**6. Upgrading of pyrolysis oil with low quality**

#### **6.1 Constant stirred tank reactor**

Pyrolytic oil is mainly composed of heavy hydrocarbons with low quality, as well as light hydrocarbons. Heavy hydrocarbons must be cracked to light hydrocarbons, in order to use as the fuel oil. The degradation experiment of pyrolytic oil is conducted by a heating rate of 10OC/min up to 420OC/min and then holding time of 5 hours at that temperature. The effects of degradation temperature and holding time at high degradation temperature on pyrolysis process are investigated. When the pyrolytic oil is degraded in a stirred semibatch reactor with a bench scale under the condition of degradation temperature programming, the low degradation temperature (at 420 OC or below, short lapse time) only distills each hydrocarbon with the corresponding boiling point within the pyrolytic oil, while at high degradation temperature and long lapse time heavy hydrocarbons are much more decomposed into light hydrocarbons like gasoline ranged components and also a little middle hydrocarbons., as a pattern of GC (gas chromatography) peaks shown in Fig. 6.

carbon number distribution of liquid PONA products over the case of low MPW, as shown in Fig. 4(a). Main liquid product was light olefin component with 9 of carbon number. This result was consistent with that of Sakata et al.(Sakata et al., 1999), who produced much more light hydrocarbon with 9 of carbon number from thermal

On the other hand, medium MPW showed highest fraction of liquid product with about 90% and lowest fraction of gas product, among three samples. In liquid product, aromatic components showed about 97% fraction and the rest was less than 2% fraction, respectively, as shown in Table 4. Moreover, phenol, aldehyde and methylester components in liquid products were not appeared and only nitro-aromatic products showed less than 2% fraction. It can be explained by the results that plastic type contained in medium MPW is mostly consisting of polymers with benzene-ring structures, especially PS among these polymers. This result can be reflected by carbon number distribution of liquid product, as shown in Fig. 4(b). Here, carbon number distribution was very short, mainly ranged from 8 to 9, as aromatic components. This result show a similar tendency in a comparison with that of Demirbas study (Demirbas, 2004), which is mainly consisting of 50-60% fraction of styrene

For pyrolysis of high MPW sample, the distribution of liquid products shows about 58% fraction in methylmethacrylate component, about 22% fraction in aromatic components and about 17% fraction in phenol components, as a main liquid product. However, straight hydrocarbon and naphthene components mainly obtained from pyrolysis of polyolefinic polymers are produced with very little amount (Lee et al., 2004). This result indicates that high MPW sample did not almost contain polyolefinic polymer type, and was mostly consisting of PMMA and then a little PS. This is demonstrated by the carbon number distribution of liquid products, as shown in Fig. 4 (c). Note the main product is methylmethacrylate monomer, producing from the pyrolysis of PMMA (Smolders &

Pyrolytic oil is mainly composed of heavy hydrocarbons with low quality, as well as light hydrocarbons. Heavy hydrocarbons must be cracked to light hydrocarbons, in order to use as the fuel oil. The degradation experiment of pyrolytic oil is conducted by a heating rate of 10OC/min up to 420OC/min and then holding time of 5 hours at that temperature. The effects of degradation temperature and holding time at high degradation temperature on pyrolysis process are investigated. When the pyrolytic oil is degraded in a stirred semibatch reactor with a bench scale under the condition of degradation temperature programming, the low degradation temperature (at 420 OC or below, short lapse time) only distills each hydrocarbon with the corresponding boiling point within the pyrolytic oil, while at high degradation temperature and long lapse time heavy hydrocarbons are much more decomposed into light hydrocarbons like gasoline ranged components and also a little middle hydrocarbons., as a pattern of GC (gas chromatography) peaks shown

degradation of PP at relatively low degradation temperature.

and 10-20% fraction of C5-C8 hydrocarbons.

**6. Upgrading of pyrolysis oil with low quality** 

**6.1 Constant stirred tank reactor** 

Baeyens, 2004).

in Fig. 6.

Fig. 6. GC peaks of product oils for thermal degradation of raw pyrolytic oil under degradation temperature programming (Lee, 2009).

