysis produces valuable

oil which can be upgraded to fuel or

become feedstock for PHA

production.

Waste Plastic

The waste plastics category

Domestic waste

polyethylene （PE）

polystyrene （PS）

polypropylene （PP）

polrvinyl chloride （PVC）

polyethylene terephthalate （PET）

Fast disposal of plastic waste without flying ash and

TCDD；

Flexible utilization of the products;

Energy self-sustain.

Advantages of Pyrolysis method

Current pyrolysis technologies

• Pyrolysis of plastics had been intensively studied from 1970s,

and the technology was applied to fuel production in different

scales.

• There are successful pyrolysis process like Veba process

(hydro cracking ), and BP process (fluidized bed pyrolysis ).

• The first plastic pyrolyis plant in China was built in 1993 in

Shan Xi.

• Pretreatment of the plastic substrates is an essential step for

following pyrolysis process.

• For BP pyrolysis process, it is required that the impurities

shouldn’t not exceed 4%，the ash content should be no more

than 4.5%，Cl content below 2.5%，and moisture within 1%；

• The substrate should be crushed, and the metal content and

impurities need to be removed in BASF pyrolysis process.

The pretreatment of plastic substrates

Table 1 Summary of the main products of pyrolytic oil with and without catalyst

Plastic Feed Dominant Products Source Remarks

Without catalyst

Polystyrene (PS) 82.80% styrene, <0.10% benzene, 1.70% toluene, 0.80%

ethylbenzene, 5.80% alpha-methylstyrene, < 0.10% 1-ethyl-2-methyl-

benzene, 0.30% biphenyl, 0.30% alpha-methyl-phenyl,1.30% styrene

dimer, 1.60% alpha-methyl-stilbene, 1.40% 1-butene-1,3-diphenyl,

3.80% unidentified

(Ward et al.,

2006)

Styrene produced as dominant

product (>50.00%) and BTEX as

minor products. This is consistent

with our previous experimental

data.

0.07% benzene, 1.70% toluene, 0.40% xylenes and ethylbenzene,

76.80% styrene

(Kaminsky,

Predel, & Sadiki,

2004)

Polyethylene (PE) 19.20% benzene, 3.90% toluene, 0.08% xylenes and ethylbenzene,

0.50% styrene

(Kaminsky,

Predel, & Sadiki,

2004)

About 17.00 to 20.00% BTXS can

be produced. These products are

not detected in our previous

experiments.

16.10 – 23.58% methane, 19.84 - 25.40% ethene, 12.20 – 19.07%

benzene, 3.60 – 3.86% toluene, 0.08 - 1.10% xylene, 0.48 - 1.10%

styrene

(Kaminsky,

1985)

Polypropylene (PP) 18.20% benzene, 6.60% toluene, 0.40% xylenes and ethylbenzene,

1.00% styrene

(Kaminsky,

Predel, & Sadiki,

2004)

About 25.00% of BTEXS can be

produced. 2,4-dimethyl-1-heptene

is also a dominant product and this

is consistent with our previous

experimental data. 18.90% 2-pentene, 12.30% 2-methyl-1-pentene, 33.60% 2,4-dimethyl-

1-heptene, 7.80% 2,4,6-trimethyl-1-nonene

(Kiang, Uden, &

Chien, 1980)

PE/PS mixture 0.12% benzene, 1.09% toluene, 0.64% ethylbenzene, 9.

00% styrene, 0.03% xylene

(Miskolczi,

Bartha, &

Deák, 2006)

Low amount of target products

(<15.00% BTEX)

0.18 – 0.24% benzene, 0.25 - 0.48% toluene, 0.32 - 0.54%

naphthalene, 0 - 1.33% methylnaphthalenes

(Williams &

Williams, 1999)

PP/PS mixture 0.02% benzene, 0.08% toluene, 0.04% p-xylene (Williams &

Williams, 1999)

Low amount of target products

(<2.00% BTEX)

Conclusion

• Relatively dominant pyrolytic products are BTEXS and 2,4-dimethyl-1-heptene,

with production potential ranging from <2.00% up to 50.00% of total pyrolytic

product

Plastic Feed Dominant Products Source Remarks

Without catalyst

PE/PP/PS mixture 14.00 – 17.40% benzene, 3.90 - 4.80% toluene, 0.20 - 0.50% xylene,

