Recikliranje odpadnih plastičnih mas s hidrotermičnimi postopki

magistrsko delo

Kaja Makoter (Author), Mojca Škerget (Mentor), Maja Čolnik (Co-mentor)

Abstract

Poliolefini, med katerimi sta najbolj zastopana predstavnika polietilen (PE) in polipropilen (PP), so daleč največji razred sintetičnih polimerov, ki se danes izdelujejo in uporabljajo. Predstavljajo več kot 40 % letno proizvedene plastike, pri čemer se ta količina povečuje in s tem se povečuje tudi letna količina proizvedenih odpadkov. Da bi lahko ta odpadni material pretvorili v uporabne produkte, smo izvedli hidrotermično razgradnjo različnih materialov iz PE in PP z nadkritično vodo. Hidrolizo smo izvedli na osnovnem in recikliranem HDPE pri različni temperaturi (425 °C in 450 °C ) in različnih reakcijskih časih (15 min do 240 min). Pri reakcijskih pogojih 450 °C in 60 min smo degradirali tudi ostale poliolefinske mešanice (metaloceniski LLDPE, dva reciklirana LDPE, dve mešanici granulata (MDPE+LLDPE in LDPE+rLDPE) in foliji iz teh dveh granulatov, folijo PP in vrečko iz LDPE materiala. Kot rezultat smo dobili produkte trdne, plinske, oljne in vodne faze. Trdne faze smo analizirali s Fourierjevo transformacijsko infrardečo spektrskopijo (FTIR), oljne in plinske faze smo analizirali s plinskim kromatografom z masnim spektrometrom (GC-MS) in vodne faze na analizatorju celokupnega ogljika (TOC). Ugotovili smo, da pri kratkih reakcijskih časih nastajajo voski, medtem ko z daljšanjem reakcijskih časov dobimo oljne produkte. V vseh primerih belega ali prozornega granulata in prozorne folije, je nastalo manj kot 1 % ostanka. Več ostanka je nastalo v primeru materialov, ki so vsebovali aditive, torej pri vHDPE (1,57 %), rLDPE2 (1,43 %) in pri vzorcu vrečke (2,97 %). Oljna faza predstavlja tudi glavni produkt razgradnje poliolefinov. Pri vseh vzorcih smo pri 450 °C in 60 min dobili izkoristek oljne faze višji od 89 %. Največji delež oljne faze pri polipropilenskem materialu so predstavljale aromatske spojine (46,77 %), med tem ko pa so v primeru polietilenskih materialov največji delež predstavljali nasičeni alifatski ogljikovodiki (med 50 % in 55 %). Pri osnovnem in recikliranem HDPE smo ugotovili, da je izkoristek plinske faze naraščal z naraščanjem reakcijskega časa (pri osnovnem od 1,32 % do 25,62 % in pri recikliranem od 1,29 % do 29,23 %). Izkoristki ostalih poliolefinskih mešanic pri pogoju 450 °C in 60 min so bili med 4 % in 10 %. Plinske faze so bile o večini sestavljene iz krajših alkanov in alkenov (C1-C6), med katerimi prevladujeta etan in propan. Najvišjo koncentracijo celokupnega ogljika v vodni fazi smo dokazali v primeru osnovnega HDPE materiala (2458 mg/L) pri 450 °C in 60 min. Rezultati te študije kažejo, da nadkritična voda predstavlja dober reakcijski medij za pretvorbo odpadnih poliolefinov v uporabne produkte.

Keywords

poliolefini;hidrotermična razgradnja;nadkritična voda;plinski kromatograf z masnim spektrometrom;Fourierjeva transformacijska infrardeča spektroskopija;analizator celokupnega ogljika;magistrske naloge;

Data

Language:	Slovenian
Year of publishing:	2023
Typology:	2.09 - Master's Thesis
Organization:	UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher:	[K. Makoter]
UDC:	66.094.941:678.742.2/.3.028.6(043.2)
COBISS:	185507075
Views:	246
Downloads:	0
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Recycling of waste plastics using hydrothermal processes
Secondary abstract:	Polyolefins, of which polyethylene (PE) and polypropylene (PP) are the most represented, constitute the largest class of synthetic polymers produced and used today. They represent more than 40 % of plastics produced each year, and this amount is increasing, so the amount of waste produced is also increasing. In order to be able to convert these waste materials into useful products, the hydrothermal decomposition of various materials from PE and PP with supercritical water was performed in this study. Hydrolysis was done on virgin and recycled HDPE at different temperatures (425 °C and 450 °C) and different reaction times (15 minutes to 240 minutes). At the reaction conditions of 450 °C and 60 min other polyolefin mixtures (metallocene LLDPE, two recycled LDPE, two granulate mixtures (MDPE+LLDPE and LDPE+rLDPE) and foils made from these two granulates, PP foil and a bag made from LDPE material) were also degraded. As a result, products in the solid, gas, oil and water phases were obtained. The solid phases were analyzed by Fourier-transform infrared spectroscopy (FTIR), the oil and gas phases by gas chromatography–mass spectrometry (GC-MS) and aqueous phases by TOC analyser. It was found that waxes were formed at shorter reaction times, while oily products are obtained at longer reaction times. In all cases of white or transparent granules and transparent film, less than 1 % of residue was formed. More residue occurred in materials containing additives, i.e. vHDPE (1,57 %), rLDPE2 (1,43 %) and the bag sample (2,97 %). The oil phase is the main product of polyolefin decomposition. For all samples, the yield of the oil phase at 450 °C and 60 min was over 89%. Aromatic compounds accounted for the largest proportion of the oil phase from polypropylene material (46,77 %), while saturated aliphatic hydrocarbons accounted for the largest proportion from polyethylene materials (between 50 % and 55 %). It was determined that the yield of the gas phase increased with increasing reaction time for virgin and recycled HDPE (from 1,32 % to 25,62 % for virgin material and from 1,29 % to 29,23 % for recycled HDPE). The yield of the gas phases of other polyolefin mixtures were between 4 % and 10 % at 450 °C and 60 min. The gas phases consisted mainly of shorter alkanes and alkenes (C1-C6), with ethane and propane dominating. The highest concentration of total organic carbon in the water phase was found in the case of virgin HDPE material (2458 mg/L) at 450 °C and 60 min. The results of this study show that supercritical water represents a good reaction medium for the conversion of waste polyolefins into useful products.
Secondary keywords:	polyolefins;hydrothermal degradation;supercritical water;GC-MS;FTIR;TOC;
Type (COBISS):	Master's thesis/paper
Embargo end date (OpenAIRE):	2026-09-21
Thesis comment:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages:	1 spletni vir (1 datoteka PDF (XIII, 52 f.))
ID:	19460302