Search

V diplomski nalogi sem se v teoretičnem delu posvetila opisu faznih diagramov čistih snovi. V računskem delu sem s Clausius-Clapeyronovo in Wagnerjevo enačbo izračunala parni tlak vode in metanola pri različnih temperaturah. Izračune obeh enačb sem grafično primerjala z eksperimentalnimi vrednostmi iz literature. S primerjavo sem ugotovila, da se izračuni Wagnerjeve enačbe dobro ujemajo z eksperimentalnimi vrednostmi v celotnem temperaturnem območju, izračuni Clausius-Clapeyronove enačbe so pa pravilni samo pri nižjih temperaturah. In my bachelor's thesis, the theoretical part focused on the description of phase diagrams of pure substances. In second part I calculated the vapor pressure of water and methanol at different temperatures using the Clausius-Clapeyron and Wagner equations. I compared the calculations of both equations with the experimental values from the literature. I found out that the calculations of Wagner equation match well with the experimental values in the entire temperature range whereas the results of Clausius-Clapeyron equation are accurate only at lower temperatures.

V diplomski nalogi smo določili fazna ravnotežja za binarni sistem (resveratrol/ogljikov dioksid) pri 40 °C ter 60 °C v območju tlakov med 40 in 500 barov ter za ternarni sistem (resveratrol/etanol/ogljikov dioksid) pri 60 °C in tlaku 300 barov. Za določitev topnosti smo uporabili statično-analitično metodo. Meritve smo izvajali v visokotlačni optični celici in tako spremljali dogajanje v celici tekom celotnega eksperimenta. Koncentracijo resveratrola v vzorcu smo izmerili spektrofotometrično. Najprej smo določili vpliv tlaka in temperature na topnost resveratrola v superkritičnem CO2. Na podlagi teh rezultatov smo določili optimalne pogoje, kjer je bila topnost resveratrola v CO2 najvišja. Pri teh pogojih smo nato izmerili topnosti resveratrola v CO2 ob prisotnosti etanola kot sotopila. Za binarni sistem smo preučili tudi vpliv gostote plina na topnost komponente. Rezultati kažejo, da lahko že z majhno spremembo tlaka in temperature vplivamo na spremembo gostote plina in posledično tudi na topnost resveratrola v sistemu. Ugotovili smo, da topnost resveratrola narašča s tlakom do 300 barov, kjer dosežemo maksimalno topnost pri konstantni temperaturi. Topnosti so podane v masnih deležih kot masa resveratrola na maso plina v binarnem sistemu, oz. v masnih deležih kot masa komponente (resveratrol, plin, topilo) na maso celotnega vzorca pri ternarnem sistemu. Topnosti resveratrola v CO2 so zelo nizke, a se z višanjem tlaka in z dodatkom sotopila višajo. Določili smo tudi tališča resveratrola pri visokih tlakih in ugotovili, da se temperatura tališča spreminja v odvisnosti od tlaka. The phase equilibrium of the binary system resveratrol/carbon dioxide has been determined at the temperatures of 40 °C and 60 °C and in the pressure range from 40 bar to 500 bar. Based on the measurements for binary system, the highest solubility has been attained at the temperature of 60 °C and a pressure of 300 bar. Accordingly, solubility in ternary system (resveratrol/ethanol/carbon dioxide) has been measured at 60 °C and a pressure of 300 bar. Solubility was determined by the means of static-analytic method. The measurements were performed in a high-pressure optical cell, allowing a visual observation of the system behavior during the entire experiment. Resveratrol concentrations in the sample were measured using spectrophotometry. The effect of pressure and temperature on the solubility of resveratrol in the supercritical CO2 has been examined. The results indicate that even a small change in pressure and temperature considerably affect solubility. The results on solubility measurements are presented as mass fractions either as mass of resveratrol to mass of gas for the binary system, or mass of component (resveratrol, gas, and solvent) to mass of the entire sample for the tertiary system. The solubility of resveratrol in CO2 is extremely low however, it increases with increasing pressure andby the addition of a co-solvent. Additionally, the melting points of resveratrol at elevated pressures have been investigated and it was found that the melting point temperature varies depending on the pressure.