0.20 - 0.90% ethylbenzene, 6.80 – 8.70% styrene, 2.10 – 2.50%

indene, 4.20 – 7.20% naphthalene, 16.20 – 20.50% methane, 10.10 –

10.30% ethene, 2.20 - 3.30% ethane, 1.00 - 3.20% propene

(Kaminsky & Kim,

1999)

Relative good production of

BTEX, styrene (~20.00%) from

synthetic waste and actual

waste stream. This is consistent

with our previous experimental

data. 13.57 – 15.60% methane, 11.15 – 13.37% ethene, 9.83 – 12.37%

benzene, 2.46 – 3.76% toluene, 1.07 – 2.39% naphthalene, 4.59 -

5.62% water

(Kaminsky, 1985)

With catalyst

PS 10.80 - 22.10% benzene, 3.20 – 4.60% toluene, 18.30 – 25.90%

ethylbenzene, 0.30% xylene, 2.90 - 3.20% styrene with FCC-catalyst

(Mertinkat,

Kirsten, Predel, &

Kaminsky, 1999)

40.00 to 50.00% BTEXS

produced, with BE as dominant

products

PE 13.20% benzene, 28.60% toluene, 18.70% xylenes, 0.80%

ethylbenzene, 1.10% ethyltoluenes, 3.50% trimethylbenzene, 0.10%

diethylbenzenes, 0.60% naphthalene, 2.80% other aromatics with H-

gallosilicate

(Takuma,

Uemichi, &

Ayame, 2000)

BTX is predominantly produced

at between 15.00 to 50.00%

2.00 – 15.00% benzene, 16.00 – 28.00% toluene, 15.00 – 20.00%

xylenes, 1.00 – 5.00% ethyltoluenes, 3.00 – 5.00% trimethylbenzenes,

5.00% other aromatics with H-gallosilicate

(Takuma,

Uemichi, Sugioka,

& Ayame, 2001)

PP 2.00 – 12.00% benzene, 16.00 – 28.00% toluene, 17.00 – 18.00%

xylenes, 1.00 – 5.00% ethyltoluenes, 5.00% trimethylbenzenes, 5.00%

other aromatics with H-gallosilicate

(Takuma et al.,

2001)

No 2,4-dimethyl-1-heptene

produced. BTX produced at

35.00 to 60.00%

PP/PE mixture 15.00% benzene, 27.00% toluene, 20.00% xylenes, 1.00%

ethyltoluenes, 5.00% trimethylbenzenes, 5.00% other aromatics with H-

gallosilicate

(Takuma et al.,

2001)

15.00 to 60.00% BTX produced

PE/PS mixture 0.20 – 0.37% benzene, 0.50 – 1.00% toluene, 2.10 – 3.50%

ethylbenzene, 6.30 – 8.80% styrene, 0.01 – 0.14% xylene, 0.30 –

0.50% alpha-methylstyrene with FCC

(Miskolczi et al.,

2006)

10.00 to 13.00% BTEXS, with

ES as dominant products

Objectives

• To study thermogravimetric analysis (TGA): weight loss vs. temperature

• To determine reaction temperature range and energy consumption

Materials and Methods

Sample preparation 1) Different products of the PS ,PE, PP and PET 2) Homogenization by grinding

TGA analysis

1) 30 °C to 900 °C

2) 10 °C/min

3) N2: 20 mL/min

TGA study of different plastic products

Thermodegradation of the mixture of the pure plastic chemicals

The TG and DTG profiles and reaction characteristics of the mixture of pure

plastics

Fig. 3 TG profiles of pure plastic mixture with equal weight proportions. (a) PE, PP and the mixture of PE & PP in 1:1 weight

proportion. (b) PE, PS and the mixture of PE & PS in 1:1 weight proportion. (c) PP, PS and the mixture of PP & PS in 1:1 weight

proportion. (d) PE, PP, PS and the mixture of PE, PP & PS in 1:1:1 weight proportion.

(a) (b)

(c) (d)

Conclusion

• The plastic mixture started degrading at 400 °C and completed its degradation at 500 °C.

• The fastest reaction of the plastic mixture occurred between 430 – 480 °C.

• Temperature range of 400 – 500 °C would be employed for lab-scale pyrolysis.

