Fixed Bed Batch Slow Pyrolysis Process for Polystyrene Waste Recycling

Abstract

This study evaluates the potential of recycling polystyrene (PS) plastic wastes via a fixed bed (batch) slow pyrolysis reactor. The novelty lies in examining the reactor design, conversion parameters, and reaction kinetics to improve the process yield, activation energy, and chemical composition. PS samples were pyrolyzed at 475–575 °C for 30 min under 10–15 psi. Process yield and product attributes were evaluated using different methods to understand PS thermal degradation characteristics better. The results show that PS decomposition started within 2 min from all temperatures, and the total decomposition point of 97% at 475 °C at approximately 5 min. Additionally, analytical results indicate that the average necessary activation energy is 191 kJ/mol. Pyrolysis oil from PS was characterized by gas chromatography–mass spectrometry. The results show that styrene was produced 57–60% from all leading oil compounds (i.e., 2,4-diphenyl-1-butene, 2,4,6-triphenyl-1-hexene, and toluene), and 475 °C has the major average of conversion effectiveness of 91.3%. The results show that the reactor temperature remains the main conversion parameter to achieve the high process yield for oil production from PS. It is concluded that pyrolysis provides a sustainable pathway for PS waste recycling and conversion to value-added products, such as resins and polymers. The proposed method and analytical results are compared with earlier studies to identify directions for future studies.

Vacuum pyrolysis depolymerization of waste polystyrene foam into high-purity styrene using a spirit lamp flame for convenient chemical recycling

“…Thermogravimetric analysis methods have proven efficient in depolymerizing PS into styrene through pyrolysis at temperatures above 400 °C, 38,39 however, the methods are not practical for recovering the monomer. Pyrolysis using (semi-)batch reactors, [40][41][42][43][44][45] xed bed reactors 46,47 or microwaves as a heat source 48 recovered styrene, but the resulting styrene oen contains other aromatic hydrocarbons like toluene, ethylbenzene and isopropylbenzene. These hydrocarbons act as chain transfer agents during the radical polymerization of styrene, leading to a decrease in the molecular weight of PS and a subsequent reduction in the mechanical strength of the resulting products.…”

“…These hydrocarbons act as chain transfer agents during the radical polymerization of styrene, leading to a decrease in the molecular weight of PS and a subsequent reduction in the mechanical strength of the resulting products. 40,49 Moreover, aromatic decomposition products, such as pyrene, phenanthrene and polycyclic compounds, pose potential carcinogenic risks. 50,51 Therefore, it is crucial to recover the high purity of styrene in order to incorporate the monomer recovery and PS reproduction processes in the closed-loop recycling system in a safe manner.…”

Thermomechanical Properties of Polymers and Their Composites with Other Materials: Advances in Thermal and Mechanical Properties of Polymeric Materials (2nd Edition)

“…Through thermal recycling, the properties of materials from recycling can match those of the original materials, and the energy used is significantly lower compared to chemical recycling. Another method of plastic recycling involves the direct recovery of energy through incineration or fuel production [14][15][16][17].…”