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Subcritical water as a green medium for extraction and processing of natural materials
Matej Ravber, 2016, doctoral dissertation

Abstract: In this doctoral dissertation, the application of subcritical water as a green medium for the extraction and processing of natural materials is presented. The work is divided into three main parts. In the first part, subcritical water is proposed as a solvent for the simultaneous extraction of oil- and water-soluble phase from oily seeds. The extraction parameters, such as temperature, time and material to solvent ratio that yield the highest amounts of both phases are examined. The quality of both obtained phases is examined. The characteristics of oils obtained using subcritical water is compared to that obtained using a conventional method. The second part of this work proposes subcritical water as an efficient solvent for the isolation of bioactive phenolic compounds from wood waste, that is produced by the forestry industry. Different wood fractions are firstly extracted in batch-mode and the fraction with the highest amounts of bioactive compounds is determined. Next, semi-continuous operation is applied, where the effects of different extraction parameters are studied on the extraction yield and quality of the extract. The effect of temperature and ethanol addition to the subcritical water on the content of single phenolic compounds identified in the extracts is observed. Lastly, the cost of manufacturing of such a product is estimated by evaluating the economics of different pilot- and industrial-scale processes operating at optimal conditions determined on the laboratory scale. The last part proposes the use of subcritical water as an efficient hydrolytic medium for glycoside bonded antioxidants, specifically those found in waste agro-industrial sources. Effect of temperature, treatment time, concentration and the atmosphere used for establishing the pressure in the reactor are first studied on a model glycoside compound - rutin and the optimal combination of reaction parameters are established for the batch-mode reactor. The degradation products of the model compound are identified and the concentration/time profiles of their degradation are observed. Furthermore, the reaction kinetics explaining the degradation of the rutin standard are evaluated. In the next step, the method is implemented on a real glycosides-containing extract. The extract is hydrolyzed at conditions obtained from the first step and the free aglycone is obtained at the highest yields possible. Lastly, the process is upgraded to continuous operation and the final hydrolyzed high-purity product is recovered.
Keywords: Subcritical water, Biowaste, Extraction, Hydrolysis, Antioxidants, Hydrothermal degradation.
Published in DKUM: 16.06.2016; Views: 1772; Downloads: 226
.pdf Full text (3,71 MB)

Matej Ravber, 2012, undergraduate thesis

Abstract: Cilj diplomskega dela je bil razviti kinetični model in mehanizem monoesterifikacije, tipične reverzibilne reakcije. Kot primer smo uporabili monoesterifikacijo etilen glikola z benzojsko kislino. Reakcija je bila katalizirana v kislem mediju ob prisotnosti α-aluminijevega oksida. Vsi eksperimenti so bili izvedeni v avtomatiziranem reakcijskem kalorimetru, opremljenim z in-line IR spektrometrom. Na osnovi IR spektrov in metodologije umeritvene krivulje smo dobili koncentracijske profile produkta. Določili smo red reakcije, obe konstanti proizvodnosti in aktivacijsko energijo. Z uporabo kinetičnih in stehiometričnih podatkov smo ugotovili reakcijski mehanizem, ki pojasnjuje opažene značilnosti reakcije.
Keywords: Monoesterifikacija, etilen glikol, reverzibilna reakcija, kinetika, mehanizem.
Published in DKUM: 11.09.2012; Views: 1643; Downloads: 201
.pdf Full text (791,39 KB)

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