Fig. 4 DTG profiles of PE, PP and PS and their mixture with equal weight proportions

Objectives

• Online analysis for the volatile products

• Offline analysis for solid and semi-solid products

Materials and Methods

1 Online analysis

2 Offline analysis (solid sample)

On-line product analysis

FTIR signal

analysis

Volatile products

transit TGA

Transfer Line

FTIR

Temperature program control

Sample preparation 1)Homogenization by grinding

Pelleting

1) Mix with KBr powder

2) Pelleting with vacuum press

FTIR analysis

1) Resolution: 4 cm-1

2) Spectrum range: 500-4000 cm-1

TGA-FTIR analysis for the pyrolysis products

Conclusion • Aliphatic hydrocarbon & CO2 was produced • Wax had longer carbon chain, more carbon-carbon double bonds and

branches

Functional group Vibrational mode Assigned (cm-

1)

-CH=CH2 or

>C=CH2

C-H stretching 3076

-CH3 C-H asymmetrical stretching 2951

-CH2- C-H asymmetrical and

symmetrical stretching

2929, 2916,

2855, 2849

CO2 CO2 stretching 2359, 668

-CH=CH2 or

>C=CH2 or -

CH=CH-

C=C stretching 1645

-CH2- C-H scissoring 1456

-CH3

C-H asymmetrical and

symmetrical bending 1456, 1376

-CH=CH2 C-H bending 990, 910

-CH=C< C-H bending 781

-(CH2)n- (n>4) CH2 plane rocking 719

CO2 C=C -CH2- -CH2- -CH3

C=C -CH2- -CH3 FTIR spectrum of pyrolysis products of LDPE pyrolysis products

LDPE pyrolysis

Conclusion • Aliphatic hydrocarbon & CO2 was produced • More branches than LDPE products • Wax had more carbon-carbon double bonds and branches

Functional group Vibrational mode Assigned (cm-

1)

-CH=CH2 or

>C=CH2

C-H stretching 3076

-CH3 C-H asymmetrical stretching 2963, 2951,

2868

-CH2- C-H asymmetrical and

symmetrical stretching

2929, 2916,

2840

CO2 CO2 stretching 2359, 668

-CH=CH2 or

>C=CH2 or -

CH=CH-

C=C stretching 1651, 1645

-CH2- C-H scissoring 1456

-CH3

C-H asymmetrical and

symmetrical bending 1456, 1376

-CH=CH- C-H bending 974, 972

>C=CH2 C-H bending 889

CO2 C=C -CH3 -CH2-

-CH3 -CH2- C=C

-CH3 -CH2-

FTIR spectrum of pyrolysis products of PP pyrolysis products

PP pyrolysis

Conclusion • Aromatic hydrocarbon was produced • Mono-substituted benzene ring • Carbon-carbon double bonds

Functional group Vibrational mode Assigned (cm-

1)

Aromatic rings C-H stretching 3074, 3031

-CH3 directly attached

to benzene rings

C-H asymmetric and

symmetric stretching 2937

-CH3 C-H symmetrical stretching 2869

Aromatic rings Summation bands 2000-1700

--CH=CH2 or >C=CH2

or -CH=CH- C=C 1637

Aromatic rings Ring mode 1620-1400

-CH3

C-H asymmetrical and

symmetrical bending 1450

Aromatic rings In-plane C-H bending 1200-1000

-CH=CH2 C-H bending 991, 915

Meta-substituted or

mono-substituted

benzene ring

Out of plane C-H bending 770

Meta-substituted or

mono-substituted

benzene ring

C-C ring bending 694

C=C -CH3

-CH2-

FTIR spectrum of pyrolysis products of PS pyrolysis products

PS pyrolysis

Conclusion • Volatiles contained alcohols, ethers, esters, as well as CO2

• Wax contained carboxylic acids

Functional group Vibrational mode Assigned (cm-1)

-OH O-H stretching 3586

-COOH O-H stretching 3500-2500

-COOH Overtone and combination

bands of lower vavenumber

C-C stretching and C-H

bending

2800-2500

CO2 CO2 stretching 2359, 2312,669

-COOC- C=O stretching 1760

-COOH Aromatic C=O stretching 1683

-OH O-H bending 1349

-COOH C-O stretching 1280

C-O-C C-O-C asymmetric

stretching

1264

-OH C-O stretching 1200-1000

Aromatic rings In-plane C-H bending 1200-1000

Out-of-plane C-H bending 900-700

C-O-C C-O-C symmetric stretching 874

CO2 -OH -COOC- -C-O-C-

-COOH

-COOC-

FTIR spectrum of pyrolysis products of LDPE pyrolysis products

PET pyrolysis

Pyrolysis set-up

N2 supply

Furnace Gas bag

Furnace temperature controller

Silicon-gel trap

DI water trap

Chiller

Glass wool trap

Cold trap (10°C) Cold

trap (0°C)

Flow meter

Objective

To test effects of different operating conditions on pyrolysis products, and the

difference between pyrolysis products from pure and waste plastics.

