Uporaba pod- in nadkritične vode za predelavo odpadne plastike

doctoral disertation

Maja Čolnik (Avtor), Mojca Škerget (Mentor), Željko Knez (Komentor)

Povzetek

Doktorska disertacija obravnava kemijsko razgradnjo najpogosteje uporabljenih plastičnih odpadkov z uporabo pod- in nadkritične vode v uporabne produkte. Doktorsko disertacijo smo razdelili na tri dele. V prvem delu doktorske disertacije smo izvedli hidrotermično razgradnjo brezbarvnih in barvnih odpadnih PET plastenk. Poskuse smo izvajali v visokotemperaturnem in visokotlačnem šaržnem reaktorju pri temperaturah od 250-400 °C in reakcijskem času od 1-30 minut. Pri hidrolizi PET odpadkov so nastali primarni in sekundarni produkti. Glavni produkt razgradnje je bila TPA, ki smo jo po reakciji prečistili in določili izkoristek reakcije. Ugotovili smo, da pri 300 °C in 30 min v podkritični vodi dobimo najvišje izkoristke TPA iz brezbarvnih (90,0 % 0,4% ) kot tudi iz barvnih (85,0 % 0,2%) PET odpadnih plastenk. Čistote nastalih TPA smo analizirali s pomočjo HPLC, FTIR in TGA/DSC metod in ugotovili, da so njihove čistote zelo visoke in znašajo med 93-98%. Tekom reakcije so nastajali sekundarni produkti, kot so benzojska kislina, 1,4-dioksan, acetaldehid, IPA in CO2. S pomočjo analiziranih komponent v vodni in plinski fazi smo predpostavili mehanizem razgradnje PET odpadkov. Ocenili smo ekonomski in okoljski vpliv hidrotermične razgradnje PET. Ugotovili smo, da če bi povečali laboratorijski proces na industrijsko merilo, bi na letni ravni dosegli dobiček od prodaje TPA in bi znašal okrog 81 000 %. Pri tem bi kemijsko degradirali skoraj 1400 ton PET odpadkov. Okoljsko analizo hidrotermične razgradnje PET smo izvedli s pomočjo programske opreme OpenLCA in bazo podatkov Ecoinvent 3.6. Ugotovili smo, da so k splošnemu obremenjevanju okolja največ prispevale kategorije morska ekotoksičnost, globalno segrevanje in toksičnost za ljudi. Prav tako smo tekom študije o razgradnji PET odpadkov v podkritični vodi predstavili tudi kinetiko razgradnje kot ireverzibilno zaporedno reakcijo, kjer smo določili, da so reakcije za vse razgradne produkte 1.reda.%V drugem delu doktorske disertacije smo v nadkritični vodi degradirali poliolefine (PE in PP). Študirali smo razgradnjo PE in PP odpadne plastike ter za primerjavo degradirali še osnovni LDPE. Prav tako smo spremljali vpliv katalizatorja ocetne kisline na potek, razgradnjo in sestavo nastalih produktov. Eksperimente smo izvajali od 380 °C do 450 °C. Tekom razgradnje so v primeru PP in PE odpadkov nastale štiri faze oljna, plinska, vodna in trdna, med tem ko so v primeru osnovnega LDPE nastale le tri faze. Trdni preostanek pri PP in PE odpadkih smo pripisali razpadu aditivov. Metodo za določevanje lahkih ogljikovodikov in CO2 v plinski mešanici smo tudi razvili in validirali. Plinska faza je vsebovala lahke ogljikovodike (C1 do C6) in CO2, medtem ko oljno fazo po večini sestavljajo nasičeni in nenasičeni alifatski ogljikovodiki, aliciklični ogljikovodiki, aromatski ogljikovodiki in alkoholi. V primeru dodatka ocetne kisline smo ugotovili rahlo povišanje nastanka metana in CO2 v nastali plinski mešanici, zaradi razgradnje ocetne kisline v nadkritični vodi. Z višanjem reakcijskih pogojev je nastajalo manj oljne in več plinske faze. Na osnovi pridobljenih podatkov smo predstavili možen mehanizem razgradnje PP in PE v nadkritični vodi. %V tretjem delu doktorske disertacije smo študirali razgradnjo PVC odpadkov v nadkritični vodi pri temperaturi od 400-425 °C in časih od 30-60 min. Ugotovili smo, da PVC odpadki razpadejo na oljno, plinsko, vodno in trdno fazo. Maso kloridnih ionov v vodni fazi smo določili s pomočjo titracijske metode. Pri 400 °C in 30 min smo dobili najvišji izkoristek. Kemijsko sestavo oljne in plinske faze smo določili s pomočjo GC/MS metode. Ugotovili smo, da oljna faza podobno kot pri PE ali PP v glavnem vsebuje nasičene in nenasičene alifatske ogljikovodike, aliciklične ogljikovodike, aromatske ogljikovodike in alkohole. V primeru PVC plastike, pa smo v oljni fazi zasledili še halogenirane ogljikovodike (kloroalkane). Plinska faza je vsebovala le lahke ogljikovodike in CO2.