Also, the catalytic degradation of pyrolytic oil using powder type FCC catalyst as a commercial cracking catalyst is investigated by a stirred tank reactor. The purpose of the catalytic degradation is to identify the possibility for utility of spent FCC catalyst as a waste catalyst, as well as the application of fresh FCC catalyst. A simple pyrolysis and catalytic degradation using spent or fresh FCC catalyst are compared by cumulative amount distribution of liquid product as a function of lapse time of reaction, as shown in Fig. 7. When a little catalyst (10%) is quickly loaded in the reactor at 420OC, the cumulative yield of liquid product is improved by the effects of catalyst, due to more cracking of heavy hydrocarbons into liquid product. Also, the cumulative yield distribution from catalytic degradation using both spent and fresh FCC catalysts is slightly deviated. This shows that spent FCC catalyst, compared to fresh FCC catalyst, has an effective result on the pyrolysis process.

Pyrolysis of Waste Polystyrene and High-Density Polyethylene 189

Boiling Point (oC)

0

commercial oils (Lee, 2012).

2012).

50

100

150

200

250

300

350

400

450

500

Gasoline Kerosene Diesel Wax

550

Mass (%) 0 10 20 30 40 50 60 70 80 90 100

Fig. 8. Boiling point distribution as a function of mass fraction for pyrolysis wax oil and

Items Liquid(wt%) Gas(wt%) Coke (wt%) ZSM-5 (HZ30) 47.18 51.04 1.78 Zeolite Y (HY80) 66.98 28.95 4.08 Zeolite Y(80%)+Clay(20%) (HYC8) 74.12 22.95 2.93 Mordenite(80%)+Clay(20%) (HMC11) 92.12 7.72 0.16 Mordenite(80%)+Alumina(20%) (HMA6) 82.59 15.11 2.3

Table 5. Product distribution for catalytic upgrading of pyrolysis wax oil at 450OC, 1hr (Lee,

The order of the zeolite for the catalytic degradation of pyrolysis wax oil to gas products is ZSM-5 > zeolite Y > mordenite. ZSM-5 catalyst with a three-dimension pore structure shows the highest activity to gas product at nearly 50%. On the other hand, the catalyst containing mordenite with a one-dimensional pore structure shows the lowest conversion of heavy hydrocarbons into gas product. This indicates that the catalyst of zeolite type plays an important role in the catalytic degradation. As the effect of supporter, the distribution of gas products and coke with both pure zeolite Y and zeolite Y(80%)+clay(20%) shows a slight difference. The catalyst containing clay has low fraction of gas product and coke, compared to pure zeolite Y. The case of mordenite with a different supporter (clay or alumina) also shows a slight difference in the product distribution. It is concluded that the adequate

Fig. 7. Cumulative yield distribution of oil product for thermal and catalytic degradation of pyrolytic oil (Lee, 2009).

#### **6.2 Fixed bed reactor**

In chemical recycling, the pyrolysis process of plastic wastes by the use of commercial rotary kiln reactor can be taken into a consideration as an efficient method. From this system, municipal plastic waste as a reactant is converted into gas product, oil product (liquid product+wax) and residue. Among pyrolytic oil, the wax oil with a high proportion has a low value for a practical use in industrial companies and moreover difficulty to supply it as an alternative fuel oil, due to its high viscosity and low quality, etc. The SIMDIST (simulated distillation) curves, as the boiling point distribution, over the pyrolysis wax oil and the commercial oils (gasoline, kerosene and diesel) are shown in Fig. 8. The pyrolysis wax oil has much higher boiling point distribution, ranging from approximately 300OC to 550OC, compared to those of commercial oils. It mainly consists of paraffin components and a very wide carbon number distribution ranging from an approximate carbon number of 10 to a carbon number of nearly 40 (Lee, 2012).

Thus, the catalytic upgrading of low-grade pyrolysis wax oil is conducted by a fixed bed reactor, as a continuous gas-phase reaction using zeolite. The distribution of liquid product, gas product and coke over several types of commercial zeolite catalysts is listed in Table 5. Five commercial zeolite catalysts (ZSM-5, zeolite Y and mordenite, with or without clay or alumina as a supporter) used have their unique and different physicochemical properties.

