Catalytic pyrolysis of polyethylene terephthalate over zeolite catalyst: Characteristics of coke and the products

Abstract

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.

Pyrolysis of bottle‐grade polyethylene terephthalate: Effect of carrier gases on carriage of pyrolysis products

“…The intensities of these compounds decreased from the highest level in the argon atmosphere to the lowest level in the nitrogen atmosphere. [ 17 ] The characteristic peaks indicating the crystallinity of compounds showed the same trend in all three atmospheres (Figure 8).…”

“…The weight loss for the char produced in the nitrogen atmosphere started at 400°C; however, it started at 500°C in the argon and helium atmospheres. [ 17 ] According to the DTG diagram, the weight loss slightly changed from 200°C to 400°C in all three gas atmospheres. The sample started to degrade completely from ~600°C.…”

“…In general, PET was stable against temperature rise at the beginning of pyrolysis in nitrogen; however, the structure started to degrade as the temperature increased, something which shows the highest weight loss. [ 17 ]…”

“…They were then further polymerized and degraded difficultly as the temperature increased. [17] F I G U R E 6 The TG and DTG curves of the wax produced by the pyrolysis. TG, thermogravimetric F I G U R E 7 The FT-IR characterization of the char produced by the pyrolysis.…”

Review of the Thermochemical Degradation of PET: an Alternative Method of Recycling

“…Another study carried out by Li et al (2021), the catalytic pyrolysis of PET in the presence of zeolite type (A4) is studied, the tests were carried out in a fluidized bed semi-batch type reactor with 15 g of material at a temperature of 500 °C for 20 minutes. The products obtained from the degradation were gas, wax, tar and carbon.…”