Conditions

Sample type: pure and waste PS

Sample Load: 30 mg

Nitrogen Flow Rate: 1-2 L/min

Heating Rate: 10-15 °C/min

Ultimate Temperature: 425-450 °C

Operation conditions selection

TGA and DTG curve of pure PS pyrolysis under 10

°C/min

Styrene production:

65.4~82.8 % /pyrolytic oil

Temperature 370~ 520 °C (Kim, Y.S., et al., 1999; Williams, P.T. and

E.A. Williams, 1999; Kaminsky, W., M.

Predel, and A. Sadiki, 2004)

From previous experiment: From literature:

Fast

reaction

range:

410-450 °C

Pyrolysis were carried out at a heating rate of 15 °C/min, and hold

on for 30 mins at 425 °C on pure PS and two different PS waste.

Pure PS PS cap PS foam

Pure and waste PS pyrolysis

Mixed pure plastics

Melted plastics

Pyrolysis char

Pyrolysis wax

Pyrolysis were carried out at a heating rate of 30 °C/min, hold on at 600 °C

for 10 mins on mixed plastics (based Singapore waste plastics composition).

Pyrolytic oil

Mixed plastic waste pyrolysis (PP/LDPE/HDPE/PS)

Pure PET pellet

Melted PET

PET Pyrolysis char

PET Pyrolysis

products

Pyrolysis were carried out at a heating rate of 15 °C/min, hold on

at 450 °C for 10 mins on pure PET.

Pure PET pyrolysis

PET pyrolysis products

Water

NaOH

Solid products from PET pyrolysis can fully dissolve in water by

adjusting PH to above 12.

PET pyrolysis products distribution is listed below

Solid products Solid char Gas

PET pure 44.3% 13.8% 41.8%

Objective

The oil products from PS pyrolysis were analyzed by the GC-MS system to

identify their components Materials and Methods

Equipment: The HP6890 GC & 5975I MS, Agilent, USA

Column: HP-5MS (30 m, I.D. 0.25 mm, film thickness 0.1

µm)

Conditions: The injection port, interface, quadruple and

ion source was set at 250, 260, 120 and 250

°C, respectively. High-purity helium as used

as a carrier gas (1.6 mL/min).

MS parameter: electron impact mode, EI; ionization

energy, 70 eV in the positive-ion mode;

repel voltage, 25 V; analytical mode,

full scan (mass range of m/z 50-150

a.m.u. with mass accuracy of 0.1

a.m.u.)

Injection volume: 1 µL

Temperature program: initial temperature at 40 °C for 2

min, then increased to 100 °C at

a rate of 20 °C/min. The total

time for each GC run was 5 min.

Sample preparation: Standards and samples are

prepared in dichloromathane

Gas chromatogram of BTEXS standard. (Peak: 1 benzene, 2 toluene, 3

ethylbenzene, 4 p-xylene, 5 styrene)

GC-MS analysis of pyrolytic oil

Gas chromatogram of PS pure chemical pyrolytic oil.

(Peak: 1 toluene, 2 ethylbenzene, 3 styrene, 4 α-Methylstyrene, 5 1,3-ditertbutyl-benzene

Gas chromatogram of PS cap chemical pyrolytic oil.

(Peak: 1 toluene, 2 styrene, 3 1,3-ditertbutyl-benzene

Gas chromatogram of PS foam pyrolyticoil. (Peak: 1

toluene, 2 ethylbenzene, 3 styrene, 4 1,3-ditertbutyl-benzene

Conclusion •A reliable GC-MS procedure was developed of aromatics separation and identification •And the components of the PS pyrolytic oil were identified •Pyrolytic oil components of different PS products were similar

Objective

To determine that amount of main products we learned form the GC-MS

system

Materials and Methods

Equipment: The HP7890 GC & FID detector, Agilent,

USA,

Column: 30-m HP-5MS

Conditions: 250 °C; helium carrier gas flow rate: 4

mL/min.

