| Abstract | Plastika je jedan od najraširenijih materijala koji se koristi u svim područjima ljudskog života zbog svojih mnogobrojnih prednosti. Zbog široke upotrebe plastike ona je također jedna od komponenti komunalnog otpada s najvećim volumnim i masenim udjelom. Plastični otpad se uspješno mehanički i kemijski reciklira, a zbog svoje visoke energetske vrijednosti pogodan je i za termičku obradu. Problem koji se javlja je nemogućnost recikliranja mješanih plastičnih tokova i višeslojne plastične ambalaže koja se sastoji od više vrsta polimera, a nalazi se u komunalnom otpadu. Zbog toga se za takvu vrstu otpada kao potencijalni način obrade nameće termo-katalitička obrada (piroliza). U ovom radu korišteni su polimerni materijali koji se nalaze u komunalnom otpadu grada Zagreba, među kojima su pronađeni: polietilen niske gustoće (LDPE), polietilen visoke gustoće (HDPE), polipropilen (PP), polistiren (PS), poli(etilen-tereftalat) (PET), ostala plastika označena identifikacijskim brojem 7, koja je podjeljena na tvrdu (7tv) i meku (7m). Ispitana je termička postojanost mješavine prethodno navedenih polimera u omjeru PET/HDPE /LDPE/PP(meki)/PP(tvrdi)/PS/ostala kruta plastika (7tv)/ostala meka plastika (7m)= 0,1/9,9/20,1/14,1/8,6/10,6/8,0/18,6 označena kao „Otpadni mix“, mješavine ostale tvrde plastike „7m“ i mješavine ostale meke plastike „7m“. Za navedene uzorke ispitana je termička postojanost u prisutnosti zeolitnih katalizatora (FCC) i FCC katalizatora modificiranog željezovim (III) nitratom (Fe(NO3)3) označenim kao Fe ZSM-5 termogravimetrijskom analizom (TGA). Uzorcima su određene temperature: maksimalne razgradnje (Tmax), početne razgradnje (T90), brzina maksimalne razgradnje (rmax) te masa ugljeniziranog ostatka (mr). Također, praćena je kinetika termo-katalitičke razgradnje uzorka TGA analizom pri tri različite brzine zagrijavanja uzorka: 5, 10 i 15 °C/min. Primjenjen je Kissinger-Akahira-Sunose (KAS) model kojim je analizirana kinetika razgradnje uzorka i razmatran mehanizam razgradnje. Izokonverzijskom KAS metodom određene su i energije aktivacije (Ea) termičke razgradnje i njena ovisnost o konverziji uzorka (α). Iz rezultata se može zaključiti da je Fe ZSM-5 katalizator pogodan za korištenje pri termičkoj obradi analiziranih polimernih mješavina. U procesu toplinske razgradnje uočena je pojava paralelnih, reverzibilnih i slijednih reakcija kao posljedica kompleksnog sastava uzoraka. Zbog pojave navedenih reakcija dobivene vrijednosti Ea ne odgovaraju stvarnim vrijednostima već su umanjene ili uvećane. |
| Abstract (english) | Plastics is one of the most widespread groups of materials used in all spheres of human life due to its many advantages. Due to the widespread use of plastic, it is also one of the components of municipal waste with the largest volume and mass share. Plastic waste is successfully mechanically and chemically recycled, and due to its high energy value it is also suitable for thermal treatment. The problem that arises is the impossibility of recycling mixed plastic streams and multilayer plastic packaging consisting of several types of polymers, which is found in municipal waste. Therefore, for this type of waste, thermo-catalytic treatment (pyrolysis) is imposed as a potential method of treatment. In this paper, polymeric materials found in municipal waste of the city of Zagreb were used, among which were found: low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), other plastics marked with identification number 7, which is divided into rigid (7tv) and flexible (7m). Using thermogravimetric analysis (TGA) the thermal stability of the mixture of previously mentioned polymers in the proportion PET/HDPE/LDPE/PP(rigid)/PP(flexible)/PS/ other rigid plastic (7tv)/other flexible plastic (7m) = 0,1/9,9/20,1/14,1/8,6/10,6/8,0/18,6 marked as "Waste mix", mixtures of other rigid plastics "7m" and mixtures of other flexible plastics "7m", and thermal stability of the same mixtures in the presence of zeolite catalyst (FCC) and FCC catalyst modified with iron (III) nitrate marked as Fe ZSM-5 was investigated. Thermal stability of these samples was investigated by determination of: temperature at maximum degradation rate (Tmax), initial degradation temperature (T90), maximum degradation rate (rmax) and mass of carbonized residue (mr). The thermo-catalytic degradation kinetics of the same samples were monitored by TGA at three different sample heating rates: 5, 10 and 15 °C/min. The Kissinger-Akahira-Sunose (KAS) model was applied, which was used to analyze the degradation kinetics of the samples and considere the degradation mechanism. The activation energies (Ea) of thermal decomposition and its dependence on sample conversion (α) were determined by the isoconversion KAS method. From the results it can be concluded that Fe ZSM-5 catalyst is suitable for use in heat treatment of analyzed polymeric waste mixtures. In the process of thermal decomposition, the occurrence of parallel, reversible and sequential reactions was observed as a consequence of the complex composition of the samples. Due to the occurrence of these reactions, the obtained values of Ea do not correspond to the actual values but are reduced or increased. |
