Catalytic degradation of expandable polystyrene waste (EPSW) over mordenite and modified mordenites

• Published in: Journal of molecular catalysis. A, Chemical Vol. 222; no. 1; pp. 133 - 141
• Main Authors: Chumbhale, Vilas Ramdas, Kim, Jun-Sik, Lee, Sang-Bong, Choi, Myoung-Jae
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.11.2004; Elsevier
• Subjects: Applied sciences; Catalytic degradation; Dealumination; Exact sciences and technology; Modified mordenite; Polymer industry, paints, wood; Polystyrene; Styrene selectivity; Technology of polymers; Waste treatment; Dealumination; Polystyrene; Catalytic degradation; Modified mordenite; Styrene selectivity; Catalytic reaction; Waste treatment; Zeolite; Experimental study; Foam(plastics); Mordenite; Styrene polymer; Kinetics; Catalyst activity; Comparative study; Plastic waste; Thermal degradation; Modified material
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2004.07.002

The performance of the several different modified mordenite zeolites in the degradation of expandable polystyrene waste (EPSW) was investigated in this study. The composition of the degradation products, especially the liquid fraction was compared to understand the role of H-mordenite and the effect of its modification through framework dealumination and metal impregnation. The degradation was carried out in a batch reactor at 360 and 400 °C. The dealuminated mordenite with SiO 2/Al 2O 3 ratio of 86 showed enhanced styrene/styrene dimer and styrene/ethylbenzene molar ratios at lower (360 °C) and higher (400 °C) temperature, respectively. This was attributed to the intermediate acid strength distribution generated on removal of framework aluminum by acid leaching. Modification of H-mordenite by metal impregnation substantially changed the acidic and catalytic properties in polystyrene degradation. The 0.64 wt.% phosphorous loading on H-mordenite showed improved EPSW conversion, styrene yield and SM/EB molar ratio at 400 °C. The 0.32 wt.% phosphorous loading facilitated the improvement in SM/EB molar ratio with higher styrene selectivity than thermal degradation at 360 °C. The thermal degradation of polystyrene proceeds by a free radical mechanism. In the absence of O 2 (in the flow of N 2) mainly disintegration of polymer chain occurs, which lead to oligomer or monomer. But the yield of monomer emission is only significant at a temp. >375 oC. However, the main components in the oils produced by solid acids (zeolites) in the EPSW degradation are styrene monomer and dimer which are considered to be formed by β-scission of C-C bonds in polystyrene main chain as follows: ▪