FID parameter: 300 °C; H2 flow 30 mL/min/; make up gas

flow 22 mL/min

Injection volume: 1 µL

Temperature program: Initial temperature at 40 °C for 1

min, then increased to 90 °C at

a rate of 40 °C/min, and then to

110 °C at a rate of 10°C/min.

The total time for each GC run

was 4 min

Sample preparation: Standards and samples are

prepared in dichloromathane

Gas chromatogram of BTEXS standard. (Peak: 1 benzene, 2 toluene, 3

ethylbenzene, 4 p-xylene, 5 styrene)

GC-FID analysis of the pyrolytic oil

Sample

ID Feed stock Pyrolysis conditions

Toluene

yield, %

Ethylbenzene

yield, %

Styrene

yield, % Total

4-6 PS pure

chemical

450 °C, 10 °C/min 3.9 5.6 86 .4 95.8

4-8 425 °C, 10 °C/min 3.8 5.9 72 .7 82.3

4-9 425 °C, 15 °C/min 3.2 4.2 60.9 68.3

4-10 PS foam 425 °C, 15 °C/min 3.6 0 96.3 99.0

4-11 PS cap 425 °C, 15 °C/min 0 0 88.9 88.9

The amount of the main products in the PS pyrolytic oil

GC-FID analysis results

Feedstock Reactor Reaction

Temperature Styrene yield, %

Note Source

PS pure chemical

Tube reactor 450 68.3 /all products Present study

PS foam Tube reactor 425 76.1 /all products Present study PS cap Tube reactor 425 70.2 /all products Present study PS pure

chemical stirred vessel batch 370 65.40 / volatile products Kim et al. 1999

PS pure chemical

stirred vessel batch 380 70.91 / volatile products Kim et al. 1999

PS pure chemical

stirred vessel batch 390 71.63 / volatile products Kim et al. 1999

PS pure chemical

stirred vessel batch 400 71.56 / volatile products Kim et al. 1999

PS pure chemical

Fluidized bed Continuous

520 82.8 / oil with boiling point under

300 °C Ward et al. 2006

PS Waste Fluidized bed continuous

520 76.8 /all product Kaminsky et al.

2004 PS pure chemical

Py-GC/MS 600 79.53 /all product Audisio et al.

1992 PS pure chemical

Py-GC/MS 750 70.17 /all product Audisio et al.

1992

Styrene yield from PS pyrolysis from different studies

Conclusion • A reliable GC-FID procedure was developed for aromatics quantitative

analysis • Styrene was the most notable product of PS pyrolysis

Conclusions

• The main pyrolysis temperature zones for different

plastics are obtained;

• Main functional groups of pyrolysis products are

identified;

• A serial of reliable analytical methods were developed

for pyrolysis oil;

• High production rate of BETXS from different waste PS

pyrolysis provides suitable feedstock for high value PHA

production.

Future directions

• Maximizing the production rate of valuable chemicals like

BTEXS and TPA by adjusting the operation condition

and utilizing catalyst.

• Integrated applications of oil products from mixed

plastics pyrolysis including PHA feedstock supply and

fuel production.

Thank you

Develop High Performance Liquid

Chromatography-Diode Array Detector (HPLC-

DAD) method for BTEXS measurements Objective

The objective of this method setup was to develop an accurate and reliable

method for analysis and quantification of BTEXS compounds.

Column: Acclaim Phenyl-1

Mobile phase: 50% (v/v) methanol

Flow rate: 1.2 mL

Detection wavelength: 210nm

Injection vol.: 20 µL

Lower detection limit: 10-4 mM

Elution order: B, T, S, E, X

Calibration curves of BTEXS in GC-FID • High correlations (>0.999) were obtained

Feedstock Activation Energy,

KJ/mol

Pre-exponential Factor,

s-1

Correlation

Coefficient

PS pure 255 4.6E+18 0.99

PS foam 194 1.9E+14 0.99

PS bottle cap 265 6.2E+18 0.99

Average 238 - -

PET pure 221 1.7E+15 0.99

PET bottle 231 2.2E+16 0.99

PET card 233 3.5E+16 0.99

Average 228 - -

Coats-Redfern method :

• Activation energy (Ea) indicates the energy consumption during pyrolysis

• Ea for different PS products vary

• Ea for different PET products have similar value

Kinetic parameters of PS and PET pyrolysis

Conclusion • The energy consumption for PET products pyrolysis was lower than PS products

• The energy required for different PS products varied, and PS foam required least

• The energy required for different PET products were similar