Predstavljeno delo obravnava raziskave na področju faznih ravnotežij, ekstrakcije in frakcioniranja maščobnih kislin v rastlinskih oljih, obogatenih s prostimi maščobnimi kislinami (FFA) pri visokih tlakih v inertnem mediju, kot je ogljikov dioksid (CO2). Podatki so ključni za nadaljnje načrtovanje visokotlačnih separacijskih procesov, saj pripomorejo k izboljšanju določenih industrijskih procesov v smeri okoljevarstva in kvalitete proizvodov. Baze podatkov že vsebujejo podatke faznih ravnotežij za sistem rastlinska olja – CO2. Zaradi širokega izbora rastlinskih olj, ki se danes nahajajo na tržišču, podatki o faznih ravnotežjih za vsa olja niso dostopni. Predvsem v literaturi ni podatkov za fazna ravnotežja pri tlakih višjih od 350 bar in podatkov o faznih inverzijah v sistemih rastlinsko olje – CO2. Delo je tako omejeno na tri rastlinska olja, ki so komercialno dostopna, to so repično olje, olje koruznih kalčkov in olje boraga. Olja so predhodno obdelana s postopkom umiljenja in na ta način obogatena s prostimi maščobnimi kislinami. Meritve faznih ravnotežij in opazovanja faznih inverzij so izvedena na sistemih FFA-obogateno repično olje – CO2, FFA-obogateno olje koruznih kalčkov – CO2 in FFA-obogateno olje boraga – CO2 v območju tlakov med 100 in 550 bar in temperaturah 35, 45, 65 in 85 °C. Vsebnost maščobnih kislin smo določili s plinsko kromatografijo in na podlagi dobljenih rezultatov določili porazdelitvene koeficiente in separacijske faktorje. Raziskave visokotlačne ekstrakcije olja iz semen s CO2 smo izvedeli na dveh naravnih materialih z visoko vsebnostjo prostih maščobnih kislin, to so semena boraga (Borago officinalis L.) in semena nočnega svetlina (Oenthera biennis L.) pri tlaku 200 in 300 bar in temperaturah 40 in 60 °C. Ekstrakcijske krivulje smo ovrednotili z dvema matematičnima modeloma, ki kar najbolje opišeta potek ekstrakcijske krivulje v območju stacionarnega prenosa snovi in v območju nestacionarnega prenosa snovi. Zaključek raziskave predstavlja frakcioniranje repičnega olja v smeri izolacije -linolenske kisline in koncentriranja FFA in -sitosterola v oljih. Pri koncentriranju FFA smo uporabili dva postopka, prvi je superkritična ekstrakcija v dveh stopnjah, ki daje zadovoljive rezultate v primerjavi s konvencionalno metodo kolonske kromatografije. This research work presents phase equilibria, extraction and fractionation of fatty acids in vegetable oils enriched with free fatty acids (FFA) at high pressures in an inert medium such as carbon dioxide (CO2). This data is the key for further planning of high-pressure separation processes, helping to improve certain industrial processes towards environmental protection and product quality. The literature already reports on phase equilibria for the system vegetable oil – CO2 for pressures ranging up to 350 bar, whereas for higher pressures less data is available. Also, at these pressures little has been reported on the phase inversion of these systems. In our experiments, three commercial vegetable oils, namely rapeseed oil, corn germ oil, and borage oil were used. For enrichment of oils with FFA the saponification process was used. Measurements of phase equilibria and observations of phase inversions were performed on the systems FFA-enriched rapeseed oil - CO2, FFA-enriched corn germ oil - CO2, and FFA-enriched borage oil - CO2 in the pressure range between 100 and 550 bar and temperatures 35, 45, 65, and 85 °C. Fatty acid content was determined by gas chromatography and based on the obtained results the distribution coefficients and separation factors were determined. Research on high pressure extraction of oil from seeds with CO2 was performed on two natural materials with a high content of free fatty acids, namely the seeds of borage (Borago officinalis L.) and the seeds of evening primrose (Oenthera biennis L.) at a pressures 200 and 300 bar and temperatures 40 and 60 °C. Extraction curves were evaluated using two mathematical models that best describe the course of the extraction curve, namely in the region of constant extraction rate and in the region of unsteady mass transfer. The final research represents fractionation of rapeseed oil in order to isolate -linolenic acid and to concentrate FFA and -sitosterol in oil. Concentrating of FFA was performed with two stage supercritical CO2 extraction. In comparison to the conventional method of column chromatography two stage supercritical extraction gives satisfactory results.

