Thermo-catalytic degradation of PE and UHMWPE over zeolites with different pore systems and textural properties

Abstract

The thermo-catalytic degradation of polyethylene (PE) and ultra-high molecular weight polyethylene (UHMWPE) was studied in the presence of zeolites (ZSM-5, ZSM-22, and ferrierite) with different pore systems and textural properties. The zeolites were physically mixed with polymers in the proportion of 30 wt% and submitted to thermogravimetric analysis at heating rates of 5, 10, 20, and 30 °C.min-1. The activation energy of the degradation process was determined using the Flynn-Wall-Ozawa method. The addition of zeolites to polymers has considerably reduced the temperature of degradation. ZSM-22 demonstrated greater efficiency in the degradation of PE because it has a smaller crystallite size, promoting a shorter diffusional path for the polymer fragments coming from the surface. Ferrierite showed a lower energy level in the degradation of UHMWPE, showing the need for synergy between the accessibility of the structure and acidity of the catalyst to promote the cracking of this polymer.

Different approaches to the synthesis of ZSM-22 zeolite with application in n-heptane cracking

“…Figure 4 shows the ammonia desorption profiles of the ZSM-22 zeolites. All samples provided two main peaks of ammonia desorption, one approximately between 100 and 320 °C and the other in the range of 320 and 550 °C, indicating the presence of Lewis and Brønsted acidity, respectively (Li, et al, 2017;Silva, et al, 2020). The first low temperature desorption event represents the weak acidic sites and the second high temperature event is attributed to the strong acidity sites (Gao, et al, 2020;Quintela, et al, 2021).…”