Result and Discussion

Catalytic Pyrolysis of Mixed Plastic Waste Using Synthesized Composite

9.3 Result and Discussion

9.2.7 Characterization of Product Oil

Fourier transform infrared spectroscopy (FTIR) was used to determine the functional groups of the product oil. The manufacturer of FTIR is Perkin Elmer, which can scan a range of 4000–450 cm⁻¹ with a resolution of 1 cm⁻¹. The physical properties of oil were determined using Indian standard methods. The viscosity of the oil was determined using an Ostwald viscometer, and the standard method was IS:448 [P:25]

(1976). The aniline point was determined by using IS:1448 [P:3] (2007) and ISO 2977 (1997). Cloud point and pour point are determined by using apparatus, and the method used was IS:1448 [P:10] (1970). The smoke point was determined by IS:1448 [P:31] (1968).

Table 9.2 Characteristics of catalyst

Catalyst Surface area (m²/g) Pore size (nm) Total acidity (mmol/g)

Kaolin 46.8 21.34 0.010

Acid-treated bentonite 128.13 37.80 0.112

Ni:Al:Mg 133.76 29.35 0.135

9.3.2 Catalytic Pyrolysis

In catalytic pyrolysis, the ratio was maintained at 10:1 (polymer:catalyst) for all the experiments. The use of kaolin catalyst has slightly increased the oil yield of PSW and its mixtures. A slight reduction in gas yield was also noted with the use of kaolin as a catalyst. This enunciates that the addition of kaolin catalyst will enhance the oil production since the catalyst has a well-formed porous structure and acid values for the degradation reaction to occur, which is shown in Table 9.2 [18]. Product yield of catalytic pyrolysis is given in Table 9.3. It should be noted that the composite catalyst Ni:Al:Mg showed a good increase in oil yield for plastic mixtures. This can be due to a reduction in reaction temperature from 482 to 475 °C, since a lower reaction temperature will increase the production of oil. The residue yield of catalytic pyrolysis shows a slight increase compared to thermal pyrolysis; the reason will be the clogging of pores after multiple reactions take place on the surface of the catalyst. In general, all three catalysts have shown a good increase in oil yield and a slight increase in residue content. Figure 9.4 shows the pyrolytic oil obtained from different types of catalysts. Recyclability experiments were performed to ensure that the catalyst could withstand multiple experimental runs. Recyclability experiments were carried out in accordance with Sect. 2.4. Kaolin recycled catalyst was able to retain an oil yield of 87.35, 2.16 wt% of residue and 10.49 wt% of gas yield. It was observed that for the first two recyclable runs, the kaolin catalyst retained its oil yield, and thereafter, gas yield started to increase. This increase in gas yield can be due to the weakening of pores and active sites [14].

9.3.3 FTIR Analysis of Product Oil

Fourier transform infrared spectroscopy is a technique for determining a sample’s chemical composition and physical state. It is used to identify the unknown compo- nents and also quantify the functional group of the sample using a standard reference.

Figure 9.5 shows the peak at 3695, 3070, 3075 and 3017 cm⁻¹ that corresponds to O–H stretching [19]. The peaks at 2840 and 2912 cm⁻¹ contain C–H stretching that implies the presence of an alkane group. Be consistent with N=N=N stretching, which contains the azide group, at 2156 cm⁻¹. 1741 and 1729 cm⁻¹ correspond to CO stretching. A peak of 1372 cm⁻¹ resembles S–O stretching, which repre- sents the sulfonate group. The peak at 1202 cm⁻¹ corresponds to C–O stretching,

Table 9.3 Yield of catalytic pyrolysis

Plastic Catalyst Ratio Temperature

oC

Time min

Oil yield (wt)

Residue yield (wt%)

Gas yield (wt%)

PSW Kaolin 10:1 472 69 89.28 1.5 9.22

PPW 506 78 78.96 0.12 20.92

PSW + PPW

491 69 82.86 0.26 16.88

PSW Acid-treated bentonite

10:1 466 71 87.22 0.16 12.62

PPW 490 77 77.67 0.05 22.28

PSW + PPW

479 71 86.94 0.19 12.87

PSW Ni:Al: Mg 10:1 469 72 86.69 1.33 11.98

PPW 503 80 77.48 0.15 22.37

PSW + PPW

475 70 86.37 0.2 13.43

Fig. 9.4 Pyrolytic oil obtained from a PSW + PPW + Kaolin b PSW + PPW + acid treated bentonite c PSW + PPW + Ni:Al:Mg

which contains the ester group. 985 cm1 is associated with C–C bending, indi- cating the presence of an alkene group. 884 cm1 and 770 cm⁻¹ correlate with C–H bending. Properties of oil describe the oil quality, ignition quality, aromaticity, igni- tion delay period, heavy/lighter fraction, engine performance, suitability of oil at cold temperatures and flow of oil.

Fig. 9.5 FTIR analysis of a PSW product oil and b PPW product oil

9.3.4 Properties of Oil

Properties of oil describe the oil quality, ignition quality, aromaticity, ignition delay period, heavy/lighter fraction, engine performance, suitability of oil at cold temper- atures and flow of oil. Table 9.4 shows the properties of oil, in which the density of PPW pyrolysis oil from both the thermal and catalytic processes have a lower value than diesel, which implies the presence of lighter hydrocarbons. Lower kine- matic viscosity pyrolysis oils than diesel provide better fuel atomization. Aniline points greater than 200 are paraffinic, lower than 150 are aromatic, and in between these two temperatures are naphthene and olefins, indicating that PSW pyrolysis oil has a higher aromatic content than PPW pyrolysis oil [20]. PPW oil has a higher API gravity than diesel, whereas PSW oil has a lower API gravity than diesel. The diesel index provides the ignition quality of oil; if the diesel index value is high, it implies the presence of a higher quantity of paraffin, and a lower value shows a higher aromatic content. Diesel with an index greater than 50 burns oil completely and is more expensive. The cetane number of PPW is higher than diesel, which implies good fuel atomization. The cloud point and pour point for the oils are lower, which indicates a lower operating condition. The flash and fire points of pyrolysis oil are lower than standards, which gives better ignition quality.

Table 9.4 Oil properties of mixed plastic waste Properties PSW + PPW PSW + PPW

+ Kaolin

PSW + PPW + acid treated catalyst

PSW + PPW + Ni:Al:Mg

Diesel (Bharat stage IV 2017)

Density (g/ml) 0.884 0.862 0.872 0.870 0.815–0.845

Kinematic viscosity (cSt)

@ 40 °C

1.102 0.980 1.103 1.064 2–4.5

Specific gravity @ 15 °C

0.929 0.847 0.868 0.861 0.84

Aniline point (°F)

98.6 109.4 113 111.2 >120

API gravity 20.81 35.52 31.61 32.82 30–40

Diesel index 20.52 38.85 35.72 36.49 <55

Cetane number

24.36 37.20 35.0 35.54 51

Cloud point (^oC)

−5 −5 −5 2 –

Pour point (°C)

<−10 <−10 <−10 −1 3

Flash point (°C)

30 30 30 30 66

Fire point (°C) 34 34 34 34 –