V disertaciji smo iz proizvodnje biodizla preučevali eno izmed več moţnosti procesiranja stranskega produkta glicerola. Dobljeni glicerol smo najprej uplinjali v visokotemperaturnem in visokotlačnem reaktorju nad kritično točko vode. Uplinjanje smo izvedli pri treh različnih temperaturah. Reakcije so bile nekatalizirane in katalizirane z dvema katalizatorjema. Z dobljenimi produkti smo najprej določili masne bilance, nato pa smo primerjali odvisnost sestave produktov in stopnjo uplinjanja od temperature in zadrţevalnega časa. Med uplinjanjem se nam je na stene katalizatorja odlagal ogljik. Tega smo poskušali odstraniti iz sistema z vodno paro. Rezultati so pokazali, da bi lahko bil to eden izmed dokaj enostavnih in ekonomičnih načinov odstranjevanja naloţenega ogljika iz sistema. Drugi del disertacije obsega fazno ravnoteţje produktov uplinjanja. S temi podatki lahko načrtujemo proces separacije. Ugotavljali smo vpliv parametrov na nadaljnjo sestavo plinske mešanice, ki jo lahko nato uporabimo v procesih sinteze. Prav tako smo preučili še fazno ravnoteţje pri visokih temepraturah in tlakih za binarni sistem ogljikov monoksid/voda in ga modelirali z Van der Waalsovo enačbo. V tretjem delu smo produkte uplinjanja ţeleli primerno procesirati, da bi pridobili edukte za nadaljnje procese. Plinsko mešanico, ki jo sestavljajo štirje plini, ţelimo uporabiti v procesu sinteze. Za to potrebujemo sintezni plin, ki je mešanica ogljikovega monoksida in vodika. Ostala plina, metan in ogljikov dioksid, lahko s procesom suhega reforminga metana presnujemo v sintezni plin. Preučevali smo moţnost tovrstne nadgradnje tako, da smo izvajali reakcije pri povišanih tlakih in temperaturah brez katalizatorja in s štirimi katalizatorji. Prav tako smo analizirali sestavo plinskih produktov in preučevali, katere reakcije še simultano tečejo v našem procesu. In this doctoral dissertation one of a few possiblities of processing biodiesel production byproduct glycerol was studied. The glycerol was gasified in a high temperature and high pressure reactor above critical point of water. Gasification was performed at three different temperatures. Reactions were non-catalyzed and catalyzed with two catalysts. From obtained products mass balances were determined. Afterwards a comparison was made from product composition and gasification rate in dependance of temperature and reaction time, respectively. During gasification carbon depostied on the walls of the reactor. Its removal from the system was also investigated with low pressure water steam. Results showed that this could be a relatively simple and economically suitable process for carbon removal from the system. Second part of the thesis represents phase equilibria of gasification products. With this data a separation process can be designed. Influence of process paramaters was investigated on the composition of the gas products for their further use in synthesis processes. Also phase equilibria at elevated temperatures and pressures of binary system of carbon monoxide/water was investigated. Results were modelled with Van der Waals equation of state. The third part covers upgrading of the gas products. The obtained gas mixture, composed of four gases, is to be used in the synthesis process. For that synthesis gas is needed, which is a mixture of carbon monoxide and hydrogen. Other two gases, methane and carbon dioxide, can be converted to syngas by dry reforming of methane. The process was also investigated at high temperatures and pressures by non-catalyzed and catalyzed reactions, with four different catalysts. Furthermore an analysis of gas products was performed and possible reactions taking place in the system are discussed.

V diplomski nalogi je bila izmerjena topnost rastlinskih olj (sončnično, sojino, kokosovo in palmino olje) v zgoščenih plinih. Topnost sončničnega in sojinega olja v propanu smo merili pri temperaturah 25 in 40oC ter pri tlakih od 1 do 20 bar, topnost sončničnega in sojinega olja v žveplovem heksafluoridu pri temperaturah 25 in 40oC ter tlakih od 1 do 500 bar in topnost palminega in kokosovega olja v žveplovem heksafluoridu pri temperaturah 40 in 60 oC pri tlakih od 1 do 500 bar s pomočjo statično-analitične metode. Izmerjeni podatki nam služijo za načrtovanje visokotlačnih procesov. In the frame of diploma thesis the solubilities of plant oils (sunflower, soybean, palm and coconut oils) in dense gases (propane and sulfur hexafluoride) were measured. Solubility of sunflower and soybean oils in the propane was measured at temperatures of 25 and 40 oC and at pressures from 1 to 20 bar. The solubility of sunflower and soybean oils in sulfur hexafluoride was measured at temperatures 25 and 40 oC and at pressures from 1 to 500 bar and the solubility of palm and coconut oils in sulfur hexafluoride was measured at temperatures of 40, 60oC and in the pressure range between 1 to 500 bar by using a static-analytic method. The measured data serve us us for the design of high-pressure processes.