## 4 Opportunities for Polymeric Materials Thermal Decomposition and Degradation  
This paper summarises pyrolysis methods, solutions, and procedures for processing polymeric materials. In recent years, technological development and the usefulness of more complex techniques and technologies have broadened this trend, indicating that thermal techniques such as pyrolysis can treat a wide range of wastes. Byproducts and chlorinated compounds hinder these approaches [33]. A strict treatment system can limit hazardous substance emissions, but it is expensive and high-tech. Compared to fuel incineration, pyrolysis emits far fewer pollutants. Process characteristics determine the final product volume and quality. Key parameters include pressure, temperature, catalyst  
Figure 6: Isomerization, cyclization and aromatization pathway (data published in accordance, with permission from Elsevier [19]). application, process agent (heat quantity or gasification agent), and fuel ratio. As with other thermal processes, these conditions are determined by the kinetic reaction rate [9; 11; 74]. The radical process is key to polymer heat breakdown [75]. These mechanisms favour less-complex matrix forms. In the presence of catalysts, these matrices generate more diverse but less complex materials. Polymer transformation into valuable chemical goods has a large environmental impact due to the high quality of the end products [76]. Catalytic thermal pyrolysis of polymeric materials has been studied extensively [63; 77; 78; 79; 80]. Fixed-bed reactors are one of the simplest solutions due to their basic design and lack of particle size constraints, resulting in low capital investments and building needs. This type of reactor is common in semi-scale, semi-laboratory, and laboratory solutions [81; 82]. The solution's continuous operation cycle affects the difficulty of controlling operating conditions (such as temperature and residence time) and the heat-transfer coefficient. Thermal inertia and limited feedstock-catalyst interactions characterise these reactors. The pyrolysis technique affects polymer quality, final product composition, and catalyst availability. Such indications determine the types of reactors used for this purpose and the process' mass, heat, and energy balance. Polyolefin waste can be converted in a fluidized bed reactor with a char removal device. In this case, pyrolytic gas with an LHV (lower heat value) of 50 MJ/m\({}^{3}\) had the highest calorific value. Hydrocarbons' high molecular weight and suitability influenced these values. Adding a catalyst changes the polymer transformation method. A catalyst accelerates and improves polymer chain isomerization, aromatization, and cracking [83]. Figure 7 depicts a stirred batch reactor scheme for PS and PP pyrolysis [84]. In this design, the controller measures pyrolysis parameters. After passing through the control-measuring device, GC (gas chromatograph) can assess the composition of the pyrolytic gas. The investigation found a correlation between the apparent increase in activation energy and the degree of material conversion during kinetics evaluation of pyrolysis at 0.5 to 2.0 \({}^{\circ}\)C/min. Retention increases the energy needed to break down organic substances. PS (polystyrene) pyrolysis was very selective for monomers and dimers, in contrast to PP (polyppropylene). Fluidized-bed reactors replace fixed-bed reactors. They are structurally and technologically superior to the previous solution. They have a better  
Figure 7: Schematic diagram of an exemplary pyrolysis reactor according to the concept of [84], with permission from Elsevier. heat transfer coefficient and can adjust temperature and resistance time. Fluidized bed reactors have better catalyst recovery and recirculation than fixed-bed reactors [85; 86; 87]. This solution reduces heat transfer better. Fluidized bed reactor materials interact effectively with the catalyst, but adequate material fragmentation is a critical technological need.