Ključne besede

nadkritična voda;podkritična voda;odpadna plastika;kemijsko recikliranje;polietilen tereftalat;polietilen;polipropilen;polivinilklorid;kinetika;tereftalna kislina;benzojska kislina;acetaldehid;izoftalna kislina;plini;ogljikovodiki;surovo olje;gorivo;doktorske disertacije;

Podatki

Jezik:	Slovenski jezik
Leto izida:	2021
Tipologija:	2.08 - Doktorska disertacija
Organizacija:	UM FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Založnik:	[M. Čolnik]
UDK:	676.08:662.767(043.3)
COBISS:	66895875
Št. ogledov:	604
Št. prenosov:	0
Ocena:	0 (0 glasov)
Metapodatki:

Ostali podatki

Sekundarni jezik:	Angleški jezik
Sekundarni naslov:	Use of sub- and supercritical water for plastic waste processing
Sekundarni povzetek:	In the first part of the dissertation, hydrothermal decomposition of colorless and colored PET waste bottles was performed. The experiments were conducted in a batch reactor at 250-400 °C and reaction time of 1-30 min. Primary and secondary products were formed during the hydrolysis of PET. The main degradation product was TPA, which was purified after the reaction and the yield of the reaction was obtained. It was found that in subcritical water at 300 °C and 30 min in subcritical water, the highest TPA yields were achieved from colorless (90.0 % 0.4 %) as well as from colored (85.0 % 0.2 %) PET waste bottles. The purities of the resulting TPAs were analyzed by HPLC, FTIR and TGA / DSC methods and found to be very high between 93-98%. During the reaction, by-products such as benzoic acid, 1,4-dioxane, acetaldehyde, IPA and CO2 were formed. Based on the results the mechanism of PET degradation in subcritical and supercritical water was proposed. The economic and environmental impacts of hydrothermal decomposition of PET were assessed. It was found that by increasing the laboratory process to an industrial scale, a profit from the sale of TPA products would be achieved on an annual basis and will be around 81000 %. By process in industrial scale 1400 tons of PET waste would be recycled annually. Environmental analysis of TPA production with hydrothermal decomposition of PET was performed using OpenLCA software and Ecoinvent 3.6 database. The categories of marine ecotoxicity, global warming and human toxicity were found to were considered contribute the most to the overall environmental impact. During the study on PET waste in subcritical water degradation, the decomposition kinetics were presented as an irreversible reaction. The individual reactions for all degraded products were of 1st order.%In the second part of the doctoral dissertation, polyolefins (PE and PP) were degraded in supercritical water. The decomposition of virgin LDPE and PE/PP waste plastics was studied. The influence of the acetic acid as catalyst on the course of reaction and the resulting products was also monitored. The experiments were performed from 380 °C to 450 °C. During decomposition of PP and PE waste oil, gas, aqueous and solid phases were formed, while in the case of virgin LDPE, only three phases appeared. The solid residue in PP and PE waste was attributed to the decomposition of additives. A method for the determination of light hydrocarbons and CO2 in a gaseous mixture was developed and validated. It was found that the oil phase consisted mostly of saturated and unsaturated aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and alcohols, while the gas phase mainly contained light hydrocarbons and CO2. In the case of the addition of acetic acid, a slightly increase in the formation of methane and CO2 in gas phase was found due to the decomposition of acetic acid in supercritical water. As the reaction conditions increased, less oil and more gas phases was formed. Based on the obtained data, a possible mechanism of decomposition of PP and PE in supercritical water is presented.%In the third part of the doctoral dissertation, the decomposition of PVC waste in supercritical water in the range of 400-425 °C at times of 30-60 min was studied. PVC waste has been found to decompose into oil, gas, aqueous and solid phases. The mass of chloride ions in the aqueous phase was determined by the titration method. At 400 °C and 30 min, the highest yield of chloride ions (47%) in water was obtained. The chemical composition of the oil and gas phases was determined using the GC/MS method. Similar to PE/PP, the oil phase contained mainly saturated and unsaturated aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and alcohols. In the case of PVC plastics, halogenated hydrocarbons (chloroalkanes) were also detected in the oil phase. The gas phase contained only hydrocarbons and CO2.
Sekundarne ključne besede:	Subcritical and supercritical water;waste plastics;chemical recycling;polyethylene terephthalate;polyethylene;polypropylene;polyvinyl chloride;kinetics;terephthalic acid;benzoic acid;acetaldehyde;1;4-dioxane;isophthalic acid;gases;hydrocarbons;crude oil;fuel.;Odpadki;Disertacije;Razgradnja;
Vrsta dela (COBISS):	Doktorsko delo/naloga
Konec prepovedi (OpenAIRE):	2023-12-30
Komentar na gradivo:	Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Strani:	XVII, 107 str.
ID:	12562402