Razgradnja polikarbonata (PC) v podkritični vodi

diplomsko delo

Špela Lepoša (Author), Mojca Škerget (Mentor), Maja Čolnik (Co-mentor)

Abstract

Uporaba plastike v vsakdanjem življenju drastično raste. Z večanjem količine plastičnih izdelkov se sorazmerno povečuje tudi število plastičnih odpadkov, kar predstavlja velik problem z vidika varovanja okolja. Razgradnja plastike v naravnem okolju je zelo počasen proces, zato raziskovalci iščejo metode za razgradnjo plastičnih mas, z namenom pridobitve dragocenih surovin, ki so primerne za nadaljnjo uporabo. Ena izmed pogosteje uporabljenih plastik je tudi polikarbonat (PC), ki se uporablja za proizvodnjo raznih izdelkov. Namen in cilj diplomskega dela je bil raziskati razgradnjo plastike iz PC v podkritični vodi in ugotoviti, katere uporabne produkte lahko pridobimo iz nje. Za proces razgradnje PC smo uporabili visokotlačni in visokotemperaturni šaržni reaktor. Eksperimente smo izvajali pri temperaturi 250 °C in reakcijskih časih 60 in 120 min, medtem ko smo pri temperaturah 300 in 350 °C reakcije izvajali pri 5, 15, 30, 60 in 120 min. Kot produkte hidrotermične razgradnje smo dobili oljno, plinsko, vodno in trdno fazo. Največji izkoristek oljne faze smo dosegli pri 350 °C po 15 min in je znašal 97,7 %. Pri 250 °C je najvišje izkoristke dosegla trdna faza, ki je predstavljala nerazgrajeno plastiko iz PC, zato se je izkazalo, da je temperatura 250 °C prenizka za uspešno razgradnjo. Analize oljne in plinske faze smo izvedli z metodo plinske kromatografije s plamensko ionizacijskim detektorjem (GC-FID), vodnim fazam smo določili totalni ogljik (TC) s TOC analizatorijem medtem ko smo trdne faze analizirali s Fourierjevo transformacijo z infrardečo spektroskopijo (FTIR). V oljni fazi smo določili tri glavne razgradne produkte: bisfenol A (BPA), 4-izopropilfenol in fenol. Maksimalni izkoristek BPA (40,9 %) smo dosegli pri 250 °C in 120 min, kar lahko pripišemo začetni razgradnji PC v glavni monomer BPA. S podaljševanjem reakcijskega časa in z naraščajočo temperaturo je izkoristek BPA upadal, zaradi pretvorbe v nadaljnje komponente (fenol in 4-izopropilfenol). V plinski fazi so bili poleg CO2 prisotni večinoma alkani in alkeni. Z naraščajočo temperaturo in podaljševanjem reakcijskega časa je naraščalo število prisotnih komponent v plinski mešanici, kot posledica razpada daljših ogljikovodikov na krajše. Ugotovili smo, da je hidrotermična razgradnja PC uspešna metoda in predstavlja alternativni pristop recikliranja plastike iz PC, s katerim lahko pridobimo vredne razgradne produkte, ki so primerni za nadaljnjo uporabo.

Keywords

hidrotermična razgradnja;polikarbonat;podkritična voda;kemijsko recikliranje;BPA;diplomske naloge;

Data

Language:	Slovenian
Year of publishing:	2024
Typology:	2.11 - Undergraduate Thesis
Organization:	UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher:	[Š. Lepoša]
UDC:	66.092.1:678.05(043.2)
COBISS:	221011971
Views:	0
Downloads:	15
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	Degradation of polycarbonate (PC) in subcritical water
Secondary abstract:	The use of plastics in everyday life is increasing dramatically. As the amount of plastic products increases, the amount of plastic waste also increases proportionally, which is a major problem from an environmental point of view. The degradation of plastics in the natural environment is a very slow process, so researchers are looking for methods by which plastics can be decomposed to recover valuable raw materials for further use. One of the most commonly used plastics is polycarbonate (PC), which is used in the manufacture of various products. The aim of this work was to investigate the degradation of plastics from PC in subcritical water and to determine which useful products can be obtained from it. A high-pressure, high-temperature batch reactor was used for the PC decomposition process. The experiments were carried out at a temperature of 250 °C and reaction times of 60 and 120 minutes, while the reactions at 300 and 350 °C took place for 5, 15, 30, 60 and 120 min. Oil, gas, aqueous and solid phases were obtained as hydrothermal degradation products. The highest yield of the oil phase was achieved at 350 °C after 15 minutes and was 97.7 %. The highest yield for the solid phase was obtained at 250 °C, which represented an undecomposed PC plastic, so it was found that the temperature of 250 °C was too low for successful decomposition. The analyses of the oil and gas phases were performed using a gas chromatography-flame ionisation detector (GC-FID), the aqueous phases were analyzed for total carbon (TC) content using a TOC analyzer, while the solid phases were analyzed by Fourier transform infrared spectroscopy (FTIR). Three main degradation products were identified in the oil phase: bisphenol A (BPA), 4-isopropylphenol and phenol. The maximum BPA content (40.9 %) was obtained at 250 °C and 120 minutes, which can be attributed to the initial degradation of PC in the main BPA monomer. With increasing reaction time and temperature, the yield of BPA decreased due to the conversion to other components (phenol and 4-isopropylphenol). Besides CO2, mainly alkanes and alkenes were present in the gas phase. With increasing temperature and reaction time, the number of components present in the gas mixture increased, which is due to the decomposition of longer hydrocarbons into shorter ones. We have found that the hydrothermal degradation of PC was successful and represents an alternative approach for the recycling of plastics from PC, which can provide valuable degradation products suitable for further use.
Secondary keywords:	hydrothermal degradation;polycarbonate;subcritical water;chemical recycling;BPA;bachelor's degrees;
Type (COBISS):	Bachelor thesis/paper
Thesis comment:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo, Kemijsko inženirstvo
Pages:	1 spletni vir (1 datoteka PDF (IX, 31 f.))
ID:	24794752