20.500.12556/DKUM-98953 Hidrotermična konverzija odpadne kokosove lupine v pod- in nadkritični vodi diplomsko delo univerzitetnega študijskega programa I. stopnje Hydrothermal conversion of waste coconut shell in sub- and supercritical water Naraščajoče količine kmetijskih odpadkov predstavljajo resen okoljski izziv, hkrati pa nudijo velik potencial kot obnovljiv vir za prehod v krožno gospodarstvo. Kokosova lupina je kompleksna lignocelulozna biomasa, ki se zaradi počasnega razkroja pogosto kopiči kot odpadek, vendar je zaradi vsebnosti lignina in bioaktivnih spojin primerna za predelavo v produkte z višjo dodano vrednostjo. Eksperimente smo izvajali v visokotlačnem in visokotemperaturnem šaržnem reaktorju pri temperaturah 200 °C, 250 °C, 300 °C in 400 °C ter reakcijskih časih 15, 30 in 60 minut. Nastale produkte smo ločili na plinsko, oljno, vodno in trdno fazo ter jih podrobno okarakterizirali. HPLC metodo smo uporabili za določanje fenolnih spojin in furfuralov, GC-MS za analizo sestave plinov in oljne faze, FTIR za preučevanje kemijske strukture trdne faze, TC za določanje skupnega ogljika v vodni fazi ter UV-Vis spektrofotometrične metode za določevanje antioksidativne aktivnosti ter vsebnosti totalnih fenolov in flavonoidov. Ugotovili smo, da temperatura bistveno bolj vpliva na stopnjo razgradnje biomase kot reakcijski čas. Izkoristek trdne faze se je z višanjem temperature strmo zmanjševal in dosegel najnižjo vrednost 7,14 % pri 400 °C in 60 minutah. Nasprotno so pri teh pogojih izkoristki plinske (43,86 %) in oljne faze (42,60 %) dosegli svoj maksimum, kar kaže na skoraj popolno pretvorbo biomase v tekoče in plinaste produkte. Analiza FTIR je potrdila postopno kemijsko preoblikovanje trdne faze, pri čemer so bile pri 400 °C opazne najizrazitejše strukturne spremembe in zmanjšanje intenzitete pasov za kisikove in alifatske funkcionalne skupine. S HPLC analizo smo ugotovili, da sta bili v ekstraktih najbolj prisotni spojini furfural (29,24 mg/g materiala pri 200 °C in 30 min) in 5-HMF (27,25 mg/g materiala pri 250 °C in 30 min). Med flavonoidi je prevladoval katehin (2,70 mg/g materiala), določili pa smo še galno kislino, elagno kislino, kvercetin, izokvercetin in kempferol. Pri temperaturah nad 300 °C večina teh spojin termično razpade, tako da sta pri 400 °C v sledovih prisotna le še 5-MF in katehin. GC-MS analiza plinov je pokazala prevlado ogljikovega dioksida, pri čemer se je z višanjem temperature njegov delež zmanjševal. V oljni fazi so prevladovale aromatske spojine (fenoli), ki izvirajo iz razgradnje lignina, in ketoni. Rezultati UV-Vis spektrofotometričnih analiz so potrdili, da je koncentracija totalnih fenolov (39,09 mg GA/g materiala) in flavonoidov (3,51 mg QU/g materiala) najvišja pri 250 °C. Kljub upadu vsebnosti določenih spojin pri višjih temperaturah je antioksidativna aktivnost vodnih faz naraščala s temperaturo in dosegla svoj vrh (93,34 %) pri 400 °C. Ugotovili smo, da hidrotermična konverzija v pod- in nadkritični vodi predstavlja učinkovito in trajnostno metodo za predelavo kokosove lupine v biogoriva in produkte z visoko dodano vrednostjo. Increasing amounts of agricultural waste represent a serious environmental challenge, while at the same time offering great potential as a renewable resource for the transition to a circular economy. Coconut shell is a complex lignocellulosic biomass which, due to its slow decomposition, often accumulates as waste. However, owing to its lignin content and bioactive compounds, it is suitable for conversion into products with higher added value. The experiments were carried out in a high-pressure and high-temperature batch reactor at temperatures of 200 °C, 250 °C, 300 °C, and 400 °C, and at reaction times of 15, 30, and 60 minutes. The resulting products were separated into gaseous, oil, aqueous, and solid phases and were thoroughly characterized. HPLC was used to determine phenolic compounds and furfurals, GC-MS to analyse the composition of the gaseous and oil phases, FTIR to study the chemical structure of the solid phase, TC to determine the total carbon content in the aqueous phase, and UV- Vis spectrophotometric methods to determine antioxidant activity as well as the content of total phenols and flavonoids. It was found that temperature had a significantly greater effect on the degree of biomass decomposition than reaction time. The yield of the solid phase decreased sharply with increasing temperature and reached its lowest value of 7.14% at 400 °C and 60 minutes. In contrast, under these conditions, the yields of the gaseous phase (43.86%) and the oil phase (42.60%) reached their maximum values, indicating an almost complete conversion of the biomass into liquid and gaseous products. FTIR analysis confirmed the gradual chemical transformation of the solid phase, with the most pronounced structural changes and a decrease in the intensity of bands corresponding to oxygen-containing and aliphatic functional groups observed at 400 °C. HPLC analysis showed that the most abundant compounds in the extracts were furfural, 29.24 mg/g material at 200 °C and 30 minutes, and 5-HMF, 27.26 mg/g material at 250 °C and 30 minutes. Among the flavonoids, catechin was predominant, 2.69 mg/g, while gallic acid, ellagic acid, quercetin, isoquercetin, and kaempferol were also detected. At temperatures above 300 °C, most of these compounds underwent thermal degradation, so that at 400 °C only trace amounts of 5-MF and catechin were still present. GC-MS analysis of the gases showed a predominance of carbon dioxide, whose proportion decreased with increasing temperature. In the oil phase, aromatic compounds, mainly phenols originating from lignin degradation, and ketones were predominant. The results of the UV- Vis spectrophotometric analyses confirmed that the concentration of total phenols, 39.09 mg GA/g material, and flavonoids, 3.51 mg QU/g material, were highest at 250 °C. Despite the decrease in the content of certain compounds at higher temperatures, the antioxidant activity of the aqueous phases increased with temperature and reached its maximum, 93.34%, at 400 °C. It was concluded that hydrothermal conversion in subcritical and supercritical water represents an effective and sustainable method for converting coconut shells into biofuels and high-value-added products. kokosova lupina podkritična voda nadkritična voda biomasa hidrotermična konverzija coconut shell subcritical water supercritical water biomass hydrothermal conversion true true false [A. Berglez] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2026-07-21 13:38:46 2026-09-16 11:06:44 2026-09-26 03:10:12 0000-00-00 00:00:00 2026 0 Maribor 0 Maribor 1 spletni vir (1 datoteka PDF (X, 40 str.)) 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 [604.4:662:579]:634.616(043.2) 292475395 UN_Berglez_Aljaz_2026.pdf UN_Berglez_Aljaz_2026.pdf 1 6DD28A9EBB0F3C59D1A1DDC520890849 ff835b0b44757cb1151fb9d3147451f26dcb377e55ab8ef648b8d9b4aa048f2e 4b6740ca-a20b-11f1-95cc-00155d0001be https://dk.um.si/Dokument.php?lang=slv&id=210720 Fakulteta za kemijo in kemijsko tehnologijo 0 0 0