Pollutec Recycling

Effect Of Addition Of Other Thermoplastics

Lee et al. [29] reported the effect of PS addition in the catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. Figure 5.14 shows the cumulative amount distributions of liquid products as a function of reaction time for the catalytic degradation of waste HDPE and PS mixture in different proportions. The increase of PS content in HDPE and PS mixture showed much high initial degradation rate and high

-•—	HDPE	PS = 100:0
-■-	HDPE	PS = 80:20
-▲-	HDPE	PS = 60:40
-T-	HDPE	PS = 40:60
-♦-	HDPE	PS = 20:80
	HDPE	PS = 0:100
	HDPE	PS = 100:0 (no-cat.)
---	Reaction temperature

Lapse time (min)

Figure 5.14 Cumulative amount distributions of liquid products for catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. (A initial degradation region; B final degradation region). (Reproduced with permission from Elsevier)

Lapse time (min)

Figure 5.14 Cumulative amount distributions of liquid products for catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. (A initial degradation region; B final degradation region). (Reproduced with permission from Elsevier)

liquid product yield, whereas that of HDPE showed high final degradation rate after a sufficient lapse in the reaction time.

According to the increase of PS content in HDPE and PS mixture, in Figure 5.15 the fraction of gasoline components in the liquid products was increased from about 85 wt% (pure HDPE) to about 98 wt% (pure PS) and the rest was kerosene + disel (C13-C24). No heavy oil (>C24) was detected. In the catalytic degradation of pure HDPE without PS, the major product was olefin components whereas the paraffin products as well as the aromatic and naphthene products with a cyclic structure were minor products. According as PS content in the reactant increased from 0 to 20 wt%, the fraction of paraffin

—•—	Paraffin
—■—	Olefin
—▲—	Naphthene
—▼—	Aromatic
o	< C13 (gasoline)
V	C13 - C24 (kerosene + diesel)
□	> C24 (heavy)

Figure 5.15 PONA and carbon number distributions of liquid products as a function of PS content for catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. (Reproduced with permission from Elsevier)

Figure 5.15 PONA and carbon number distributions of liquid products as a function of PS content for catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. (Reproduced with permission from Elsevier)

products was sharply increased whereas that of olefin products were decreased, because of the increase of paraffin products by the availability of hydrogen in the carbenium ion from PS degradation to olefinic intermediates [30, 31]. However, in the range of PS content 20 wt% or above, the fraction of aromatic products as a function of PS content was sharply increased whereas that of paraffin products was sharply decreased. The PONA distribution of liquid products was influenced by the interaction of the degraded intermediates from HDPE and PS degradation. Furthermore, the aromatic product was accelerated with the cyclization of paraffinic and olefinic intermediates from HDPE degradation as well as the aromatic fragments from PS degradation. In aromatic products, as shown in Figure 5.16, the increase of PS content in the mixture was linearly increased the styrene product fraction, but decreased the ethylbenzene product fraction. Styrene product was

	- Benzene
	- Toluene
	- Ethylbenzene (EB)
	- C3+ benzene
	- Styrene
	- C1+ styrene
.....-A----	• EB+Styrene

Figure 5.16 Selectivity in aromatic products as a function of PS content for catalytic degradation of waste HDPE and PS mixture using spent FCC catalyst at 400°C. (Reproduced with permission from Elsevier)

mainly produced from the degradation of PS while ethylbenzene product was influenced by HDPE content, due to the cyclization of the olefinic and paraffinic intermediates obtained by the first catalytic degradation of HDPE. Also their fraction with two carbon numbers in the side group showed the highest selectivity of 60 wt% or above. The addition of PS in the catalytic degradation of HDPE using spent FCC catalyst accelerated the production of ethylbenzene and styrene in pores of spent FCC catalyst as shape selectivity.

Lapse time (min)

Figure 5.17 Yield of liquid product as a function of lapse time for catalytic degradation of waste HDPE and mixed plastics (HDPE:LDPE:PP:PS = 33%:22%:33%:11%) using spent FCC catalyst at 350°C and 370°C (solid line: mixed plastic; dotted line: HDPE)

Lapse time (min)

Figure 5.17 Yield of liquid product as a function of lapse time for catalytic degradation of waste HDPE and mixed plastics (HDPE:LDPE:PP:PS = 33%:22%:33%:11%) using spent FCC catalyst at 350°C and 370°C (solid line: mixed plastic; dotted line: HDPE)

Walendziewski [1] was reported the thermal and catalytic degradation of PE, PP, PS and their mixture using alkaline catalyst. The catalytic degradation of PE + PS, compared with that of PE, showed high aromatic content and low boiling temperature, and also high density, high RON and MON values in the gasoline fraction.

According to the type of plastics, the characteristics of oil product in thermoplastics was clearly differed. Figure 5.17 shows the cumulative yield distributions of liquid product as a function of reaction time for catalytic degradation of pure waste HDPE and mixed plastic (HDPE:LDPE:PP:PS = 33%:22%:33%:11%) at 350 and 370°C, respectively. Here the ratio in the mixed plastic was the average weight ratio of general thermoplastics generated in Korea. The mixed plastic showed much higher initial rate of liquid product yield than that of pure HDPE. Also, the catalytic degradation of mixed plastic occurred at lower reaction temperature (by about 20°C) than that of pure HDPE plastic, because it was included the plastics with low degradation temperature in the mixed plastic.

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