PYROLYSIS OF POLYLACTIC ACID USING BIFUNCTIONAL CATALYST

Date

2024-12-04

Author

Sökmen, Uğur

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Polylactic acid is a promising polymer thanks to being biodegradable. PLA could be utilized to diminish environmental problems caused by non-biodegradable petroleum-based polymers. However, misconceptions about the biodegradability of PLA lead to PLA waste. Nature lacks the proper conditions, such as temperature, pH, etc., that PLA requires to decompose easily; therefore, PLA waste is inevitable. Thus, the aim of this study was to investigate PLA degradation using a catalyst. In this study support material mesoporous silica aerogel was synthesized via sol-gel method. Al and Fe metals were loaded to silica aerogels at different Al to Fe weight ratios via the wet impregnation method. Metal-loaded silica aerogels were characterized using various characterization techniques. The effects of Al/Fe weight ratio, temperature, and reaction time on the product yield and distribution in the depolymerization of PLA were investigated in a pyrolysis system. Regarding the Al/Fe weight ratio, the best-performing catalyst was found to be SimSAU0.5Al14.5Fe in terms of lowest solid yield (11.5 %) and highest condensable product yield (51 %). Thus, the effect of temperature and reaction time was investigated only for the best-performing catalyst. Increasing the temperature yielded less condensable products, and more non-condensable products. Main condensable products were DL, L, and Meso L. The concentration of the main condensable products decreased with an increase in temperature. Main non-condensable products were acetaldehyde, and carbon monoxide. Whereas acetaldehyde concentration increased with an increase in temperature, carbon monoxide concentration decreased. Eventually, when the reaction time was increased from 60 minutes to 120 minutes at 225 ℃ no solid was observed. Moreover, a slight increase in condensable product yield was also observed with the increase in reaction time. The highest lactide yield was obtained at 225 ℃ and 120 minutes.

Subject Keywords

Polylactic acid, Biodegradable Polymers, Pyrolysis, Silica Aerogel, Bifunctional Catalyst, Lactide, Lactic Acid

URI

https://hdl.handle.net/11511/113004

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Graduate School of Natural and Applied Sciences, Thesis