Summary Polyethylene terephthalate (PET) is highly used in the packaging industry, which triggered the pile‐up of a huge amount of waste in the environment. Catalytic pyrolysis can convert PET waste into fuel in solid, liquid, and gaseous products. In this study, the catalytic pyrolysis of PET granules in the presence of zeolite (A4 type) was studied. The results indicated that zeolite could remarkably influence the yields, properties, and compositions of the products by affecting the secondary and primary reactions. The yields of H2 and light hydrocarbons increased in the gaseous product due to the higher rate of dehydrogenation and cracking reactions catalyzed by the zeolite catalyst. In addition, the zeolite catalyst could crack down wax and char, increasing the yields of gas and tar while simultaneously reducing the yield of acids and aromatics inside the tar. The obtained char from the catalytic pyrolysis was more aliphatic and less aromatic, but the formation of the graphite‐type structure was enhanced. The coke, containing oxygen‐rich aliphatic species and aromatics, deposited on the catalyst, blocked pores, and significantly reduced the activity of the catalyst. In addition, the contents of metals increased on the surface of the zeolite catalyst due to the migration of inorganics from PET.

The production of widely-used bottle-grade polyethylene terephthalate (PET) is now considered an environmental problem on a global scale. The urgent need for renewable energy reveals the necessity of employing thermochemical recycling methods. The use of a carrier gas is among the parameters affecting the pyrolysis process, for it is responsible for carrying pyrolysis products to separate condensable products. In this study, PET granules were pyrolyzed at 500 C with three carrier gases: N 2 , He, and Ar. According to the results, using a gas with lower molecular weights increased the production of gaseous products (30.94%). However, using a gas with higher molecular weights led to the production of further char (20.2%) associated with the increased reforming reaction rate and hydrogen production in the gaseous phase. The presence of different carrier gases changed tar composition and aromatics; therefore, the highest acid benzoic level was detected in the nitrogen atmosphere. Evaluating the thermal stability of wax and char indicated that the weight loss of char was larger in nitrogen (44.8 wt%) than in the other two carrier gases. However, there were further heavy oxygenated components in wax under the helium and nitrogen atmospheres. Those components degraded more difficultly.

Polyethylene terephthalate, the main material used for beverage bottle packaging, accounts for an average of 7.6% of all plastic waste in Europe. This material is not biodegradable and takes several centuries to decompose. The pyrolysis process in the presence of a catalyst and carrier gases can convert PET waste into solid, liquid, and gaseous materials that can be utilized as fuel. This study evaluated the effects of different carrier gases on the pyrolysis of PET waste in the presence and absence of a zeolite catalyst (A4). The results showed that the catalyst affected the pyrolysis yield; it increased the liquid and gaseous products, as well as the benzoic acid content. However, the effect declined when replacing the carrier gas with a larger molecular weight carrier gas. The alcohol content of the char was larger than that of the wax. The maximum alcohol content was detected under He, implying the direct impact of the carrier on the pyrolysis products. The hydrocarbons identified in the char were affected by changing the carrier gas, and a different distribution of hydrocarbon groups was found by converting the aromatic group into aliphatic compounds. Broadly speaking, in the presence of helium gas and the catalyst, the lowest amount of coke and the lightest compounds were observed. The amount of coke in the presence of nitrogen gas was the same as that of helium gas, but it had heavier compounds. Meanwhile in the presence of argon gas, which has a high molecular mass, more coke and heavier compounds were obtained. © 2022 Society of Chemical Industry (SCI).