Loading time of catalyst

Temperature (OC)

0

100

Thermal degrad. Spent FCC Fresh FCC Thermal degrad. Spent FCC Fresh FCC

200

300

400

500

Time (min) 0 100 200 300 400

Fig. 7. Cumulative yield distribution of oil product for thermal and catalytic degradation of

In chemical recycling, the pyrolysis process of plastic wastes by the use of commercial rotary kiln reactor can be taken into a consideration as an efficient method. From this system, municipal plastic waste as a reactant is converted into gas product, oil product (liquid product+wax) and residue. Among pyrolytic oil, the wax oil with a high proportion has a low value for a practical use in industrial companies and moreover difficulty to supply it as an alternative fuel oil, due to its high viscosity and low quality, etc. The SIMDIST (simulated distillation) curves, as the boiling point distribution, over the pyrolysis wax oil and the commercial oils (gasoline, kerosene and diesel) are shown in Fig. 8. The pyrolysis wax oil has much higher boiling point distribution, ranging from approximately 300OC to 550OC, compared to those of commercial oils. It mainly consists of paraffin components and a very wide carbon number distribution ranging from an approximate carbon number of 10 to a

Thus, the catalytic upgrading of low-grade pyrolysis wax oil is conducted by a fixed bed reactor, as a continuous gas-phase reaction using zeolite. The distribution of liquid product, gas product and coke over several types of commercial zeolite catalysts is listed in Table 5. Five commercial zeolite catalysts (ZSM-5, zeolite Y and mordenite, with or without clay or alumina as a supporter) used have their unique and different

Cumulative yield of liquid product (wt%)

0

carbon number of nearly 40 (Lee, 2012).

physicochemical properties.

pyrolytic oil (Lee, 2009).

**6.2 Fixed bed reactor** 

20

40

60

80

100

Fig. 8. Boiling point distribution as a function of mass fraction for pyrolysis wax oil and commercial oils (Lee, 2012).


Table 5. Product distribution for catalytic upgrading of pyrolysis wax oil at 450OC, 1hr (Lee, 2012).

The order of the zeolite for the catalytic degradation of pyrolysis wax oil to gas products is ZSM-5 > zeolite Y > mordenite. ZSM-5 catalyst with a three-dimension pore structure shows the highest activity to gas product at nearly 50%. On the other hand, the catalyst containing mordenite with a one-dimensional pore structure shows the lowest conversion of heavy hydrocarbons into gas product. This indicates that the catalyst of zeolite type plays an important role in the catalytic degradation. As the effect of supporter, the distribution of gas products and coke with both pure zeolite Y and zeolite Y(80%)+clay(20%) shows a slight difference. The catalyst containing clay has low fraction of gas product and coke, compared to pure zeolite Y. The case of mordenite with a different supporter (clay or alumina) also shows a slight difference in the product distribution. It is concluded that the adequate

Pyrolysis of Waste Polystyrene and High-Density Polyethylene 191

highest fraction of aromatic products through the cyclization of light paraffins and olefins. Aromatic products are mainly C6, C7 and C8 components of benzene, toluene, xylene and ethylbenzene, as shown in Fig. 9, due to shape selectivity of ZSM-5. The case of zeolite Y mainly used in a commercial cracking process like FCC process and the hydrocracking process shows also different PONA pattern. Zeolite Y has the highest fraction of branched hydrocarbons with high octane number and also high fraction of aromatic products in the liquid products, which mainly produces gasoline ranged components in liquid product. However, the catalysts containing mordenite with a one-dimension pore structure shows a PONA distribution similar to raw pyrolysis wax oil and also has a wide carbon number distribution ranging from approximately 10 to 40, as shown in Fig. 9. The catalysts contained mordenite do not sufficiently crack for pyrolysis wax oil into light hydrocarbons,

