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Emerald beauty
No full textV diplomskem delu raziskujem vpliv fotografije na ohranjanje narave. Predstavljene so nekatere znane organizacije, ki se ukvarjajo z varovanjem naravnega okolja in ozaveščanjem javnosti o pomenu njegovega ohranjanja, pri čemer se pogosto izražajo skozi umetniška dela. Teoretični del naloge je povezan s fotografsko serijo, ki prikazuje kontrast reke Soče. Na eni strani je predstavljena neokrnjena slovenska stran reke, na drugi pa italijanska stran, ki je v seriji prikazana kot onesnažena in degradirana. S tem vizualnim kontrastom želim opozoriti na različne pristope k ravnanju z naravnim okoljem ter spodbuditi razmislek o pomenu njegovega varovanja.In my thesis, I explore the impact of photography on nature conservation. Several well-known organizations that focus on environmental protection and raising public awareness about the importance of preserving nature are presented, many of which express their messages through artistic works. The theoretical part of the thesis is connected to a photographic series that presents the contrast of the Soča River. On one side, the unspoiled Slovenian part of the river is shown, while on the other side the Italian part is depicted as polluted and degraded. Through this visual contrast, I aim to highlight different approaches to environmental management and encourage reflection on the importance of protecting the natural environment
Determining source specific organic aerosol and black carbon emission rates by coupling source apportionment and atmospheric dynamics
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Reakcije, mehanizmi in kinetika karboksilacije aromatov z ogljikovim dioksidom
No full textThe depletion of fossil fuel reserves, the environmental impact of their ever-growing utilization, global competition, and geopolitical tensions pose a significant threat to the industrial sector, particularly the chemical industry. Through implementation of biomass valorization and carbon dioxide utilization, these threats can be mitigated, and eventually terminated. Lignin, a key component of lignocellulosic biomass, and its aromatic monomers offer significant potential as substrates for the sustainable production of value-added chemicals. The utilization of carbon dioxide as an abundant and inexpensive resource, along with underutilized lignin-derived aromatics, has great potential for the production of various industrially relevant carboxylated aromatic products. This doctoral thesis investigates the carboxylation reactions of various lignin-derived aromaticsa traditionally known KolbeSchmitt-type reactions. Primary investigation was focused on understanding the two-step reaction, involving the preparation of metal-phenoxides, using various strong bases and phenol, the simplest lignin-derived aromatic hydroxide, and then its subsequent carboxylation with gaseous CO2. The efficiency of preparing metal phenoxides was found to be directly correlated with the yield of aromatic carboxylates and was strongly influenced by the choice of strong base (NaOH), solvent (toluene), reaction temperature (120 °C), and reaction setup (reflux). Significant yields of monocarboxylated phenols, salicylic acid and 4-hydroxybenzoic acid, and dicarboxylated 4-hydroxyisophthalic acid (important chemicals for pharmaceutical, cosmetics, and polymer industries), have proven the concept of carboxylation of lignin-derived aromatics to be feasible, and provided valuable inputs for further studies. To optimize the reaction parameters, the carboxylation of commercially available sodium and potassium phenoxides was thoroughly examined. A systematic investigation of various reaction parameters, including temperature (90-225 °C), CO₂ pressure (0-40 bar), reaction duration (1-3 hours), and reactant loadings (0.15-0.6 g), revealed the sensitivity of potassium phenoxide due to water retention and subsequent degradation. Conversely, carboxylation of sodium phenoxide was successfully carried out under all reaction conditions, producing a large amount of data points that were used to develop a kinetic model of sodium phenoxide carboxylation. Lastly, the kinetic model successfully confirmed the proposed reaction mechanism, emphasizing the effect of the presence of water and humidity, which convert the newly formed monocarboxylated salts into acidified analogues that easily degrade back into phenol, thus limiting product yield. The exhaustive experimental data, along with the kinetic model, provide valuable information for the valorization of other, more complex, ligninderived aromatics and their potential for upgrading through carboxylation. To pursue the carboxylation of more complex lignin-derived aromatics, 14 various compounds were successfully carboxylated using the Marasse version of the Kolbe-Schmitt method. Using potassium carbonate for a one-pot carboxylation, besides phenol, compounds such as dihidroxybenzenes (catechol, resorcinol, hydroquinone), methylphenols (o-, m-, and p-cresols), methoxyphenols (guaiacol, anisole, 4-methylphenol, and syringol) and alkylphenols (4-propylphenol, eugenol, and 2-methoxy-4-propylphenol) were screened under two reaction temperatures (150 °C and 200 °C) and three reaction times (1, 2, and 3 hours). The results confirmed the necessity of a hydroxyl group for successful Kolbe-Schmitt-type carboxylation of aromatics. Besides producing great amount of mono- and dicarboxylated aromatic analogues, with great importance to various industries, the obtained data is a first of a kind, providing such a great amount of data points, including lignin-derived aromatics. Lastly, successful direct carboxylation of organosolv lignin at 150 °C for 2 hours confirmed the concept of combining biomass valorization and CO₂ utilization, thus crowning this extensive work. Through systematic investigation of various reaction conditions in both steps of the reaction, development of novel synthesis and analytical methods, construction of a kinetic model, and synthesis of numerous industrially relevant mono- and dicarboxylic aromatic hydroxides, this thesis provides an in-depth study of the carboxylation of lignin-derived aromatics. This doctoral thesis makes a significant contribution to the fields of biomass valorization and CO₂ utilization by providing a plethora of new materials and setting the foundation for further studies on lignin carboxylation and process optimization. Thus, this thesis successfully confirms the initial hypotheses and demonstrates the feasibility of significant carboxylation of lignin-derived aromatics
Visokokvalitetno obrazovanie i studiranje bez školarina
No full textČe razmišljate o študiju v tujini, je Slovenija odlična destinacija, ki ponuja visokokakovosten študij, evropsko diplomo in številne druge prednosti, ki jih prinaša študentski status
Photothermal investigation of magnesium oxysulfate cement
No full textThe effect of polyvinyl acetate polymer (PVAc) on thermal performance and compressive
strength of magnesium oxysulfate cement has been investigated. The PVAc polymer was added to the
cement matrix of 0%, 5%, 10%, 15% and 20% of MOS weight. The thermal properties of MOS cement
were determined by Photothermal Deflection Technique (PTD). Thermal properties such as thermal
conductivity and thermal diffusivity is measured by fitting the experimental curves of photothermal signal
to the best corresponding theoretical curves. The results revealed that the incorporation of PVAc polymer
enhance the thermal insulation and reduce the compressive strength of MOS cement. The addition of 10%
PVAc polymer has been improved the thermal performance of cement compared to others specimens. The
key to reducing properties is the size and amount of air bubbles formed in the cement matrix