Characterization of Styrene Recovery from the Pyrolysis of Waste Expandable Polystyrene

Abstract

Catalytic and thermal degradation of waste expandable polystyrene (WEPS) have been studied in a semi-batch reactor with continuous flow of nitrogen to achieve greater oil yield and maximize styrene monomer recovery. Effect of temperature, nature of catalyst and its size, reaction time of catalytic pyrolysis, and effect of repyrolysis have been also investigated. Higher reaction temperature favors the oil yield and also decreases the reaction time with maximum styrene selectivity (76.31 wt %) at 450 °C. Among the catalysts studied, solid base BaO is found to be the most efficient and increases the styrene selectivity (84.29 wt %) significantly at a reaction temperature of 350 °C in comparison to thermal and acid catalytic degradation. Modified catalyst Fe−A/Al (A = basic material) also shows better activity than Fe2O3 or Fe/Al. Increase in the size of the catalyst and repyrolysis decrease the oil yield, and styrene production also decreases on repyrolysis.

Styrene recovery from polystyrene by flash pyrolysis in a conical spouted bed reactor

“…Although the dimer yield is not highly affected by temperature, an increase in temperature from 450°C to 550°C leads to a reduction in the formation of the dimer, thus increasing the formation of lower molecular weight compounds, but an increase from 550°C to 600°C gives way to the formation of the dimer. Park et al (2003) observed the same trend, although it is not very pronounced, for the yield of styrene dimer with temperature, i.e., it slightly decreases from 9.5 wt% at 400°C to 8.8 wt% at 450°C and increases to 9.5 wt% when temperature is increased to 480°C.…”

“…They obtained a styrene yield of 78 wt% at this temperature. Park et al (2003) reported a styrene yield of around 70 wt% at 450°C in a batch thermal reactor, but the yield was considerably higher when BaO or ZnO catalysts were used. Chauhan et al (2008) operated in a fixed bed reactor from 350 to 500°C under vacuum conditions, and they obtained a styrene yield higher than 80 wt% at 500°C.…”

“…In fact, thermal pyrolysis of PS has been extensively studied, especially for monomer recovery (Aguado et al, 2003;Park et al, 2003;Kaminsky et al, 2004;Undri et al, 2014;Mo et al, 2014;Achilias et al, 2007). Thermal degradation of PS takes place by radical formation, in which three steps are distinguished (Marczewski et al, 2013): (i) initiation; (ii) depolymerising propagation; (iii) radical coupling, whose development in a DTG run evolves with temperature.…”

Pyrolysis of Waste Polystyrene to Recover Styrene over Alkaline Mesoporous Molecular Sieve K2O-BaO/MCM-41

“…PS can be depolymerized to monomer styrene, which can be polymerized to polystyrene again and be widely used to synthesize other chemicals. It is known that waste PS can be converted into styrene by simple thermal degradation [4][5][6][7][8][9], but the temperature is too high such as 873K. By using suitable catalysts, the degradation temperature can be lowered with a higher yield of styrene monomer.…”

Pyrolysis of polystyrene in coal tar and ethylene tar pitches

“…In PS pyrolysis, the yield of low-molecular-weight mononuclear aromatic compounds exceeds 95%. Therefore, this process is actively studied as a method for recirculation of the waste polymer [3].The yields and composition of PS pyrolysis products depend on the temperature, presence of catalysts and solvents, type and design of the reactor, and other process conditions [3][4][5][6][7][8][9]. Performing the polymer pyrolysis in solvents allows the conditions of mass and heat transfer in the reaction medium to be improved (otherwise these conditions are unfavorable because of high viscosity of polymer melts) and the process temperature to be decreased [9][10][11].…”