A. Demirbas, Pyrolysis of municipal plastic wastes for recovery of gasoline-range

A. Marcilla, J. C. Garcia-Quesada, S. Sanchez, R. Ruiz, Study of the catalytic pyrolysis

A. Marcilla, M. I. Beltran, R. Navarro, Thermal and catalytic pyrolysis of polyethylene over

D. S. Achilias, C. Roupakias, P. Megalokonomos, A. A. Lappas, E. V. Antonakou, Chemical

G. Buekens, H. Huang, Catalytic plastic cracking for recovery of gasoline-range

J. A. Onwudili, N. Insura, P. T. Williams, Composition of products from the pyrolysis of

J. Scheirs, W. Kaminsky, Feedstock recycling and pyrolysis of waste plastics: Converting waste plastics into diesel and other fuels, John Wiley & Sons, Ltd(2006) K.-H. Lee, N.-S Noh, D.-H. Shin, Y.-H Seo, Comparison of plastic types for catalytic

K.-H. Lee, D.-H. Shin, Y.-H. Seo, Liquid-phase catalytic degradation of mixtures of waste high-

proportions of reactants, Polymer Degradation and Stability, 84(2004) 123-127 K.-H. Lee, D.-H. Shin, Influence of plastic type on pyrolysis of waste thermoplastics into oil

K.-H. Lee, Pyrolysis of municipal plastic wastes separated by difference of specific gravity, J.

behavior of polyethylene-polypropylene mixtures. J Anal Appl Pyrolysis 74 (2005)

HZSM-5 and HUSY zeolites in a batch reactor under dynamic conditions, Applied

recycling of plastic wastes from polyethylene and polypropylene. J Hazard

hydrocarbons from municipal plastic wastes, Resources, Conversion and Recycling,

polyethylene and polystyrene in a closed batch reactor: Effects of temperature and

degradation of waste plastics into liquid product with spent FCC catalyst, Polymer

density polyethylene and polystyrene over spent FCC catalyst.-Effect of mixing

hydrocarbons, J. Anal. Appl. Pyrolysis, 72 (2004) 97-102

residence time, J. Anal. Appl. Pyrolysis, 86(2009) 293-303

recovery, J. Korea Soc. Waste Management, 21 (2004) 646-651

Degradation and Stability, 78(2002) 539-544

Anal. Appl. Pyrolysis, 79(2007) 362-367

Catalysis B : Environ., 86(2009) 168-176

Materials, 149 (2007) 536-42.

23(1998) 163-181

as its relatively low activity.

387-392.

**7. References** 

design of both zeolite as a role of main reaction and supporter is a major key to determine the product distribution.

This result can be also sufficiently illustrated by the distribution of the liquid paraffin (normal/iso), olefin (normal/iso), naphthene and aromatic (PONA) products according to zeolite catalysts, as shown in Table 6. Raw pyrolysis wax oil is composed of predominantly normal paraffins and small amount of normal olefins. Among zeolites, ZSM-5 shows the


Table 6. Composition of liquid paraffin, olefin, naphthene and aromatic products for catalytic upgrading of pyrolysis wax oil at 450OC, 1hr (Lee, 2012).

Fig. 9. Carbon number distributions of product oil for catalytic upgrading of raw pyrolysis wax oil at 450OC (Lee, 2012).

highest fraction of aromatic products through the cyclization of light paraffins and olefins. Aromatic products are mainly C6, C7 and C8 components of benzene, toluene, xylene and ethylbenzene, as shown in Fig. 9, due to shape selectivity of ZSM-5. The case of zeolite Y mainly used in a commercial cracking process like FCC process and the hydrocracking process shows also different PONA pattern. Zeolite Y has the highest fraction of branched hydrocarbons with high octane number and also high fraction of aromatic products in the liquid products, which mainly produces gasoline ranged components in liquid product. However, the catalysts containing mordenite with a one-dimension pore structure shows a PONA distribution similar to raw pyrolysis wax oil and also has a wide carbon number distribution ranging from approximately 10 to 40, as shown in Fig. 9. The catalysts contained mordenite do not sufficiently crack for pyrolysis wax oil into light hydrocarbons, as its relatively low activity.
